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Profiling of Virulence-associated Factors in Shigella Species Isolated from Acute Pediatric Diarrheal Samples in Tehran, Iran.

ABSTRACT: The genus Shigella comprises the most infectious and diarrheagenic bacteria causing severe diseases, mostly in children under five years of age. This study aimed to detect nine virulence genes (ipaBCD, VirA, sen, set1A, set1B, ial, ipaH, stx, and sat) in Shigella species (spp.) using multiplex polymerase chain reaction (MPCR) and to determine the relation of Shigella spp. from pediatric diarrheal samples with hospitalization and bloody diarrhea in Tehran, Iran.Shigella spp. were isolated and identified using standard microbiological and serological methods. The virulence genes were detected using MPCR.Seventy-five Shigella spp. (40 S. sonnei, 33 S. flexneri, 1 S. dysenteriae, and 1 S. boydii) were isolated in this study. The prevalence of ial, sen, sat, set1A, and set1B was 74.7%, 45.4%, 28%, 24%, and 24%, respectively. All S. flexneri isolates, while no S. sonnei, S. dysenteriae, or S. boydii isolates, contained sat, set1A, and set1B. All isolates were positive for ipaH, ipaBCD, and virA, while one (1.4%) of the isolates contained stx. The highest prevalence of virulence determinants was found in S. flexneri serotype IIa. Nineteen (57.6%) of 33 S. flexneri isolates were positive for ipaBCD, ipaH, virA, ial, and sat. The sen determinants were found to be statistically significantly associated with hospitalization and bloody diarrhea (p = 0.001).This study revealed a high prevalence of enterotoxin genes in S. flexneri, especially in serotype 2a, and has presented relations between a few clinical features of shigellosis and numerous virulence determinants of clinical isolates of Shigella spp.

SUBMITTER: Yaghoubi S

PROVIDER: S-EPMC5525559 | biostudies-other | 2017 Jun

REPOSITORIES: biostudies-other

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Project description:Aeromonas spp. are emerging human pathogens causing intestinal and extra-intestinal infections. Since their relevance in Western Europe as gastrointestinal pathogens is not well established, we investigated Aeromonas spp. prevalence in diarrheal fecal samples in an Italian University Hospital and characterized the virulence mechanisms of the isolates. Aeromonas spp. isolated from diarrheic stools using standard culture methods were identified by molecular techniques. Antimicrobial resistance was assessed by the micro broth dilution. Toxins, flagella, and type III secretion system genes were evaluated by polymerase chain reaction. Biofilm was quantified by crystal-violet staining. Interaction with human intestinal epithelial cells (Caco-2) was assessed by quantifying adhesion, interleukin (IL)-8 secretion, and epithelial barrier integrity. Aeromonas spp. represented 20.6% of bacterial pathogens isolated from diarrheic feces, the second most common enteropathogen. A. cavieae constituted 75% of the identified species, showing a relatively low clustering value. About 52% of Aeromonas isolates showed resistance to amikacin, whereas only 7.5% showed multiple drug resistance. Four or more virulence genes were identified in 66.7% of A. cavieae isolates and 100% of A. dakensis. Aeromonas isolates (82.5%) showed moderate or important biofilm-producing ability. Adhesion to Caco-2 cells correlated to fla+ gene, whereas ascV+ and aexU+ strains significantly induced IL-8 release from Caco-2. Aeromonas aer+ strains caused ZO1 and occluding redistribution and a significative reduction in trans-epithelial resistance. Aeromonas spp. emerge as relevant human intestinal pathogens with a disparate arsenal of pathogenicity factors causing diarrhea through different mechanisms. IMPORTANCE In this work, we demonstrate the epidemiologic relevance of the Aeromonas genus as the cause of infective diarrhea in North East Italy, both in children and adult subjects, with the significative presence of highly pathogenic strains. Aeromonas strains possess a heterogeneous armamentarium of pathogenicity factors that allows the microbe to affect a wide range of human intestinal epithelial cell processes that justify the ability to induce diarrhea through different mechanisms and cause diseases of variable severity, as observed for other gastrointestinal pathogens. However, it remains to be determined whether specific genotype(s) are associated with clinical pictures of different severity to implement the diagnostic and therapeutic approaches for this relevant enteric pathogen.

Project description:BackgroundShigella spp. are major cause of diarrhoeal disease in both developing and developed countries. Shigella sonnei is the serogroup of Shigella most frequently responsible for sporadic and epidemic enteritis in developed countries. In recent years the emergence and spread of S. sonnei biotype g carrying class 2 integron have been frequently reported in many countries. Recently, S. sonnei has been reported as the prevalent serogroup of Shigella in Iran. The present study was carried out to investigate phenotypic and genetic characteristics of Shigella sonnei isolates identified in the years 2002 and 2003 in Tehran, Iran.MethodsBiotyping, drug susceptibility testing, pulsed field gel electrophoresis (PFGE) and analysis of class 2 integrons have been carried out on 60 S. sonnei isolates, including 57 sporadic isolates from paediatric cases of shigellosis occurring in 2002 and 2003, two sporadic isolates recovered in 1984 and the ATCC 9290 strain.ResultsBiotype g and resistance to streptomycin, sulfamethoxazole-trimethoprim and tetracycline were exhibited by 54 of the 57 recent isolates. Of the 54 biotype g isolates, 28 exhibited a class 2 integron of 2161 bp, and 24 a class 2 integron of 1371 bp, respectively. Class 2 integrons were not detected in four isolates only, including the two endemic isolates recovered in 1984 and two strains from recent sporadic cases. PFGE divided the strains into eight pulsotypes labeled A to H, three major pulsotypes - A to C - including the large majority of the recent sporadic S. sonnei isolates. Pulsotypes A and C were the most prevalent groups, accounting for 41.6% and 35.0%, respectively, of the isolates under study.ConclusionThe results suggest that biotype g, class 2 integron carrying S. sonnei are prevalent in our geographic area. S. sonnei isolated in the years 2002 and 2003 could be attributed to a few predominant clusters including, respectively, strains with pulsotypes B and C carrying a 2161 bp class 2 integron, and those having pulsotype A and a 1371 bp class 2 integron. A few epidemic clones are responsible for the apparently endemic occurrence of shigellosis in Tehran, Iran.

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Profiling of Virulence-associated Factors in Shigella Species Isolated from Acute Pediatric Diarrheal Samples in Tehran, Iran.

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