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Characterisation of fluoroquinolone-resistant clinical isolates of Streptococcus pyogenes in Barcelona, Spain
Abstract
Resistance mechanisms and clonal relationships were determined for six Streptococcus pyogenes isolates with low- or high-level ciprofloxacin resistance. Four isolates displayed reduced susceptibility to ciprofloxacin and levofloxacin and had alterations in ParC: Ser80-->Pro (isolate emm3.1); Ser79-->Ala (two isolates emm6.0); and a double substitution Ser79-->Phe and Ala121-->Val (isolate emm12.27). Two isolates (emm12.26) displayed high-level resistance to ciprofloxacin and levofloxacin, as well as to other quinolones. These isolates had the same double substitution in ParC as isolate emm12.27, and an additional substitution (Ser81-->Tyr) in GyrA. Resistance patterns, emm typing and sequencing of the quinolone resistance-determining regions defined two clusters containing three and two isolates, respectively.
Supplementary resources (2)
Nucleotide Sequence
September 2004
Nucleotide Sequence
September 2004
... Fluoroquinolones are newer antibiotics that are widely used to treat many infections. Several microorganisms have developed resistance to fluoroquinolones, including S. pyogenes (Malhotra-Kumar et al., 2005;Malhotra-Kumar et al., 2009;Montes et al., 2010;Orscheln et al., 2005;Rivera et al., 2005;Van Heirstraeten et al., 2012;Yan et al., 2000;Yan et al., 2008). The development of fluoroquinolone resistance in S. pyogenes is primarily mediated by point mutations in the quinolone resistance-determining regions (QRDRs) of the genes encoding DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE). ...
... Despite the increased prevalence of S. pyogenes with reduced susceptibility to fluoroquinolones in the United States and Europe (Malhotra-Kumar et al., 2005;Malhotra-Kumar et al., 2009;Montes et al., 2010;Orscheln et al., 2005;Rivera et al., 2005;Van Heirstraeten et al., 2012;Yan et al., 2000Yan et al., , 2008, these drug-resistant strains are still infrequently described in other countries. The aim of this study was to survey the epidemiology and clonalities of fluoroquinolonenonsusceptible S. pyogenes in Taiwan using emm typing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). ...
... Geographical variations in emm types among fluoroquinolonenonsusceptible S. pyogenes have been noted (Malhotra-Kumar et al., 2005;Orscheln et al., 2005;Pires et al., 2010;Rivera et al., 2005;Wajima et al., 2008). In our study, the major emm type of fluoroquinolonenonsusceptible S. pyogenes was emm12, and half of the emm12 isolates were nonsusceptible to ciprofloxacin and levofloxacin. ...
Fluoroquinolone-nonsusceptible Streptococcus pyogenes has rapidly emerged in several countries. The aim of this study was to survey the epidemiology and molecular characteristics of fluoroquinolone-nonsusceptible S. pyogenes in Taiwan. A total of 350 consecutive S. pyogenes isolates were collected between January 2005 and December 2012, including 152 (43.4%) invasive and 198 (56.6%) noninvasive isolates. Thirty-nine isolates (11.1%) of S. pyogenes were nonsusceptible to fluoroquinolones, including one emm1/ST28, 4 emm4/ST39, 33 emm12/ST36, and 1 emm87/ST62. Of all the isolates, emm12 (50%) demonstrated the highest prevalence of fluoroquinolone nonsusceptibility. Alterations of Ser79Phe and Ala12Val in ParC were the most frequently mutations in fluoroquinolone-nonsusceptible S. pyogenes isolates. There were no amino acid substitutions in GyrB, and 1 emm87 isolate exhibited 3 nonsynonymous mutations in ParE. Our study reveals the emergence of fluoroquinolone-nonsusceptible S. pyogenes emm12/ST36 in Taiwan. Regular surveillance of fluoroquinolone susceptibility in S. pyogenes is suggested.
Copyright © 2015. Published by Elsevier Inc.
... Streptococcus pyogenes clinical isolates with reduced susceptibility to fluoroquinolones (1,3,8,14,16,18,27,29) or with high-level resistance (15,16,(23)(24)(25)28) have been described previously, and the reduced susceptibility to fluoroquinolones is mediated by point mutations in the quinolone resistancedetermining region (QRDR) of the parC gene (3,16,18) whereas high-level resistance has been associated with mutations in the QRDRs of both parC and gyrA genes (23,28). To the best of our knowledge, there are no reports documenting the prevalence and characterization of fluoroquinolone-nonsusceptible S. pyogenes associated with asymptomatic colonization. ...
... Quinolone resistance characterization. Detection of point mutations in the parC quinolone resistance-determining region (QRDR) was performed by PCR (4,25) and by restriction fragment length polymorphism (RFLP) (Fig. 1) (2). ...
... No ParC substitutions at codon S79 or D83 were detected in the emm89/ST101 isolate, but instead, replacements were observed at codons D91, S107, and S140 (Table 2). This isolate was also investigated for the presence of mutations in the QRDRs of gyrA, gyrB, and parE, as described previously (4,25,29), and no mutations were found. Moreover, specific genes qnrA, qnrB, qnrC, and aac(6Ј)-Ib-cr, which confer resistance to fluoroquinolones in Enterobacteriaceae, were not detected after PCR screening assays (5,13). ...
We describe 66 ciprofloxacin-nonsusceptible Streptococcus pyogenes isolates recovered from colonized and infected children. The ParC S79A substitution was frequent and associated with the
emm6/sequence type 382 (emm6/ST382) lineage. The ParC D83G substitution was detected in two isolates (emm5/ST99 and emm28/ST52 lineages). One isolate (emm89/ST101) had no quinolone resistance-determining region codon substitutions or other resistance mechanisms. Five of 66 isolates
were levofloxacin resistant. Although fluoroquinolones are not used in children, they may be putative disseminators of fluoroquinolone-nonsusceptible
strains in the community.
... emm typing. The emm gene was amplified and sequenced as described previously (Rivera et al., 2005) and by Beall et al. (1996). emm type and subtype assignments were determined as described on the Centers for Disease Control and Prevention (CDC) website (http://www.cdc.gov/ncidod/biotech/strep/doc.htm). ...
... In tetracycline-resistant isolates, tet(M) and tet(O) were also detected by PCR using primers described by Ng et al. (2001). Characterization of mutational changes in parC, parE, gyrA and gyrB were determined previously in isolates with a levofloxacin MIC of ¢2 mg ml 21 (Rivera et al., 2005). ...
... showed reduced susceptibility to levofloxacin (MIC 2–3 mg ml 21 ) and carried mutational changes in parC. A detailed characterization of these isolates has been published previously (Rivera et al., 2005). ...
