Haemophilus influenzae type B resistant to tetracycline isolated from children with meningitis.

During a three-year-period, 1971-73 inclusive, haemophili isolated from 96 children with severe infections, of whom 73 had meningitis and 19 acute epiglottitis, were serotyped and tested for sensitivity to antibacterial drugs. All strains were identified as Haemophilus influezae type b, and were sensitive to ampicillin, chloramphenicol, and trimethoprim. However, 3 isolates--from a boy aged 11 months and a girl aged 1 year with meningitis, and a girl aged 2 years with epiglottitis--were highly resistant to tetracycline, with a median minimal inhibitory concentration of 50 mug tetracycline hydrochloride per ml (resistance ratio greater than or equal to 50). Resistance was also demonstrated to doxycycline, oxytetracycline, and rolitetracycline and, in one strain, to minocycline. No evidence was obtained that the resistant organisms were capable of inactivating tetracyclines.