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Verotoxigenic Escherichia coli and Methicillin-resistant Staphylococcus aureus (MRSA) in some locally manufactured dairy products and their public health hazard
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Milk contains many nutrients including carbohydrate, protein, fat, vitamins and minerals. Milk protein has high nutritional value because it contains all the essential amino acids. Considering the nutritive value, milk is widely consumed by the people as an ideal food. The biochemical changes in milk and milk products by microorganisms can be either desirable or undesirable. The safety of milk and milk products with respect to food borne diseases is of great concern around the world. Therefore, the present study was undertaken to determine the prevalence of Escherichia coli in milk and milk product with their antibiogram assay. A total of 150 milk and milk product (yogurt) samples were collected from Rajshahi Metropolitan area of Bangladesh and analyzed by cultural, staining and biochemical tests for the isolation and identification of E. coli. Antibiogram assay of all the isolates were done by disk diffusion method. The overall prevalence of E. coli was 20.0% in milk and milk product (yogurt) in Rajshahi Metropolitan area. The prevalence of E. coli was 26.0% and 34.0% in raw milk and in milk product (yogurt), respectively. E. coli was not detected in pasteurized milk in this study. In antibiogram assay, isolated E. coli showed 100.0%, 60.0%, 40.0%, 40.0%, 33.3%, 33.3%, 20.0%, and 10.0% resistance to penicillin, gentamycin, ampicillin, streptomycin, amoxycillin, sulfamethoxasole-trimethoprim, nalidixic acid, and ciprofloxacin, respectively. The isolates also showed 73.3%, 60.0%, 53.3%, 53.3%, 30.0%, 23.3%, and 20% sensitive to ciprofloxacin, nalidixic acid, sulfamethoxasole-trimethoprim, streptomycin, amoxycillin, ampicillin, and gentamycin, respectively. The findings of this experiment speculated that the use of ciprofloxacin and nalidixic acid may have the preference in the clinical control of milk borne E. coli infection in Bangladesh. J. Bio-Sci. 29(2): 81-91, 2021 (December)
Objective:
This work investigated the antimicrobial resistance (AMR) and virulence of Escherichia coli and Staphylococcus aureus in communally consumed cheeses in Egypt.
Materials and methods:
This study examined 100 samples of Domiati, Tallaga, Cheddar, and Ras cheese collected from several shops and supermarkets. Samples were spread on selective media to isolate bacterial strains. Molecular characterization of bacterial isolates was carried out using polymerase chain reaction to determine Shiga toxin 1 (stx1), Shiga toxin 2 (stx2), eaeA, and nuc genes. The isolates were tested for susceptibility to 14 antibiotics by disk diffusion assay.
Results:
In this study, several E. coli serotypes were identified. E. coli O26:H11, O103:H2, and O111:H2 expressed stx1/2, E. coli O114:H4 expressed stx1, E. coli O17:H18, O21:H7 and O146:H21 expressed stx2, while only E. coli O26:H11 and O111:H2 expressed eaeA. The E. coli isolates were resistant to at least one antibiotic, while most isolates (82.4%) showed multidrug resistance (MDR). AMR to erythromycin was the highest (100%), followed by nalidixic acid (94.1%), cefotaxime (82.4%), vancomycin and cephalothin (64.7%), penicillin G (52.9%), sulfamethoxazole (47.1%), amikacin and kanamycin (35.3%), ampicillin (29.4%), tetracycline and ciprofloxacin (23.5%), and doxycycline (11.8%), while gentamicin showed the least resistance (5.9%). The multiple antibiotic resistance (MAR) index of the isolated E. coli ranged from 0.071 to 1 (mean = 0.478). All S. aureus isolates expressed the nuc gene and demonstrated resistance to at least one antibiotic, and 90% of isolates were MDR. AMR to kanamycin and cephalothin was the highest (100%), followed by penicillin (90%), doxycycline (70%), nalidixic acid and sulfamethoxazole (60%), erythromycin (50%), tetracycline, cefotaxime, and gentamicin (40%), ciprofloxacin and ampicillin (30%), and amikacin (20%). In comparison, vancomycin showed the least resistance (10%). MAR index of isolated S. aureus ranged from 0.143 to 1 (mean = 0.529).
Conclusion:
The antimicrobial-resistant E. coli and S. aureus are potential risks for public health and may have a role in disseminating AMR to other pathogenic and non-pathogenic microbes.
Objectives
Microbes can contaminate foodstuffs resulting in foodborne illnesses. Investigating microbial hazards in foods at the point of sale with rapid tools is required to avoid foodborne illness outbreaks. The current study aimed to identify the microbial hazards in food samples collected from retail shops at sale points using MALDI-TOF MS.
Results
Food samples were collected from stores and supermarkets in four Delta cities (Tanta, Kutour, Kafr-Elzayat and Benha). Analysis of 178 samples of fish, meat and dairy products revealed 20 different bacterial species. 44.76% of isolates were identified as E. coli , 17.44% were identified as Enterobacter spp., and E. cloacae was predominant. 12.2% were identified as Citrobacter spp., and C. braakii was predominant, and 8.7% were identified as Klebsiella spp., and K. pneumoniae was predominant. Moreover, eight Proteus mirabilis , six Morganella morganii , five Staphylococcus hominis , three Serratia marcescens , two Pseudomonas aeruginosa , one Salmonella typhimurium and one Enterococcus faecalis were detected. Foodstuffs not only be contaminated during production and processing but also during storage and transport. Identification of harmful human pathogens in foodstuffs is alarming and consider threatening to public health. Identification of microbiological hazards in foods using MALDI-TOF MS provides an efficient tool for identifying foodborne pathogens.