Group A streptococcus (GAS) has been described as an emerging cause of severe invasive infections. A retrospective hospital-based study was conducted, including GAS isolates causing invasive or non-invasive infections from January 1999 to June 2003 in Barcelona. Demographic and clinical information on the invasive cases was obtained from medical files. GAS isolates collected from 27 patients with invasive infections and 99 patients with non-invasive infections were characterized by emm type and subtype, superantigen (SAg) gene profile (speA-C, speF-J, speL, speM, ssa and smeZ), allelic variants of speA and smeZ genes, antibiotic susceptibility and genetic resistance determinants. The most prevalent emm type was emm1 (17.5%), followed by emm3 (8.7%), emm4 (8.7%), emm12 (7.1%) and emm28 (7.1%). The smeZ allele and SAg gene profiles were closely associated with the emm type. The speA2, speA3 and speA4 alleles were found in emm1, emm3 and emm6 isolates, respectively. Overall, 27.8, 25.4 and 11.9% of isolates were resistant to erythromycin, tetracycline or both agents, respectively. Reduced susceptibility to ciprofloxacin and levofloxacin (MIC 2-4 microg ml(-1)) was found in 3.2% of isolates. mef(A)-positive emm types 4, 12 and 75, and erm(B)-positive emm types 11 and 25 were responsible for up to 80% of the erythromycin-resistant isolates. No significant differences in emm-type distribution, SAg gene profile or resistance rates were found between invasive and non-invasive isolates. The SAg and antibiotic resistance genes appeared to be associated with the emm type and were independent of the disease type.
... DNA gyrase and topoisomerase IV enzymes are homologues, with each enzyme consisting of a tetramer with two subunits (two gyrA and two gyrB molecules in DNA gyrase, two parC and two parE molecules in topoisomerase IV). In the last few years, S. pyogenes isolates with low-level resistance to FQs have been reported by several authors (1,3,8,11,12,15,23,27), but isolates with a high level of resistance have been detected very infrequently (2,13,21,22,26). To our knowledge, S. pyogenes isolates with low-or high-level resistance to ciprofloxacin (LR and HR isolates, respectively) without a mutation in the parC gene have not been described. ...
... Unlike S. pneumoniae, the isolation of S. pyogenes with HR, to date, occurs infrequently throughout the world (2,13,(21)(22)(23)26). However, given the high prevalence of isolates with a mutation in the parC gene, in the near future this number may increase since only one new mutation in the gyrA gene is required, as recently shown by Malhotra-Kumar et al. (13). ...
The aim of this study was to determine the prevalence and characteristics of non-fluoroquinolone (FQ)-susceptible Streptococcus pyogenes isolates and to study their mechanisms of resistance. We performed a prospective prevalence study with 468 isolates collected
from 2005 to 2007 and a retrospective study that was based on the examination of existing data collected from 1999 to 2008.
The retrospective study included data for isolates with high-level resistance (HR) to ciprofloxacin (MIC ≥ 32 μg/ml) (HR isolates)
and isolates with the same emm types as those reported in the literature with low-level resistance (LR) to ciprofloxacin (MICs, 2 to 8 μg/ml) (LR isolates,
n = 205). Genetic characterization of the isolates was performed by means of emm typing and multilocus sequence typing. The prevalence of LR ranged from 1.9% in 2005 to 30.8% in 2007. This increase was
mainly due to the circulation of an emm6 subtype (emm6.4) that represented 77.1% of the LR isolates in 2007. Notably, another emm6 subtype, also detected in 2007 (emm6.37), showed coresistance to 14- and 15-membered macrolides mediated by the mefA gene. Only three HR isolates were detected (isolates emm68.1/ST247/T3,13,B3264, emm77/ST399/T28, and emm28/ST52/T28), and all were identified in the retrospective study. Overall, the 673 isolates represented 25 emm types. All LR isolates were clustered into two emm types: emm6 (six emm6 subtypes) and emm75. All the 156 emm6 isolates had LR, harbored the Ser79/Ala mutation in the parC gene product, and had the same sequence type (ST), ST382. Most (21/33) of the emm75 isolates had LR, showed the Ser79/Phe plus Asp91/Asn double mutation in the parC gene product, and were ST150. The Asp91/Asn mutation by itself did not confer resistance to FQs.
... The increasing antibiotic resistance of biofilm has drawn attention to the study of alternative sources of antibiofilm agents [39,40]. Many authors analyse essential oils as potential antibiofilm agents [16,21,[41][42][43]. ...
This study aimed to analyze the biological activity of the essential oil Pogostemon cablin (PCEO) to determine the antioxidant, antimicrobial, antibiofilm, insecticidal activity, and chemical composition of the essential oil. We analyzed the structure of biofilms on various surfaces using the MALDI-TOF MS Biotyper and evaluated the antimicrobial effect of the vapor phase of the essential oil in a food model. We determined the main volatile components of PCEO as patchouli alcohol 31.0%, α-bulnesene 21.3%, and α-guaiene 14.3%. The free radical scavenging activity was high and reached 71.4 ± 0.9%, corresponding to 732 ± 8.1 TEAC. The antimicrobial activity against bacteria was weak to moderate. We recorded strong activity against yeast. The antifungal activity was very weak in the contact application. Biofilm-producing bacteria were moderately inhibited by PCEO. The change in biofilm structure due to essential oil was demonstrated by MALDI-TOF MS Biotyper analysis. Vapor phase application in a food model showed relatively strong effects against bacteria and significantly higher antifungal efficacy. The insecticidal activity was observed only at higher concentrations of essential oil. Based on the findings, PCEO can be used in the food industry as an antifungal substance in extending the shelf life of bakery products and as protection in the storage of root vegetables.
... The global dissemination of emm6 strains was suggested to be the main reason for the increased proportion of FQ-non-susceptible S. pyogenes in Belgium and Spain (Montes et al., 2010;Van Heirstraeten et al., 2012). All six emm6 isolates identified in this study were a single FQ-non-susceptible clone on the basis of PFGE, and harbored the same ParC QRDR S79A mutation (parC allele of SHparC7) with those emm6 isolates from USA and Spain (Orscheln et al., 2005;Rivera et al., 2005). In this study, the emm6 clone was also resistant to erythromycin, clindamycin, and tetracycline. ...
