Sandra Menting's research while affiliated with University of Amsterdam and other places

Background Current diagnostic methods for VL include parasitology and serology (with rK39 dipstick test and direct agglutination test). These methods have limitations (patient safety or diagnostic accuracy), and molecular testing is proposed to improve diagnosis. Current molecular tools have high accuracy for detecting VL, however their complexity and high costs make their use unsuitable for endemic areas with limited resources. Consequently, there is a need for a simple molecular diagnostic test that can be implemented in resource limited setting. Methods We have developed a miniaturized direct-on-blood PCR nucleic acid lateral flow immunoassay (mini-dbPCR-NALFIA) as an innovative, easy-to-use molecular assay for the diagnosis of VL in these particular settings. Unlike other simplified molecular methods, such as LAMP, the mini-dbPCR-NALFIA does not require DNA extraction and utilizes a handheld, portable thermal cycler powered by a solar-charged power pack enabling to perform the test without any laboratory infrastructure. Reading of results is done using a rapid lateral flow strip. In the present study we have conducted a laboratory evaluation on the mini db-PCR-NALFIA to determine its diagnostic accuracy. Patient samples (N=146) with suspected VL were tested using the mini db-PCR-NALFIA and compared to conventional PCR (reference test). Sensitivity and specificity represented the accuracy. Cohen’s k determined the degree or agreeableness between the mini db-PCR-NALFIA and other diagnostic tests (PCR and rk39 rapid test). Results Compared to qPCR, the mini db-PCR-NALFIA for VL had a sensitivity of 95.83% (95% CI, 88.30%-99.13%) and a specificity of 97.22% (95% CI, 90.32% - 99.66%). The agreement between both tests was excellent (k-value: 0.93). The Limit of Detection of the platform is around 10 parasites per microliter of blood (spiked with promastigotes). Conclusion The VL-mini-db-PCR-NALFIA has a very good diagnostic performance and is now ready for large field evaluations in disease endemic countries.

Background Low peripheral parasitemia caused by sequestration of Plasmodium falciparum in the placenta hampers the diagnosis of malaria in pregnant women, leading to microscopy or conventional rapid diagnostic tests (co-RDTs) false-negative results. Although mainly asymptomatic, maternal malaria remains harmful to pregnant women and their offspring in endemic settings and must be adequately diagnosed. Ultra-sensitive RDTs (uRDTs) are thought to be more sensitive than co-RDTs, and their diagnostic performance was assessed in the present study in pregnant women living in Kinshasa, a stable malaria transmission area in the Democratic Republic Congo. Methods To assess and compare the performances of both co-RDTs and uRDTs, 497 peripheral blood samples were tested using microscopy and quantitative polymerase chain reaction (qPCR) as the index and the reference tests respectively. The agreement between uRDT, co-RDT, microscopy and qPCR was determined by Cohen’s Kappa test. Results The median parasite density by qPCR was 292 p/μL of blood [IQR 292 (49.7–1,137)]. Using qPCR as the reference diagnostic test, microscopy was the least sensitive test [55.7% (95% CI: 47.6–63.6)], followed by co-RDT [81.7% (95%CI:74.7–87.3)] and uRDT [88% (95% CI:81.9–92.6)]. The corresponding specificity was respectively: 98.5% (95% CI:96.6–99.5), 95.2% (95% CI:92.5–97.2) and 94.4% (95% CI:91.4–96.6). The agreement between qPCR and uRDT was almost perfect (kappa=0.82). For parasite density (qPCR) below 100p/µL, the sensitivity of co-RDT was 62% (95%CI:47.1–75.3) compared to 68% (95%CI:53.3–80.4). Between 100 and 200p/µL, the sensitivity of co-RDT tended to be lower compared to uRDT: 89.4%(95%CI:66.8–98.7) versus 100%(95%CI:82.3–100) for uRDT. In both cases, microscopy was lower, with 20% (95%CI:10–33.7) and 47.3% (95%CI:24.4–71.1) respectively. Conclusion uRDT tended to be more sensitive than co-RDT in the detection of malaria in pregnant women. Therefore, it has the potential to improve malaria management in pregnant women. Microscopy shows poor performance for the diagnosis of malaria in pregnancy.