Navaneeth Narayanan,1,2 Christopher D Adams,1 David W Kubiak,3 Serena Cheng,4 Robyn Stoianovici,5 Leonid Kagan,1,6 Luigi Brunetti1,61Department of Pharmacy Practice, Rutgers University, Ernest Mario School of Pharmacy, Piscataway, NJ, USA; 2Division of Infectious Diseases, Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ, USA; 3Department of Pharmacy, Brigham and Women’s Hospital, Boston, MA, USA; 4Department of Pharmacy, VA San Diego Healthcare System, San Diego, CA, USA; 5Department of Pharmacy, University of California, Davis Medical Center, Sacramento, CA, USA; 6Department of Pharmaceutics, Rutgers University, Ernest Mario School of Pharmacy, Piscataway, NJ, USAAbstract: Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a major cause of infection in both the hospital and community setting. Obesity is a risk factor for infection, and the prevalence of this disease has reached epidemic proportions worldwide. Treatment of infections in this special population is a challenge given the lack of data on the optimal antibiotic choice and dosing strategies, particularly for treatment of MRSA infections. Obesity is associated with various physiological changes that may lead to altered pharmacokinetic parameters. These changes include altered drug biodistribution, elimination, and absorption. This review provides clinicians with a summary of the literature pertaining to the pharmacokinetic and pharmacodynamic considerations when selecting antibiotic therapy for the treatment of MRSA infections in obese patients.Keywords: obesity, methicillin-resistant Staphylococcus aureus, antibiotics, pharmacokinetics
Staphylococcus aureus is one of the most important food-borne pathogens globally. It produces various toxins and invasive enzymes and can be found in numerous food products. Milk is an important source of staphylococcal food poisoning. After pasteurization, this microorganism or its enterotoxins might still remain in pasteurized milk. Therefore, this study was to investigate the contamination of S. aureus in 258 pasteurized milk from 39 cities of China. The prevalence and levels of S. aureus in these samples as well as antibiotic susceptibility profiles, virulence genes, biofilm formation, and biofilm related genes, spa typing and MLST were used to determine the characterization among the isolates. It was found 3.9% of samples were detected S. aureus in 8 of 39 cities in China. The contaminated level were not very excessive which showed the MPN values of the most positive samples (9/10) were less than 1 MPN/g. All pasteurized milk-related S. aureus isolates have ability to produce biofilm and harbored icaA, icaD, eno, clfA, clfB, fnbA, fnbB, fib genes, other biofilm related genes icaC were showed in 91.7% of isolates and cna gene were showed in 50%, except bap gene which were free in all isolates. The antibiotic susceptibility test showed that all isolates were resistant or intermediate-resistant to different concentrations of the antibiotics. Furthermore, 75.0% of the isolates were resistant to three or more antibiotic classes, which indicated multidrug resistance. The isolates had virulence potential, which showed 66.7% (8/12) of the isolates carried one or more virulence-associated genes. Molecular typing by MLST and spa typing enabled classification of these isolates into a total of 11 sequence types (STs) and spa types, which indicated high genetic diversity. Most of these types were related to various clinical S. aureus infections. Thus, the findings of this study reflect the potential risk of S. aureus infection in China. Our study also provides comprehensive analysis of the prevalence of S. aureus in pasteurized milk and helps ensure more accurate treatment of human infection with effective antibiotics.
Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging pathogen that is difficult to treat due to the multiresistance of the bacteria upon infection. From 2011 to 2016, 1581 S. aureus strains were isolated from 4300 samples from retail foods covering most provincial capitals in China. To determine the prevalence of food-related MRSA and its genetic background in China, antibiotic resistance, staphylococcal toxin genes, staphylococcal cassette chromosome mec (SCCmec) typing, spa-typing and MLST were carried out in this study. In total, 108 (7.4%) isolates were confirmed for MRSA by phenotyping (cefoxitin) and genotyping (mecA/mecC gene). A total of 52.8% (57/108) of the MRSA isolates belonged to clonal complex 59 (CC59) (ST59, ST338, and ST3355), which was the predominant clone in this study. These CC59 isolates carried SCCmec elements of type IV, V, or III and exhibited spa type t437, t441, t543, t163, t1785, or t3485, and half of them carried major virulence genes, such as the Panton-Valentine leucocidin (PVL) gene. The secondary clones belonged to ST9 (15.7%, 17/108) with a type of t899-SCCmec III and showed a broader range of antimicrobial resistance. The remaining MRSA isolates (31.5%, 34/108) were distributed in 12 different STs and 18 different spa types. All isolates harbored at least one of the enterotoxin genes, whereas only 4 isolates (3.70%) were positive for the toxic shock syndrome toxin tsst alleles. For antibiotic susceptibility testing, all isolates were resistant to more than three antibiotics, and 79.6% of the isolates were resistant to more than 10 antibiotics. Amoxycillin/clavulanic acid, ampicillin, cefoxitin, penicillin, ceftazidime, kanamycin, streptomycin, clindamycin, and telithromycin was the most common antibiotic resistance profile (55.6%, 60/108) in the study. In summary, the results of this study implied that the major food-related MRSA isolate in China was closer to community-associated MRSA, and some of the remaining isolates (ST9-t899-SCCmec III) were supposed to livestock-associated MRSA. In addition, most MRSA isolates showed resistance to multiple drugs and harbored staphylococcal toxin genes. Thus, the pathogenic potential of these isolates cannot be ignored. In addition, further studies are needed to elucidate the transmission routes of MRSA in relation to retail foods and to determine how to prevent the spread of MRSA.
Staphylococcus aureus is the main contaminant pathogenic agent in fresh artisanal cheeses. The main objectives of this work have been to verify the occurrence of Staphylococcus aureus in 23different artisanal cheeses of Andalusia (Spain), to detect the toxins SEs A to E by the use of VIDAS system directly from cheeses, and to identify by PCR the occurrence of the SEs (types A to D) genes, as well as the toxic shock syndrome toxin (TSST)-1 gen from the strains isolated from cheeses. The results show that of the 24cheeses analyzed in 19 (80%) was positive to Staphylococcus coagulase positive, with five (20%) negative in the isolation. Coagulase positive staphylococcal counts were less than 105CFU/g. Of the 19strains positives, were confirmed by biochemical tests such as Staphylococcus aureus. In the automated imunoenzymatic qualitative detection of enterotoxins all the cheese samples analyzed were negative. In PCR made for the identification of genes of the toxins Sea, Seb, Sec, Sed and TSST were positive four samples for the Sec gene. We can believe that the amount of Staphylococcus aureus in the cheeses was insufficient for the formation of the enterotoxins. The presence of genetically viable Staphylococcus aureus for the formation of enterotoxins demonstrates the importance of compliance with desirable quality criteria and the adoption of appropriate hygiene practices in the processing of raw materials in cheese factories to obtain a safe final product.
The molecular evolutionary genetics analysis (Mega) software implements many analytical methods and tools for phylogenomics and phylomedicine. Here, we report a transformation of Mega to enable cross-platform use on Microsoft Windows and Linux operating systems. Mega X does not require virtualization or emulation software and provides a uniform user experience across platforms. Mega X has additionally been upgraded to use multiple computing cores for many molecular evolutionary analyses. Mega X is available in two interfaces (graphical and command line) and can be downloaded from www.megasoftware.net free of charge.
