Aztreonam susceptibility testing. A retrospective analysis.
Aztreonam is a structurally and immunologically unique beta-lactam antibiotic with activity exclusively against aerobic gram-negative micro-organisms. Between 1983 and 1988, its antimicrobial spectrum was evaluated against more than 5,800 fresh clinical isolates at a 300-bed community teaching hospital. Only 1.1 percent of Enterobacteriaceae isolates were resistant to aztreonam over the five-year study period, an incidence similar to that observed with aminoglycoside antibiotics. Aztreonam was found to be more active than third-generation cephalosporins and comparable with mezlocillin against Enterobacter spp., Morganella, and Citrobacter freundii. Although aztreonam was somewhat less active against nonfermenting gram-negative bacilli, such as Pseudomonas and Acinetobacter, overall more than 90 percent of Pseudomonas aeruginosa isolates were susceptible. Ceftazidime was the most active beta-lactam tested against nonfermenters. Against aerobic gram-positive cocci, aztreonam possessed no clinically useful activity. No significant change in susceptibility to aztreonam was observed over the five-year study period for Enterobacteriaceae. For third-generation cephalosporins, however, a trend toward increased resistance was noted, particularly for Enterobacter spp. and C. freundii. A 50 percent increase in resistance to aztreonam was observed over the five-year study period for nonfermenters, particularly P. aeruginosa and Acinetobacter anitratus. Similar increases in resistance were seen with other beta-lactams and gentamicin. Based on its potent in vitro activity, aztreonam appears to be a useful agent and a desirable alternative to aminoglycoside antibiotics for the treatment of pure aerobic gram-negative bacillary infections, or as a component in combination therapy against mixed infections.
Parry
M F
MF
Stamford Hospital, Connecticut 06904.
D000667:Ampicillin / Q000494:pharmacology; D001398:Aztreonam / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D002439:Cefotaxime / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D005839:Gentamicins / Q000494:pharmacology; D008802:Mezlocillin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests
D005839:Gentamicins; D000667:Ampicillin; D002442:Ceftazidime; D001398:Aztreonam; D002439:Cefotaxime; D008802:Mezlocillin