Background Low peripheral parasitaemia caused by sequestration of Plasmodium falciparum in the placenta hampers the diagnosis of malaria in pregnant women, leading to microscopy or conventional rapid diagnostic tests (RDTs) false-negative results. Although mainly asymptomatic, maternal malaria remains harmful to pregnant women and their offspring in endemic settings and must be adequately diagnosed. Ultra-sensitive RDTs (uRDTs) are thought to be more sensitive than RDTs, and their diagnostic performance was assessed in the current study in pregnant women living in Kinshasa, a stable malaria transmission area in the Democratic Republic of the Congo. Methods To assess and compare the diagnostic performances of both RDTs and uRDTs, 497 peripheral blood samples were tested using microscopy and quantitative polymerase chain reaction (qPCR) as the index and the reference tests, respectively. The agreement between the different diagnostic tests assessed was estimated by Cohen's Kappa test. Results The median parasite density by qPCR was 292 p/μL of blood [IQR (49.7–1137)]. Using qPCR as the reference diagnostic test, the sensitivities of microscopy, RDT and uRDT were respectively [55.7% (95% CI 47.6–63.6)], [81.7% (95%CI 74.7–87.3)] and [88% (95% CI 81.9–92.6)]. The specificities of the tests were calculated at 98.5% (95% CI 96.6–99.5), 95.2% (95% CI 92.5–97.2) and 94.4% (95% CI 91.4–96.6) for microscopy, RDT and uRDT, respectively. The agreement between qPCR and uRDT was almost perfect (Kappa = 0.82). For parasite density (qPCR) below 100 p/µL, the sensitivity of RDT was 62% (95% CI 47.1–75.3) compared to 68% (95% CI 53.3–80.4) for uRDT. Between 100 and 200 p/µL, the sensitivity of RDT was higher, but still lower compared to uRDT: 89.4% (95% CI 66.8–98.7) for RDT versus 100% (95% CI 82.3–100) for uRDT. In both cases, microscopy was lower, with 20% (95% CI 10–33.7) and 47.3% (95% CI 24.4–71.1) respectively. Conclusions uRDT has the potential to improve malaria management in pregnant women as it has been found to be slightly more sensitive than RDT in the detection of malaria in pregnant women but the difference was not significant. Microscopy has a more limited value for the diagnosis of malaria during the pregnancy, because of its lower sensitivity.

There is a need to have more accessible molecular diagnostic tests for the diagnosis of severe acute respiratory syndrome coronavirus 2 disease in low- and middle-income countries. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) may provide an attractive option as this technology does not require a complex infrastructure. In this study, the diagnostic performance of a SARS-CoV-2 RT-LAMP was evaluated using RT-PCR-confirmed clinical specimens of COVID-19-positive (n = 55) and -negative patients (n = 55) from the Netherlands. The observed sensitivity of the RT-LAMP test was 97.2% (95% CI: 82.4–98.0%) and the specificity was 100% (95% CI: 93.5–100%). The positive predictive value of the RT-LAMP was 100%, the negative predictive value 93.2% (95% CI: 84.3–97.3%), and the diagnostic accuracy was 96.4% (95% CI: 91.0–99.0%). The agreement between the RT-LAMP and the RT-PCR was “almost perfect” (κ-value: 0.92). The evaluated RT-LAMP might provide an attractive alternative molecular diagnostic tool for SARS-CoV-2 in resource limited settings.