Abstract
This study was undertaken to determine the occurrence and the zoonotic importance of methicillin resistant Staphylococcus aureus (MRSA) in raw milk of sheep, goats and buffaloes, some dairy products and dairy workers at Ismailia City, Egypt. A total of 150 samples were collected randomly and cultured on Baird Parker agar and CHROMagar MRSA. Culturing on Baird Parker agar, the results revealed that 46.7 % of raw goat milk, 40% of raw sheep milk, 40% of raw buffaloes' milk, 80% of yogurt, 36.7% of ice cream, 63.3% of Kareish cheese and 63.3% of human swabs' samples were contaminated by coagulase positive Staphylococcus aureus. The isolation rates of MRSA on CHROMagar MRSA in relation to the number of the examined samples and the number of S. aureus isolates were (33.3 and 71.4%), (20 and 50%), (13.3 and 33.3%), (40 and 50%), (13.3 and 36.4%), (33.3 and 52.6%) and (13.3 and 21.1%) from the examined milk samples (goat, sheep, and buffaloes), yogurt, ice cream, Kareish cheese and human swabs' samples, respectively. PCR results showed that all the isolates that were classified as MRSA on CHROMagar contained mecA gene. Results of the disk diffusion test revealed that the resistance rates of MRSA strains to penicillin, gentamycin, vancomycin, clindamycin, amikacin, erythromycin and oxacillin were 91.2%, 67.6%, 14.7%, 94.1%, 91.2%, 82.4% and 100%, respectively. The effectiveness of some hand cleansing agents against the selected MRSA isolates was assessed. It was found that hand gel rub based on alcohol and triclosan together was the most effective agent. The findings of the present study necessitate exerting more efforts for effective control of MRSA in dairy products.
Keywords: MRSA, Milk, Dairy products, Humans, Antibiotic, Antiseptic
Aim: Shiga toxigenic Escherichia coli (STEC) strains as emerging groups of foodborne pathogens are responsible for most foodborne illnesses. The aim of this study was to determine the antibiotic resistance pattern in STEC isolated from traditional milk products and their molecular characterization.
Materials and Methods: A total of 116 samples were randomly purchased from local markets in Kashan, Iran, and evaluated for the occurrence of STEC by culturing and molecular methods. The antibiotic resistance of obtained isolates was determined by Kirby Bauer method. Furthermore, isolates were assayed for the presence of Shiga toxins (stx1 and stx2) and intimin gene (eae).
Results: The incidence of E. coli in 60 ice cream, 30 yoghurt, and 26 cheese samples was 8.33%, 10%, and 11.54%, respectively. The findings showed that 11 out of 11 (100%) E. coli had both stx1 and stx2 while eae gene was not found in E. coli isolated of traditional milk products. For E. coli strains carrying stx1 and stx2, highest antibiotic sensitive levels were related to trimethoprim/sulfamethoxazole, norfloxacin, chloramphenicol, and ciprofloxacin, respectively.
Conclusion: The results showed relationship between the presence of virulence factors and antimicrobial resistance. These results can be used for further studies on STEC as an emerging foodborne pathogen.
Staphylococcus aureus is a gram-positive, coccus-shaped facultative anaerobe and a member of the Staphylococcaceae family. In recent years, alimentary toxicosis caused by S. aureus is a very serious problem worldwide, which constitutes a great threat to public health. In this review, we tried to summarize the conventional methods and newly developed rapid detection techniques of S. aureus (traditional detection method, biochemical detection, immunology method, molecular biology, and biosensor method) for their principles, advantages, disadvantages, and applications. Furthermore, the future perspectives of S. aureus detection methods were forecasted at last.
Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), is a life-threatening pathogen in humans, and its presence in food is a public health concern. MRSA has been identified in foods in China, but little information is available regarding MRSA in ready-to-eat (RTE) foods. We aimed to investigate the prevalence of S. aureus and MRSA in Chinese retail RTE foods. All isolated S. aureus were tested for antimicrobial susceptibility, and MRSA isolates were further characterized by multilocus sequence typing (MLST) and staphylococcal cassette chromosome mec (SCCmec) typing. Of the 550 RTE foods collected from 2011 to 2014, 69 (12.5%) were positive for S. aureus. Contamination levels were mostly in the range of 0.3–10 most probable number (MPN)/g, with five samples exceeding 10 MPN/g. Of the 69 S. aureus isolates, seven were identified as MRSA by cefoxitin disc diffusion test. Six isolates were mecA-positive, while no mecC-positive isolates were identified. In total, 75.8% (47/62) of the methicillin-susceptible S. aureus isolates and all of the MRSA isolates were resistant to three or more antibiotics. Amongst the MRSA isolates, four were identified as community-acquired strains (ST59-MRSA-IVa (n=2), ST338-MRSA-V, ST1-MRSA-V), while one was a livestock-associated strain (ST9, harboring an unreported SCCmec type 2C2). One novel sequence type was identified (ST3239), the SCCmec gene of which could not be typed. Overall, our findings showed that Chinese retail RTE foods are likely vehicles for transmission of multidrug-resistant S. aureus and MRSA lineages. This is a serious public health risk and highlights the need to implement good hygiene practices.
In consequence of previous study of bacterial propagation in milk and yogurt samples, present investigation endeavored to determine the existence of drug resistant Staphylococcus aureus especially the methicillin resistant S. aureus (MRSA) in raw milk and cheese samples collected from different areas in Dhaka City, Bangladesh. Total 80 samples (40 raw milk and 40 cheese samples) were microbiologically analyzed through cultural and the confirmative biochemical identification. Out of 80 samples studied, 17 (9 raw milk and 8 cheese) were found to harbor S. aureus. The drug resistance pattern of the staphylococcal isolates was determined against six antibiotics i.g. novobiocin (30μg), ciprofloxacin (5 μg), nalidixic acid (5 μg), methicillin (5 μg), oxacillin (1 μg) and erythromycin (15 μg) by the agar well diffusion method on Muller- Hinton agar. Three isolates from cheese samples and 8 isolates from raw milk samples were found to be resistant against at least two commonly used antibiotics. The highest resistance was found against methicillin (5μg, 58.82%) and oxacillin (1μg, 100%). The presence of methicillin resistant staphylococcal species as found from this study may pose a great public health threat, especially to the children.
