COMPARATIVE STUDIES ON ACTIVITIES OF ANTIMICROBIAL AGENTS AGAINST CAUSATIVE ORGANISMS ISOLATED FROM URINARY TRACT INFECTIONS (1985)

III. SECULAR CHANGES IN SUSCEPTIBILITY

Abstract

Sensitivities to antimicrobial agents of Escherichia coli, Klebsiella spp., Citrobacter spp., Enterobacter spp., Proteus spp., Pseudomonas aeruginosa and Serratia marcescens isolated from infected patients were evaluated and compared according to the types of their infections, i.e., simple and complicated urinary tract infections with or without indwelling catheter.
There were no apparent decreases in the sensitivity of E. coli isolated from patients with simple urinary tract infections. When data obtained in 1982-1985 were summarized, it was found that a new quinoline derivative, ofloxacin (OFLX), showed the strongest activity among oral antimicrobial and antibiotic agents. This agent inhibited 100% of bacterial growth at MIC of 1.56μg/ml. The next strongest activity was found with mecillinam (MPC) which showed 89.3% growth inhibition at the same concentration. Cefaclor (CCL) also showed 84.9% growth inhibition at the same concentration.
When sensitivities of E. coli isolated from patients with complicated urinary tract infections with or without indwelling catheter to first and second generation cephems were determined, cefotiam (CTM), which inhibited 88.9%: 91.4% bacterial growth at MIC of 0.39μg/ml, had the strongest activity among CTM, cefazolin (CEZ), cefoxitin (CFX) and cefmetazole (CMZ).
Among third generation cephems, including cefmenoxime (CMX), latamoxef (LMOX), ceftizoxime (CZX), cefotaxime (CTX) and cefoperazone (CPZ), the strongest activity was observed with CZX, and the agent having the next strongest activity was CMX. LMOX and CPZ showed relatively low activities. Carumonam (CRMN) and aztreonam (AZT), monobactams, showed strong activities against E. coli.
As for Klebsiella spp., activities of pencillins against these strains were low. When activities of oral cephems (cephalexin (CEX) and CCL) and of a quinoline derivative OFLX against these strains were determined, OFLX showed strong activity; i.e., the growth of Klebsiella spp. isolated from complicated urinary tract infections was inhibited at 87.2%; 82.1% at MIC of 0.20μg/ml.
Klebsiella spp. isolated from patients having urinary tract infections with or without indwelling catheter were found to show a relatively high sensitivity to a first generation cephem, CEZ, and second generation cephems, CTM, CMZ and CFX, as follows: CTM inhibited 86.4%: 76.7/growth at MIC of 0.39μg/ml; the inhibition rate of CMZ was slightly lower at the same concentration, but was 75.3%; 65.8% at MIC of 0.78μg/ml; antibiotic potencies of CTM and CMZ against Klebsiella spp. isolated from patients with indwelling catheter were relatively low, i.e., some strains showed MIC over 100μg/ml.
Activities of third generation cephems, including CMX, CZX, CTX, LMOX and CPZ, were also determined similarly. CMX and CZX inhibited 83.3%; 71.2% and 91.7%: 83.6% growths at concentrations below 0.10μg/ml, respectively. At concentrations of ≤0.10μg/ml, LMOX and CTX inhibited 58.3%; 45.2% and 81.0%. 74.0% growths, respectively. When monobactams, CRMN and AZT, were determined for their activities, CRMN inhibited 92.3%: 85.7/ growth and AZT inhibited 82.1%; 64.3% growth, both at MIC´s below 0.10μg/ml.
As for Proteus spp., penicillins, oral cephems and first generation cephems showed only poor activities.
When sensitivities of Proteus spp., to second generation cephems were determined, Proteus spp. isolated from patients with complicated urinary tract infections with indwelling catheter showed low sensitivity. CMZ inhibited 59.7% growth at 1.56μg/ml in 1982-1985. At the same concentration, CTM inhibited 35.8% growth.
CZX, CMX and CTX of the third generation cephem group showed activities against Proteus spp. at about the same levels.