Are some strains of haemophilus influenzae resistant to antibiotics?

Abstract

H. influenzae is the principal cause of meningitis and acute epiglottitis in children. There have been recent reports of antibiotic-resistant strains of Haemophilus, including isolates resistant to ampicillin. During a period of 3 yr, isolates of H. influenzae from 73 cases of meningitis and 19 of acute epiglottitis were typed, and tested for sensitivity to ampicillin, chloramphenicol, tetracycline, trimethoprim and co-trimoxazole by a disc diffusion technique. All 92 isolates were identified as H. influenzae type b. Resistance to ampicillin, chloramphenicol, trimethoprim and co-trimoxazole was not encountered. Forty-two strains were also tested by a plate titration technique and all were inhibited by 0.5 μg ampicillin/ ml and by 1.0 μg chloramphenicol/ml, indicating full sensitivity to these antibiotics. Three strains of H. influenzae were resistant to tetracycline. These were isolated from a boy aged 11 mth and a girl aged 1 yr, both with meningitis, and a girl aged 2 yr with acute epiglottitis. The minimal inhibitory concentrations of the haemophili ranged from 50 to 75 μg tetracycline hydrochloride/ml. The possibility of successful therapy with tetracycline is precluded by such high degrees of drug resistance. Cross-resistance was demonstrated to docycycline, minocycline, oxytetracycline and rolitetracycline. H. influenzae is the principal cause of meningitis and acute epiglottitis in children. There have been recent reports of antibiotic-resistant strains of Haemophilus, including isolates resistant to ampicillin. During a period of 3 yr, isolates of H. influenzae from 73 cases of meningitis and 19 of acute epiglottitis were typed, and tested for sensitivity to ampicillin, chloramphenicol, tetracycline, trimethoprim and co-trimoxazole by a disc diffusion technique. All 92 isolates were identified as H. influenzae type b. Resistance to ampicillin, chloramphenicol, trimethoprim and co-trimoxazole was not encountered. Forty-two strains were also tested by a plate titration technique and all were inhibited by 0.5 μg ampicillin/ ml and by 1.0 μg chloramphenicol/ml, indicating full sensitivity to these antibiotics. Three strains of H. influenzae were resistant to tetracycline. These were isolated from a boy aged 11 mth and a girl aged 1 yr, both with meningitis, and a girl aged 2 yr with acute epiglottitis. The minimal inhibitory concentrations of the haemophili ranged from 50 to 75 μg tetracycline hydrochloride/ml. The possibility of successful therapy with tetracycline is precluded by such high degrees of drug resistance. Cross-resistance was demonstrated to docycycline, minocycline, oxytetracycline and rolitetracycline.