Streptococcus pyogenes, also known as group A Streptococcus (GAS), is one of the top 10 infectious causes of death worldwide. Macrolide and tetracycline resistant GAS has emerged as a major health concern in China coinciding with an ongoing scarlet fever epidemic. Furthermore, increasing rates of fluoroquinolone (FQ) non-susceptibility within GAS from geographical regions outside of China has also been reported. Fluoroquinolones are the third most commonly prescribed antibiotic in China and is an therapeutic alternative for multi-drug resistant GAS. The purpose of this study was to investigate the epidemiological and molecular features of GAS fluoroquinolone (FQ) non-susceptibility in Shanghai, China. GAS (n = 2,258) recovered between 2011 and 2016 from children and adults were tested for FQ-non-susceptibility. Efflux phenotype and mutations in parC, parE, gyrA, and gyrB were investigated and genetic relationships were determined by emm typing, pulsed-field gel electrophoresis and phylogenetic analysis. The frequency of GAS FQ-non-susceptibility was 1.3% (30/2,258), with the phenotype more prevalent in GAS isolated from adults (14.3%) than from children (1.2%). Eighty percent (24/30) of FQ-non-susceptible isolates were also resistant to both macrolides (ermB) and tetracycline (tetM) including the GAS sequence types emm12, emm6, emm11, and emm1. Genomic fingerprinting analysis of the 30 isolates revealed that non-susceptibility may arise in various genetic backgrounds even within a single emm type. No efflux phenotype was observed in FQ non-susceptible isolates, and molecular analysis of the quinolone resistance-determining regions (QRDRs) identified several sequence polymorphisms in ParC and ParE, and none in GyrA and GyrB. Expansion of this analysis to 152 publically available GAS whole genome sequences from Hong Kong predicted 7.9% (12/152) of Hong Kong isolates harbored a S79F ParC mutation, of which 66.7% (8/12) were macrolide and tetracycline resistant. Phylogenetic analysis of the parC QRDR sequences suggested the possibility that FQ resistance may be acquired through inter-species lateral gene transfer. This study reports the emergence of macrolide, tetracycline, and fluoroquinolone multidrug-resistant clones across several GAS emm types including emm1 and emm12, warranting continual surveillance given the extensive use of fluoroquinolones in clinical use.
... The growing cause of drug resistance among GAS biofilms (Rivera et al., 2005;Roberts et al., 2012) has impelled the need to explore alternate sources for anti-biofilm agents against GAS. Owing to the recent advances in the exploration of EOs as a potential therapeutic agent against a number of diseases afflicting humans, numerous studies are being carried out to investigate if EOs also have the ability to suppress the virulence traits of several pathogens (Nostro et al., 2007;Kerekes et al., 2013;Curvelo et al., 2014). ...
Streptococcus pyogenes (Group A Streptococcus [GAS]) is an important human pathogen that causes several superficial infections and invasive diseases. The ability of GAS to form biofilms, renders the pathogen resistant to several antimicrobials resulting in antibiotic treatment failure. As essential oils (EOs) from plants have been promising sources of anti-biofilm agents, the present study shows that EOs from the genus Pogostemon exhibit anti-biofilm activity against pharyngitis causing GAS. The biofilm inhibition ability of the EOs varied depending upon the serotype of GAS, which was evident from confocal microscopy. Fourier transfer infra red (FT-IR) spectroscopy indicated that both the EOs disrupted the fatty acid membrane of the biofilms in all the serotypes. Overall, this study forms a first report on the anti-biofilm activity of the EOs of Pogostemon species and this can be a novel natural resource to combat drug resistant pathogenic biofilms.
... The growing cause of drug resistance among GAS biofilms (Rivera et al., 2005; Roberts et al., 2012) has impelled the need to explore alternate sources for anti-biofilm agents against GAS. Owing to the recent advances in the exploration of EOs as a potential therapeutic agent against a number of diseases afflicting humans, numerous studies are being carried out to investigate if EOs also have the ability to suppress the virulence traits of several pathogens (Nostro et al., 2007; Kerekes et al., 2013; Curvelo et al., 2014). ...
Streptococcus pyogenes (Group A Streptococcus [GAS]) is an important human pathogen that causes several superficial infections and invasive diseases. The ability of GAS to form biofilms, renders the pathogen resistant to several antimicrobials resulting in antibiotic treatment failure. As essential oils (EOs) from plants have been promising sources of anti-biofilm agents, the present study shows that EOs from the genus Pogostemon exhibit anti-biofilm activity against pharyngitis causing GAS. The biofilm inhibition ability of the EOs varied depending upon the serotype of GAS, which was evident from confocal microscopy. Fourier transfer infra red (FT-IR) spectroscopy indicated that both the EOs disrupted the fatty acid membrane of the biofilms in all the serotypes. Overall, this study forms a first report on the anti-biofilm activity of the EOs of Pogostemon species and this can be a novel natural resource to combat drug resistant pathogenic biofilms.
... The increasing use of fluoroquinolones (FQs) due to their excellent activities against some other bacterial pathogens, has led to the emergence of FQs resistant S. pyogenes strains 9 . Several studies showed the emergence of FQs resistance in S. pyogenes isolates though these were not used against S. pyogenes infections [10][11][12] . It has been implied that subinhibitory concentrations (sub-MICs) of certain antibiotics can suppress the formation of biofilms by disrupting the adhering capacity 13 and higher concentrations of FQs may result in the induction of resistance 14 . ...
Background & objectives:
Subinhibitory concentrations (sub-MICs) of antibiotics, although not able to kill bacteria, but influence bacterial virulence significantly. Fluoroquinolones (FQs) which are used against other bacterial pathogens creates resistance in non-targeted Streptococcus pyogenes. This study was undertaken to characterize the effect of sub-MICs of FQs on S. pyogenes biofilm formation.
Methods:
Biofilm forming six M serotypes M56, st38, M89, M65, M100 and M74 of S. pyogenes clinical isolates were challenged against four FQs namely, ciprofloxacin, ofloxacin, levofloxacin and norfloxacin. The antibiofilm potential of these FQs was analysed at their subinhibitory concentrations (1/2 to 1/64 MIC) using biofilm assay, XTT reduction assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).
Results:
Among the four FQs tested, ofloxacin and levofloxacin at 1/2 MIC showed the maximum inhibition (92%) of biofilm formation against M56 and M74 serotypes. FQs effectively interfered in the microcolony formation of S. pyogenes isolates at 1/2 to 1/8 sub-MICs. Inhibition of biofilm formation was greatly reduced beyond 1/16 MICs and allowed biofilm formation. XTT reduction assay revealed the increase in metabolic activity of S. pyogenes biofilm against the decrease in FQs concentration. SEM and CLSM validated the potential of sub-MICs of FQs against the six S. pyogenes.
Interpretation & conclusions:
Our results showed that the inhibitory effect all four FQs on S. pyogenes biofilm formation was concentration dependent. FQs at proper dosage can be effective against S. pyogenes and lower concentrations may allow the bacteria to form barriers against the antibiotic in the form of biofilm.
... Although S. pyogenes were and are still highly susceptible to fluoroquinolones, low incidences (≤8%) of ciprofloxacin resistance have been found globally; fluoroquinolone resistance in Japan is almost nonexistent [297][298][299][300][301][302][303][304][305][306][307][308][309][310][311][312][313][314][315]. In Belgium, fluoroquinolone resistance increased from 2.8% to 13.1% from 2003 to 2005 and decreased thereafter to 8.9% in 2006 [307]. ...
