Thanuncha Athajariya. The study of serotypes and virulence genes of vibrio parahaemolyticus in healthy carriers at frozen seafood plants . Master's Degree(Infectious Diseases and Epidemiology). Mahidol University. : Mahidol University, 2004.
The study of serotypes and virulence genes of vibrio parahaemolyticus in healthy carriers at frozen seafood plants
Abstract:
Many studies show that Vibrio parahaemolyticus can be detected from healthy
contacts of diarrheal patients, villagers living near the sea, and healthy employees
from seafood processed plants without showing any symptom of diarrhea. The carrier
state of these healthy carriers who harbour V. parahaemolyticus has not been
characterized. In this research, serotypes and virulence genes of V. parahaemolyticus
were studied in 10,214 rectal swab samples from healthy workers of the frozen
seafood plant and frozen processed seafood plant at Samut Prakan province during
July 2002 to August 2003. V. parahaemolyticus was found in 147 samples (1.4%)
from 139 healthy workers throughout the year. Heiberg’s type VII and type V of
V. parahaemolyticus were found in 64% and 18% of the samples, respectively. The
isolates from another 18% of the samples tested positive for both Heiberg types. A
total of 64 O:K serotypes were identified among 999 isolates of V. parahaemolyticus
from 147 positive samples, with O1:KUT (untypable) which was the most dominant
serotype (11.9%), followed by O5:KUT (11.5%), O10:KUT (8.0%) and O11:KUT
(7.1%). Only 1.7% of 999 isolates produced both thermostable direct hemolysin
(TDH) and urease enzyme (TRH), whereas 32.8% of isolates produced only TDH and
8% produced only urease enzyme. Furthermore, 269 of 999 isolates were selected on
the basis of their different Heiberg types and serotypes from all positive samples to
determine their virulence genes (tdh and trh) by using multiplex PCR and
antimicrobial susceptibility pattern. Both tdh and trh genes were positive in 4.8% of
the isolates, 25.3% contained only tdh+, 4.8% only trh+ and 65.1% only tdh-trh-. All
isolates with trh+ produced urease enzyme and 7.4% of tdh+ isolates did not produce
TDH. Antimicrobial susceptibility of the 269 isolates were tested with 8 antimicrobial
agents, and more than 96% of them were susceptible to norfloxacin, nalidixic acid,
nitrofurantoin, tetracycline, cotrimoxazole and gentamicin. Of the isolates, 27.9% and
17.8% were resistant to ampicillin and colistin, respectively. Multidrug resistant
patterns were also found in 7.8% of 269 isolates, in which 5.9% showed resistance to
ampicillin and colistin. Five transient healthy carriers from the frozen processed
seafood plant were V. parahaemolyticus positive two to three times during the study
period. However, all isolates from each transient healthy carrier were of different
serotypes and strains. TDH with tdh+ isolate and TRH with trh+ isolate were
identified in two carriers. This study has shown the significant findings and
characteristics of V. parahaemolyticus among healthy carriers in the frozen seafood
plants. Further research is suggested on the roles of carriers in transmission,
pathogenic mechanism and virulence gene expression.