Background Point-of-care diagnosis of malaria is currently based on microscopy and rapid diagnostic tests. However, both techniques have their constraints, including poor sensitivity for low parasitaemias. Hence, more accurate diagnostic tests for field use and routine clinical settings are warranted. The miniature direct-on-blood PCR nucleic acid lateral flow immunoassay (mini-dbPCR-NALFIA) is an innovative, easy-to-use molecular assay for diagnosis of malaria in resource-limited settings. Unlike traditional molecular methods, mini-dbPCR-NALFIA does not require DNA extraction and makes use of a handheld, portable thermal cycler that can run on a solar-charged power pack. Result read-out is done using a rapid lateral flow strip enabling differentiation of Plasmodium falciparum and non-falciparum malaria infections. A laboratory evaluation was performed to assess the performance of the mini-dbPCR-NALFIA for diagnosis of pan-Plasmodium and P. falciparum infections in whole blood. Methods Diagnostic accuracy of the mini-dbPCR-NALFIA was determined by testing a set of Plasmodium-positive blood samples from returned travellers (n = 29), and Plasmodium-negative blood samples from travellers with suspected malaria (n = 23), the Dutch Blood Bank (n = 19) and intensive care patients at the Amsterdam University Medical Centers (n = 16). Alethia Malaria (LAMP) with microscopy for species differentiation were used as reference. Limit of detection for P. falciparum was determined by 23 measurements of a dilution series of a P. falciparum culture. A fixed sample set was tested three times by the same operator to evaluate the repeatability, and once by five different operators to assess the reproducibility. Results Overall sensitivity and specificity of the mini-dbPCR-NALFIA were 96.6% (95% CI, 82.2%–99.9%) and 98.3% (95% CI, 90.8%–100%). Limit of detection for P. falciparum was 10 parasites per microlitre of blood. The repeatability of the assay was 93.7% (95% CI, 89.5%–97.8%) and reproducibility was 84.6% (95% CI, 79.5%–89.6%). Conclusions Mini-dbPCR-NALFIA is a sensitive, specific and robust method for molecular diagnosis of Plasmodium infections in whole blood and differentiation of P. falciparum. Incorporation of a miniature thermal cycler makes the assay well-adapted to resource-limited settings. A phase-3 field trial is currently being conducted to evaluate the potential implementation of this tool in different malaria transmission areas.

Objectives Antibiotics efficacy is severely threatened due to emerging resistance worldwide, but there is a paucity of antibiotics efficacy data for the West African region in general. Therefore, this study aimed to determine the antibiotic susceptibility profile of bacterial isolated from febrile children under 5 years of age in Nanoro (Burkina Faso). Methods Blood, stool and urine samples were collected from 1099 febrile children attending peripheral health facilities and the referral hospital in Nanoro Health district. Bacterial isolates from these samples were assessed for their susceptibility against commonly used antibiotics by Kirby–Bauer method. Results In total, 141 bacterial isolates were recovered from 127 febrile children of which 65 from blood, 65 from stool and 11 from urine. Salmonella isolates were most frequently isolated and found to be highly resistant to ampicillin (70%; 56/80) and trimethoprim–sulphamethoxazole (65%; 52/80). Escherichia coli isolates showed a high resistance rate to trimethoprim–sulphamethoxazole (100%), ampicillin (100%), ciprofloxacin (71.4%; 10/14), amoxicillin–clavulanate (64.3%; 9/14), ceftriaxone (64.3%; 9/14) and gentamycin (50%; 7/14). Moreover, half of the E. coli isolates produced ß‐lactamase suggesting multi‐drug resistance against β‐lactam as well as non‐β‐lactam antibiotics. Multi‐drug resistance was observed in 54.6% (59/108) of the isolates, mainly Gram‐negative bacteria. Conclusions This study showed high resistance rates to common antibiotics used to treat bacterial infections in Nanoro. The work prompts the need to expand antibiotic resistance surveillance studies in Burkina Faso.

