Background: The genus
Aeromonas include gram-negative, motile, facultative anaerobic, rod shaped and
oxidase positive bacteria comprising several species, associated with the
aquatic environment. Aeromonas species have been implicated in human
pathogenesis and are linked with gastroenteritis, muscle infections, septicemia,
and skin diseases. In fish they are renowned as enteric pathogens causing
haemorrhagic septicemia, fin rot, soft tissue rot and furunculosis resulting in
major die-offs and fish kills.
Aim: This study reports the occurrence of
potential pathogenic Aeromonas sp. in tropical seafood (Squids, Prawns and
Mussels), aquafarms and mangroves of Cochin, Kerala, South India.
Materials
and Methods: Tropical seafood (Squid, Prawn and Mussel), sediment and water
samples from aquafarms and associated mangroves were screened for Aeromonas
contamination. The isolates were identified by 16S rDNA sequence analysis and
subjected to morphological and biochemical characterization. Haemolytic assay
was used for determining pathogenicity of the organisms. Antibiotic
susceptibility against 12 antibiotics were performed and the MAR index was
calculated.
Results: A total of 134 isolates were recovered from the
samples of which 15 were identified as Aeromonas species by 16S rDNA sequence
analysis and were assigned to 5 species namely, A. hydrophila, A.
enteropelogenes, A. caviae, A. punctataand A. aquarorium. Morphological,
biochemical and phylogenetic analyses revealed relatedness and variability among
the strains. All the isolates were haemolytic on blood agar indicating their
pathogenicity. The isolates exhibited varying degrees of resistance to
vancomycin (86.66%), ampicillin (46.66%), nalidixic acid (20%), tetracycline
(6.66%), co-trimaxozole (6.66%) and rifampicin (6.66%) and were susceptible to
antibiotics like gentamycin, streptomycin, trimethoprim, azithromycin, cefixime
and chloramphenicol. 20% of Aeromonas sp. showed MAR index > 0.2 indicative of
the high risk environment. Conclusion: The presence of Aeromonas sp. has
been recognised as a potential health risk and surveillance of this pathogen is
crucial for successful disease management and control.
Keywords: 16S rDNA
analysis, Aeromonas sp., antibiotic susceptibility tests, aquafarm, mangrove,
pathogenic, phylogenetic tree, seafood
