Correlation of Mannitol Fermentation with Virulence-Associated Genotypic Characteristics inVibrio vulnificusIsolates from Oysters and Water Samples in the Gulf of Mexico

Abstract

Vibrio vulnificus strains (n = 469) isolated from the Gulf of Mexico oysters and waters over a period of 2 years were subjected to phenotypic and genotypic characterizations. Of the strains that could be definitively genotyped (n = 465), 58% were classified as genotype A, 29% as genotype B, and 13% as genotype A/B by 16S rRNA genotyping. When the same strain bank was characterized by virulence-correlated gene (vcg) typing, 65% were genotype E while 35% were genotype C. Further analysis focusing on strains falling into typical genotype categories (i.e., 16S rRNA types A or B, excluding type A/B strains) showed a high degree of concordance (93%) when comparing the two genotyping methods. d-Mannitol fermentation was also predictive of genotype, with an 86% agreement between 16S rRNA genotype and mannitol fermentation patterns, and an 85% agreement between vcg genotype and mannitol fermentation patterns. d-Mannitol fermentation should be considered as a simple and less expensive alternative to screen V. vulnificus isolates for virulence potential, particularly when analyzing large strain banks.

Genotypic Diversity and Virulence Characteristics of Clinical and Environmental Vibrio vulnificus Isolates from the Baltic Sea Region

“…A correlation with MLST cluster II (designated lineage 1) was already described for nanA (45). Both markers showed a significant correlation with the isolation source and may be relevant for virulence, since they can promote a selective advantage by enabling the use of alternative carbon and nitrogen sources (48,51). The nanA gene may be of particular importance, as it is a component of the sialic acid catabolism (SAC) cluster, whose gene products confer the ability of enteropathogens or commensals to metabolize sialic acid components of mucins in the human intestine (52), and was already found to be essential for pathogenicity of V. vulnificus (46).…”

“…For assessment of potential pathogenicity, the presence/absence of pathogenicity region XII, the mannitol fermentation operon, or nanA can be studied quickly by simple PCR assays. As traditional biochemical typing is still performed by routine laboratories, mannitol fermentation could also be used for risk assessment of potentially pathogenic strains (48). These rapid tests may be complemented by human serum resistance assays that allow easy and highthroughput screening of large V. vulnificus strain collections.…”

“…Mannitol fermentation has recently been correlated with clinical genotypes (vcg type C and 16S rRNA type B), and mannitol transport and fermentation genes were found to be predominantly present in the C genotype (48,49). Of the 47 biotype 1 isolates in our study, mannitol fermentation was observed in 15 of 19 (79%) isolates from human cases, but in only 5 of 28 (18%) isolates from environmental sources (Table 5).…”

Genotype Is Correlated with but Does Not Predict Virulence of Vibrio vulnificus Biotype 1 in Subcutaneously Inoculated, Iron Dextran-Treated Mice

“…These genes are interesting because they could explain the unusually high virulence of 99-738 DP-B5 and include genomic island XII identified by Cohen et al (14), sialic acid catabolism, and mannitol catabolism. Jeong et al (23) recently determined that the nanA gene involved with sialic acid catabolism is essential for virulence in V. vulnificus, and mannitol fermentation has been linked to the clinically associated genotypes (16). Because most of the systems commonly used to genotype V. vulnificus are not based on virulence genes and because the profiles do not enable prediction of virulence potential, it is crucial that the virulence genes that underlie the pathogenicity of V. vulnificus be identified.…”

“…DNA polymorphism at the vcg locus, detected by a simple PCR method, identified vcgC versus vcgE genotype strains predominantly associated with clinical or environmental isolation, respectively (48). vcg typing generally matched rrn typing (11,16,49). Bisharat et al (4,5) used multilocus sequence typing (MLST) of housekeeping genes to type 159 V. vulnificus strains and constructed an online database for V. vulnificus MLST (http://pubmlst.org /vvulnificus/).…”