Antibiotic Susceptibility Pattern of Shigella spp. Isolated from Patients Suspected of Acute Gastroenteritis

Shigellosis, an intestinal infection caused by Shigella species, is manifested by bloody diarrhea. Due to the surge in multidrug-resistant (MDR) Shigella species, the control of shigellosis has been a big challenge. This study aims to determine the prevalence and assess the antibiotic susceptibility pattern of Shigella species. During our study period of five months from April 2014 to August 2014 at Sukraraj Tropical and Infectious Disease Hospital, Teku, Kathmandu, a total of 653 stool samples were collected from the patients suspected of acute gastroenteritis. The standard microbiological procedure was followed for the isolation and identification of Shigella species. Assessment of antibiotic susceptibility pattern of the Shigella species was done by Kirby-Bauer disk diffusion method following CLSI guidelines. The study found 25(3.82%) cases were Shigella positive. Among them, 18(72%) were S. flexneri, 6(24%) were S. dysenteriae, and 1(4%) was S. sonnei. The patients in the age group 16-45 years were highly susceptible to infection as the higher proportion 16(64%) of Shigella species were isolated from this age group (p> 0.05). Shigella species were found to be highly susceptible to Cefotaxime (100%), a third-generation cephalosporin. Nalidixic acid, on the other hand, was the least effective antibiotic as 20(80%) of the Shigella isolates were resistant, followed by Ampicillin 18(72%), Cotrimoxazole 13(52%), and Ciprofloxacin 9(36%). A higher proportion of [10(40%)] of our study isolates were MDR. Our results show that Nalidixic acid, Ampicillin, Cotrimoxazole, Ciprofloxacin, and Ofloxacin cannot be used as empirical therapy for the treatment of Shigella infection as Shigella species were highly resistant to these antibiotics. So, for the MDR Shigella infection, we suggest third-generation cephalosporin as an option.

Epidemiological fectors and antibiotic susceptibility pattern of Salmonella spp

serovars Typhi and Paratyphi are known to cause enteric fever. Multidrug resistance in and has emerged as a cause of concern. To evaluate antimicrobial susceptibility patterns of Salmonella enteric serovar Typhi () and obtained from blood culture.: All isolates obtained from blood cultures of clinically suspected cases of enteric fever coming to microbiology laboratory, Nirmal hospital, from January 2015 to September 2017 were included in the study. Antimicrobial susceptibility patterns were determined using commercial antimicrobial disks chloramphenicol (30 μg), nalidixic acid (30 μg), ampicillin (10 μg), azithromycin (15 μg), cotrimoxazole (1.25/23.75 μg), ciprofloxacin (5 μg), and ceftriaxone (30 μg). Antimicrobial susceptibility testing was performed in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines of respective year by KirbyBauer disc diffusion method.: Total 330 isolates of salmonella are there out of that 298 is . 32 are Salmonella para A, while 1 is of Salmonella para B. Enteric fever cases pick month are April, May, June and July. Sensitivity to first line drugs are > 80%, Nalidixic acid resistant Salmonella (NARS) are 79%, while Multi drug resistant (resistant to ampicillin, chloramphenicol and co-trimoxazole all three)Salmonella are 3%.: Periodic evaluation of antibiotic susceptibility pattern is necessary to see changing pattern of antibiotics. Evaluation of Nalidixic acid resistant Salmonella and periodic evaluation of multi drug resistant Salmonella is also important as emergence of MDR strain is observed in our study.

Genomic Characterization of a Nalidixic Acid-Resistant Salmonella Enteritidis Strain Causing Persistent Infections in Broiler Chickens

Virulent strains of Salmonella enterica subsp. enterica serovar Enteritidis (SE) harbored by poultry can cause disease in poultry flocks and potentially result in human foodborne illness. Two broiler flocks grown a year apart on the same premises experienced mortality throughout the growing period due to septicemic disease caused by SE. Gross lesions predominantly consisted of polyserositis followed by yolk sacculitis, arthritis, osteomyelitis, and spondylitis. Tissues with lesions were cultured yielding 59 SE isolates. These were genotyped by Rep-PCR followed by whole-genome sequencing (WGS) of 15 isolates which were clonal. The strain, SE_TAU19, was further characterized for antimicrobial susceptibility and virulence in a broiler embryo lethality assay. SE_TAU19 was resistant to nalidixic acid and sulfadimethoxine and was virulent to embryos with 100% mortality of all challenged broiler embryos within 3.5 days. Screening the SE_TAU19 whole-genome sequence revealed seven antimicrobial resistance (AMR) genes, 120 virulence genes, and two IncF plasmid replicons corresponding to a single, serovar-specific pSEV virulence plasmid. The pef, spv, and rck virulence genes localized to the plasmid sequence assembly. We report phenotypic and genomic features of a virulent SE strain from persistently infected broiler flocks and present a workflow for SE characterization from isolate collection to genome assembly and sequence analysis. Further SE surveillance and investigation of SE virulence in broiler chickens is warranted.

