Fifteen of 192 hospitals enrolled in the L.A. County Meningitis Surveillance Program were identified as caring for all patients with Hemophilus influenzae meningitis in the county in 1975. The prevalence of β-lactamase positive Hemophilus influenzae (βLPHI) was estimated by a survey of bacteriology records at these hospitals. Four of 217 (1.8%) Hemophilus influenzae meningitis patients had β-lactamase positive CSF isolates in 1975. An additional patient with mastoiditis, and CSF pleocytosis with a positive direct CSF Quelling for Hemophilus influenzae type B, but negative CSF culture, had βLPHI isolated from a middle ear aspirate. Seven other βLPHI were reported in 1975 including one from blood culture. These same hospitals reported 19 βLPHI in 1976 including five from CSF and two from blood. MICs of ampicillin for 13 CSF and blood isolates ranged from 1.6 to 200 ugm/ml with a mean of 58 ugm/ml. All strains tested were inhibited by ≤ 1.6 ugm/ml of chloramphenicol. All patients with positive CSF cultures for βLPHI were treated with chloramphenicol 8/9 recovered without sequelae and one expired. Two patients with positive blood cultures for βLPHI, one each with septic arthritis and facial cellulitis, and the patient with CSF pleocytosis and mastoiditis, were treated with ampicillin or penicillin and made a full recovery.
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