The possible effects of dairy consumption on diabetes prevention remain controversial. The aim of this study was to investigate the association between the dairy consumption and type 2 diabetes (T2D) risk in an elderly Mediterranean population at high cardiovascular risk.
We prospectively followed 3,454 non-diabetic individuals from the PREDIMED study. Dairy consumption was assessed at baseline and yearly using food frequency questionnaires and categorized into total, low-fat, whole-fat, and subgroups: milk, yogurt, cheeses, fermented dairy, concentrated full fat, and processed dairy. Hazard ratios (HRs) were calculated using Cox proportional hazards regression models.
During a median follow-up of 4.1 years, we documented 270 incident T2D cases. After multivariate adjustment, total dairy product consumption was inversely associated with T2D risk [0.68 (95 % CI 0.47-0.98); P-trend = .040]. This association appeared to be mainly attributed to low-fat dairy; the multivariate HRs (95 % CIs) comparing the highest versus the lowest tertile consumption were 0.65 (0.45-0.94) for low-fat dairy products and 0.67 (0.46-0.95) for low-fat milk (both P-trend <.05). Total yogurt consumption was associated with a lower T2D risk [HR 0.60 (0.42-0.86); P-trend = .002]. An increased consumption of total low-fat dairy and total yogurt during the follow-up was inversely associated with T2D; HRs were 0.50 (0.29-0.85), 0.44 (0.26-0.75), and 0.55 (0.33-0.93), respectively. Substituting one serving/day of a combination of biscuits and chocolate and whole grain biscuits and homemade pastries for one serving/day of yogurt was associated with a 40 and 45 % lower risk of T2D, respectively. No significant associations were found for the other dairy subgroups (cheese, concentrated full fat, and processed dairy products).
A healthy dietary pattern incorporating a high consumption of dairy products and particularly yogurt may be protective against T2D in older adults at high cardiovascular risk.
Shiga toxin producing Escherichia coli (STEC) O157 is a major cause of food-borne illnesses in humans. This study investigated the presence of STEC O157 in milk and milk products in Ogun State, Nigeria. Of a total of 202 samples 10 (5%) were positive for STEC O157 including 1 (2%) of 50 raw milk samples, 3 (6%) of 50 samples of fresh local cheese, 1 (2%) of 50 samples of fried local cheese and 5 (9.6%) of 52 fermented milk samples. There was no significant difference (p>0.05) in the prevalence of STEC O157 among the sample types. Of 10 isolates, shiga toxin 1 gene (stx1) was detected only in 2 samples (20%), shiga toxin 2 (stx2) was extracted only in 6 samples (60%), stx1 /stx2 in 2 samples (20.0%), intimin gene (eaeA) in 5 samples (50%), and enterohaemolysin (E-hlyA) gene was isolated in 7 (70%) samples. Rates of resistance of the STEC O157 isolates were: amoxicillin/clavulanic acid 100%, ampicillin 100%, chloramphenicol 60%, nalidixic acid 20%, norfloxacin 10%, streptomycin 30%, sulphamethoxazole/trimethprim 20%, and tetracycline 90%. The isolates were all susceptible to ciprofloxacin and neomycin. The presence of virulent multidrug resistant E. coli O157 strains in milk and milk products as revealed by this study unveils a risk of human exposure to these potentially fatal pathogens following consumption of contaminated products.
Food safety is increasingly becoming an important public health issue, as foodborne diseases present a widespread and growing public health problem in both developed and developing countries. The rapid and precise monitoring and detection of foodborne pathogens is one of the most effective ways to control and prevent human foodborne infections. Traditional microbiological detection and identification methods for foodborne pathogens are well known to be time consuming and laborious as they are increasingly being perceived as insufficient to meet the demands of rapid food testing. Recently, various kinds of rapid detection, identification and monitoring methods have been developed for foodborne pathogens, including nucleic acid based methods, immunological methods, and biosensor based methods, etc. This article reviews the principles, characteristics, and applications of recent rapid detection methods for foodborne pathogens.
This study was conducted to determine the prevalence rate, enterotoxigenecity, and antimicrobial resistance of S. aureus isolated from dairy products in Iran. From September 2010 to July 2011, a total of 347 samples from various dairy products, traditional and commercial, were collected from randomly selected retail stores. Overall, 20 samples (5.8%) were found to be contaminated with S. aureus. The highest prevalence of S. aureus was found in traditional cheese (11.1%), followed by traditional ice-cream (5.9%), cream (5.6%), and butter (5.3%). The ability to synthesize classical staphylococcal enterotoxins (SEA-E) was determined in 7 of 20 (35%) isolates by using ELISA. SE type C was the most common enterotoxin found in the isolated S. aureus (42.9%), followed by SE type A (28.6%), SEA+SEC and SE type D (14.3%). Of the 20 isolates, 16 (80.0%) were positive for one or more entrotoxin genes and 8 different genotypes were observed. Susceptibilities of the isolates were determined for 14 antimicrobial drugs using the disk diffusion assay. Most of the isolates (95.0%) were resistant to one or more two antimicrobial agent and 45.0% of the isolates were resistant to three or more of drugs. Resistance to ampicillin was the most common finding (55.0%), followed by tetracycline (40.0%) and penicillin G (30.0%). The results of this study showed the wide spread of enterotoxigenic and multidrug-resistant S. aureus strains in traditional dairy products in Iran and highlighted their public health hazards.
