Abstract
The performance characteristics of two lots of Haemophilus Test Medium (HTM) prepared in-house at Mayo Clinic, one lot obtained from BBL (Cockeysville, Md.) and one lot obtained from Remel (Lenexa, Kans.), for disk diffusion susceptibility testing of ampicillin against 81 Haemophilus strains were assessed. Insufficient growth occurred in 2.5 to 13.6% of strains, depending on the HTM used, and was most frequent for beta-lactamase-negative, ampicillin-resistant strains when they were tested with one lot of HTM prepared in-house. Results for all 14 beta-lactamase-positive Haemophilus strains were in complete agreement for all lots of HTM when either 1990 or 1993 National Committee for Clinical Laboratory Standards (NCCLS) interpretive guidelines were followed. However, these beta-lactamase-positive Haemophilus strains could be as precisely, but more rapidly, identified by the cefinase disk method. Results for 56 beta-lactamase-negative, ampicillin-susceptible strains and 11 beta-lactamase-negative, ampicillin-resistant strains varied significantly among all HTM lots tested and as to whether 1990 or 1993 NCCLS interpretive guidelines were followed. We conclude that in our hands disk diffusion testing with HTM prepared in-house or obtained from two commercial sources and following either 1990 or 1993 NCCLS guidelines is an unacceptable method for determining the susceptibilities of Haemophilus strains to ampicillin.
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Selected References
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- Barry A. L., Packer R. R. Performance of Haemophilus Test Media prepared with 12 different lots of Mueller-Hinton agar from four manufacturers. J Clin Microbiol. 1992 May;30(5):1145–1147. doi: 10.1128/jcm.30.5.1145-1147.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Doern G. V. In vitro susceptibility testing of Haemophilus influenzae: review of new National Committee for Clinical Laboratory Standards recommendations. J Clin Microbiol. 1992 Dec;30(12):3035–3038. doi: 10.1128/jcm.30.12.3035-3038.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Doern G. V., Jorgensen J. H., Thornsberry C., Preston D. A., Tubert T., Redding J. S., Maher L. A. National collaborative study of the prevalence of antimicrobial resistance among clinical isolates of Haemophilus influenzae. Antimicrob Agents Chemother. 1988 Feb;32(2):180–185. doi: 10.1128/aac.32.2.180. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Heelan J. S., Chesney D., Guadagno G. Investigation of ampicillin-intermediate strains of Haemophilus influenzae by using the disk diffusion procedure and current National Committee for Clinical Laboratory Standards guidelines. J Clin Microbiol. 1992 Jul;30(7):1674–1677. doi: 10.1128/jcm.30.7.1674-1677.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kohner P. C., Rosenblatt J. E., Cockerill F. R., 3rd Comparison of agar dilution, broth dilution, and disk diffusion testing of ampicillin against Haemophilus species by using in-house and commercially prepared media. J Clin Microbiol. 1994 Jun;32(6):1594–1596. doi: 10.1128/jcm.32.6.1594-1596.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mendelman P. M., Wiley E. A., Stull T. L., Clausen C., Chaffin D. O., Onay O. Problems with current recommendations for susceptibility testing of Haemophilus influenzae. Antimicrob Agents Chemother. 1990 Aug;34(8):1480–1484. doi: 10.1128/aac.34.8.1480. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Scriver S. R., Hoban D. J., McGeer A., Moore T. C., Walmsley S. L., Low D. E. Surveillance of susceptibility testing methodologies for Haemophilus influenzae in Canada, including evaluation of disk diffusion test. J Clin Microbiol. 1994 Aug;32(8):2013–2015. doi: 10.1128/jcm.32.8.2013-2015.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Scriver S. R., Walmsley S. L., Kau C. L., Hoban D. J., Brunton J., McGeer A., Moore T. C., Witwicki E. Determination of antimicrobial susceptibilities of Canadian isolates of Haemophilus influenzae and characterization of their beta-lactamases. Canadian Haemophilus Study Group. Antimicrob Agents Chemother. 1994 Jul;38(7):1678–1680. doi: 10.1128/aac.38.7.1678. [DOI] [PMC free article] [PubMed] [Google Scholar]