(1) Background: nasopharynx colonization by resistant Staphylococcus aureus and Streptococcus pneumoniae can lead to serious diseases. Emerging resistance to antibiotics commonly used to treat infections due to these pathogens poses a serious threat to the health system. The present study aimed to determine the antibiotic susceptibility of S. aureus and S. pneumoniae isolates from the febrile children’s nasopharynx under 5 years in Nanoro (Burkina Faso). (2) Methods: bacterial isolates were identified from nasopharyngeal swabs prospectively collected from 629 febrile children. Antibiotic susceptibility of S. aureus and S. pneumoniae isolates was assessed by Kirby–Bauer method and results were interpreted according to the Clinical and Laboratory Standard Institute guidelines. (3) Results: bacterial colonization was confirmed in 154 (24.5%) of children of whom 96.1% carried S. aureus, 3.2% had S. pneumoniae, and 0.6% carried both bacteria. S. aureus isolates showed alarming resistance to penicillin (96.0%) and S. pneumoniae was highly resistant to tetracycline (100%) and trimethoprim–sulfamethoxazole (83.3%), and moderately resistant to penicillin (50.0%). Furthermore, 4.0% of S. aureus identified were methicillin resistant. (4) Conclusion: this study showed concerning resistance rates to antibiotics to treat suspected bacterial respiratory tract infections. The work highlights the necessity to implement continuous antibiotic resistance surveillance.

Background: The curative power of antimicrobials is severely threatened due to emerging resistance to first-line antibiotics worldwide. With a limited reserve of antibiotics, increasing antimicrobial resistance has become a global concern, but there is a paucity of such data in Burkina Faso, and the West African region in general. Therefore, this study aims to determine the antibiotic susceptibility profile of bacterial species isolated from febrile children under 5 years of age in Nanoro (Burkina Faso). Methods: Clinical specimens (blood, stool, and urine) were collected from 1099 febrile children attending the peripheral health facilities and the referral hospital in Nanoro. Bacterial isolates from these clinical specimens were assessed for their susceptibility against commonly used antibiotics by standard disc diffusion procedure and minimal inhibitory concentration method (when appropriate). Results: In total, 141 bacterial strains were recovered from 127 febrile children of which 65 strains were isolated from blood, 65 from the stool, and 11 from urine. Predominant bacterial isolates were Salmonella species (56.7%; 80/141) followed by Escherichia coli (33.3%; 47/141). Antibiotic susceptibility testing revealed Salmonella species were highly resistant to ampicillin (70%; 56/80), trimethoprim-sulfamethoxazole (65%; 52/80), and chloramphenicol (63.8%; 51/80). E. coli isolates were highly resistant to trimethoprim-sulfamethoxazole (100%), ampicillin (100%), ciprofloxacin (71.4%; 10/14), amoxicillin-clavulanate (64.3%; 9/14), ceftriaxone (64.3%; 9/14), and gentamycin (50%; 7/14). Moreover, 7 out of 14 E. coli isolates were producers of the ß-lactamase enzyme, suggesting multi-drug resistance against b-lactam as well as non-b-lactam antibiotics. S. pneumoniae isolates were fully resistant to tetracycline and 50% to penicillin G. Multi-drug resistance was observed in 54.6% (59/108) of the isolates of which 56 (54.9%) were Gram-negative bacteria and 3 (50.0%) Gram-positive bacteria. Conclusions: The antibiotic susceptibility profiling showed an alarming high resistance to commonly used antibiotics to treat bacterial infections in the study region. The work prompts the need to expand antibiotic resistance surveillance studies in Burkina Faso, and probably the whole region (West Africa).

