Abstract
By using agar dilution as the standard method, we determined the ability of broth microdilution, disk diffusion, and an automated system (AMS Vitek) to detect three different levels of vancomycin resistance among six enterococcal isolates. Enterococcus gallinarum AIB-38 and AIB-39 exhibited low-level resistance (MIC, 16 to 32 micrograms/ml) that was detected only by agar and broth dilution methods. E. faecalis V583, E. faecium AIB-42, and E. faecalis AIB-41 showed moderately high-level resistance (MIC, 128 to 256 micrograms/ml) that was detected by dilution methods but not by disk diffusion unless prolonged incubation or an inoculum 10-fold greater than the standard was used. Similarly, this level of resistance was detected by AMS Vitek only when an inoculum 10-fold larger than recommended was used. The high resistance demonstrated by E. faecium AIB-40 (MIC, 2,048 micrograms/ml) was readily detected by all methods studied. Variation in the ability of different methods to detect vancomycin resistance among enterococci complicates monitoring the incidence of these organisms and could result in very major susceptibility reporting errors.
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Selected References
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- Facklam R. R., Collins M. D. Identification of Enterococcus species isolated from human infections by a conventional test scheme. J Clin Microbiol. 1989 Apr;27(4):731–734. doi: 10.1128/jcm.27.4.731-734.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kaplan A. H., Gilligan P. H., Facklam R. R. Recovery of resistant enterococci during vancomycin prophylaxis. J Clin Microbiol. 1988 Jun;26(6):1216–1218. doi: 10.1128/jcm.26.6.1216-1218.1988. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Leclercq R., Derlot E., Duval J., Courvalin P. Plasmid-mediated resistance to vancomycin and teicoplanin in Enterococcus faecium. N Engl J Med. 1988 Jul 21;319(3):157–161. doi: 10.1056/NEJM198807213190307. [DOI] [PubMed] [Google Scholar]
- Leclercq R., Derlot E., Weber M., Duval J., Courvalin P. Transferable vancomycin and teicoplanin resistance in Enterococcus faecium. Antimicrob Agents Chemother. 1989 Jan;33(1):10–15. doi: 10.1128/aac.33.1.10. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ruoff K. L., de la Maza L., Murtagh M. J., Spargo J. D., Ferraro M. J. Species identities of enterococci isolated from clinical specimens. J Clin Microbiol. 1990 Mar;28(3):435–437. doi: 10.1128/jcm.28.3.435-437.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sahm D. F., Kissinger J., Gilmore M. S., Murray P. R., Mulder R., Solliday J., Clarke B. In vitro susceptibility studies of vancomycin-resistant Enterococcus faecalis. Antimicrob Agents Chemother. 1989 Sep;33(9):1588–1591. doi: 10.1128/aac.33.9.1588. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shlaes D. M., Al-Obeid S., Shlaes J. H., Boisivon A., Williamson R. Inducible, transferable resistance to vancomycin in Enterococcus faecium, D399. J Antimicrob Chemother. 1989 Apr;23(4):503–508. doi: 10.1093/jac/23.4.503. [DOI] [PubMed] [Google Scholar]
- Shlaes D. M., Bouvet A., Devine C., Shlaes J. H., al-Obeid S., Williamson R. Inducible, transferable resistance to vancomycin in Enterococcus faecalis A256. Antimicrob Agents Chemother. 1989 Feb;33(2):198–203. doi: 10.1128/aac.33.2.198. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Swenson J. M., Hill B. C., Thornsberry C. Problems with the disk diffusion test for detection of vancomycin resistance in enterococci. J Clin Microbiol. 1989 Sep;27(9):2140–2142. doi: 10.1128/jcm.27.9.2140-2142.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Uttley A. H., Collins C. H., Naidoo J., George R. C. Vancomycin-resistant enterococci. Lancet. 1988 Jan 2;1(8575-6):57–58. doi: 10.1016/s0140-6736(88)91037-9. [DOI] [PubMed] [Google Scholar]
- Williamson R., Al-Obeid S., Shlaes J. H., Goldstein F. W., Shlaes D. M. Inducible resistance to vancomycin in Enterococcus faecium D366. J Infect Dis. 1989 Jun;159(6):1095–1104. doi: 10.1093/infdis/159.6.1095. [DOI] [PubMed] [Google Scholar]