Consumers are increasingly concerned about the safety of their food and uncertain about food production practices. Potential threats to human health related to dairy products and dairy farming include errors in pasteurization, consumption of raw milk products, con- tamination of milkproducts by emerging heat-resistant pathogens, emergence of antimicrobial resistance in zoonotic pathogens, chemical adulteration of milk, transmission of zoonotic pathogens to humans through animal contact, and foodborne disease related to cull dairy cows. Most dairy farmers feel responsible for the safety of milk and beef that originate on their farms, but linkage between farm production practices and the quality of processed products have been weak. The safety of dairy products can be enhanced by adoption of a numberof management practices. Sourcesof micro- bial contamination of milk must be minimized by adop- tion of hygienic standards that can be easily evaluated. Uniform adoption of milking practices that reduce mi- crobial contamination of milk should be emphasized. The diagnosis of salmonellosis or listeriosis on a dairy farm should be regarded as an indication that other potentiallyinfectedanimalsmaybepresentintheherd. Coliform counts on bulk tank milk should be routinely performed as an indicator of fecal contamination. A reduction in the national regulatory limit for somatic cells in bulk tank milk should be considered based on potential enhancements in milk safety. Dairy farmers must take responsibility for the market cattle leaving their farms. The inappropriate or prophylactic use of antimicrobial agents must be minimized to ensure that antimicrobial resistance does not develop in animal pathogens. Consumers can have confidence in food safetyprogramsondairyfarmsthatpromoteawareness
Raw- milk cheese is considered as a risk for food borne STEC contamination. In this study, one hundred twenty-four raw milk cheese samples (64 Kareish and 60 Damietta cheese samples) were assayed for the presence of STEC using molecular detection of virulence markers such as shiga toxins (stx1 and stx2) and intimin gene (eae) and by serotyping. By PCR, 14 E. coli strains showed the presence of the stx2 gene, either single or in association with the stx1 and were considered positive for STEC. The isolated non-O157 STEC in this study (from serotypes O22:H8, O26:H11, O86:H21, O103:H2, O113:H21 and O146:H21) were inoculated in 10% skim milk and were compared to O157:H7 reference strain for their survival under different stress conditions (pH levels between 4.5 and 6.5 and salt concentrations between 1% and 6%) along 8 days storage at refrigeration temperature (4°C). Strikingly, our results showed that O26:H11 survived significantly better than O157: H7 under acidic pH and higher salt concentration. © 2012 The Authors Letters in Applied Microbiology © 2012 The Society for Applied Microbiology.
In this study, a molecular beacon-based duplex real-time PCR assay was developed for the simultaneous detection of Listeria monocytogenes and Salmonella spp. by targeting their virulence genes hly and invA, respectively. The detection sensitivity of the assay in reconstituted non-fat dried milk (11%) was 3 and 4logcfumL−1 for L. monocytogenes and Salmonella spp., respectively, without any pre-enrichment. However, after pre-enrichment of the samples in brain heart infusion broth
for 6h, the assay could detect as low as 1logcfu of both the pathogens. The assay was quantifiable for the respective pathogens
over 5 and 4logcfumL−1 with regression coefficient of 0.9956 and 0.9905. On application of the developed assay on 60 dairy products, one sample
of raw milk was positive for L. monocytogenes, while Salmonella spp. was detected in one sample of ice cream. The performance of the duplex assay was validated using microbiological methods
and commercial individual pathogen detection kits, which further affirmed the performance of the assay by positively detecting
the same samples. The developed assay can be used to monitor the quality of dairy products in context of L. monocytogenes and Salmonella spp.
本研究以李斯特单胞菌毒力基因 hly 和沙门氏菌的毒力基因 invA 为靶点, 建立了同时检测上述两种病原菌的分子信标-双重实时PCR (qPCR) 的分析方法。该方法对未经富集的还原脱脂乳 (11%) 中李斯特单胞菌和沙门氏菌的检测灵敏度分别是1×103和1×104cfu mL-1。当样品在脑心浸液肉汤 (BHI)
培养基中富集培养6小时候, 该方法对两种病原菌的最低检测线可达1×101cfu mL-1。该方法对李斯特单胞菌和沙门氏菌两种致病菌的定量范围分别为1×105和1×104, 线性回归系数分别为0.9956和0.9905。采用该方法检对60个乳制品样品进行了检测,
其中一份鲜奶样品中检测出李斯特单胞菌, 而在一份冰激凌样品中检测出沙门氏菌。根据微生物学方法和商业生产的试剂盒法的验证结果, 证明本研究建立的双重实时 PCR 方法是有效的, 可以通过检测李斯特单胞菌和沙门氏菌来监控乳制品的质量。
Keywords
Listeria monocytogenes
–Molecular beacon–
Salmonella
–qPCR
关键词李斯特单胞菌–分子信标–沙门氏菌–实时PCR
Verotoxin-producing of Escherichia coli O157 is an increasingly common cause of severe
gastrointestinal illness, enlisted among the most important emerging pathogens. The present study
was conducted to investigate the presence of E. coli O157 and E. coli O157: H7 strains and to detect
the presence of the stx1, stx2, eae and ehxA insolates derived from 290 samples (120 samples from
traditional fresh cheese, 120 samples from traditional ice cream and 50 samples from yoghurt). The
samples were purchased from the Isfahan, Chaharmahal, Bakhtyari and Khuzestan provinces in Iran,
over a period 6-month from August 2010 to February 2011. Standard cultural method and polymerase
chain reaction were applied for these analyses. E. coli O157 was detected in nine of the 290 (3.1%)
samples tested (five isolated from traditional cheese and 4 isolated from traditional ice cream samples),
whereas E. coli O157: H7 was not detected in any samples. The genes stx1 and stx2 were detected in
three E. coli isolated obtained from traditional cheese samples none of the stx1, stx2, eae and ehxA was
detected in the E. coli isolates obtained from traditional ice cream samples. Susceptibilities of nine E.
coli O157 isolates were determined for ten antimicrobial drugs using the disk diffusion assay.
Resistance to ampicillin and gentamycin was the most common finding (44.4%), followed by resistance
to erythromycin (33.3%), amoxicillin (11.1%), tetracycline (11.1%) and nalidixic acid (11.1%). All E. coli
O157 isolates were susceptible to chloramphenicol, cefuroxime, and streptomycin. Thus, traditional
cheese and ice cream manufactured from unpasteurized milk have appositional risk as a result of E.
Non-O157 Shiga toxin-producing Escherichia coli (STEC) strains are clinically significant food-borne pathogens. However, there is a dearth of information on serotype prevalence
and virulence gene distribution, data essential for the development of public health protection monitoring and control activities
for the meat and dairy industries. Thus, the objective of this study was to examine the prevalence of non-O157 STEC on beef
and dairy farms and to characterize the isolates in terms of serotype and virulence markers. Bovine fecal samples (n = 1,200) and farm soil samples (n = 600) were collected from 20 farms throughout Ireland over a 12-month period. Shiga toxin-positive samples were cultured
and colonies examined for the presence of stx1 and/or stx2 genes by PCR. Positive isolates were serotyped and examined for a range of virulence factors, including eaeA, hlyA, tir, espA, espB, katP, espP, etpD, saa, sab, toxB, iha, lpfAO157/OI-141, lpfAO113, and lpfAO157/OI-154. Shiga toxin and intimin genes were further examined for known variants. Significant numbers of fecal (40%) and soil (27%)
samples were stx positive, with a surge observed in late summer-early autumn. One hundred seven STEC isolates were recovered, representing
17 serotypes. O26:H11 and O145:H28 were the most clinically significant, with O113:H4 being the most frequently isolated.