This paper on the fluoroquinolone resistance epidemiology stratifies the data according to the different prescription patterns by either primary or tertiary caregivers and by indication. Global surveillance studies demonstrate that fluoroquinolone resistance rates increased in the past years in almost all bacterial species except S. pneumoniae and H. influenzae, causing community-acquired respiratory tract infections. However, 10 to 30% of these isolates harbored first-step mutations conferring low level fluoroquinolone resistance. Fluoroquinolone resistance increased in Enterobacteriaceae causing community acquired or healthcare associated urinary tract infections and intraabdominal infections, exceeding 50% in some parts of the world, particularly in Asia. One to two-thirds of Enterobacteriaceae producing extended spectrum β-lactamases were fluoroquinolone resistant too. Furthermore, fluoroquinolones select for methicillin resistance in Staphylococci. Neisseria gonorrhoeae acquired fluoroquinolone resistance rapidly; actual resistance rates are highly variable and can be as high as almost 100%, particularly in Asia, whereas resistance rates in Europe and North America range from <10% in rural areas to >30% in established sexual networks. In general, the continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some guidelines, for example, treatment of urinary tract, intra-abdominal, skin and skin structure infections, and traveller's diarrhea, or even precludes the use in indications like sexually transmitted diseases and enteric fever.
... The first description of a GAS clinical isolate resistant to ciprofloxacin [minimal inhibitory concentration (MIC) >32 mg/L) was reported in 2000 [7]. So far, seven cases of highly resistant strains have been described [7] [8] [9] [10] [11]. At the same time, GAS with reduced susceptibility to FQs have been increasingly reported worldwide [4] [12] [13]. ...
Clonal emergence of group A streptococci (GAS) with reduced susceptibility to fluoroquinolones (FQs) has been increasingly reported. Non-susceptibility is associated with various point mutations in the target-encoding genes and has only been described in a few emm types. We used a well-characterised GAS clinical paediatric collection from Brussels (Belgium) and Brasília (Brazil) to analyse the molecular basis of FQ non-susceptibility. GAS strains were tested for ciprofloxacin susceptibility and were screened for mutations in DNA gyrase- and topoisomerase IV-encoding genes. Genetic relationships between the different emm types were assessed by phylogenetic analysis of the whole surface-exposed part of the M protein. A high proportion (22.5%) of ciprofloxacin-non-susceptible isolates (minimal inhibitory concentration > or = 2mg/L) was found among the Belgian strains. They belonged mostly to emm type 6 (87%). In Brazil, 6% of the isolates, belonging to seven distantly related emm types, were non-susceptible. Our phylogenetic analysis showed that non-susceptibility may arise in various genetic backgrounds. Sequence comparison of the quinolone resistance-determining regions (QRDRs) of the ParC- and ParE-encoding genes from susceptible and non-susceptible isolates revealed that most of the mutations were found in both classes of isolates, indicating an emm type-linked polymorphism. In conclusion, we observed a clonal spreading of non-susceptible emm type 6 GAS strains in Brussels and a polyclonal distribution of non-susceptible isolates in Brazil. All the Brazilian and Belgian emm type 6 strains displayed a S79A/F mutation in parC that convincingly explains the non-susceptible phenotype.
... The amino acid change Ser80Pro in ParC is another relevant but infrequent mutation described among S. pyogenes (Powis et al., 2005;Rivera et al., 2005). In terms of MIC increase, the impact of the other mutations in or outside the QRDR, as Asp91Asn or Ser140Pro, is still debated. ...
We report the 1st case of primary peritonitis caused by Streptococcus pyogenes with a reduced susceptibility to fluoroquinolones in a healthy woman, leading to a clinical and microbiological treatment failure. DNA sequencing of parC and gyrA revealed the association of the following 3 substitutions in ParC: Ser80Pro, Asp91Asn, and Ser140Pro.
... In addition, a silent mutation was found at position Gly-103 (GGG → GGC) of gyrA. Although only anecdotal cases of high-level fluoroquinolone-resistant S. pyogenes have been published [2,3,15,16], our results are consistent with previous reports demonstrating that high-level fluoroquinolone resistance results from alterations in the QRDR of both parC and gyrA genes. In our isolates, mutations observed in parC were identical to those previously identified, such as replacement of Ser-79 by Phe and of Asp-91 by Asn [15]. ...
The resistance mechanisms and clonal relationship were determined for two Streptococcus pyogenes isolates with high-level resistance to levofloxacin as well as to other fluoroquinolones. DNA amplification and sequencing revealed a serine-81-->phenylalanine substitution in GyrA and a double substitution in ParC of serine-79-->phenylalanine and aspartic acid-91-->asparagine. Pulsed-field gel electrophoresis analysis and emm typing determined that both isolates were emm type 28 and were genetically indistinguishable.
This study investigated quinolone nonsusceptible Streptococcus canis with point mutations in quinolone resistance-determining regions (QRDRs). After selecting targets from 185 isolates, we conducted antimicrobial susceptibility testing using levofloxacin, ciprofloxacin, norfloxacin, and moxifloxacin. We also determined amino acid sequences of QRDRs in gyrA/ gyrB/parC/parE genes and their point mutations. Finally, we performed S. canis-derived M-like protein (SCM) allele typing, multilocus sequence typing, and antimicrobial resistance genotyping. Correlations between nonsusceptible strains and their related factors were examined. We found 13 (7.0%) nonsusceptible isolates consisting of two classes, high-level minimum inhibitory concentrations (MICs) (n = 7, 3.8%), and low-level MICs (n = 6, 3.2%). The mutations Ser81Phe/Ser81Tyr/Glu85Lys in gyrA, Ser67Phe/Ser67Tyr/Asp71Tyr in parC, Asp438Asn in parE, and Gly408Asp in gyrB were observed in these nonsusceptible strains. The common mutations were Ser81 and Ser67/Asp71, whereas we found one strain each with Glu85, Asp438 and Gly408 mutations. There was a significant correlation between the nonsusceptible isolates and presence of SCM allele type 2, sequence type 46, tetracycline-resistance genes, and macrolide/lincosamide-resistance genes. These results could be used in the future by veterinarians while treating companion animals with clinical symptoms of streptococcal infections.
