[Clinical and bacteriological studies of Streptococcus pneumoniae. Yearly changes in isolation frequencies from clinical specimens, serotype distributions and drug susceptibilities, especially those of beta-lactam-resistant strains].

Although chemotherapeutics have markedly reduced the mortalities of infectious diseases caused by Streptococcus pneumoniae, it has recently been recognized that S. pneumoniae is still clinically significant for the infants, highly-aged and high-risk patients. This work was planned to examine the isolation frequency of S. pneumoniae from clinical specimens and its drug-susceptibilities, especially to beta-lactam antibiotics. The strains were obtained from in- and out-patients in Main and Branch Hospitals of Juntendo University from 1961 to 1985. Drug-susceptibility tests were carried out against 39 different drugs including 10 penicillins, 16 cephalosporins, 3 tetracyclines, 3 macrolides, chloramphenicol, gentamicin, vancomycin, 3 pyridone carboxylic acids and sulfamethoxazoletrimethoprim using agar dilution method. The sero-typing of the isolates was made by the Quellung technique using Diagnostic Pneumococcal Anti-Sera (Statens Seruminstitut, Copenhagen). The following results were obtained: S. pneumoniae was isolated mostly from sputum and throat swabs, but rarely from the blood and cerebrospinal fluid. S. pneumoniae was also isolated from the pus and discharges of ears, sinuses and eyes. The isolation frequency of S. pneumoniae was higher in Branch Hospital where subjects were mostly out-patients than in the Main Hospital. Frequent sero-types of S. pneumoniae were groups 23, 6, 19, and type 3, regardless of clinical specimens and years. Against tetracycline and chloramphenicol, approximately 40 to 70% of the strains were resistant, while against maclorides, resistant strains were few. Resistant strains were still fewer against beta-lactam antibiotics. Tetracycline- and chloramphenicol-resistant strains are recently decreasing, while macrolides- and beta-lactam-resistant strains are somewhat increasing. Nine beta-lactam-resistant strains of S. pneumoniae were isolated from sputum and throat swabs, with benzylpenicillin-MICs ranging from 0.39 to 3.13 micrograms/ml. Three (2 of 23F and 1 of 23A) out of the 9 strains were resistant to beta-lactams, tetracycline, chloramphenicol, erythromycin and lincomycin. Four strains (3 of 23F and 1 of group 23) were resistant to beta-lactams, tetracycline, erythromycin and lincomycin. One strain (type 45) was resistant to beta-lactams, tetracycline and chloramphenicol. One strain (23A) was resistant to beta-lactams only. Those 9 beta-lactam-resistant strains were isolated mostly from children. Most of the patients had been given beta-lactam antibiotics before those resistant strains were isolated.(ABSTRACT TRUNCATED AT 400 WORDS)