Vibrio cholerae O1 clinical strains isolated in 1992 in Kolkata with progenitor traits of the 2004 Mozambique variant

Abstract

Retrospective analysis led to the detection of two Vibrio cholerae variant O1 strains (VC51 and VC53), which were isolated in 1992 in Kolkata from clinical cases, with identical traits to 2004 Mozambique variant O1 strains. The Mozambique O1 strains that caused a huge outbreak in 2004 have been shown to have phenotypic traits of both classical and El Tor biotypes, and thereby have been reported as variant. Our study demonstrated that two O1 strains isolated in Kolkata during 1992 were of the El Tor background as evidenced by polymyxin B (50 U ml "1 ) resistance, positivity in Voges-Proskauer reactions and sensitivity to biotype-specific vibrio phages. With the features of classical CTX prophage, localization in the small chromosome, and an absence of RS1 and pTLC, both Mozambique and Kolkata strains appeared to be identical. Furthermore, two Kolkata strains exhibited an identical ribotype to that of the Mozambique variant, displaying ribotype pattern RI that had been assigned to Kolkata V. cholerae O1 strains isolated on or before 1992. NotI pulsotype analysis indicated that these 1992 Kolkata strains along with the Mozambique variant O1 belonged to very closely related clones. Considering the chronological events, and the typical identity at the phenotypic and the genotypic level between the two O1 strains isolated during 1992 from Kolkata and during 2004 from Mozambique, we propose that some of the 1992 Kolkata O1 strains might have acted as progenitors for Mozambique variant O1 strains.

Molecular evidence favouring step-wise evolution of Mozambique Vibrio cholerae O1 El Tor hybrid strain

“…Since the Mozambique hybrid strain evolved in 2004, and the Kolkata hybrid strains were isolates of 1992, the latter strains may thus be the progenitors of the former strain. Recently Chatterjee et al (2009) have also provided evidence in favour of this conclusion by using ribotyping and other molecular methods. The small chromosomal arrangement of the classical CTX prophage is identical in the Mozambique and Kolkata hybrid El Tor strains (Faruque et al, 2007;Das et al, 2007), which also supports their ancestry.…”

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

“…Genetic analysis of the tcpA gene also is routinely conducted to verify the biotype background of V. cholerae isolates (4,11,34,45) and was used in this study. The tcpA gene in all clinical variants in this study was sequenced and confirmed to be of the El Tor biotype, with three mutations (Table 5).…”

“…Although evidence has been presented demonstrating that the El Tor biotype has globally displaced the classical biotype (19,42), the emergence of El Tor variants has warranted the use of standard genotypic and phenotypic assays to determine the biotype background of new isolates. 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.…”

“…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).…”

Emergence and progression of Vibrio cholerae O1 El Tor variants and progenitor strains of Mozambique variants in Kolkata, India

“…In a previous study, 2 V. cholerae strains, VC51 and VC53, isolated in 1992 in Kolkata were identified as progenitor of 2004 Mozambique variants (Chatterjee et al, 2009). Subsequent analysis of archived strains revealed complete replacement of ctxB El by the ctxB cl in Kolkata strains since 1995 .…”