We investigated the prevalence, genetics, and clonality of fluoroquinolone non-susceptible isolates of Streptococcus pyogenes in the central part of Italy. S. pyogenes strains (n = 197) were isolated during 2012 from patients with tonsillopharyngitis, skin, wound or invasive infections and screened for fluoroquinolone non-susceptibility (resistance to norfloxacin and levofloxacin minimum inhibitory concentration (MIC) = 2 mg/L) following EUCAST guidelines. First-step topoisomerase parC and gyrA substitutions were investigated using sequencing analysis. Clonality was determined by pulsed field gel electrophoresis (PFGE; SmaI digestion) and by emm typing. The fluoroquinolone non-susceptible phenotype was identified in 18 isolates (9.1 %) and correlated with mutations in parC, but not in gyrA, the most frequent leading to substitution of the serine at position 79 with an alanine. Most of the fluoroquinolone non-susceptible isolates belonged to the emm-type 6, even if other emm-types were also represented (emm75, emm89, and emm2). A significant level of association was measured between PFGE and both emm type and substitutions in parC. The prevalence of fluoroquinolone non-susceptible Streptococcus pyogenes isolates in Italy is of concern and, although the well-known emm type 6 is dominant, other types are appearing and spreading.
Streptococcus pyogenes causes various diseases in humans. While the prevalence of fluoroquinolone-resistant S. pyogenes isolates has been increasing since 2000 in the USA and Europe, it has remained very low in Japan. We isolated a fluoroquinolone-resistant S. pyogenes strain and analysed its genetics.
TU-296, a strain of S. pyogenes resistant to levofloxacin (MIC 16 mg/L), was isolated from the throat of a patient in their thirties with pharyngitis in autumn 2007. We carried out susceptibility tests for various antimicrobial agents and PCR analysis of the genes gyrA, gyrB, parC and parE in the quinolone resistance-determining region, followed by sequencing of the PCR products to find mutation(s) and the resulting amino acid substitution(s). We then sequenced the PCR product of the emm gene and determined the emm genotype.
S. pyogenes TU-296 was found to have the following mutations and amino acid substitutions: adenine 476 to cytosine in gyrA and cytosine 367 to thymine in parC, resulting in Glu-85→Ala in GyrA and Ser-79→Phe in ParC. The genotype of the isolate was emm11.
Amino acid substitutions in fluoroquinolone-resistant S. pyogenes have already been reported from Europe and the USA, including Ser-81→Phe or Tyr and Met-99→Leu in GyrA, as well as Ser-79→Phe, Tyr or Ala and others in ParC. Numerous point mutations were found in parC and parE of S. pyogenes TU-296. In addition, a new amino acid substitution was detected (Glu-85→Ala in GyrA). To our knowledge, there have been no previous reports of this substitution in a clinical isolate of S. pyogenes.
To determine the prevalence of macrolide antibiotic and levofloxacin resistance in infections with Streptococcus pyogenes (group A streptococcus or GAS), strains were collected from 45 medical institutions in various parts of Japan between October 2003 and September 2006. Four hundred and eighty-two strains from patients with GAS infections were characterized genetically. Strains were classified into four groups according to the type of infection: invasive infections (n=74) including sepsis, cellulitis and toxic-shock-like syndrome; acute otitis media (AOM; n=23); abscess (n=53); and pharyngotonsillitis (n=332). Among all strains, 32 emm types were identified; emm1 was significantly more common in invasive infections (39.2 %) and AOM (43.5 %) than in abscesses (3.8 %) or pharyngotonsillitis (10.2 %). emm12 and emm4 each accounted for 23.5 % of pharyngotonsillitis cases. Susceptibility of GAS strains to eight beta-lactam agents was excellent, with MICs of 0.0005-0.063 mug ml(-1). Macrolide-resistant strains accounted for 16.2 % of all strains, while the percentages of strains possessing the resistance genes erm(A), erm(B) and mef(A) were 2.5 %, 6.2 % and 7.5 %, respectively. Although no strains with high resistance to levofloxacin were found, strains with an MIC of 2-4 mug ml(-1) (17.4 %) had amino acid substitutions at either Ser-79 or Asp-83 in ParC. These levofloxacin-intermediately resistant strains included 16 emm types, but macrolide-resistant strains were more likely than others to represent certain emm types.
Beta-hemolytic streptococci are common bacterial pathogens that can cause serious invasive disease, and although this group of species has remained susceptible to the fluoroquinolone class, resistant strains have been reported. This multicenter investigation determined the rate of fluoroquinolone-resistant beta-hemolytic streptococci using the SENTRY Antimicrobial Surveillance Program network data (1997-2004). Forty-seven surveillance culture isolates of beta-hemolytic streptococci from North America and Europe with elevated levofloxacin MIC results (2 to >32) microg/mL were tested for susceptibility to other fluoroquinolones including ciprofloxacin, garenoxacin, gatifloxacin, gemifloxacin, and moxifloxacin using reference broth microdilution and Etest (BIODISK, Solna, Sweden) methods. Strains were characterized using polymerase chain reaction and sequencing to detect mutations in the quinolone-resistance determining region (QRDR). The beta-hemolytic streptococci isolates with reduced fluoroquinolone susceptibility included the following Lancefield groups: A (Streptococcus pyogenes; 9 strains), B (Streptococcus agalactiae; 24 strains), C and G (14 strains). Vitek and API 20 strep (bioMerieux, Hazelwood, MO) identification systems, as well as conventional biochemical methods and colony morphology, were used to confirm the organism identifications. The overall potency (MIC90 in microg/mL) for the fluoroquinolones against all tested beta-hemolytic streptococci showed the following rank order: gemifloxacin (0.06) > garenoxacin (0.12) > moxifloxacin (0.25) > gatifloxacin (0.5) > levofloxacin = ciprofloxacin (1). The rate of levofloxacin-resistant beta-hemolytic streptococci in the SENTRY program was 0.14% (Europe) and 0.51% (North America) during the study period. All levofloxacin-resistant strains tested by molecular methods had significant mutations in either parC (position 79 or 83) and/or gyrA (position 81 or 85). All but 2 isolates with high-level resistance to levofloxacin (>32 microg/mL) had gyrA mutations. Strains with lower MIC values to levofloxacin (2-4 microg/mL) only had mutations in parC. The increasing rate of fluoroquinolone-resistant streptococci including Streptococcus pneumoniae, viridans group streptococci, and the more recently reported beta-hemolytic streptococci, is becoming a clinical concern due to the morbidity and mortality caused by these pathogens.
To perform a systematic analysis of point mutations in the quinolone resistance determining regions (QRDRs) of the DNA gyrase and topoisomerase genes of emm type 6 and other emm types of Streptococcus pyogenes strains after in vitro exposure to stepwise increasing concentrations of levofloxacin.
Twelve parent strains of S. pyogenes, each with a different emm type, were chosen for stepwise exposure to increasing levels of levofloxacin followed by selection of resistant mutants. The QRDRs of gyrA, gyrB, parC and parE correlating to mutants with increased MICs were analysed for point mutations.