Prevalence and antimicrobial resistance phenotypes of Salmonella species recovered at various stages of broiler operations in Hathazari, Bangladesh

Background and Aim: Dissemination of multidrug-resistant (MDR) Salmonella through food chains has serious health implications, with higher rates of morbidity and mortality. Broiler meat remains a major reservoir of Salmonella contamination. The lack of proper hygiene in local broiler operations has, therefore, prompted this research into the assessment of Salmonella contamination in local shops and associated antimicrobial resistance (AMR) phenotypes. Materials and Methods: A total of 55 broiler samples including skin, meat, and swab samples from chopping and dressing sites were included in the study. The samples were collected from broiler shops in Hathazari, Bangladesh, and screened for the presence of Salmonella strains using culture-based methods. The isolates were biochemically characterized and further tested for AMR to eight common antibiotics using the disk diffusion technique. Results: Salmonella contaminations were identified in 29% (16/55) of the broiler samples. Swab samples collected from the chopping sites appeared to be contaminated in higher proportions (33%) than those collected from the dressing areas (25%). On the other hand, the skin samples (50%) were detected with a higher percentage of contamination than the meat samples (25%). All Salmonella isolates showed resistance toward at least one of the eight antibiotics used. Although none of the isolates was resistant to all antibiotics, 18.75% showed resistance to a maximum of seven antibiotics. Resistance to nalidixic acid was most prevalent (87.5%), followed by sulfamethoxazole-trimethoprim (81.25%), erythromycin (81.25%), tetracycline (75%), streptomycin (56.25%), ampicillin-clavulanic acid (50%), chloramphenicol (43.75%), and cefotaxime (18.75%). The resistance patterns of the isolates were found to be highly diverse. The most frequently observed pattern was the following: Ampicillin-clavulanic acid-sulfamethoxazole-trimethoprim-nalidixic acid-tetracycline-chloramphenicol-streptomycin-erythromycin. Conclusion: The relatively high prevalence of MDR strains in the samples underlies an urgent need for surveillance and control measures concerning hygiene and antibiotic use in local broiler operations.

Validation of Pefloxacin for detection of fluoroquinolone (FQ) resistance among Salmonella Typhi with special reference to GyrB mutations

Introduction. Fluoroquinolone (FQ) resistant Salmonella are classified as high priority pathogens by WHO. FQ resistance among Salmonella Typhi has emerged rapidly and is predominantly mediated by mutations in the topoisomerase genes gyrA, and parC. Mutations in GyrA result in classical FQ resistance (DCS-NAR) i.e. decreased susceptibility to ciprofloxacin (MIC of 0.12 to 0.5 µg ml−1) (DCS) and resistance to nalidixic acid (NAR). Previously a nalidixic acid disc test was proposed for detection of DCS. Recently isolates with non-classical FQ resistance caused by plasmid-mediated quinolone resistance (PMQR) and mutations in GyrB have emerged. These mechanisms also result in DCS but are nalidixic acid susceptible (NAS) and thus pose diagnostic challenges. CLSI and EUCAST have recommended use of 5 µg pefloxacin discs for detection of DCS in Salmonella . Hypothesis. The CLSI and EUCAST recommendations for use of 5 µg pefloxacin for detection of DCS has not been validated on typhoidal Salmonella and resistance mediated by GyrB mutation in Salmonella species. Aim. The aim of the present study was to validate the performance of the 5 µg pefloxacin discs to detect isolates of S. Typhi with DCS with special reference to GyrB mutations. Methodology. A total of 180 clinical isolates of Salmonella Typhi (2005–2014) were investigated for genetic mechanisms of resistance. Zone diameters for nalidixic acid (30μg), ciprofloxacin (5μg) and pefloxacin (5µg) and minimum inhibitory concentration (MIC) for ciprofloxacin were determined using CLSI guidelines. Performance of the three discs was evaluated to detect FQ resistance in S. Typhi. Results. Topoisomerase mutations in GyrB +/ ParC and GyrB were detected in 112 and 34 isolates respectively. Different mutations have a varied effect on the MIC for ciprofloxacin. The current breakpoints for susceptible (≤0.06 µg ml−1) and non-susceptible (≥0.125 µg ml−1), failed to detect all isolates with a resistance mechanism. Performance of both ciprofloxacin and pefloxacin discs were excellent compared to nalidixic acid in differentiating isolates with non-classical resistance mediated by GyrB from wild-type. Conclusion. The pefloxacin disc can be used to detect FQ resistance among S. Typhi. This is the first report of validation of pefloxacin for detection of FQ resistance in S. Typhi mediated by GyrB mutation.