Failure of ampicillin treatment of β-lactamase-negative, ampicillin resistant Haemophilus influenzae type b meningitis associated with sensitivity to β-lactam antibiotics

Abstract

Ampicillin (ABPC) treatment failed in a 4-month-old boy with Haemophilus influenzae type b meningitis. The isolate was β-lactamase-negative (B-L-N) and ABPC resistant. Subdural effusion which was one of the complications of meningitis was successfully treated by chloramphenicol. In our hospital 22%(13/59) of the H. influenzae strains were β-lactamase-positive (B-L-P) in 1993 and 10%(6/61) in 1996. The percentages of β-lactamase-negative, ABPC-resistant H. influenzae strains, of which the MICs were over 1.56μg/ml, were about 15% in 1993 and 29% in 1996. After inhibition by β-lactamase, several strains of B-L-P, H. influenzae were resistant to ABPC. The standard disk containing 30μg of ABPC for sensitivity testing could not detect ABPC resistance in B-L-N strains. Because of the prevalence of ABPC resistant H. influenzae, ABPC should not be used in the tratment of H. influenzae meningitis. While a few strains resistant to cefotaxime were recovered, cefotaxime may be preferable for treating H. influenzae meningitis.