Multiple mutants with significantly increased MICs were generated from each strain. The amino acid substitutions identified were consistent regardless of emm type and were similar to the mechanisms of resistance reported in clinical isolates of S. pyogenes. The number of induction/selection cycles required for the emergence of key point mutations in gyrA and parC was variable among strains. For each parent-mutant set, when MIC increased, serine-81 of gyrA and serine-79 of parC were the primary targets for amino acid substitutions. No point mutations were found in the QRDRs of gyrB and parE in any of the resistant mutants sequenced.
Despite its intrinsic polymorphism in the QRDR of parC, emm type 6 is not more likely to develop high-level resistance to fluoroquinolones when compared with other emm types. All emm types seem equally inducible to high-level fluoroquinolone resistance.
Clinical isolates of Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes, and Moraxella catarrhalis were gathered from 19 different clinical laboratories throughout the continental United States. The in vitro activities of 12 orally administered antimicrobial agents were compared by broth microdilution tests with 3,151 bacterial isolates. Among 890 H. influenzae isolates, 30% were capable of producing beta-lactamase enzymes (12 to 41% in different medical centers). Most of the 619 beta-lactamase-negative H. influenzae strains were susceptible to ampicillicin (MIC, < or = 1.0 micrograms/ml): 5 strains were intermediate in susceptibility (MIC, 2.0 micrograms/ml) and 1 strain was ampilicillin resistant (MIC, 4.0 micrograms/ml). Ninety-two percent of 698 M. catarrhalis strains were beta-lactamase positive. Of 799 S. pneumoniae isolates, 15% were intermediate in susceptibility to penicillin and 7% were resistant to penicillin. The prevalence of penicillin-susceptible pneumococci in different institutions ranged from 63 to 95%. Only 1% of 764 S. pyogenes isolates were resistant to the macrolides, but 5% of S. pneumoniae isolates were macrolide resistant. Only 71% of 58 penicillin-resistant S. pneumoniae isolates were erythromycin susceptible, whereas 97% of the 622 penicillin-susceptible strains were erythromycin susceptible. Penicillin-resistant pneumococci were also relatively resistant to the cephalosporins and amoxicillin. Penicillin-susceptible pneumococci were susceptible to amoxicillin-clavulanic acid (MIC for 90% of isolates tested [MIC90], < or = 0.12/0.06 microgram/ml), cefixime (MIC90, 0.25 microgram/ml), cefuroxime axetil (MIC90, < or = 0.5 microgram/ml), cefprozil (MIC90, < or = 0.5 micrograms/ml), cefaclor (MIC90, 0.5 microgram/ml), and loracarbef (MIC90, 1.0 microgram/ml). Most strains of the other species remained susceptible to the study drugs other than amoxicillin.
The genes encoding the ParC and ParE subunits of topoisomerase IV of Streptococcus pneumoniae, together with the region encoding amino acids 46 to 172 (residue numbers are as in Escherichia coli) of the pneumococcal GyrA subunit, were partially characterized. The gyrA gene maps to a physical location distant from the gyrB and parC loci on the chromosome, whereas parC is closely linked to parE. Ciprofloxacin-resistant (Cpr) clinical isolates of S. pneumoniae had mutations affecting amino acid residues of the quinolone resistance-determining region of ParC (low-level Cpr) or in both quinolone resistance-determining regions of ParC and GyrA (high-level Cpr). Mutations were found in residue positions equivalent to the serine at position 83 and the aspartic acid at position 87 of the E. coli GyrA subunit. Transformation experiments suggest that ParC is the primary target of ciprofloxacin. Mutation in parC appears to be a prerequisite before mutations in gyrA can influence resistance levels.
The mechanism of high-level fluoroquinolone resistance was studied in strains of Streptococcus pneumoniae, either selected in vitro or isolated from clinical samples. By using DNA from these high-level-resistant strains, low-level-resistant transformants (MIC of pefloxacin, > or = 32 micrograms/ml; MIC of ciprofloxacin, 4 micrograms/ml; MIC of sparfloxacin, 0.50 micrograms/ml) were obtained at high frequencies (ca.10(-2)), while high-level-resistant transformants (MIC of pefloxacin, > or = 64 micrograms/ml; MIC of ciprofloxacin, 16 to 64 micrograms/ml; MIC of sparfloxacin, > or = 8 micrograms/ml) were obtained only at low frequencies (ca.10(-4)). This suggested that mutations in at least two unlinked genes were necessary to obtain high-level resistance. Low-level resistance was associated with ParC mutations (change from Ser to Tyr at position 79 [Ser79Tyr], Ser79Phe, or Asp83Gly). ParC mutations were associated, in high-level-resistant strains and transformants, with alterations in the quinolone resistance-determining region of GyrA (Ser84Tyr, Ser84Phe, and/or Glu88Lys). Low-level resistance was shown to be necessary for expression of the gyrA mutations. No mutation in the region corresponding to the quinolone resistance-determining region of GyrB and no alteration of drug accumulation were found.
The nucleotide sequences of the quinolone resistance-determining regions (QRDRs) of the parC and gyrA genes from seven ciprofloxacin-resistant (Cpr) isolates of viridans group streptococci (two high-level Cpr Streptococcus oralis and five low-level Cpr Streptococcus mitis isolates) were determined and compared with those obtained from susceptible isolates. The nucleotide sequences of the QRDRs of the parE and gyrB genes from the five low-level Cpr S. mitis isolates and from the NCTC 12261 type strain were also analyzed. Four of these low-level Cpr isolates had changes affecting the subunits of DNA topoisomerase IV: three in Ser-79 (to Phe or Ile) of ParC and one in ParE at a position not previously described to be involved in quinolone resistance (Pro-424). One isolate did not show any mutation. The two high-level Cpr S. oralis isolates showed mutations affecting equivalent residue positions of ParC and GyrA, namely, Ser-79 to Phe and Ser-81 to Phe or Tyr, respectively. The parC mutations were able to transform Streptococcus pneumoniae to ciprofloxacin resistance, while the gyrA mutations transformed S. pneumoniae only when mutations in parC were present. These results suggest that DNA topoisomerase IV is a primary target of ciprofloxacin in viridans group streptococci, DNA gyrase being a secondary target.
In this study, we assessed the activity of ciprofloxacin, levofloxacin, sparfloxacin, and trovafloxacin against clinical isolates of Streptococcus pneumoniae that were resistant to the less-recently developed fluoroquinolones by using defined amino acid substitutions in DNA gyrase and topoisomerase IV. The molecular basis for resistance was assessed by using mutants selected with trovafloxacin, ciprofloxacin, and levofloxacin in vitro. This demonstrated that the primary target of trovafloxacin in S. pneumoniae is the ParC subunit of DNA topoisomerase IV, similar to most other fluoroquinolones. However, first-step mutants bearing the Ser79-->Phe/Tyr substitution in topoisomerase IV subunit ParC were susceptible to trovafloxacin with a minimum inhibitory concentration of 0.25 microg/ml, and mutations in the structural genes for both topoisomerase IV subunit ParC (parC) and the DNA gyrase subunit (gyrA) were required to achieve levels of resistance above the breakpoint. The data also suggest that enhanced activity of trovafloxacin against pneumococci is due to a combination of factors that may include reduced efflux of this agent and an enhanced activity against both DNA gyrase and topoisomerase IV.
