“…The role of the gene product of the rtxC gene which is present in all non-O1, non-O139 strains is, so far, unclear; it may be necessary for posttranslational activation of MARTX by acetylation [9]. However, rtxC -negative mutants seem to produce a functional MARTX protein [34]. Fig.…”
Vibrio cholerae belonging to the non-O1, non-O139 serogroups are present in the coastal waters of Germany and in some German and Austrian lakes. These bacteria can cause gastroenteritis and extraintestinal infections, and are transmitted through contaminated food and water. However, non-O1, non-O139 V. cholerae infections are rare in Germany. We studied 18 strains from German and Austrian patients with diarrhea or local infections for their virulence-associated genotype and phenotype to assess their potential for infectivity in anticipation of possible climatic changes that could enhance the transmission of these pathogens. The strains were examined for the presence of genes encoding cholera toxin and toxin-coregulated pilus (TCP), as well as other virulence-associated factors or markers, including hemolysins, repeats-in-toxin (RTX) toxins, Vibrio seventh pandemic islands VSP-1 and VSP-2, and the type III secretion system (TTSS). Phenotypic assays for hemolysin activity, serum resistance, and biofilm formation were also performed. A dendrogram generated by incorporating the results of these analyses revealed genetic differences of the strains correlating with their clinical origin. Non-O1, non-O139 strains from diarrheal patients possessed the TTSS and/or the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin, which were not found in the strains from ear or wound infections. Routine matrix-assisted laser desorption/ionization (MALDI-TOF) mass spectrometry (MS) analysis of all strains provided reliable identification of the species but failed to differentiate between strains or clusters. The results of this study indicate the need for continued surveillance of V. cholerae non-O1, non-O139 in Germany, in view of the predicted increase in the prevalence of Vibrio spp. due to the rise in surface water temperatures.Electronic supplementary materialThe online version of this article (doi:10.1007/s10096-013-2011-9) contains supplementary material, which is available to authorized users.
“…The role of the gene product of the rtxC gene which is present in all non-O1, non-O139 strains is, so far, unclear; it may be necessary for posttranslational activation of MARTX by acetylation [9]. However, rtxC -negative mutants seem to produce a functional MARTX protein [34]. Fig.…”
Vibrio cholerae belonging to the non-O1, non-O139 serogroups are present in the coastal waters of Germany and in some German and Austrian lakes. These bacteria can cause gastroenteritis and extraintestinal infections, and are transmitted through contaminated food and water. However, non-O1, non-O139 V. cholerae infections are rare in Germany. We studied 18 strains from German and Austrian patients with diarrhea or local infections for their virulence-associated genotype and phenotype to assess their potential for infectivity in anticipation of possible climatic changes that could enhance the transmission of these pathogens. The strains were examined for the presence of genes encoding cholera toxin and toxin-coregulated pilus (TCP), as well as other virulence-associated factors or markers, including hemolysins, repeats-in-toxin (RTX) toxins, Vibrio seventh pandemic islands VSP-1 and VSP-2, and the type III secretion system (TTSS). Phenotypic assays for hemolysin activity, serum resistance, and biofilm formation were also performed. A dendrogram generated by incorporating the results of these analyses revealed genetic differences of the strains correlating with their clinical origin. Non-O1, non-O139 strains from diarrheal patients possessed the TTSS and/or the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin, which were not found in the strains from ear or wound infections. Routine matrix-assisted laser desorption/ionization (MALDI-TOF) mass spectrometry (MS) analysis of all strains provided reliable identification of the species but failed to differentiate between strains or clusters. The results of this study indicate the need for continued surveillance of V. cholerae non-O1, non-O139 in Germany, in view of the predicted increase in the prevalence of Vibrio spp. due to the rise in surface water temperatures.Electronic supplementary materialThe online version of this article (doi:10.1007/s10096-013-2011-9) contains supplementary material, which is available to authorized users.
“…All strains harbor the rtxC gene encoding an acyltransferase which has been described as an activator of MARTX toxin. The role of the acyltransferase in infection is unclear, as the rtxC gene product is not necessary for MARTX function in an animal model (Cheong et al, 2010). While the rtxC gene is highly similar (identity > 91%) in all strains, the rtxA genes encoding MARTX vary considerably.…”
Vibrio cholerae
is a natural inhabitant of aquatic ecosystems globally. Strains of the serogroups O1 and O139 cause the epidemic diarrheal disease cholera. In Northern European waters,
V. 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. 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. 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. The latter group comprised hemolysins, RTX toxins, cholix toxin, pandemic islands, and type III secretion system (TTSS). Phenotypic assays for hemolytic activity against human and sheep erythrocytes were also performed. The results of the MLST analysis revealed a considerable heterogeneity of sequence types (in total 74 STs). The presence of virulence genes was also variable and 30 profiles were obtained by PCR. One profile was found in 38 environmental strains and six clinical strains. Whole genome sequencing (WGS) was performed on 15 environmental and 7 clinical strains that were ST locus variants in one, two, or three alleles. 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. In few strains, more virulence factors are acquired through horizontal gene transfer (i.e., TTSS, genomic islands). A distinction between clinical and environmental strains based on virulence gene profiles is not possible for our strains. Probably, many virulence traits of
V. 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. These findings indicate the need for surveillance of
Vibrio
spp. in Germany, as due to global warming abundance of
Vibrio
will rise and infections are predicted to increase.
“…An rtxC gene similar to the hlyC acyltransferase gene required for maturation of E. coli α-hemolysin is located in the same operon with the rtxA gene ( Lin et al , 1999 ). The recent data indicate that rtxC is not necessary for the MARTX toxin function in V. cholerae , but the MARTX toxin without rtxC activation showed reduced actin cross-linking activity ( Cheong et al , 2010 ), while a deletion of rtxC had no effect on the virulence of V. vulnificus ( Lee et al , 2007 ; Liu et al , 2007 ;). These results suggest that acylation may not be essential for all MARTX toxins ( Satchell, 2007 ).…”
Repeats-in-toxin (RTX) exoproteins of Gram-negative bacteria form a steadily growing family of proteins with diverse biological functions. Their common feature is the unique mode of export across the bacterial envelope via the type I secretion system and the characteristic, typically nonapeptide, glycine- and aspartate-rich repeats binding Ca2+ ions. In this review, we summarize the current state of knowledge on the organization of rtx loci and on the biological and biochemical activities of therein encoded proteins. Applying several types of bioinformatic screens on the steadily growing set of sequenced bacterial genomes, over 1000 RTX family members were detected, with the biological functions of most of them remaining to be characterized. Activities of the so far characterized RTX family members are then discussed and classified according to functional categories, ranging from the historically first characterized pore-forming RTX leukotoxins, through the large multifunctional enzymatic toxins, bacteriocins, nodulation proteins, surface layer proteins, up to secreted hydrolytic enzymes exhibiting metalloprotease or lipase activities of industrial interest.
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