Drug Resistance in Streptococcus pyogenes and Haemophilus influenzae

Abstract

Drug resistance of Streptococcus pyogenes and Haemophilus influenzae isolated from respiratory tract were surveyed. Drug resistance and resistance patterns of S. pyogenes strains isolated in various districts in Japan were compared with those of the strains isolated in Europe. Of 1021 strains isolated in Japan, tetracycline (TC) -, macrolide antibiotic (Mac) -, lincomycin (Lcm) -and chloramphenicol (CM) -resistant strains were demonstrated respectively, at the frequencies of 80.3, 62.3, 60.8, and 57.9%. It was characteristic that quadruple and triple resistance to TC, Mac, Lcm and CM were manifested among the strains and their serotype was confined to the T type 12. The emergence of multiply resistant streptococcal strains was due mostly to the rapid increase in the isolation fre quency of Mac- and Lcm-resistant strains. Of 258 strains isolated in Europe, TC-resistant strains were merely demonstrated at the frequency of 23.6%.To know the presence of drug resistance plasmid curing of resistance to Mac, TC, and CM was tested. These resistances were lost after cultivation at 41°C or in the presence of acriflavine (0.2, μ g/ ml). These results suggest that the determinants governing resistance to these antibiotics are located on extrachromosomal genetic elements (plasmid) that are widely distributed in streptococci.From 60 strains of H. influenzae, TC-and APC-resistant strains were demonstrated at frequencies of 8.3% and 5.0%, respectively. No other antibiotic-resistant strains were isolated. Drug resistances were not conjugally transferred. Curing of resistance to TC and APC was tested. APC resistance was lost after cultivation in the presence of ethidium bromide (1μ g/ml). APC-resistant H. influenzae MI-74 produced a type I β-lactamase (PCase). This strain carried nonconjugative plasmid and its size was estimated to be 18 μm.