Molecular characterization of Aeromonas spp. and Vibrio cholerae O1 isolated during a diarrhea outbreak

Abstract

SUMMARYThis work aimed to assess pathogenic potential and clonal relatedness of Aeromonas sp. and Vibrio cholerae isolates recovered during a diarrhea outbreak in Brazil. Clinical and environmental isolates were investigated for the presence of known pathogenic genes and clonal relatedness was assessed by intergenic spacer region (ISR) 16S-23S amplification. Four Aeromonas genes (lip, exu, gcat, flaA/B) were found at high overall frequency in both clinical and environmental isolates although the lip gene was specifically absent from selected species. A fifth gene, aerA, was rarely found in A. caviae, the most abundant species. The ISR profile revealed high heterogeneity among the Aeromonas isolates and no correlation with species identification. In contrast, in all the V. cholerae isolates the four genes investigated (ctxA, tcpA, zot and ace) were amplified and revealed homogeneous ISR and RAPD profiles. Although Aeromonas isolates were the major enteric pathogen recovered, their ISR profiles are not compatible with a unique cause for the diarrhea events, while the clonal relationship clearly implicates V. cholerae in those cases from which it was isolated. These results reinforce the need for a better definition of the role of aeromonads in diarrhea and whether they benefit from co-infection with V. cholerae.

Genetic diversity and virulence potential of clinical and environmental Aeromonas spp. isolates from a diarrhea outbreak

“…This study involved 119 Aeromonas spp. isolates (103 from diarrheal patient feces and 16 from the aquatic environment) obtained from March to June 2004 during a diarrhea outbreak that occurred in São Bento do Una, a Brazilian city located in Pernambuco state [ 7 , 8 ]. Clinical isolates were numbered from 251 to 374 and environmental isolates were numbered from 420 to 707.…”

“…isolates was analyzed by sequencing the 16S rRNA and gyrB genes to identify isolates at the species level. Polymerase Chain Reactions (PCR) were executed as previously described [ 6 , 8 ]. The amplicons (~1503 base pairs (bp) for the 16S rRNA and ~1100 bp for gyrB ) were purified using ExoSAP-IT PCR Cleanup (Affymetrix, Cleveland, OH, USA) according to the vendor.…”

“…The 119 isolates were analyzed by PCR to determine the presence of the virulence genes alt , ast and hlyA as described [ 8 ]. The sequence of primers used to amplify the target genes: alt (~338 bp), ast (260 bp) and hlyA (597 bp) are listed in Table 1 .…”

“…To shed some light on the virulence panorama of the Aeromonas isolates, we analyzed the frequency pattern for seven virulence genes: alt , ast and hlyA determined in the present study and aerA , exu , lip and flaA / B , as previously determined [ 8 ].…”

“…The infections were attributed to the precariousness of the drinking water supply lacking microbiological control in the region, where a local river both receives untreated sewage and serves as a drinking water source. Despite the higher prevalence of Aeromonas isolates in patient feces, V. cholerae O1 was entailed as the etiological agent of the outbreak [ 8 ]. This issue invited further characterization of those Aeromonas isolates.…”