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A molecular study on the prevalence and virulence potential of Aeromonas spp. recovered from patients suffering from diarrhea in Israel.

ABSTRACT: BACKGROUND: Species of the genus Aeromonas are native inhabitants of aquatic environments and have recently been considered emerging human pathogens. Although the gastrointestinal tract is by far the most common anatomic site from which aeromonads are recovered, their role as etiologic agents of bacterial diarrhea is still disputed. Aeromonas-associated diarrhea is a phenomenon occurring worldwide; however, the exact prevalence of Aeromonas infections on a global scale is unknown. METHODOLOGY/PRINCIPAL FINDINGS: The prevalence and virulence potential of Aeromonas in patients suffering from diarrhea in Israel was studied using molecular methods. 1,033 diarrheal stools were sampled between April and September 2010 and Aeromonas species were identified in 17 (?2%) patients by sequencing the rpoD gene. Aeromonas species identity and abundance was: A. caviae (65%), A. veronii (29%) and Aeromonas taiwanensis (6%). This is the first clinical record of A. taiwanensis as a diarrheal causative since its recent discovery from a wound infection in a patient in Taiwan. Most of the patients (77%) from which Aeromonas species were isolated were negative for any other pathogens. The patients ranged from 1 to 92 years in age. Aeromonas isolates were found to possess different virulence-associated genes: ahpB (88%), pla/lip/lipH3/apl-1 (71%), act/hlyA/aerA (35%), alt (18%), ast (6%), fla (65%), lafA (41%), TTSS ascV (12%), TTSS ascF-ascG (12%), TTSS-dependent ADP-ribosylating toxins aexU (41%) and aexT (6%) in various combinations. Most of the identified strains were resistant to beta-lactam antibiotics but susceptible to third-generation cephalosporin antibiotics. CONCLUSIONS: Aeromonas may be a causative agent of diarrhea in patients in Israel and therefore should be included in routine bacteriological screenings.

SUBMITTER: Senderovich Y

PROVIDER: S-EPMC3280246 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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A molecular study on the prevalence and virulence potential of Aeromonas spp. recovered from patients suffering from diarrhea in Israel.

Senderovich Yigal Y Ken-Dror Shifra S Vainblat Irina I Blau Dvora D Izhaki Ido I Halpern Malka M

PloS one 20120215 2

<h4>Background</h4>Species of the genus Aeromonas are native inhabitants of aquatic environments and have recently been considered emerging human pathogens. Although the gastrointestinal tract is by far the most common anatomic site from which aeromonads are recovered, their role as etiologic agents of bacterial diarrhea is still disputed. Aeromonas-associated diarrhea is a phenomenon occurring worldwide; however, the exact prevalence of Aeromonas infections on a global scale is unknown.<h4>Meth ...[more]

PMID: 22355306

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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:Aeromonas spp. are ubiquitous bacteria that have received increasing attention as human pathogens because of their widespread occurrence in food, especially seafood and vegetables. The aim of this work was to assess the species identity and phylogenetic relationship of 118 Aeromonas strains isolated from fresh retail sushi from three producers, and to characterize the isolates with respect to genetic and phenotypic virulence factors. We also evaluate the potential hazard associated with their presence in ready-to-eat seafood not subjected to heat treatment. Mesophilic Aeromonas salmonicida was most prevalent (74%), followed by A. bestiarum (9%), A. dhakensis (5%), A. caviae (5%), A. media (4%), A. hydrophila (2%), and A. piscicola (1%). All isolates were considered potentially pathogenic due to the high prevalence of genes encoding hemolysin (hlyA) (99%), aerolysin (aerA) (98%), cytotoxic enterotoxin (act) (86%), heat-labile cytotonic enterotoxin (alt) (99%), and heat-stable cytotonic enterotoxin (ast) (31%). The shiga-like toxins 1 and 2 (stx-1 and stx-2) were not detected. Moreover, there was heterogeneity in toxin gene distribution among the isolates, and the combination of act/alt/hlyA/aerA was most commonly detected (63%). β-hemolysis was species-dependent and observed in 91% of the isolates. All A. media and A. caviae strains were non-hemolytic. For isolates belonging to this group, lack of hemolysis was possibly related to the absence of the act gene. Swimming motility, linked to adhesion and host invasion, occurred in 65% of the isolates. Partial sequencing of the gyrB gene demonstrated its suitability as a genetic marker for Aeromonas species identification and for assessment of the phylogenetic relationship between the isolates. The gyrB sequence divergence within a given species ranged from 1.3 to 2.9%. A. bestiarum, A. salmonicida, and A. piscicola were the most closely related species; their sequences differed by 2.7-3.4%. The average gyrB sequence similarity between all species was 93%, demonstrating its acceptable taxonomic resolution. The presence of multiple species of potential pathogenic Aeromonas in fresh retail sushi raises new food safety issues related to the increased consumption of ready-to-eat food composed of raw ingredients.

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A molecular study on the prevalence and virulence potential of Aeromonas spp. recovered from patients suffering from diarrhea in Israel.

Publications

A molecular study on the prevalence and virulence potential of Aeromonas spp. recovered from patients suffering from diarrhea in Israel.

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