Characterization of Vibrio cholerae isolates from 1976 to 2013 in Shandong Province, China

Abstract

Cholera continues to be a serious public health issue in developing countries. We analyzed the epidemiological data of cholera from 1976 to 2013 in Shandong Province, an eastern coastal area of China. A total of 250 Vibrio cholerae isolates were selected for PCR analysis of virulence genes and pulsed-field gel electrophoresis (PFGE). The analysis of the virulence genes showed that the positive rates for tcpA and tcpI were the highest among strains from the southwest region, which had the highest incidence rate of cholera. Low positive rates for tcpA, tcpI and ctxAB among isolates from after 2000 may be an influencing factor contributing to the contemporary decline in cholera incidence rates. Spatiotemporal serotype shifts (Ogawa, Inaba, Ogawa, Inaba and O139) generally correlated with the variations in the PFGE patterns (PIV, PIIIc, PIa, PIIIb, PIIIa, PIb, and PII). O1 strains from different years or regions also had similar PFGE patterns, while O139 strains exclusively formed one cluster and differed from all other O1 strains. These data indicate that V. cholerae isolates in Shandong Province have continually undergone spatiotemporal changes. The serotype switching between Ogawa and Inaba originated from indigenous strains, while the emergence of serogroup O139 appeared to be unrelated to endemic V. cholerae O1 strains.

Characterization of Vibrio cholerae O1 isolates responsible for cholera outbreaks in Kenya between 1975 and 2017

“…37,38 Serotype conversion in endemic strains has been linked to environmental factors and immune pressure within the population. [38][39][40] The results of the phenotypic and genetic characterization reveal that earlier strains isolated in Kenya from 1975 to 1984 had typical El Tor characters, which is in agreement with previous studies done in Kenya. 32 Cholera outbreaks occurring between 2007 and 2017 were caused by new variants of V. cholerae O1 that had traits of both the classical and El Tor biotypes and were classified as hybrid type, El Tor variants, or unclassified (for those that did not fit in any category).…”

“…It has been attributed to a change in the genetic make‐up of the wbtT gene that determines the Ogawa specificity . Serotype conversion in endemic strains has been linked to environmental factors and immune pressure within the population …”

Virulence, antimicrobial and heavy metal tolerance, and genetic diversity of Vibrio cholerae recovered from commonly consumed freshwater fish

“…In this study, the established ERIC-PCR condition generated the amplicons mainly ranged from 100 to 5000 bp in size. Moreover, in this study, the 400 V. cholerae isolates were differentiated into 328 ERIC-genotypes (82.0%), which was more than 179 pulsotypes (71.6%) from 250 V. cholerae isolates, and 218 pulsotypes (38.4%) from 568 V. cholerae isolates based on Not I-PFGE (pulsed-field gel electrophoresis) genotyping technique (Gu et al 2014; Lu et al 2017). These data demonstrated the considerable genetic diversity of the 400 V. cholerae isolates recovered from the four freshwater fish species.…”

Pandemics, pathogenicity and changing molecular epidemiology of cholera in the era of global warming

“…It has been hypothesised that the serological switching and genetic diversity of strains between pandemics and epidemics may be influenced by climate variations, with global warming making the environment favourable for cholera outbreaks by switching of virulence factors. This hypothesis is supported by studies of V. cholerae outbreaks in India [9], Bangladesh [10] and China [11], as well as a literature review of the influence of environmental factors on V. cholerae presence [12]. Furthermore, experimental studies have demonstrated variation with changes in environmental conditions in expression of ChiA2 and TfoX, key regulators of V. cholerae horizontal gene transfer [13].…”