In vivo examination of pathogenicity and virulence in environmentally
isolated Vibrio vulnificus
Abstract
Human exposures to the Gram-negative, halophilic environmental pathogen,
Vibrio vulnificus, are on the rise, yet pathogenicity and virulence
mechanisms remain poorly understood. There are hundreds of cases of
Vibrio vulnificus-related infections yearly, and these infections result
in hospitalizations 92% of the time, with a mortality rate of 35%.
This infection is severe, with patients typically contracting the
bacteria via consumption of contaminated food, or through an open wound
while swimming in contaminated water, which can result in necrotizing
fasciitis and amputation of infected tissue. Several genes have been
implicated in contributing to the pathogenicity of this organism (rtxA1,
vvpE, vvhA), but no defined mechanism for pathogenicity has been
discovered. Here, we focus on environmentally isolated Vibrio vulnificus
strains and use a Zebrafish model (Danio rerio) to address the virulence
capabilities of these strains. We found that virulence varied greatly
between individual strains, and the commonly used marker gene of
disease-causing strains of vcgC, did not accurately predict the more
virulent strains. To this point, the least virulent strain from the
study, V. vulnificus Sept WR1-BW6, which was positive for vcgC, vvhA,
and rtxA1, did not produce severe disease in the fish and was the only
strain that did not produce a single mortality throughout the study. Our
study shows that virulence between different environmental strains
varies greatly, and cannot accurately be predicted based on genotype
alone.