[Susceptibility of Pseudomonas aeruginosa to aztreonam in comparison to other pseudomonas-active beta-lactam antibiotics and gentamicin].

The in vitro activity of aztreonam, a synthetic monobactam, was evaluated against 245 strains of Pseudomonas aeruginosa, 130 of them being recent clinical isolates from patients and 115 from hospital environment. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and bactericidal kinetics were determined. The possibility of resistance development in vitro was studied. Gentamicin, cefsulodin, piperacillin and azlocillin were used as comparative agents with known antipseudomonal activity. At a concentration of 8 mg/l 83.3%, at 16 mg/l 92% of the tested strains were susceptible to aztreonam. Thus, the activity of aztreonam against Pseudomonas aeruginosa is equivalent to that of gentamicin and cefsulodin and better than that of piperacillin and azlocillin in terms of resistance. Bactericidal kinetics with fourfold MIC, which is equivalent to MBC, are nearly identical for aztreonam, piperacillin and cefsulodin. In vitro induced resistance additionally causes increased resistance against the other beta-lactam antibiotics.