Changes in susceptibility ofSalmonella enteritidis,Salmonella typhimurium,andSalmonella virchow to six antimicrobial agents in a Spanish hospital, 1980–1994

To determine changes in the susceptibility patterns ofSalmonella enteritidis, Salmonella typhimurium, andSalmonella virchow over time, resistance to ampicillin, chloramphenicol, tetracycline, gentamicin, trimethoprim/sulfamethoxazole, and nalidixic acid was studied by the disk diffusion method in 1,024, 191, and 61 clinical isolates of these organisms, respectively. All isolates were recovered from 1980 to 1994 at a hospital in Madrid, Spain.Salmonella enteritidis isolates were less resistant (10.9%) thanSalmonella typhimurium (43.5%) andSalmonella virchow (36.1%; p<0.001). The incidence of resistance ofSalmonella enteritidis to ampicillin increased from 2.7% during the period 1980–1982 to 15.6% during 1992–1994 (p<0.001). The resistance ofSalmonella typhimurium to ampicillin, chloramphenicol, and tetracycline increased from 15.2%, 7.6%, and 21.2% respectively in 1980–1982 to 73.3%, 46.7%, and 73.3% in 1992–1994 (p<0.001). These marked increases in antimicrobial resistance suggest the need for public health interventions, several of which are discussed.