title: Ampicillin treatment failure of apparently beta-lactamase-negative Haemophilus influenzae type b meningitis due to novel beta-lactamase.
abstract: Documented ampicillin treatment failures of systemic Haemophilus influenzae type b infections have been associated with synthesis of a TEM-1 beta-lactamase. A patient with H. influenzae type b meningitis in whom ampicillin treatment failed is described; the isolate was beta-lactamase-negative according to the cell suspension chromogenic cephalosporin assay. The false-negative result occurred in a strain which elaborated a novel, plasmid-mediated beta-lactamase with characteristics which distinguish it from TEM-1 beta-lactamase. Clinically important ampicillin resistance in H. influenzae type b occurs by mechanisms other than by synthesis of TEM-1 beta-lactamase. Diagnostic microbiology laboratories should perform antibiotic susceptibility tests in addition to tests for beta-lactamase production.
mesh_terms: D000667:Ampicillin / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006193:Haemophilus influenzae / Q000145:classification / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D006801:Humans; D007223:Infant; D008583:Meningitis, Haemophilus / Q000188:drug therapy*; D010403:Penicillin Resistance; D010957:Plasmids; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics
chemical_list: D000667:Ampicillin; D001618:beta-Lactamases