Background:
The surveillance of
Vibrio parahaemolyticus
in the Chilean coast has been mainly performed by
multiplex PCR amplification of three different hemolysin genes, which are specie-specific virulence factors.
These genes are also employed in the determination of
V. parahaemolyticus pathogenic load in seafood and for
characterization of pathogenic strains associated to diarrhea cases in human. During environmental
surveillance that we performed every summer, we occasionally observed a thermolabile hemolysin (
tlh) PCR
product of a slightly smaller size than expected, which was coincident with low loads of
V. parahaemolyticus in
the environment. In order to understand this observation, we probed the specificity of
tlh primers for the
detection of
V. parahaemolyticus at different bacterial loads and DNA concentrations.
Results:
Primers used for the detection of
V. parahaemolyticus specific
tlh amplified a slightly smaller
tlh gene,
which is found in
Vibrio alginolyticus
and other related strains. These amplicons were observed when
V. parahaemolyticus was absent or in undetectable loads in the environment.
Conclusions:
Surveillance of
V. parahaemolyticus using
tlh primers can be imprecise because amplification of a
V. parahaemolyticus specific marker in
V. alginolyticus and other related strains occurs. This situation
complicates potentially the estimation of bacterial load in seafood, because do not ensure the correct
identification of
V. parahaemolyticus when his load is low. Additionally, it could complicate the tracking of
outbreaks of
V. parahaemolyticus infections, considering the genetic markers used would not be specie-specific.