However, O2:H27, O13/O15:H2, and ONT:H27 also carried stx1 and/or stx2 and eaeA and may be emerging pathogens.
The aim of this study was to assess the hygienic quality of raw milk used in the manufacture of São Jorge, a Protected Denomination of Origin Portuguese semihard cheese, as well as to ascertain the sanitary conditions prevailing during its processing. Viable counts of Enterobacteriaceae and Micrococcaceae were accordingly obtained, pertaining to 21 independent batches (including samples of raw milk, curd, and cheeses after 1, 3, and 4 months of ripening), from 7 dairy farms. Standard plate counts (log CFU per milliliter or per gram) ranged from 6.1 to 8.6 in raw milk, whereas they ranged from 7.0 to 8.0 in 4-month-old cheeses. Viable counts of Enterobacteriaceae ranged between 5.9 and 7.0 in raw milk and between 0.0 and 1.3 in 4-month-old cheeses. Species identified within this family encompassed Klebsiella oxytoca, Klebsiella cloacae, Klebsiella pneumoniae, Enterobacter sakazakii, and Escherichia coli; Klebsiella ornithinolytica, Klebsiella terrigena, and Serratia odorifera were detected only in raw milk. No Salmonella whatsoever could be detected in any of the samples. Viable counts of Micrococcaceae ranged between 4.7 and 5.9 and between 1.3 and 3.3 in raw milk and 4-month-old cheeses, respectively. Species identified within this family encompassed Staphylococcus sciuri, Staphylococcus epidermidis, Staphylococcus saprophyticus (which was found mainly in ripened cheeses), and Staphylococcus aureus (which was not detected in 4-month-old cheeses). Accompanying physicochemical analyses included determination of moisture, salt, and pH. Statistical analyses revealed a negative correlation between salt content and viable numbers of Enterobacteriaceae in cheese, whereas in the case of Micrococcaceae, a more negative correlation was found between viable numbers and moisture content than between viable numbers and pH. The results of our study indicate, in general, poor milk handling conditions in all farms, given that the indicators total mesophile and Enterobacteriaceae counts were high, between 100- and 1,000-fold those enforced by international standards pertaining to the matrices in question. However, by the time of regular consumption (i.e., after 4 months of ripening), São Jorge cheeses exhibit low levels of contamination by Enterobacteriaceae and S. aureus, as well as absence of Salmonella.
Staphylococci are the most abundant skin-colonizing bacteria and the most important causes of nosocomial infections and community-associated skin infections. Molecular determinants of staphylococcal skin colonization include surface polymers and proteins that promote adhesion and aggregation, and a wide variety of mechanisms to evade acquired and innate host defenses. Antimicrobial peptides (AMPs) likely play a central role in providing immunity to bacterial colonization on human epithelia. Recent research has shown that staphylococci have a broad arsenal to combat AMP activity, and can regulate expression of AMP-resistance mechanisms depending on the presence of AMPs. While direct in vivo evidence is still lacking, this suggests that the interplay between AMPs and AMP resistance mechanisms during evolution had a crucial role in rendering staphylococci efficient colonizers of human skin.
An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) involving 27 patients and 14 health-care workers (HCW) was studied. The outbreak started in the hematology unit of the University Hospital Rotterdam, Dijkzigt, The Netherlands, and spread to the surgical unit. Twenty-one patients (77.8%) developed clinical disease, and five died. Subsequently, MRSA was detected in food and in the throat of one of the HCW who prepared food for hematology patients. Food contaminated by an HCW most likely caused the first case of MRSA septicemia. This route of transmission has not been described before. The outbreak strain was probably transmitted to the surgical unit by a colonized nurse, where it caused an explosive outbreak. Airborne probably transmitted to the surgical unit by a colonized nurse, where it caused an explosive outbreak. Airborne MRSA transmission played an important role in disseminating the organism. The outbreak was controlled within 6 months by intensifying surveillance, temporarily closing the affected wards, treating carriers, and instituting an MRSA ward outside the hospital. Phage typing, insertion sequence probing, protein A gene typing, and DNA fingerprinting by PCR revealed that all outbreak-related isolates were identical. By pulsed-field gel electrophoresis, all but one of the outbreak-related isolates were determined to be identical. Protein A gene typing identified numerous (11) repeat units in all outbreak-related isolates, which supports the suggestion that the outbreak strain may have been more virulent and more transmissible than other MRSA strains. Pheno- and genotyping studies underlined the value of DNA fingerprinting methods for investigation of MRSA epidemiology. Optimal discriminatory power was achieved by combining the results of four genotyping methods.
Purpose
This paper aims to evaluate the microbial quality of some traditional cheese samples (sheep, cow and koopeh cheeses) consumed in northwest of Iran, and to detect Shiga-like-toxin-producing Escherichia coli (STEC) and methicillin-resistant Staphylococcus aureus (MRSA) in cheese samples by polymerase chain reaction (PCR) method.
Design/methodology/approach
Almost half of the project was based on counting the population of Staphylococcus aureus, total coliforms, Escherichia coli, and total aerobic mesophilic bacteria, also the other section was related to the isolation and the detection of the STEC and MRSA in cheese samples. The findings were compared with standard maximum and threshold values.
Findings
The results revealed that 36.99, 30.14 and 100% of cheeses exceeded the standard threshold value of E. coli (102), total coliforms (104) and S. aureus (102). However, total coliforms, in any of the cheese samples examined, did not reach the maximum value and only 24.66% of samples exceeded the maximum value of E. coli. Also, no significant difference (p > 0.05) in counts of each bacterial group examined in sheep, cow and koopeh cheeses was observed. The colony PCR method demonstrated the existence of 19 MRSA and 2 STEC isolates.
Originality/value
This research showed a general overview of the bacterial quality of cheeses in northwest of Iran.
