Abstract
With the growing pet market, various types of pet food become available. Pet foods, especially raw meat-based diets (RMBDs), are contaminated with pathogens and antimicrobial-resistant bacteria, leading to health concerns for pets and humans. The bacterial contamination levels in pet food, including the presence of antimicrobial-resistant bacteria, have not been extensively studied in Japan. To address this issue in commercial pet foods in Japan, we evaluated the standard plate counts (SPCs) of various pet food samples, and isolated and characterized Escherichia coli and Enterococcus spp. A total of 129 pet foods (48 RMBDs, 21 heat-treated foods, and 60 treats) were purchased, and SPC quantification and isolation of E. coli and Enterococcus spp. were performed. SPCs in RMBD were significantly higher than in heat-treated foods and treats. Specifically, 50.0 % of the RMBD samples had SPCs exceeding 10(6) CFU/g. E. coli was isolated only from 62.5 % of RMBDs. Four cephalosporin-resistant E. coli strains harboring bla genes were detected, among which, one carried mcr conferring resistance to colistin. Enterococcus spp. were isolated from 89.6 % of RMBDs and 23.3 % of treats. Linezolid-non-susceptible E. faecalis harboring optrA or poxtA genes were detected in four RMBDs. Pet food may be contaminated with bacteria; some RMBDs are contaminated at concentrations >10(6) CFU/g, and with veterinary and human clinically important antimicrobial-resistant bacteria. To prevent health risks in both humans and pets associated with pet food, ensuring the hygienic management of pet food, especially RMBDs, and promoting accurate knowledge among pet owners are important.