Dataset Information

Phenotypic and genotypic characterization of biofilm forming capabilities in non-O157 Shiga toxin-producing Escherichia coli strains.

ABSTRACT: The biofilm life style helps bacteria resist oxidative stress, desiccation, antibiotic treatment, and starvation. Biofilm formation involves a complex regulatory gene network controlled by various environmental signals. It was previously shown that prophage insertions in mlrA and heterogeneous mutations in rpoS constituted major obstacles limiting biofilm formation and the expression of extracellular curli fibers in strains of Escherichia coli serotype O157:H7. The purpose of this study was to test strains from other important serotypes of Shiga toxin-producing E. coli (STEC) (O26, O45, O103, O111, O113, O121, and O145) for similar regulatory restrictions. In a small but diverse collection of biofilm-forming and non-forming strains, mlrA prophage insertions were identified in only 4 of the 19 strains (serotypes O103, O113, and O145). Only the STEC O103 and O113 strains could be complemented by a trans-copy of mlrA to restore curli production and Congo red (CR) dye affinity. RpoS mutations were found in 5 strains (4 serotypes), each with low CR affinity, and the defects were moderately restored by a wild-type copy of rpoS in 2 of the 3 strains attempted. Fourteen strains in this study showed no or weak biofilm formation, of which 9 could be explained by prophage insertions or rpoS mutations. However, each of the remaining five biofilm-deficient strains, as well as the two O145 strains that could not be complemented by mlrA, showed complete or nearly complete lack of motility. This study indicates that mlrA prophage insertions and rpoS mutations do limit biofilm and curli expression in the non-serotype O157:H7 STEC but prophage insertions may not be as common as in serotype O157:H7 strains. The results also suggest that lack of motility provides a third major factor limiting biofilm formation in the non-O157:H7 STEC. Understanding biofilm regulatory mechanisms will prove beneficial in reducing pathogen survival and enhancing food safety.

SUBMITTER: Chen CY

PROVIDER: S-EPMC3874044 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Phenotypic and genotypic characterization of biofilm forming capabilities in non-O157 Shiga toxin-producing Escherichia coli strains.

Chen Chin-Yi CY Hofmann Christopher S CS Cottrell Bryan J BJ Strobaugh Terence P TP Paoli George C GC Nguyen Ly-Huong LH Yan Xianghe X Uhlich Gaylen A GA

PloS one 20131227 12

The biofilm life style helps bacteria resist oxidative stress, desiccation, antibiotic treatment, and starvation. Biofilm formation involves a complex regulatory gene network controlled by various environmental signals. It was previously shown that prophage insertions in mlrA and heterogeneous mutations in rpoS constituted major obstacles limiting biofilm formation and the expression of extracellular curli fibers in strains of Escherichia coli serotype O157:H7. The purpose of this study was to t ...[more]

PMID: 24386426

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Project description:Shiga toxin-producing Escherichia coli (STEC) are zoonotic enteric pathogens associated with human gastroenteritis worldwide. Cattle and small ruminants are important animal reservoirs of STEC. The present study investigated animal reservoirs for STEC in small rural farms in the Culiacan Valley, an important agricultural region located in Northwest Mexico. A total of 240 fecal samples from domestic animals were collected from five sampling sites in the Culiacan Valley and were subjected to an enrichment protocol followed by either direct plating or immunomagnetic separation before plating on selective media. Serotype O157:H7 isolates with the virulence genes stx2, eae, and ehxA were identified in 40% (26/65) of the recovered isolates from cattle, sheep and chicken feces. Pulse-field gel electrophoresis (PFGE) analysis grouped most O157:H7 isolates into two clusters with 98.6% homology. The use of multiple-locus variable-number tandem repeat analysis (MLVA) differentiated isolates that were indistinguishable by PFGE. Analysis of the allelic diversity of MLVA loci suggested that the O157:H7 isolates from this region were highly related. In contrast to O157:H7 isolates, a greater genotypic diversity was observed in the non-O157 isolates, resulting in 23 PFGE types and 14 MLVA types. The relevant non-O157 serotypes O8:H19, O75:H8, O111:H8 and O146:H21 represented 35.4% (23/65) of the recovered isolates. In particular, 18.5% (12/65) of all the isolates were serotype O75:H8, which was the most variable serotype by both PFGE and MLVA. The non-O157 isolates were predominantly recovered from sheep and were identified to harbor either one or two stx genes. Most non-O157 isolates were ehxA-positive (86.5%, 32/37) but only 10.8% (4/37) harbored eae. These findings indicate that zoonotic STEC with genotypes associated with human illness are present in animals on small farms within rural communities in the Culiacan Valley and emphasize the need for the development of control measures to decrease risks associated with zoonotic STEC.

Project description:Shiga toxin-producing Escherichia coli (STEC) causes diarrhea and hemorrhagic colitis with life-threatening complications, such as hemolytic uremic syndrome. The aim of this study was to assess the molecular epidemiologic features of non-O157 STEC strains from different resources in China and illustrate the role of animal reservoirs or animal-derived foodstuffs in human STEC infections. A collection of 301 non-O157 STEC isolates from domestic and wild animals (i.e., cattle, goat, pig, yak, pika, and antelope), raw meats (i.e., beef, pork, mutton, chicken, and duck), diarrheal patients, and healthy carriers in different regions of China were selected in this study. Of the 301 analyzed STEC isolates, 67 serogroups, and 118 serotypes were identified; this included some predominant serogroups associated with human disease, such as O26, O45, O103, O111, and O121. Eighteen different combinations of stx subtypes were found. Eleven isolates carried the intimin gene eae, 93 isolates contained ehxA, and 73 isolates carried astA. The prevalence of other putative adhesion genes saa, paa, efa1, and toxB was 28.90% (87), 6.98% (21), 2.31% (7), and 1% (3), respectively. The phylogenetic distribution of isolates was analyzed by multilocus sequence typing (MLST). Ninety-four sequence types were assigned across the 301 isolates. A subset of isolates recovered from yak and pika residing in the similar wild environments, Qinghai-Tibetan plateau, showed similar genetic profiles and more tendencies to cluster together. Isolates from goat and mutton exhibited close genetic relatedness with those from human-derived isolates, providing evidence that transmission may have occurred locally within intraspecies or interspecies, and importantly, from animal reservoirs, or raw meats to humans. Comparing isolates in this study with highly virulent strains by MLST, along with serotyping and virulence profiles, it is conceivable that some of isolates from goat, yak, or raw meats may have potential to cause human diseases.

Dataset Information

Phenotypic and genotypic characterization of biofilm forming capabilities in non-O157 Shiga toxin-producing Escherichia coli strains.

Publications

Phenotypic and genotypic characterization of biofilm forming capabilities in non-O157 Shiga toxin-producing Escherichia coli strains.

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