Susceptibility of bacteria isolated from the patients with lower respiratory tract infections to antibiotics (1984)]

Collaborated studies on species of respiratory tract infection (RTI)-related organisms for their identification and drug susceptibilities have been carried out since 1981 at about 20 centers in Japan. On this occasion, the data obtained between 1982 and 1985 were reanalyzed to determine whether or not drug susceptibilities differed depending upon diseases, from which the organisms were isolated. The results summarized below were obtained in this study. 1. Among Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae and Pseudomonas aeruginosa examined, differences in drug susceptibilities according to different diseases were found among S. aureus and also mucoid strains of P. aeruginosa. 2. Susceptibility to beta-lactam antibiotics was definitely lower in S. aureus strains isolated from pneumonia than in those isolated from chronic bronchitis and bronchiectasia. 3. The isolation frequency of methicillin-and cefazolin-resistant strains of S. aureus was 30.3% and 25.9%, respectively, and was especially high among strains isolated from pneumonia. The antibiotic potency of minocycline against S. aureus, including methicillin resistant S. aureus, was the strongest among 9 drugs examined; S. aureus maintained relatively sufficient sensitivity to dicloxacillin among beta-lactam antibiotics. 4. Mucoid producing strains of P. aeruginosa isolated from chronic bronchitis had slightly lower drug susceptibility than those isolated from bronchiectasia. 5. When drug susceptibilities of H. influenzae were compared among groups separated according to diseases using MIC50, MIC80 and MIC90 as indicators, there were no clear differences. The isolation frequency of ampicillin (ABPC)-resistant strains, however, was clearly different among diseases; namely, resistant strains were the most and the least frequently isolated from chronic bronchitis and from pneumonia, respectively. In addition, the drug susceptibility of H. influenzae isolated in 1985 was analyzed in relation to the production of beta-lactamase. As a result, it was suspected that some factors, other than beta-lactamase, participated in the mechanism of ABPC-resistance. 6. These results suggest that drugs to be used for the chemotherapy of RTI should be selected considering the fact that drug susceptibilities of the pathogens differ, even among the same species, according to diseases.