Phenotypic and Molecular Characterization of Isolated from Indian Oil Sardine Marketed in Cochin

ABSTRACT
Fish are commonly marketed in chilled condition under aerobic storage.
Pseudomonas spp. and Shewanella putrefaciens are the major microbial flora seen
under aerobic ice storage. In this study phenotypic and genotypic characterization of
P. aeruginosa was done considering its role as an opportunistic pathogen and its
ability to cause acute and chronic infections which are life threatening. Samples were
collected from 3 major markets in Cochin within a period of 8 months. A total of 48
unique isolates were obtained, which were then subjected to a series of biochemical
tests for the confirmation of the genus Pseudomonas. Thirty six isolates were
presumptively identified as Pseudomonas sp. of which 9 were further confirmed as P.
aeruginosa by 16SrRNA PCR. All these 9 P. aeruginosa isolates were then checked
for the presence of 7 major virulent genes namely, oprI, oprL, lasB, toxA, exoS, nan1
and phz by PCR using specific primers. All the isolates were found to be positive for
oprI and oprL genes which are unique factors used for the rapid identification of this
species. Further, lasB gene was detected in all the 9 isolates, whereas exoS gene was
detected only in 6 isolates. None of these isolates were found to be positive for toxA,
nan1 and phz by PCR. Antibiogram analysis was performed against a set of 18
clinically used antibiotics. All were found to be sensitive to gentamycin, tobramycin,
amikacin, aztreonam, ciprofloxacin, doripenem, imipenem, meropenem, norfloxacin,
colistin and polymyxin B, but showed intermediate status to pipperacillin tazobactum.
Only one isolate named as PA05 carrying lasB gene, was found to be resistant to 4
antibiotics namely, ceftazidime, ciprofloxacin, norfloxacin and ofloxacin and MAR
index was calculated as 0.22. Altogether, the study demonstrated the prevalence of P.
aeruginosa in common seafood consumed domestically in Kochi and provides basic
information on the virulent and antibiotic resistance profile of this pathogen, one of
the most challenging organisms involved in a variety of nosocomial infections of
humans.