COMPARATIVE STUDIES ON ACTIVITIES OF ANTIMICROBIAL AGENTS AGAINST CAUSATIVE ORGANISMS ISOLATED FROM URINARY TRACT INFECTIONS (1986)

III. SECULAR CHANGES IN SUSCEPTIBILITY

Abstract

Changes in the susceptibility of various infectious microorganisms to antimicrobial agents from 1982 to 1986 were evaluated. The microorganisms investigated were Escherichia colt, Klebsiella spp.,Citrobacter spp., Enterobacter spp., Proteus spp., Serratia marcescens and Pseudomonas aeruginosa isolated from patients with urinary tract infections. We compared susceptibilities of microorganisms obtained from simple urinary tract infections with those from complicated infections with or without indwelling catheter.
Among penicillins, mecillinam (MPC) showed the strongest activity against E. coli obtained from the patients: 3.13 to 6.25 μg/ml of MPC inhibited the growth of over 90% of the isolates. Among the second and the third generation cephalosporins, cefotiam and cefmenoxime (CMX) showed the strongest activity and the growth of isolates was inhibited at concentrations of 0.39 to 0.78 μg/ml and below 0.10 to 0.20 μg/ml, respectively.
The activities of penicillins against Klebsiella spp. were weak. CMX showed strong activity against Klebsiella spp; 91.7% of the isolates from patients with simple infections were inhibited at 0.39 μg/ml of the agent; 90.7% and 91.6% of isolates from patients with complicated infections with or without indwelling catheter were inhibited at 0.78 μg/ml and 1.56 μg/ml of the agent, respectively. Gentamicin (GM) also showed strong activity against isolates from patients with simple infections and weaker activity against isolates from patients with complicated infections with the catheter; 0.78 μg/ml of ofloxacin (OFLX) inhibited the growths of 90% of the isolates from these patients.
Penicillins showed weak activity against Citrobacter spp. obtained from the patients. Among the second and the third generation cephalosporins, CMX and latamoxef (LMOX) showed strong activities against the Citrobacter isolates; about 50% of the isolates were inhibited at 0.20 μg/ml of either agent. 1.56 μg/ml of minocycline inhibited the growth of 75 to 90% of the isolates and 1.56 μg/ml of OFLX inhibited the growth of 93 to 100% of the isolates.
Against isolates of Proteus spp. penicillins also showed weak activities. Among them, however, piperacillin (PIPC) inhibited the growth of over 90% of the isolates at concentrations ranging from 0.78 to 1.56 μg/ml. Among the second and the third generation cephalosporins, CMX and LMOX showed strong activities; 0.20 μg/ml of CMX inhibited the growth of 94.4%, 90.4%, and 83.1% of isolates from the 3 types of the patients, respectively. 0.20 μg/ml of LMOX inhibited the growth of 94.4%, 91.8%, and 88.3% of the isolates, respectively.
Enterobacter spp. showed resistance to the β-lactam antibiotics. OFLX showed strong activity; 0.39 μg/ml of the agent inhibited the growth of over 80% of the isolates.
S. marcescens was also resistant to antimicrobial agents. Among the β-lactam antibiotics, CMX showed strong activity; 1.56 μg/ml of CMX inhibited the growth of 43.5% of isolates from patients with simple infections and of 38 to 43% of isolates from patients with complicated infections. GM showed strong activity; 1.56 μg/ml of the agent inhibited the growth of 58.8% of isolates from patients with simple infections and of 66 to 70% of isolates from patients with complicated infections.
Penicillins showed weak activity against P. aeruginosa; 6.25 μg/ml of PIPC inhibited the growth of 62 to 71% of the isolates. Among the second and the third generation cephalosporins, ceftazidime exhibited the strongest activity against the P. aeruginosa isolates; 1.56 μg/ml of the agent inhibited the growth of 68.4% of isolates from patients with simple infections and of 72.2 to 66.3% of isolates from patients with complicated infections.