COMPARATIVE STUDIES OF ANTIMICROBIAL AGENTS AGAINST CAUSATIVE ORGANISMS ISOLATED FROM URINARY TRACT INFECTIONS (1984)

I. SUSCEPTIBILITY DISTRIBUTION

Abstract

Our research group was engaged for 3 years (1979-1981) in a study on sensitivities to antibiotics of 4 bacterial groups including representative pathogenic bacteria found in cases of urinary tract infections; i.e. E. coli, Klebsiella spp., Citrobacter spp., and Proteus spp. Since 1982, all the bacterial strains isolated by our group from patients with urinary tract infections and deemed by doctors in charge as pathogens were sent to the Laboratory of Clinical Pathology of Juntendo University, where they were refixed and subjected to MIC determination. This is the third year of the new study. E. coli was detected most frequently from patients with urinary tract infections and the detection frequency was 28% (323/1, 153) this year (1984), whereas it was 35.3% (304/860) last year, showing a 7% decline from last year to this year. E. faecalis was next frequent organism (12.7% or 147/1, 153) followed by P. aeruginosa (10.8% or 124/1, 153). This order, however, was reversed from last year. Other pathogens, in a decreasing order of isolation frequencies following the above three, were as follows: Proteus spp.(9.5% or 109/1, 153), S. marcescens (6.2% or 71/1, 153), S. epidermidis (5.4% or 62/1, 153), K. pneumoniae (4.9% or 56/1, 153), Enterobacter spp.(2.4% or 28/1, 153) and Citrobacter spp.(2.3% or 27/1, 153).
The results of the determination of the sensitivity of bacterial strains to the antibiotics are described below.
1. Of all the oral antibacterial and antibiotic agents used against E. coli, mecillinam (MPC), cefaclor (CCL) and pipemidic acid (PPA) proved to have high antibacterial potency, and their MIC₉₀ (the concentration to inhibit growths of 90% of the objective bacteria) was 3.13μg/ml. The MIC₉₀'s of cefotiam (CTM), cefotaxime (CTX), ceftizoxime (CZX), cefmenoxime (CMX) and latamoxef (LMOX) were less than 0.39μg/ml. The MIC₉₀'s of cefmetazole (CMZ) and cefoperazone (CPZ) were invariably 1.56μg/ml.
2. K. pneumoniae was not sensitive to ampicillin (ABPC) and did not show much sensitivity to other oral antibacterial and antibiotic agents also. Of all the injectable preparations of antibiotics, cephem antibiotics of the third generation showed the most potent antibacterial effects against K. pneumoniae, and their MIC₉₀'s were lower than 0.10μg/ml for CZX, 0.20μg/ml for CTX, 0.39μg/ml for CMX, and 0.78μg/ml for LMOX, while MIC₉₀'s of CPZ was 6.25μg/ml, which was equal to that of CMZ. The MIC90, of CTM was 0.78μg/ml which was identical to that of LMOX.
3. The sensitivity of Citrobacter spp. to the objective antibacterial and antibiotic agents was low, but showed some sensitivity to MPC, nalidixic acid (NA), PPA and sulfamethoxazole-trimethoprim (ST). Of all the injectable antibiotics, LMOX and CMX were the most effective against Citrobacter spp., showing MIC₈₀ of 6.25μg/ml and 12.5μg/ml, respectively.
4. Fairly strong antibacterial activity was shown by MPC to Enterobacter spp. and its MIC₈₀ was 12.5μg/ml. The Enterobacter spp. showed low sensitivity to the injectable preparations of cephem antibiotics of the first and the second generations except for CTM, and the MIC₈₀ was invariably higher than 200μg/ml. The MIC₈₀ of CTM was 6.25μg/ml. The MIC₈₀'s of the cephem antibiotics were 12.5μg/ml for CMX, 25μg/ml for both LMOX and CTX, and 50μg/ml for both CZX and CPZ.
5. P. mirabilis was very sensitive to cephem antibiotics of the third generation. The MIC₉₀'s of CZX, CTX and CMX were lower than 0.10μg/ml, while that of LMOX was 0.20μg/ml.
6. P. vulgaris was less sensitive to cefazolin (CEZ) and CTM than to cefoxitin (CFX) or CMZ.