Microbiological and clinical evaluation of aztreonam in treatment of gram negative bacterial infections

Abstract

The in vitro antibacterial activity of aztreonam against 351 gram negative microorganisms were determined by using a two-fold serial agar dilution method. Aztreonam inhibited 90% of strains (N) of Aeromonas spp. (N = 30), Escherichia coli (N = 66), Klebsiella spp. (N = 52), Proteus spp. (N = 19), Salmonella spp. (N = 28), Serratia spp. (N = 20) and Shigella spp. (N = 32) at a concentration of < 2 ug/ml. Fifty percent (50%) of strains of Enterobacter spp. (N = 53) were inhibited by 0.15 ug/ml aztreonam and 90% by 10 ug/ml. Aztreonam also inhibited 90% of strains of P. aeruginosa (N = 29) and Acinetobacter spp. (N = 22) at concentrations of 11.9 ug/ml and 86 ug/ml respectively. In clinical studies, aztreonam was administered to 10 pediatric patients with gram negative infections which included urinary tract infection (90%) and skin infection (10%). The patients were 5 males and 5 females with the ages ranged from 3 months to 14 years. The etiological organisms were P. aeruginosa, P. mirabilis, E. coli, K. pneumonfae, and E. cloacae. Based on the severity of the infections, aztreonam was given for a mean duration of 10.6 + 2.65 days, i.v. (30 mg/kg, 6 – 8 hourly) in 9 patients and i.m. (30 mg/kg, 8 hourly) in one patient. At the end of the treatment, one patient was clinically cured, 8 improved and one failed to respond to the antibiotic treatment. All of the initial pathogens were eradicated at the completion of treatment. Superinfection occurred in one patient and colonization with other bacteria or fungi were developed in five patients. All of these patients had other compromising underlying conditions. Aztreonam’s serum levels were over the MIC90 to most of gram negative bacteria at the eighth hour after injection. Adverse effects of the antibiotic were minimal. It is very suggestive that aztreonam can be used effectively and safely in the treatment of gram negative bacterial infections.