Phenotypic and genotypic analysis of antimicrobial resistance and population structure of gastroenteritis-related Aeromonas isolates.

BACKGROUND: The population structure and the correlation between antimicrobial resistance (AMR) phenotypes and genotypes in Aeromonas species isolated from patients with gastroenteritis are not well understood. The aims of the study were to: (1) investigate the antimicrobial susceptibility profiles of Aeromonas species isolated from patients with gastroenteritis; (2) explore the relationship between AMR genes and resistance phenotypes; and (3) describe the population structure of these isolates and provide evidence of transmission events among them. METHODS: This microbiological survey was performed at the Microbiology Laboratory of the Emek Medical Center in Afula, Israel. Cultivation of Aeromonas was attempted from stool samples that tested positive by PCR. Antimicrobial susceptibility testing (AST) was performed using the Sensititre GN3F microdilution panel. Whole genome sequencing (WGS) was done using the Illumina NextSeq500/550 system. Phylogenetic studies involved multi-locus sequence typing (MLST) and core genome (cg) MLST. Resistance mechanisms were identified using the Comprehensive Antibiotic Resistance Database and compared with the AST results. RESULTS: The study included 67 patient-unique isolates. The species that were identified included A. caviae (n = 58), A. dhakensis (n = 3), A. media (n = 2), A. veronii (n = 2) and A. hydrophila (n = 2). Isolates were almost uniformly susceptible to amikacin, gentamicin, aztreonam, cefepime, ceftazidime, ciprofloxacin and meropenem. All isolates with the exception of 1-2 isolates were resistant to ampicillin, cefazolin and ampicillin-sulbactam which was compatible with the presence of the blaOXA genes. Variable resistance rates were observed to cefuroxime, cefoxitin, ceftriaxone, piperacillin-tazobactam that were not correlated with the presence of other ß-lactamase genes. Resistance to tetracycline and trimethoprim-sulfamethoxazole correlated with the presence of tetA and sul1, respectively. The population structure of A. caviae was highly diverse with the minority of the isolates (16/57) clustering into six defined sequence types. A cgMLST-based distance of four genes was found in one pair of isolates, suggesting common source transmission. CONCLUSIONS: A. caviae is the dominant species related to gastroenteritis and is characterized by a diverse population structure, with almost no evidence for common-source transmission. Resistance rates to most antimicrobial agents were low and partially matched with the presence of resistance genes.

The effect of the transition to molecular diagnosis on the epidemiology and the clinical characteristics of bacterial gastroenteritis in Northern Israel.

BACKGROUND: The transition to PCR-based diagnosis of bacterial gastroenteritis (BGE) can increase the sensitivity but might reduce the clinical specificity. The aims of this study were (1) to compare the effect of the change from culture to PCR-based diagnostics on the reported incidence and positivity rates of BGE due to Salmonella, Shigella and Campylobacter species and (2) to compare the demographics, medical background, clinical characteristics and pre-analytic variables between cases with PCR-positive, culture-negative samples to cases with PCR-positive, culture-positive samples. METHODS: The study was performed at the Emek Medical Centre that serves a population of 0.5 million people in Northern Israel. The study included two parts: (1) a retrospective cohort study, comparing the incidence and positivity rates of laboratory-diagnosed BGE from January 2016 until December 22nd, 2019 when culture was the sole method to January 2020 until April 2023 when PCR was used; (2) a prospective cohort study, conducted between November 2020 until April 2023 that compared the demographics and clinical characteristics of BGE cases that were diagnosed by PCR alone versus cases that were diagnosed by both PCR and culture. RESULTS: The incidence rate between-periods comparability ratio was only 113% since the incidence rate did not increase during 2020, the first year of the COVID-19 pandemic. The sample positivity rate increased since 2020, with between-periods comparability ratio of 159%. In the second period, the sample positivity rates of culture vs. PCR alone differed between the pathogens and were 90.2%, 63.8% and 54.2% for Salmonella, Campylobacter and Shigella species, respectively (p < 0.001). The following variables were identified as independent predictors of culture positivity: (1) Salmonella infection (O.R. = 10.6, 95% C.I. 3.6-31.1, p < 0.001); (2) Shigella infection (O.R. = 0.46, 95% C.I.0.23-0.93, p = 0.032); (3) time from sample submission to culture (O.R.=0.73, 95% C.I. 0.58-0.92, p = 0.008); (4) the presence of abdominal pain (O.R. = 1.98, 95% C.I. 1.04-3.79, p = 0.038) and the PCR mean Ct value (O.R. = 0.89, 95% C.I.0.85-0.94, p < 0.001). CONCLUSIONS: The use of PCR had led to improved sensitivity, without noticeable decrease in the clinical specificity. This was especially important in the case of the more fastidious organisms.

Early effectiveness of BNT162b2 Covid-19 vaccine in preventing SARS-CoV-2 infection in healthcare personnel in six Israeli hospitals (CoVEHPI).

