Abstract
After the worldwide cholera epidemic in 1993, permanent environmental monitoring of hydrographic basins was established in Pernambuco, Brazil, where cholera is endemic. After a quiescent period, 4 rfbN (serogroup O1) positive water samples that were culture negative were detected by multiplex single-tube nested PCR (MSTNPCR); 2 of these were also ctxA (cholera toxin) positive. From May to June 2012, 30 V. cholerae O1 isolates were obtained by culturing samples. These isolates were analyzed for the presence of virulence genes by PCR, intergenic spacer region 16S-23S PCR (ISR-PCR), and pulsed field gel electrophoresis (PFGE). The isolates were positive for the rfbN gene and negative for the assessed pathogenic genes and were classified into 2 groups by ISR and the same profile by PFGE. Close genetic similarity was observed between them (2012) and environmental strains from 2004 to 2005, indicating the permanence of endemic V. cholerae O1 in the region.
Highlights
Vibrio cholerae has played a prominent role in human history and has caused several epidemics that caused many deaths worldwide
In Brazil, the O1 serogroup has been recognized as the causative agent of past epidemics, but it is likely that other serogroups were involved in recent small outbreaks [4, 5]
multiplex single-tube nested PCR (MSTNPCR) analysis of water samples from aquatic basins of PE, Brazil, from May to June 2012 resulted in the detection of four rfbN-positive samples, of which two were ctxA positive
Summary
Vibrio cholerae has played a prominent role in human history and has caused several epidemics that caused many deaths worldwide. Estadual de Saude (SES/PE)) has established permanent environmental monitoring of the hydrographic basins in the state for the detection of V. cholerae [7]. This investigation was first based on the standard culture procedures of water samples, and later a molecular technique, multiplex singletube nested PCR (MSTNPCR), is used to target the ctxA gene, which encodes cholera toxin subunit A, and the rfbN gene, which is specific to serogroup O1 [8]. In May 2012, four rfbN positive but not culturable water samples, of which two were ctxA (cholera toxin) positive, were detected by MSTNPCR. The monitoring was intensified and, from May to June 2012, 30 V. cholerae O1-positive cultures were unexpectedly isolated from four hydrographic basins
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