A total of 188
Pseudomonas aeruginosa isolates from clinical specimens in the Showa University Fujigaoka Hospital during the 20 months from April 1992 to November 1993 were epidemiologically examined, by O-serotyping and determination of MICs of various anti-
Pseudomonas β-lactam antibiotics. The following results were obtained.
1. Of the total isolates, 79 (42%), 55 (29%), and 38 (20%) were isolated from the respiratory tract, urinary tract, and pus specimens, respectively. Most of them were distributed in the wards of the emergency center, and department of urology, surgery, gastroenterology, and respiratory medicine.
2. Of the total isolates, 55 (29%), 34 (18%), and 19 (10%) were O-serotypes E, G, and A, respectively. These values were higher than those for the othter O-serotypes such as B, C, D, F. H, I, K, and M. No serotype J and L strains were isolated.
3. The MIC
50 of the carbapenems such as imipenem, panipenem, meropenem, and biapenem ranged from 0.39 to 1.56μg/ml. The MIC
50 and MIC
90 of cefclidin were 0.39 and 25μg/ml, and those of ceftazidime were 1.56 and 12.5μg/ml, respectively. These antibiotics had higher antibacterial activities against the isolates tested than cefotaxime, latamoxef, cefsulodin, cefoperazone, aztreonam, piperacillin, and ticarcillin.
4. Only 10 (5%) of the total isolates were resistant to the carbapenems. Six (60%) of these isolates were isolated from respiratory tract specimens.
5. Eighteen (64%) of the 28 strains resistant to cefclidin (14% of the total isolates) were isolated from the urinary tract specimens, and 3 (11%) were from the respiratory tract specimens.
6. Only 1 (3%) of the 37 strains resistant to the carbapenems or cefclidin was cross-resistant.
7. Twenty-one (38%) of the serotype E strains had a higher cefclidin-resistance rate than any other serotype strains. Two (11%) of the serotype A strains had a higher carbapenem-resistance rate.
8. No serotype G strain resistant to cefclidin was isolated.
9. All the cefclidin-resistant strains were significantly dissociated from the regression line for the relationship between the MICs of cefclidin and ceftazidime. The MICs of cefclidin against these isolates were lower than those of ceftazidime, suggesting that the mechanism of resistance to the two cephalosporins in
P. aeruginosa was different.
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