Epidemiology of antimicrobial resistance in Salmonella isolated from pork, chicken meat and humans in Thailand.

Forty samples each of pork and chicken meat were collected from local retail markets in Khon Kaen, northeast Thailand, for Salmonella isolation and identification during 2003. Fifty-four isolates of Salmonella obtained from diarrheal patients admitted at a hospital located in the same town were serotyped. All isolates were also tested for antimicrobial sensitivity against amoxicillin (Amx), chloramphenicol (Chl), norfloxacin (Nor), ciprofloxacin (Cip), gentamicin (Gm), sulfamethoxazole and Trimethoprim (Sxt), Tetracycline (Tet), Streptomycin (Str) and sulfamethoxazole (Sulfa). The results showed that 26 (65%) pork samples and 30 (75%) chicken meat samples were contaminated with Salmonella. The most prevalent serovar in pork was S. Rissen (61.5%), followed by S. Stanley and S. Lexington (11.5%). In chicken meat, the most prevalent serovar was S. Anatum (33.3%), followed by S. Rissen (16.7%). Among isolates from human patients, S. Rissen (20.4%) and S. Stanley (18.5%) were the most frequently identified serovars. All the isolates were resistant to Str and Sulfa. None were resistant to Nor and Cip. Resistance to Amx, Chl, Gm, Sxt, and Tet in pork was 15.4, 15.4, 3.9, 15.4 and 88.5%, respectively. The resistance to those antimicrobial agents in chicken meat was 30.0, 26.7, 6.7, 20 and 100%, respectively, and in human patients was 27.8, 20.4, 5.6, 31.5 and 92.6%, respectively. Statistical analysis found no difference in the rate of resistance to Amx, Chl, Gm, and Sxt among the different sources of the Salmonella isolates (p > 0.05 for each antimicrobial agent). Our results indicate that antimicrobial resistant Salmonella strains were widely spread among pork and chicken meat, and in humans.