Vspd-016
cholerae strains do not possess these two virulence factors and belong to other serogroups. While the genes for CTX are part of the genome of the filamentous phage CTXΦ ( McLeod et al., 2005 Bhattacharya et al., 2006), genes for the TCP biosynthesis are located within a pathogenicity island designated as Vibrio pathogenicity island VPI-1 ( Karaolis et al., 1998 Murphy and Boyd, 2008). Major virulence factors of the toxigenic O1 and O139 strains are the cholera toxin (CTX) and the toxin-coregulated pilus (TCP), which are both encoded on mobile genetic elements integrated into the chromosome of the toxigenic strains ( Harris et al., 2012). Poor sanitation as a result of damaged infrastructure occurring through natural catastrophes or human-caused disasters has led to cholera epidemics ( Zuckerman et al., 2007). Strains of the serogroups O1 and O139 can cause the diarrheal disease cholera which affects millions of people in countries where the supply with clean drinking water is problematic. The species Vibrio cholerae comprises Gram-negative bacteria which are distributed in aquatic ecosystems throughout the world. in Germany, as due to global warming abundance of Vibrio will rise and infections are predicted to increase. These findings indicate the need for surveillance of Vibrio spp. cholerae evolved in response to biotic and abiotic pressure and serve adaptation purposes in the natural aquatic environment, but provide a prerequisite for infection of susceptible human hosts. A distinction between clinical and environmental strains based on virulence gene profiles is not possible for our strains. In few strains, more virulence factors are acquired through horizontal gene transfer (i.e., TTSS, genomic islands). Comparison of WGS results revealed that a set of virulence genes found in some clinical strains is also present in most environmental strains irrespective of the ST. Whole genome sequencing (WGS) was performed on 15 environmental and 7 clinical strains that were ST locus variants in one, two, or three alleles. One profile was found in 38 environmental strains and six clinical strains. The presence of virulence genes was also variable and 30 profiles were obtained by PCR. The results of the MLST analysis revealed a considerable heterogeneity of sequence types (in total 74 STs). Phenotypic assays for hemolytic activity against human and sheep erythrocytes were also performed. The latter group comprised hemolysins, RTX toxins, cholix toxin, pandemic islands, and type III secretion system (TTSS). The strains were characterized by MLST and examined by PCR for the presence of virulence genes encoding the cholera toxin, the toxin-coregulated pilus (TCP), and other virulence-associated accessory factors.
For this study, environmental strains from the German coastal waters of the North Sea and the Baltic Sea were selected (100 strains) and compared to clinical strains (10 isolates) that were from patients who contracted the infections in the same geographical region. cholerae bacteria belonging to other serogroups (designated non-O1, non-O139) are present, of which some strains have been associated with gastrointestinal infections or extraintestinal infections, like wound infections or otitis. Strains of the serogroups O1 and O139 cause the epidemic diarrheal disease cholera. Vibrio cholerae is a natural inhabitant of aquatic ecosystems globally.
Department Biological Safety, German Federal Institute for Risk Assessment, Berlin, Germany.
Keike Schwartz, Jens Andre Hammerl, Cornelia Göllner and Eckhard Strauch *