Oropharyngeal samples from 60 hospitalized patients (30 fluoroquinolone [FQ]-treated and 30 non-FQ-treated patients) and 30
untreated nonhospitalized healthy control subjects yielded 20 isolates of viridans group streptococci with reduced susceptibility
to FQ, mostly from the hospitalized patients. An efflux phenotype was commonly encountered, expressed either alone or with
topoisomerase mutations. Interspecies transfer of the efflux phenotype was demonstrated via transformation of Streptococcus pneumoniae R6 with DNA fromS. mitis and S. oralis.
A strain of Streptococcus pyogenes resistant to multiple fluoroquinolones was isolated from the blood of an immunocompromised patient. Resistance to fluoroquinolones
in S. pyogenes has not been previously studied. Compared to 10 sensitive strains of S. pyogenes, the fluoroquinolone-resistant clinical isolate of S. pyogenespresented point mutations in gyrA, predicting that serine-81 was changed to phenylalanine and that methionine-99 was changed to leucine, and in parC, predicting that serine-79 was changed to tyrosine. The mechanism of fluoroquinolone resistance in this isolate of S. pyogenes appears to be analogous to previously reported mechanisms for Streptococcus pneumoniae.
We report on amino acid substitutions in the quinolone resistance-determining region of type II topisomerases and the prevalence
of reserpine-inhibited efflux for 70 clinical isolates ofS. pneumoniae for which the ciprofloxacin MIC is ≥4 μg/ml and 28 isolates for which the ciprofloxacin MIC is ≤2 μg/ml. The amino acid substitutions
in ParC conferring low-level resistance (MICs, 4 to 8 μg/ml) included Phe, Tyr, and Ala for Ser-79; Asn, Ala, Gly, Tyr, and
Val for Asp-83; Asn for Asp-78; and Pro for Ala-115. Isolates with intermediate-level (MICs, 16 to 32 μg/ml) and high-level
(MICs, 64 μg/ml) resistance harbored substitutions of Phe and Tyr for Ser-79 or Asn and Ala for Asp-83 in ParC and an additional
substitution in GyrA which included either Glu-85-Lys (Gly) or Ser-81-Phe (Tyr). Glu-85-Lys was found exclusively in isolates
with high-level resistance. Efflux contributed primarily to low-level resistance in isolates with or without an amino acid
substitution in ParC. The impact of amino acid substitutions in ParE was minimal, and no substitutions in GyrB were identified.
A nationwide multicenter susceptibility surveillance study which included 1,684 Streptococcus pneumoniae and 2,039 S. pyogenes isolates was carried out over 1 year in order to assess the current resistance patterns for the two most important gram-positive microorganisms responsible for community-acquired infections in Spain. Susceptibility testing was done by a broth microdilution method according to National Committee for Clinical Laboratory Standards M100-S10 interpretative criteria. For S. pneumoniae, the prevalences of highly resistant strains were 5% for amoxicillin and amoxicillin-clavulanic acid; 7% for cefotaxime; 22% for penicillin; 31% for cefuroxime; 35% for erythromycin, clarithromycin, and azithromycin; and 42% for cefaclor. For S. pyogenes, the prevalence of erythromycin resistance was 20%. Efflux was encountered in 90% of S. pyogenes and 5% of S. pneumoniae isolates that exhibited erythromycin resistance. Erythromycin resistance was associated with clarithromycin and azithromycin in both species, regardless of phenotype. Despite the different nature of the mechanisms of resistance, a positive correlation (r = 0.612) between the two species in the prevalence of erythromycin resistance was found in site-by-site comparisons, suggesting some kind of link with antibiotic consumption. Regarding ciprofloxacin, the MIC was >or=4 microg/ml for 7% of S. pneumoniae and 3.5% of S. pyogenes isolates. Ciprofloxacin resistance (MIC, >or=4 microg/ml) was significantly (P < 0.05) associated with macrolide resistance in both S. pyogenes and S. pneumoniae and with penicillin nonsusceptibility in S. pneumoniae.
The pattern of susceptibility to a range of antimicrobials was tested for 1485 isolates of Streptococcus pyogenes and 1547 isolates of Staphylococcus aureus included in the international PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) surveillance study (1999-2000). Overall, almost 10% of S. pyogenes isolates were erythromycin A resistant. There was a wide heterogeneity of resistance, with high levels of macrolide resistance in Poland (42%), Hong Kong (28%), Italy (25%), Portugal (24%) and Spain (21%), and no macrolide resistance in Indonesia, Austria, Belgium, the Netherlands or the UK. Using NCCLS tentative breakpoints, 97.6% of isolates were susceptible to telithromycin, with MIC(90) < or = 0.015 mg/L in most regions. Resistance among S. pyogenes to the beta-lactams (MIC(90) < or = 0.12 mg/L for all except cefaclor) and fluoroquinolones was not detected. Macrolide resistance was present among the S. aureus isolates, and as with S. pyogenes, there was a wide heterogeneity of resistance, with lower rates in Australia, Indonesia, Hungary, Austria, Germany, the Netherlands, Portugal, Sweden and Switzerland. Methicillin-resistant isolates were resistant to the beta-lactams and the macrolides. Resistance to telithromycin was detected in methicillin-resistant isolates in Latin and North America, Asia and Europe. Telithromycin resistance was non-existent or low (MIC(90 )range 0.06-0.25 mg/L) in Australia, Indonesia, Hungary, Austria, Germany, the Netherlands, Portugal, Sweden and Switzerland. Regardless of methicillin susceptibility, resistance to linezolid, teicoplanin or vancomycin was not apparent globally.
Streptococcus pyogenes is responsible for high rates of morbidity due to an increase in invasive group A streptococcal infections and bacteremia worldwide during the last decade (2, 3). The goal of this study was to elucidate the mechanism of fluoroquinolone resistance in S. pyogenes BM4513 isolated in 2000 from the pharynx of a patient at the Hospital de Basurto, Bilbao, Spain.
Streptococcus pyogenes isolated from blood and urine samples obtained from a 78-year-old woman was tested for susceptibility, and fluoroquinolone resistance (minimum inhibitory concentration of levofloxacin, 16 microg/mL) was found. DNA amplification and sequencing revealed a serine81-->tyrosine substitution in gyrA and 2 substitutions in parC: serine79-->phenylalanine and alanine121-->valine. This is the second report of a clinical isolate of S. pyogenes with high-level fluoroquinolone resistance.
