Bacterial Isolates from Bivalve Clams (Galatea paradoxa, Born 1778): Occurence, Multi-drug Resistance, Location of Antibiotic Resistance Marker and Plasmid Profiles

The occurrence of bacterial isolates in Galatea paradoxa (Born 1778) was determined using standard bacteriological method. The multi-drug resistance, location of antibiotic markers, plasmid DNA extraction and electrophoresis was determined by disc diffusion, acridine orange, TENS alkaline lysis and 0.8% agarose gel electrophoresis, respectively. Of the 63 bacterial isolates from G. paradoxa, Staphylococcus aureus and Streptococcus pyogenes had the highest and lowest percentage of occurrence with 40.0% and 5.0%, respectively. Escherichia coli was 25.0%, Pseudomonas aeruginosa (17.5%), Enterococcus spp and Salmonella spp (15.0%) each, Bacillus subtilis (12.5%), Klebsiella pneumoniae and Enterococcus faecalis (10.0%) each while Vibrio cholerae was (7.5%). The results showed Streptomycin and Ciprofloxacin as the most effective antibiotics against bacterial isolates from G. paradoxa. Bacillus subtilis and P. aeruginosa displayed 100% sensitivity to Streptomycin; Salmonella spp and E. faecalis were 100% sensitive to Augmentin. V. cholerae and S. pyogenes showed 100% resistance to Penicillin and Rifampicin, respectively. Of the 63 bacterial isolates, 43 (68.3%) were multidrug resistant (MDR) isolates, of which S. aureus and E. coli had the widest multiple antibiotic resistance (MAR) indices ranging from 0.3 to 0.8, while S. pyogenes had the least MAR ≤ 0.5. Of the 43 MDR bacterial isolates, 16.3%, 23.3% and 60.5% had their entire antibiotic resistance encoded on plasmid, chromosome and both plasmid and chromosome, respectively. The agarose gel electrophoresis showed that MDR bacterial isolates from G. paradoxa had plasmid DNA with molecular weights ranging from 23.1 to 31.5kb. This study has showed that G. paradoxa harboured bacteria which could pose serious health risks and G. paradoxa should be adequately cooked before consumption.