CHARACTERIZATION OF AN AMPICILLIN-RESISTANT STRAIN OF HAEMOPHILUS INFLUENZAE ISOLATED IN JAPAN

Abstract

An ampicillin-resistant strain TK 156 of Haemophilus influenzae, isolated from pharynx of a patient with acute respiratory infection at Teikyo University Medical School Hospital in 1977, was examined for the 8-lactamase production, plasmid DNA and the transferability of drug resistance, and attempted some discussion on these subjects.
1. The strain TK 156 produces TEM type j9-lactamase of the group of Type III penicillinase.
2. Ampicillin resistance of the strain TK 156 was eliminated for 63.9% of the total cells when treated with 25 mg/ml acridine orange for 1 week.
3. TK 156 and TK 156 E (ampicillin-susceptible variant of TK 156) strains were examined for the presence or absence of plasmid DNA. The strain TK 156 contained 30.6×10⁶ dalton plasmid DNA, but TK 156 E did not contain satellite DNA. From this finding, it was strongly suggested that the ampicillin-resistant gene of TK 156 strain was located on plasmid.
4. In the transfer experiment of drug resistance by conjugation with TK 156 strain as a donor and ampicillin-sensitive strains of H. influenzae, H. parainfluenzae, E. coli and Pseudomonas aeruginosa as recipients, resistance transfer failed to take place.
5. The aforesaid characteristics of ampicillin resistance of the strain TK 156 were compared with those of ampicillin resistance of H. influenzae reported in Western countries.