Background: The curative power of antimicrobials is severely threatened due to emerging resistance to first-line antibiotics worldwide. With a limited reserve of antibiotics, increasing antimicrobial resistance has become a global concern, but there is a paucity of such data in Burkina Faso, and the West African region in general. Therefore, this study aims to determine the antibiotic susceptibility profile of bacterial species isolated from febrile children under 5 years of age in Nanoro (Burkina Faso). Methods: Clinical specimens (blood, stool, and urine) were collected from 1099 febrile children attending the peripheral health facilities and the referral hospital in Nanoro. Bacterial isolates from these clinical specimens were assessed for their susceptibility against commonly used antibiotics by standard disc diffusion procedure and minimal inhibitory concentration method (when appropriate). Results: In total, 141 bacterial strains were recovered from 127 febrile children of which 65 strains were isolated from blood, 65 from the stool, and 11 from urine. Predominant bacterial isolates were Salmonella species (56.7%; 80/141) followed by Escherichia coli (33.3%; 47/141). Antibiotic susceptibility testing revealed Salmonella species were highly resistant to ampicillin (70%; 56/80), trimethoprim-sulfamethoxazole (65%; 52/80), and chloramphenicol (63.8%; 51/80). E. coli isolates were highly resistant to trimethoprim-sulfamethoxazole (100%), ampicillin (100%), ciprofloxacin (71.4%; 10/14), amoxicillin-clavulanate (64.3%; 9/14), ceftriaxone (64.3%; 9/14), and gentamycin (50%; 7/14). Moreover, 7 out of 14 E. coli isolates were producers of the ß-lactamase enzyme, suggesting multi-drug resistance against b-lactam as well as non-b-lactam antibiotics. S. pneumoniae isolates were fully resistant to tetracycline and 50% to penicillin G. Multi-drug resistance was observed in 54.6% (59/108) of the isolates of which 56 (54.9%) were Gram-negative bacteria and 3 (50.0%) Gram-positive bacteria. Conclusions: The antibiotic susceptibility profiling showed an alarming high resistance to commonly used antibiotics to treat bacterial infections in the study region. The work prompts the need to expand antibiotic resistance surveillance studies in Burkina Faso, and probably the whole region (West Africa). Moreover, it implies the need of a revision of the antibiotic-treatment guidelines by the Ministry of Health in Burkina Faso to avoid further development of resistance.

Background: There is significant need for accurate diagnostic tools for Cryptosporidium spp. and Giardia duodenalis infections in resource limited countries where diarrhoeal disease caused by these parasites is often prevalent. The present study assessed the diagnostic performance of three commercially available rapid diagnostic tests (RDTs) based on faecal-antigen detection for Cryptosporidium spp. and/or G. duodenalis infections in stool samples of children admitted with severe acute malnutrition (SAM) and diarrhoea. An established multiplex PCR was used as reference test. Methods: Stool samples from children with SAM and diarrhoea enrolled in a randomized controlled trial (registered at clinicaltrials.gov/ct2/show/NCT02246296) in Malawi (n = 175) and Kenya (n = 120) between December 2014 and December 2015 were analysed by a multiplex PCR for the presence of Cryptosporidium spp., G. duodenalis or Entamoeba histolytica parasite DNA. Cryptosporidium-positive samples were species typed using restriction fragment length polymorphism analysis. A sub-sample of the stool specimens (n = 236) was used for testing with three different RDTs. Diagnostic accuracy of the tests under evaluation was assessed using the results of PCR as reference standard using MedCalc software. Pearson Chi-square test and Fisher's exact test were used to determine (significant) difference between the number of cryptosporidiosis or giardiasis cases found by PCR in Malawi and Kenya. The overall diagnostic accuracy of each RDT was calculated by plotting a receiver operating characteristic (ROC) curve for each test and to determine the area under the curve (AUC) using SPSS8 software. Results: Prevalence of Cryptosporidium spp. by PCR was 20.0 and 21.7% in Malawi and Kenya respectively, mostly C. hominis. G. duodenalis prevalence was 23.4 and 5.8% in Malawi and Kenya respectively. E. histolytica was not detected by PCR. RDT testing followed the same pattern of prevalence. RDT sensitivities ranged for cryptosporidiosis from 42.9 to 76.9% and for G. duodenalis from 48.2 to 85.7%. RDT specificities ranged from 88.4 to 100% for Cryptosporidium spp. and from 91.2 to 99.2% for G. duodenalis infections. Based on the estimated area under the curve (AUC) values, all tests under evaluation had an acceptable overall diagnostic accuracy (> 0.7), with the exception of one RDT for Cryptosporidium spp. in Malawi. Conclusions: All three RDTs for Cryptosporidium spp. and Giardia duodenalis evaluated in this study have a moderate sensitivity, but sufficient specificity. The main value of the RDTs is within their rapidness and their usefulness as screening assays in surveys for diarrhoea.