To analyse the mutations and epidemiology associated with fluoroquinolone-resistant pneumococci collected as part of the PROTEKT global surveillance programme during 1999-2000.
Sixty-nine centres in 25 countries submitted a total of 3362 Streptococcus pneumoniae isolates, for which the MICs of antimicrobial agents were determined using NCCLS methodology.
Levofloxacin resistance was low overall (1% worldwide), with higher rates in: Hong Kong (14.3%), South Korea (2.9%), USA (1.8%), Mexico (1.5%), Canada (1.4%) and Japan (1.3%). Levofloxacin resistance was very low or absent in European countries, and absent in Australia. Worldwide, there was a total of 35 levofloxacin-resistant isolates, of which 22 (63%) were resistant and 10 (29%) were intermediate to moxifloxacin. All levofloxacin-resistant isolates were susceptible to telithromycin (< or =0.5 mg/L), linezolid (< or =2 mg/L) and quinupristin/dalfopristin (< or =1 mg/L). One or more mutations in the topoisomerase genes were identified in all levofloxacin-resistant isolates; most of these isolates (33/35) had a mutation in one of the DNA gyrase encoding genes (gyrA, gyrB) and one of the topoisomerase IV encoding genes (parC, parE). Eighteen (51%) isolates carried the same combination of amino acid substitutions: Ser-81-->Phe in GyrA and Ser-79-->Phe in ParC. Isolates displaying a levofloxacin MIC of 2-4 mg/L generally had no mutation or one mutation in either a DNA gyrase or a topoisomerase IV gene, although most mutations were in parC.
Most levofloxacin-resistant isolates possess two mutations (one in DNA gyrase and one in topoisomerase IV). Although multilocus sequence typing demonstrated that most of these isolates were unrelated, 12 (34%) were the Spain23F-1 clone: 10 from Hong Kong and one each from Saskatchewan, Canada and Sao Paulo, Brazil.
Streptococcus pyogenes is a common pathogen which may be associated with significant morbidity and mortality. Recent information is not readily available, in Canada, regarding the susceptibility of clinical isolates to penicillin, extended spectrum and/or newer agents. We collected and tested 1003 isolates of S. pyogenes to seven antimicrobial agents and found the following susceptibility rates: azithromycin 97%, ceftriaxone 100%, ciprofloxacin 99.4%, clarithromycin 98.5%, clindamycin 99.9%, erythromycin 96.5% and penicillin 100%. These results indicate that antimicrobial resistance is not yet a problem of S. pyogenes in Canada.
Gatifloxacin, grepafloxacin, moxifloxacin and trovafloxacin are fluoroquinolones with enhanced Gram-positive activity while retaining broad-spectrum activity against Gram-negative pathogens. Levofloxacin and ciprofloxacin are older quinolones with broad activity against Gram-negative pathogens and borderline activity against some Gram-positive organisms. We compared the in vitro activity of these compounds against 4151 Gram-negative and -positive organisms. Gatifloxacin, grepafloxacin, moxifloxacin and trovafloxacin were highly active against penicillin sensitive and resistant Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes and Streptococcus agalactiae. Ciprofloxacin and levofloxacin were active but less potent. All compounds were highly active (overall) against Gram-negative pathogens with ciprofloxacin being the most active agent against Pseudomonas aeruginosa. Our data indicate that the advanced fluoroquinolones will be important compounds for treating infections caused by Gram-positive and Gram-negative pathogens.
The in vitro activity of moxifloxacin was compared with that of ciprofloxacin, levofloxacin, ofloxacin and trovafloxacin against 710 strains (180 Streptococcus pneumoniae, 180 Haemophilus influenzae, 160 Moraxella catarrhalis and 190 Streptococcus pyogenes) isolated from patients with community-acquired respiratory tract infections. MIC values for moxifloxacin, trovafloxacin were 0.25/0.25, 0.03/0.03, 0.06/0.03 and 0.125/0.0125 mg/l for S. pneumoniae, H. influenzae, M. catharralis and S. pyogenes. Based upon the MIC(90) values and the MIC distributions, moxifloxacin and trovafloxacin were the most active of the quinolones tested. They showed enhanced activity against Gram-positive organisms including penicillin non susceptible S. pneumoniae strains. Moxifloxacin was also highly active against ciprofloxacin-resistant S. pneumoniae strains.
This study evaluated current levels of antimicrobial resistance and associated demographic trends among clinical isolates of Streptococcus pyogenes in the United States as part of the LIBRA surveillance initiative. In 1999, 2,742 isolates of S. pyogenes (2,039 respiratory; 405 skin and soft tissue; 148 blood) were collected from 324 clinical laboratories and centrally tested for antimicrobial susceptibility by the broth microdilution method. All isolates were susceptible to penicillin (MIC(90,) < or = 0.06 microg/mL), ceftriaxone (MIC(90,) < or =0.03 microg/mL), vancomycin (MIC(90,) 0.5 microg/mL), levofloxacin (MIC(90,) 1 microg/mL), and moxifloxacin (MIC(90,) 0.25 microg/mL). Twenty-four (0.9%) azithromycin-intermediate (MIC, 1 microg/mL) and 170 (6.2%) azithromycin-resistant (MIC, > or = 2 microg/mL) isolates were identified. Regionally, azithromycin resistance varied by < 5%, ranging from 3.0% in New England to 7.7% in the Pacific region. Azithromycin resistance was significantly higher (P < 0.001) among patients aged 15-64 years (8.3%) than patients < or =14 years (4.3%). This study found higher rates of macrolide resistance among S. pyogenes than previously reported in the United States and suggests that macrolide resistance is common among respiratory isolates from both younger and older patients. Fluoroquinolones (moxifloxacin > levofloxacin) demonstrated potent in vitro activity against all isolates of S. pyogenes tested, including those from skin and soft tissue infections. Given the higher rates of macrolide resistance reported in other countries and the seriousness of invasive infections, continued antimicrobial surveillance of S. pyogenes in the United States would be prudent.
An isolate of Streptococcus pyogenes isolated from a 63-year-old woman with a serious wound infection was found to be highly resistant to fluoroquinolones (levofloxacin MIC > or = 32 mg/L). DNA amplification and sequencing revealed a serine-81 to phenylalanine substitution in gyrA and three substitutions in parC: serine-79 to phenylalanine, aspartic acid-91 to asparagine, and serine-140 to proline. To our knowledge, this is the first report from a European country of a clinical isolate of S. pyogenes with high-level fluoroquinolone resistance.
Gram-negative and Gram-positive organisms
Gram-negative and Gram-positive organisms. Int J Antimicrob Agents 2000; 14: 45-50.