These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


PUBMED FOR HANDHELDS

Search MEDLINE/PubMed


  • Title: Evaluation of disk diffusion methods to detect low-level β-lactamase-negative ampicillin-resistant Haemophilus influenzae.
    Author: Nørskov-Lauritsen N, Ridderberg W, Erikstrup LT, Fuursted K.
    Journal: APMIS; 2011 Jun; 119(6):385-92. PubMed ID: 21569097.
    Abstract:
    We evaluated the efficacy of disk diffusion methods for detection of low-level β-lactamase-negative ampicillin-resistant (low-BLNAR) Haemophilus influenzae. Four hundred and seventy unselected, recent clinical isolates were tested with ampicillin (10 μg), cefaclor (30 μg) and cefuroxime (30 μg) on iso-Sensitest agar enriched with nicotinamide adenine dinucleotide (NAD) and horse blood [ST agar; Swedish Reference Group for Antibiotics (SRGA) guidelines], and on chocolate agar (in-house guidelines). Selected isolates (n = 147) were subjected to partial sequencing of the ftsI gene. Forty-seven strains (10.0%) were genotypically identified as low-BLNAR, which was confirmed by determination of minimal inhibitory concentration (MIC) using microbroth dilution method: only low level resistance to ampicillin was detected [MIC ≤1 μg/mL; MIC(50) = 0.5 μg/mL, implying susceptibility by Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antibiotic Susceptibility Testing (EUCAST) interpretative criteria]. The MIC of cefuroxime varied between 1 and 4 μg/mL (MIC(50) = 2 μg/mL), indicating susceptibility to cefuroxime by CLSI but not by EUCAST guidelines. Disk diffusion methods were able to discriminate low-BLNAR H. influenzae from the wild-type population with sensitivities ranging from 87% to 98% and specificities from 96% to 99%. Cefaclor was found to be superior to cefuroxime and ampicillin. Cefaclor zone diameter breakpoints of 30/29 and 23/22 mm are suggested for ST agar and chocolate agar, respectively.
    [Abstract] [Full Text] [Related] [New Search]