Susceptibility of human isolates of Salmonella typhimurium DT 104 to antimicrobial agents used in human and veterinary medicine.
Multiple antibiotic resistance is frequently observed among strains of Salmonella typhimurium DT104. We examined the antibiotic resistance patterns of 240 human isolates submitted from central and northern Alberta to our laboratory for confirmatory testing during 1996-1999. Broth microdilution MIC panels included antibiotics proposed by the Canadian National Enteric Disease Surveillance Committee for human and animal isolates. Seven different susceptibility patterns were observed. The two most common patterns accounted for 83% of isolates; 48% were susceptible to all antibiotics tested and 35% were resistant to ampicillin, tetracycline, chloramphenicol and amoxicillin-clavulanate. All strains were susceptible to enrofloxacin and trovafloxacin with variable resistance to kanamycin and chloramphenicol. There were more susceptible isolates observed in 1996 and 1997 than in 1998 and 1999, but multiple resistant isolates were found throughout the study period.