title: Haemophilus influenzae ATCC 49766, an alternative quality control strain for monitoring broth microdilution susceptibility tests with selected beta-lactams.
abstract: A beta-lactamase-negative, ampicillin-resistant strain of Haemophilus influenzae is currently used for quality control of broth microdilution tests performed with Haemophilus test medium (HTM). Studies with eight lots of HTM broth documented the fact that MIC limits for some antimicrobial agents are unrealistically stringent; i.e., only three of eight lots of HTM broth were satisfactory for testing cefaclor. An alternative, ampicillin-susceptible strain of H. influenzae (ATCC 49766) was found to provide much more reproducible results with five problematic drugs (cefaclor, cefuroxime, cefamandole, loracarbef, and cefonicid). Multilaboratory studies defined MIC control limits for both control strains tested against 12 antimicrobial agents.
authors.affiliation: Clinical Microbiology Institute, Tualatin, Oregon 97062.
authors.forename: A L
authors.initials: AL
authors.lastname: Barry
authors.forename: J H
authors.initials: JH
authors.lastname: Jorgensen
authors.forename: D J
authors.initials: DJ
authors.lastname: Hardy
authors.forename: S D
authors.initials: SD
authors.lastname: Allen
authors.forename: C N
authors.initials: CN
authors.lastname: Baker
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003470:Culture Media; D004352:Drug Resistance, Microbial; D005069:Evaluation Studies as Topic; D006193:Haemophilus influenzae / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards*; D010403:Penicillin Resistance; D011786:Quality Control; D013045:Species Specificity
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D000667:Ampicillin