Isolation of Vibrio cholerae O1 strains similar to pre-seventh pandemic El Tor strains during an outbreak of gastrointestinal disease in an island resort in Fiji

Abstract

Five strains of Vibrio cholerae O1, one each from an Australian and a New Zealand tourist with gastrointestinal illness returning from an island resort in Fiji and the remaining three from water sources located in the same resort, were extensively characterized. Conventional phenotypic traits that are used for biotyping of O1 V. cholerae categorized all five strains as belonging to the El Tor biotype. Genetic screening of 11 regions that are associated with virulence in V. cholerae showed variable results. The absence of genes comprising Vibrio seventh pandemic island-I (VSP-I) and VSP-II in all the strains indicated that these strains were very similar to the pre-seventh pandemic V. cholerae O1 El Tor strains. The ctxAB genes were absent in all strains whereas orfU and zot were present in four strains, indicating that the strains were non-toxigenic. Four strains carried a truncated CTX prophage. Although epidemiological and molecular studies suggested that these strains did not cause cholera amongst tourists at the resort, their similarity to pre-seventh pandemic strains, their prior association with gastrointestinal illness and their presence in the island resort setting warrant more attention.

Neglected Tropical Diseases of Oceania: Review of Their Prevalence, Distribution, and Opportunities for Control

“…In 2009, an outbreak occurred in PNG, eventually reaching 8,997 cases by the end of 2010, with the highest incidence in the Madang Province [95], [96]. In addition, an outbreak was reported from a resort in Fiji [97]. In Australia, four cases, all imported were reported in 2009.…”

Characterization of Vibrio cholerae O1 El Tor Biotype Variant Clinical Isolates from Bangladesh and Haiti, Including a Molecular Genetic Analysis of Virulence Genes

“…These incidents included a large outbreak in west Pakistan in 1968 and the appearance of the classical biotype in Bangladesh in 1979, with a continuous presence until the end of 1992 (5). However, since 2001, a series of reports have been published revealing clinical isolates, from as far back as the early 1990s, that are of El Tor biotype background but possess some classical biotype traits (3,4,28,34,35,36,43). For example, the ctxA gene, which is the first gene of the ctx phage operon and codes for the A subunit of the cholera toxin, is completely conserved in sequence between the two O1 biotypes.…”

“…These clinical El Tor O1 strains were found to contain the classical biotype cholera toxin B subunit gene (ctxB) and have since been termed El Tor variants (34,39). These El Tor variants have become a major focus of research, since other El Tor variants also have been identified in Asia and Mozambique (29,34,35,38) and recently have been a focus of attention in Haiti (1,6,7,8,9). Of particular concern are the recently published results indicating that some of the clinically isolated El Tor variants produce different levels of cholera toxin, including some isolates that produce higher levels than classical biotype strains (16).…”

“…Standard phenotypic assays, including polymyxin B resistance, hemolysis assays, phage sensitivities, and the Voges-Proskauer tests, are frequently employed in some combination (4,11,45). Genetic markers, such as the ctxB gene, have been used to distinguish the cholera toxin between classical and El Tor biotypes (11,33,35) to classify isolates as El Tor variants. The sequences of tcpA, which codes for the pilin subunits of the TcpA apparatus, and rstR, the repressor found in the RS1 element, which codes for the regulatory region for phage replication, also have been used in determining the biotypes of new isolates (4,11,39,45).…”

Genetic Screens and Biochemical Assays to Characterize Vibrio cholerae O1 Biotypes: Classical and El Tor

“…This set of protocols details some of the different genetic and phenotypic assays commonly utilized when characterizing Vibrio cholerae clinical or environmental isolates (Lan and Reeves, 2002;Nair et al, 2002Nair et al, , 2006aAnsaruzzaman et al, 2004Ansaruzzaman et al, , 2007Safa et al, 2006). Basic Protocol 1 details a genetic screen commonly used to examine the sequences of the cholera toxin B subunit (ctxB; Nair et al, 2006a;Morita et al, 2008;Chatterjee et al, 2009) and the major pilin protein TcpA (tcpA; Safa et al, 2008;Chatterjee et al, 2009). Cholera toxin, composed of the A and B subunits, is the major virulence factor that is directly responsible for the rice-water diarrhea associated with The proteolysis assay performed on milk agar plates is suggestive of HapR-regulated protease activity.…”