The objective of this study was to estimate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the production chain of dairy products. Of 367 tested samples (36 bulk tank milk (BTM), 19 dairy products, 72 human, 185 animal, 55 equipment), 212 (57.8%) were found positive for S. aureus. Almost all isolates (99.6%) were resistant to at least one antimicrobial and 13.3% were multi-drug resistant (MDR), exhibiting resistance to three or more antibiotic classes. Eleven samples (3%) were found contaminated by MRSA carrying the mecA gene. None of the MRSA isolates carried the mecC or the Pandon-Valentine leucocidin (PVL) genes. Four spa types were identified among the MRSA isolates: t127, t3586, t1773, t4038, with t127 being the most prevalent (7 out of 11). Two of them, t3586 and t1773, were isolated for the first time in Greece. Furthermore, Pulse-Field Gel Electrophoresis (PFGE) analysis indicated clonal circulation through the dairy production chain. The presence of MDR S. aureus, and especially MRSA, in animals and dairy products represents a potential threat for the spread of this pathogen in the community. The results indicated that human, animal and environmental sources could be involved in the contamination of dairy products along their production chain and therefore further investigation of contamination sources is needed to control the dispersion of MRSA in the community.
Significance and impact of the study:
This review evaluates the potential of methicillin-resistant Staphylococcus aureus (MRSA) as food-borne pathogens based on the current knowledge about the epidemiology of MRSA, their prevalence in livestock, foods of animal origin and humans, and their ability to produce enterotoxins.
Opportunities for post-processing contamination of cheese may occur in deli retail establishments, either during the further cheese ripening (at maximum 14 °C), during storage and display in the refrigeration cabinet (at maximum 7 °C) or during slicing. A L. monocytogenes post-processing contamination was simulated by inoculation either on the cheese slicing surface or the cheese rind of three soft cheeses (one white-molded raw cow's milk cheese, one pasteurized cow's milk cheese with spicy herbs, one washed rind pasteurized cow and sheep's milk cheese) and two semi-hard cheeses (one smear-ripened raw cow's milk cheese and one natural-ripened raw cow's milk cheese). L. monocytogenes challenge testing was performed on 3 batches of each cheese to assess the growth potential of L. monocytogenes after 14 days storage at either 7 or 14 °C. Substantial growth of L. monocytogenes (>0.5 log CFU/g) was obtained in 79.2% of all individual challenge tests (n = 178) that were performed although huge variation in growth potential was noted among the different cheese types and storage conditions. The growth potential on soft cheeses stored at 7 °C ranged from 1.8 to 4.0 log units and from 3.6 to 5.5 log units upon storage at 14 °C, whilst on semi-hard cheese, this was in general lower, and ranged from 0.1 to 1.4 log units at 7 °C and from 0.0 to 3.0 log units at 14 °C. Overall, increased outgrowth of L. monocytogenes was noted when inoculation was performed on the cheese slicing surface compared to the cheese rind. Thus if occasional post-processing contamination takes place during storage or handling of the cheese, L. monocytogenes has the potential to grow to elevated numbers throughout a reasonably expected storage period of up to 14 days notwithstanding the presence of high numbers of indigenous lactic acid bacteria in these cheeses. Also for a defined cheese type both a considerable inter-batch and intra-batch variability was sometimes noted from the replicate testing, indicating no consistent behavior of L. monocytogenes in these fermented dairy products. As such it is recommended that appropriate hygienic measures are taken to prevent post-processing contamination. Noting the growth potential, absence of L. monocytogenes in 25 g of cheese using a multiple sample subunit approach (n = 5) at the time of production is important to ensure compliance to EU legislation 2073/2005.
Staphylococcus aureus (S. aureus) is an important food-borne pathogen in dairy products contaminated through raw ingredients or improper food handling. Rapid detection of S. aureus with high sensitivity is of significance for food quality and safety. In this study, a new method was developed for detecting S. aureus in milk by coupling immunomagnetic separation with enzyme linked cell wall binding domain (CBD) of lysin plyV12, which can bind to S. aureus with high affinity. There are millions of binding sites present on the cell surface of S. aureus for the CBD attachment, which greatly improves the detection sensitivity. The method has the overall testing time of only 1.5h with the detection limit of 4×10(3)CFU/mL in spiked milk. Because it is simple, rapid and sensitive, this method could be used for the detection of S. aureus in various food samples.
From May 2001 to April 2003, various types of specimens from cattle, pigs, and chickens were collected and examined for the presence of methicillin (oxacillin) -resistant Staphylococcus aureus (MRSA). S. aureus was isolated and positively identified by using Gram staining, colony morphology, tests for coagulase and urease activities, and an API Staph Ident system. Among 1,913 specimens collected from the animals, 421 contained S. aureus; of these, 28 contained S. aureus resistant to concentrations of oxacillin higher than 2 mug/ml. Isolates from 15 of the 28 specimens were positive by PCR for the mecA gene. Of the 15 mecA-positive MRSA isolates, 12 were from dairy cows and 3 were from chickens. Antimicrobial susceptibility tests of mecA-positive MRSA strains were performed by the disk diffusion method. All isolates were resistant to members of the penicillin family, such as ampicillin, oxacillin, and penicillin. All isolates were also susceptible to amikacin, vancomycin, and trimethoprim-sulfamethoxazole. To determine molecular epidemiological relatedness of these 15 animal MRSA isolates to isolates from humans, random amplified polymorphic DNA (RAPD) patterns were generated by arbitrarily primed PCR. The RAPD patterns of six of the isolates from animals were identical to the patterns of certain isolates from humans. The antibiotypes of the six animal isolates revealed types similar to those of the human isolates. These data suggested that the genomes of the six animal MRSA isolates were very closely related to those of some human MRSA isolates and were a possible source of human infections caused by consuming contaminated food products made from these animals.
Staphylococcus aureus is one of the main pathogens in dairy and meat products; therefore, developing a highly sensitive and rapid method for its detection is necessary. In this study, a quantitative detection method for Staph. aureus was developed using silica-coated magnetic nanoparticles and thermophilic helicase-dependent isothermal amplification. First, genomic DNA was extracted from lysed bacteria using silica-coated magnetic nanoparticles and amplified using thermophilic helicase-dependent isothermal amplification. After adding the nucleic-acid dye SYBR Green I to the amplicons, the fluorescence intensity was observed using a UV lamp or recorded using a fluorescence spectrophotometer. This detection system had a detection limit of 5 × 10(0) cfu/mL in pure culture and milk-powder samples and 5 × 10(1) cfu/mL in pork samples using a UV light in less than 2 h. In addition, a good linear relationship was obtained between fluorescence intensity and bacterial concentrations ranging from 10(2) to 10(4) cfu/mL under optimal conditions. Furthermore, the results from contaminated milk powder and pork samples suggested that the detection system could be used for the quantitative analysis of Staph. aureus and applied potentially to the food industry for the detection of this pathogen.
Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
In the context of the prevailing trend toward more natural products, there seems to be an increasing preference for raw milk consumption as raw milk is associated with several perceived health benefits that are believed to be destroyed upon heating. However, many human pathogens can be isolated from raw cow milk. The prevalence of foodborne pathogens in raw cow milk varies, but their presence has been demonstrated in many surveys and foodborne infections have been repeatedly reported for Campylobacter, Salmonella spp. and human pathogenic verocytotoxin-producing Escherichia coli. In industrialized countries, milk-borne and milk product-borne outbreaks represent 2–6% of the bacterial foodborne outbreaks.The aim of this review is to present scientifically sound data regarding the risks and benefits related to the consumption of raw and heated cow milk. Both microbiological aspects (e.g., the prevalence of milk-borne pathogens, pathogen growth inhibition by antimicrobial systems and by lactic acid producing bacteria, probiotic bacteria, etc.) and nutritional or health aspects (nutritional value, immunity, allergies, lactose intolerance, diabetes, milk digestibility, etc.) are considered.As such, it is demonstrated that consumption of raw milk poses a realistic health threat due to a possible contamination with human pathogens. It is therefore strongly recommended that milk should be heated before consumption. With the exception of an altered organoleptic profile, heating (in particularly ultra high temperature and similar treatments) will not substantially change the nutritional value of raw milk or other benefits associated with raw milk consumption.
Staphylococcus aureus is a major human pathogen, and considerable research efforts have been put forward to improve our understanding of its complex pathogenesis. In spite of these efforts, the burden of staphylococcal infections is still on the rise. This review focuses on a selected set of crucial unresolved questions regarding this pathogen, namely: (i), the nature of the driving forces behind the rise and decline of methicillin-resistant S.aureus (MRSA) clones; (ii), the mechanisms by which a commensal becomes a pathogen; (iii), the molecular underpinnings of toxin overexpression in hypervirulent MRSA clones such as USA300; and (iv), the repeated failures of anti-S.aureus vaccine approaches.
Contamination of dairy products with Staphylococcus aureus can be of animal or human origin. The host pathogen relationship is an important factor determining genetic polymorphism of the strains and their potential virulence. The aim of the present study was to carry out an extensive characterization of virulence factors and to study the genetic variability of S. aureus strains isolated from raw ewe's milk cheese. A total of 100 S. aureus strains isolated from cheese samples produced in 10 artisan cheese factories were analyzed for the presence of enterotoxins (sea-see) and enterotoxins-like genes (seh, sek, sel, sem, seo, sep), leukocidins, exfoliatins, haemolysins, toxic shock syndrome toxin 1 (TSST-1) and the accessory gene regulator alleles (agr). Strains were also typed using pulsed-field gel electrophoresis (PFGE). AMOVA analysis carried out on PFGE and PCR data showed that the major component explaining genetic distance between strains was the dairy of origin. Of the total isolates 81% had a pathogenicity profile ascribable to "animal" biovar while 16% could be related to "human" biovar. The biovar allowed to estimate the most likely origin of the contamination. Minimum inhibitory concentrations (MICs) of nine antimicrobial agents and the presence of the corresponding genes coding for antibiotic resistance was also investigated. 18 strains carrying blaZ gene showed resistance to ampicillin and penicillin and 6 strains carrying tetM gene were resistant to tetracycline. The presence of mecA gene and methicillin resistance, typical of strains of human origin, was never detected. The results obtained in the present study confirm that S. aureus contamination in artisan cheese production is mainly of animal origin.
Escherichia coli O157 is an uncommon but serious cause of gastroenteritis. This bacterium is noteworthy because a few, but significant, number of infected people develop the haemolytic uraemic syndrome, which is the most frequent cause of acute renal failure in children in the Americas and Europe. Many infections of E coli O157 could be prevented by the more effective application of evidence-based methods, which is especially important because once an infection has been established, no therapeutic interventions are available to lessen the risk of the development of the haemolytic uraemic syndrome. This Review takes into account the evolution and geographical distibution of E coli O157 (and its close pathogenic relatives); the many and varied routes of transmission from its major natural hosts, ruminant farm animals; and other aspects of its epidemiology, its virulence factors, the diagnosis and management of infection and their complications, the repercussions of infection including costs, and prevention.
Escherichia coli K-12 strains producing high levels of Shiga-like toxin type II (SLT-II) but not SLT-I were previously shown to be virulent in an orally infected, streptomycin-treated mouse model. In this investigation, we tested the virulence of several SLT-II-producing enterohemorrhagic E. coli (EHEC) isolates from patients with hemorrhagic colitis or hemolytic uremic syndrome. All of the strains tested were able to colonize the mouse intestine. However, only two strains were consistently virulent for mice: O91:H21 strain B2F1 (Strr), which was previously shown to carry two copies of slt-II-related toxins, and O91:H21 strain H414-36/89 (Strr), which was found in this study to contain three genes from the slt-II group. The oral 50% lethal doses of strains B2F1 (Strr) and H414-36/89 (Strr) when fed to streptomycin-treated mice were less than 10 bacteria. Histological sections from moribund mice fed the O91:H21 strains demonstrated extensive renal tubular necrosis; however, hematological results were not consistent with a diagnosis of hemolytic uremic syndrome. The central role of SLT in the virulence of the O91:H21 EHEC strains was supported by the finding that streptomycin-treated mice preinoculated with monoclonal antibody specific for SLT-II survived oral challenge with either B2F1 (Strr) or H414-36/89 (Strr). The basis for the variation in virulence among the SLT-II-producing EHEC strains tested was not determined. However, a correlation between the capacity of an EHEC strain to grow in small intestinal mucus and lethality in the streptomycin-treated mice was observed.
Sixteen cases of verotoxin producing Escherichia coli (VTEC) O 157:H7 Phage Type 49 infection were identified in the North West of England from 1 September to 1 November 1991, eight of whom lived in or around the same large town. Eleven of the cases were aged 10 years or less, and five of the affected children developed haemolytic uraemic syndrome. A case control study demonstrated a strong association between VTEC O 157:H7 PT 49 infection and the consumption of a locally produced live yoghurt. This is the first time that an outbreak of VTEC O 157 infection has been linked to the consumption of yoghurt and this vehicle of infection should be considered when investigating such outbreaks in future.