THE INCIDENCE OF RESPIRATORY-TRACT PATHOGENS AND ANTIMICROBIAL SUSCEPTIBILITIES OF STREPTOCOCCUS-PNEUMONIAE, HAEMOPHILUS-INFLUENZAE AND MORAXELLA (BRANHAMELLA) CATARRHALIS ISOLATED BETWEEN 1990 AND 1993

Using a quantitative culture of sputum, the incidence of pathogenic ba cteria in respiratory infection in our laboratory between 1990 and 199 3 were investigated. While Haemophilus influenzae, Streptococcus pneum oniae and Moraxella (Branhamella) catarrhalis mere isolated at high ra tes (67 similar to 78%) from the specimens of outpatients throughout t he study period, the incidence of S. pneumoniae has increased graduall y. The antimicrobial susceptibilities of these three pathogens were ex amined with the agar dilution method. A marked increase of penicillin (PC) resistant S. pneumoniae (MIG greater than or equal to 0.1 mu g/ml ) was observed with a resistance rate of 2.1% in 1990 and 25% in 1993. Resistance to erythromycin (EM, MIC greater than or equal to 1.56 mu g/ml) was 8.5% in 1990 but then increased to 34% in 199'2. Most of the PC resistant isolates were resistant to multidrugs such as EM, minocy cline and clindamycin. The MICs of all beta-lactams examined for S. pn eumoniae increased along with the MICs of PC, though the level varied between drugs. The rates of beta-lactamase positive H. influenzae grad ually decreased, being 14.3% in 1990 and 7.4% in 1993, whereas those o f M. (B) catarrhalis were consistently high (>90%) every year. In addi tion to beta-lactamase production, the emergence of strains of H. infl uenzae and M.(B) catarrhalis resistant to new quinolone drugs should b e noted.