BACKGROUND: Methodologically rigorous studies on Covid-19 vaccine effectiveness (VE) in preventing SARS-CoV-2 infection are critically needed to inform national and global policy on Covid-19 vaccine use. In Israel, healthcare personnel (HCP) were initially prioritized for Covid-19 vaccination, creating an ideal setting to evaluate early real-world VE in a closely monitored population. METHODS: We conducted a prospective study among HCP in 6 hospitals to estimate the effectiveness of the BNT162b2 mRNA Covid-19 vaccine in preventing SARS-CoV-2 infection. Participants filled out weekly symptom questionnaires, provided weekly nasal specimens, and three serology samples - at enrollment, 30 days and 90 days. We estimated VE against PCR-confirmed SARS-CoV-2 infection using the Cox Proportional Hazards model and against a combined PCR/serology endpoint using Fisher's exact test. RESULTS: Of the 1567 HCP enrolled between December 27, 2020 and February 15, 2021, 1250 previously uninfected participants were included in the primary analysis; 998 (79.8%) were vaccinated with their first dose prior to or at enrollment, all with Pfizer BNT162b2 mRNA vaccine. There were four PCR-positive events among vaccinated participants, and nine among unvaccinated participants. Adjusted two-dose VE against any PCR-confirmed infection was 94.5% (95% CI: 82.6%-98.2%); adjusted two-dose VE against a combined endpoint of PCR and seroconversion for a 60-day follow-up period was 94.5% (95% CI: 63.0%-99.0%). Five PCR-positive samples from study participants were sequenced; all were alpha variant. CONCLUSIONS: Our prospective VE study of HCP in Israel with rigorous weekly surveillance found very high VE for two doses of Pfizer BNT162b2 mRNA vaccine against SARS-CoV-2 infection in recently vaccinated HCP during a period of predominant alpha variant circulation. FUNDING: Clalit Health Services.

Evidence for increased breakthrough rates of SARS-CoV-2 variants of concern in BNT162b2-mRNA-vaccinated individuals.

The BNT162b2 mRNA vaccine is highly effective against SARS-CoV-2. However, apprehension exists that variants of concern (VOCs) may evade vaccine protection, due to evidence of reduced neutralization of the VOCs B.1.1.7 and B.1.351 by vaccine sera in laboratory assays. We performed a matched cohort study to examine the distribution of VOCs in infections of BNT162b2 mRNA vaccinees from Clalit Health Services (Israel) using viral genomic sequencing, and hypothesized that if vaccine effectiveness against a VOC is reduced, its proportion among breakthrough cases would be higher than in unvaccinated controls. Analyzing 813 viral genome sequences from nasopharyngeal swabs, we showed that vaccinees who tested positive at least 7 days after the second dose were disproportionally infected with B.1.351, compared with controls. Those who tested positive between 2 weeks after the first dose and 6 days after the second dose were disproportionally infected by B.1.1.7. These findings suggest reduced vaccine effectiveness against both VOCs within particular time windows. Our results emphasize the importance of rigorously tracking viral variants, and of increasing vaccination to prevent the spread of VOCs.

Evaluation of Bio-Rad® discs for antimicrobial susceptibility testing by disc diffusion and the ADAGIO™ system for the automatic reading and interpretation of results.

The disc diffusion test is used for antimicrobial susceptibility testing worldwide. In this study, the performance of both Bio-Rad® antibiotic discs (as compared with Oxoid® discs) and the ADAGIO™ automated system for the reading of disc diffusion test results was evaluated with American Type Culture Collection (ATCC) quality control (QC) and wild strains of bacteria. Inhibition zones of both disc brands were read manually and through use of the ADAGIO™ system. Categorized interpretation of the results for each strain and antibiotic combination was summarized according to the Clinical Laboratory Standards Institute MS-100 (2017 update) manual and ADAGIO™ readings. Eight ATCC QC strains and 120 different wild strains were evaluated, to give a total of 1226 antibiotic/bacteria combinations and 2486 manual readings. One major error and four minor errors (0.08% and 0.34%, respectively) were detected via manual readings of the Bio-Rad® discs as compared with the Oxoid® discs. For the same number of antibiotic/bacteria combinations, five minor errors and one major error (0.42% and 0.08%, respectively) were detected with the Bio-Rad® discs read by the ADAGIO™ system. In addition, the number of times the automatic reading needed manual edition with Bio-Rad® discs was statistically lower than it did with Oxoid® discs (3.7% vs. 5.7%, p < 0.05). These findings support the hypothesis that Bio-Rad discs are not inferior to Oxoid® discs, and the performance of the ADAGIO™ system is comparable to that of manual readings with both disc brands.

Detection of Ureaplasma Species by a Semi-Quantitative PCR Test in Urine Samples: Can It Predict Clinical Significance?

BACKGROUND: Ureaplasma species (Usp) are the most prevalent genital Mycoplasma isolated from the urogenital tract of both men and women. Usp may be commensals in the genital tract but may also be contributors to a number of pathological conditions of the genital tract. Because they can also just colonize the genital tract of healthy people, their pathogenic role can be difficult to prove. OBJECTIVES: The aim of the study was to evaluate the efficacy of a quantitative polymerase chain reaction (qPCR) method for the discrimination between infection and colonization by measuring prevalence of Usp in asymptomatic versus symptomatic patients. METHODS: Urine samples were tested for U. parvum and U. urealyticum using a semi-quantitative multiplex PCR technique for sexually transmitted diseases (Anyplex™ STI-7 Detection Kit, Seegene, South Korea). A total of 250 symptomatic and 250 asymptomatic controls were included. RESULTS: A strong positive result for U. parvum was significantly more prevalent in symptomatic compared to asymptomatic patients. This finding was observed especially in women and in the young group (15-35 years of age). No significant differences were observed between the prevalence in symptomatic and asymptomatic patients of U. parvum with low strength of positivity and for U. urealyticum in all groups by age, gender, and strength of positivity. CONCLUSIONS: The significant difference between the symptomatic and asymptomatic group in the highest positivity group for U. parvum using the Anyplex™ STI-7 detection kit in urine may indicate a high probability of infection rather than colonization, especially in women and young patients.