[High incidence of ampicillin resistance in Salmonella spp non typhi]. / Alta frecuencia de elevada resistencia a ampicilina en Salmonella spp no typhi.

Salmonella spp non typhi is a common cause of gastroenteritis and, more rarely, extraintestinal infections in humans. The type of syndrome determines the choice and duration of antibiotic therapy. Extraintestinal infections by this organism require correct antibiotic therapy. In the present study, the susceptibility to antibiotics of 59 strains of Salmonella spp non typhi from clinical sources, isolated during a period of three and a half months, were evaluated. Fifty one of them were S. enteritidis, 7 S. typhimurium and 1 S. schwarzengrund. A high frequency (45.8%) of resistance to ampicillin (MIC greater than 256 micrograms/ml) was found. Other antibiotics had good or excellent in vitro activity: 90% of strains were sensitive to tetracyclines, 93% to chloramphenicol, 97% to co-trimoxazole, and 100% to cefotaxime and ciprofloxacine. It was concluded that the high frequency of ampicillin resistance to ampicillin precludes its use as first choice antibiotic in our area for suspected extraintestinal infections caused by Salmonella spp non typhi.