Comparing antibiotic resistance in commensal and pathogenic bacteria isolated from wild-caught South Carolina shrimps vs. farm-raised imported shrimps

Abstract

The objective of this study was to assess and differentiate wild-caught South Carolina (SC) shrimps from imported shrimps on the basis of microbiological analysis. Seven wild-caught SC shrimp and 13 farm-raised imported shrimp samples were analyzed. Total plate counts from wild-caught shrimp samples ranged from 4.3 to 7.0 log10 CFU/g, whereas counts from imported shrimp samples ranged from 3.2 to 5.7 log10 CFU/g. There was no difference (P > 0.05) between total bacterial counts of wild-caught SC shrimp and farm-raised imported shrimp. However, the percentages of bacteria with reduced susceptibility towards ceftriaxone and tetracycline were higher (P < 0.05) for farm-raised shrimp than for wild-caught samples. Salmonella spp. detected only in one farm-raised sample was resistant to ampicillin, ceftriaxone, gentamicin, streptomycin, and trimethoprim. Vibrio vulnificus was detected in both wild-caught and farm-raised shrimp samples; however, only the isolate from farm-raised shrimp was resistant to nalidixic acid and trimethoprim. Escherichia coli detected in one wild-caught sample was resistant to ampicillin. Both Listeria spp. and Salmonella spp. were absent with wild-caught SC samples. Therefore, the presence of more ceftriaxone- and tetracycline-resistant bacteria and the observed antimicrobial resistance phenotypes of isolates from the imported shrimp may reflect the possible use of antibiotics in raising shrimp in those countries.