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Detection and characterization of the hemolysin genes in Aeromonas hydrophila and Aeromonas sobria by multiplex PCR.

ABSTRACT: A multiplex PCR assay was designed to amplify the Aeromonas hydrophila and A. veronii bv. sobria hemolysin and aerolysin genes. The assay was evaluated by using 121 clinical isolates and 7 reference strains of Aeromonas spp., and these were divided into five genotypes on the basis of the results of the multiplex PCR. The five genotypes were characterized as type 1 for those carrying the ahh1 gene only (36% of isolates), type 2 for those carrying the asa1 gene only (8.5% of isolates), type 3 for those carrying both the ahh1 and the asa1 genes (4% of isolates), type 4 for those carrying the ahh1 gene and the A. hydrophila aerA (aerolysin) gene (37.5% of isolates), and type 5 for those in which no hemolysin genes were detected (14% of isolates). The most common single hemolysin gene carried among all the Aeromonas isolates examined was ahh1, with 99 of 128 (77%) of isolates testing positive for this gene either alone or in combination with other hemolysin genes. Phenotypic expression of toxins was evaluated in a Vero cell culture cytotoxicity assay. These results indicated that there is a statistically significant correlation between the cytotoxin titers and the hemolysin genotype. Isolates belonging to genotype 4 (carrying both the ahh1 gene and the aerolysin and hemolysin aerA genes) expressed higher cytotoxin titers than isolates of the other genotypes (P < 0.001). These isolates were more cytotoxic in cell culture and may have greater clinical significance.

SUBMITTER: Wang G

PROVIDER: S-EPMC150266 | biostudies-literature | 2003 Mar

REPOSITORIES: biostudies-literature

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Detection and characterization of the hemolysin genes in Aeromonas hydrophila and Aeromonas sobria by multiplex PCR.

Wang Gehua G Clark Clifford G CG Liu Chenyi C Pucknell Chad C Munro Cindy K CK Kruk Tamara M A C TM Caldeira Richard R Woodward David L DL Rodgers Frank G FG

Journal of clinical microbiology 20030301 3

A multiplex PCR assay was designed to amplify the Aeromonas hydrophila and A. veronii bv. sobria hemolysin and aerolysin genes. The assay was evaluated by using 121 clinical isolates and 7 reference strains of Aeromonas spp., and these were divided into five genotypes on the basis of the results of the multiplex PCR. The five genotypes were characterized as type 1 for those carrying the ahh1 gene only (36% of isolates), type 2 for those carrying the asa1 gene only (8.5% of isolates), type 3 for ...[more]

PMID: 12624028

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Project description:UNLABELLED:Aeromonas hydrophila has increasingly been implicated as a virulent and antibiotic-resistant etiologic agent in various human diseases. In a previously published case report, we described a subject with a polymicrobial wound infection that included a persistent and aggressive strain of A. hydrophila (E1), as well as a more antibiotic-resistant strain of A. hydrophila (E2). To better understand the differences between pathogenic and environmental strains of A. hydrophila, we conducted comparative genomic and functional analyses of virulence-associated genes of these two wound isolates (E1 and E2), the environmental type strain A. hydrophila ATCC 7966(T), and four other isolates belonging to A. aquariorum, A. veronii, A. salmonicida, and A. caviae. Full-genome sequencing of strains E1 and E2 revealed extensive differences between the two and strain ATCC 7966(T). The more persistent wound infection strain, E1, harbored coding sequences for a cytotoxic enterotoxin (Act), a type 3 secretion system (T3SS), flagella, hemolysins, and a homolog of exotoxin A found in Pseudomonas aeruginosa. Corresponding phenotypic analyses with A. hydrophila ATCC 7966(T) and SSU as reference strains demonstrated the functionality of these virulence genes, with strain E1 displaying enhanced swimming and swarming motility, lateral flagella on electron microscopy, the presence of T3SS effector AexU, and enhanced lethality in a mouse model of Aeromonas infection. By combining sequence-based analysis and functional assays, we characterized an A. hydrophila pathotype, exemplified by strain E1, that exhibited increased virulence in a mouse model of infection, likely because of encapsulation, enhanced motility, toxin secretion, and cellular toxicity. IMPORTANCE:Aeromonas hydrophila is a common aquatic bacterium that has increasingly been implicated in serious human infections. While many determinants of virulence have been identified in Aeromonas, rapid identification of pathogenic versus nonpathogenic strains remains a challenge for this genus, as it is for other opportunistic pathogens. This paper demonstrates, by using whole-genome sequencing of clinical Aeromonas strains, followed by corresponding virulence assays, that comparative genomics can be used to identify a virulent subtype of A. hydrophila that is aggressive during human infection and more lethal in a mouse model of infection. This aggressive pathotype contained genes for toxin production, toxin secretion, and bacterial motility that likely enabled its pathogenicity. Our results highlight the potential of whole-genome sequencing to transform microbial diagnostics; with further advances in rapid sequencing and annotation, genomic analysis will be able to provide timely information on the identities and virulence potential of clinically isolated microorganisms.

Dataset Information

Detection and characterization of the hemolysin genes in Aeromonas hydrophila and Aeromonas sobria by multiplex PCR.

Publications

Detection and characterization of the hemolysin genes in Aeromonas hydrophila and Aeromonas sobria by multiplex PCR.

Similar Datasets

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