Purpose: Examine AMR and characterize clinical and environmental strains of V. parahaemolyticus isolated from Canada between 1998 and 2011.
Methods: In total, 360 V. parahaemolyticus strains, including clinical (n=64) and environmental (n=296) isolates, were selected for analysis. Environmental strains were predominantly isolated from BC, with 18 strains isolated from Atlantic Canada. AMR phenotypes were determined by disc diffusion assay using a panel of 20 antimicrobial agents. All strains were screened for the presence of toxin genes (tdh, trh) by multiplex PCR.
Results: Of the 360 V. parahaemolyticus isolates analyzed, 53% (n=34) and 7% (n=20) of the clinical and environmental strains, respectively, possessed tdh and/or trh. Overall, V. parahaemolyticus isolates were susceptible to most antibiotics. The most common resistances observed were to sulfisoxazole (95.3%), ampicillin (90.0%), cephalothin (28.3%), streptomycin (3.6%), and piperacillin (2.2%). Reduced susceptibility to various antimicrobials was observed, including erythromycin (99.7%), kanamycin (47.8%), polymyxin B (23.6%), ceftiofur (16.4%), ciprofloxacin (3.9%), trimethoprim/sulfamethoxazole (2.2%), enrofloxacin (1.1%), and oxolinic acid (1.1%). Resistance to three or more antibiotics was observed in two (3.1%) clinical and 96 (32.4%) environmental strains, whilst two pathogenic strains isolated from one BC geographic area were resistant to five antimicrobial agents.
Significance: AMR profiles of V. parahaemolyticus strains characterized in this study are similar to data published in other countries. Although overall levels of AMR are low, reduced susceptibility to extended-spectrum β-lactams and fluoroquinolones is noteworthy. Current work is being performed to further characterize these phenomena.