Comparative in vitro activity of aztreonam and other antimicrobial agents against Salmonella species

The in vitro activity of aztreonam, the first monobactam antibiotic, was compared with that of 17 other antimicrobial agents against 79 strains of Salmonella species. The microorganisms were isolated from hospitalized patients, surface waters and seafoods during the decade 1975-1984. They included the following species: Salmonella typhi 63, Salmonella typhimurium 5, Salmonella wien 5, Salmonella heidelberg 2, Salmonella arizonae 2, Salmonella paratyphi B 1 and Salmonella enteritidis 1. The minimum inhibitory concentration (MIC) values of the antibiotics were determined using a serial dilution method in agar. A final inoculum size of 10(5) colony-forming units (CFU) X ml-1 of the tested microorganisms was used. Aztreonam exhibited a superior antimicrobial activity to that of the other antibiotics tested. Aztreonam inhibited 90% of the strains by 0.8 micrograms X ml-1 (MIC range was 0.05 to 1.56 micrograms X ml-1). There was no major difference between minimum bactericidal concentration and MIC values of aztreonam and the effect of inoculum size upon MIC values was observed at 10(7) CFU X ml-1.