Antibiotic resistance and Caco-2 cell invasion of Pseudomonas aeruginosa isolates from farm environments and retail products.

The potential pathogenicity of Pseudomonas aeruginosa isolates from food animals, retail meat products, and food processing environments was evaluated by determining their antibiotic resistance profiles and invasiveness into human intestinal Caco-2 cell. In general, the genomically diversified isolates of P. aeruginosa were resistant to beta-lactams (ampicillin, amoxicillin-clavulanic acid, cefoxitin, ceftiofur, and cephalothin), chloramphenicol, tetracycline, kanamycin, nalidixic acid, and sulfamethoxazole-trimethoprim. Acquisition of any other antibiotic resistance genes, such as class 1 integrons and other beta-lactamase genes, was not found in the tested isolates. The expression of OprM membrane protein, which is associated with a multidrug efflux system, played a major role in their antibiotic resistance. Single mutation in the GyrA to confer resistance to nalidixic acids was also found in the tested isolates, indicating that these factors could synergistically affect the resistance of the P. aeruginosa isolates. The number of bacteria invading into the Caco-2 cells was 2.5 log(10) CFU/ml on average. Therefore, the public health concern of P. aeruginosa could be relevant since its occurrence in food animals could cross contaminate the retail meat products during food handling and processing.