Abstract
Recent reports of bona fide ampicillin resistance among strains of Haemophilus influenzae have emphasized the need for improved methods of susceptibility testing of clinical isolates. A simplified medium composed of only Mueller-Hinton medium plus supplement C (yeast autolysate and hematin) was used successfully for ampicillin susceptibility testing of 20 recent clinical isolates of H. influenzae, including six strains with confirmed ampicillin resistance. With this medium, susceptible strains were inhibited by less than 1 μg of ampicillin per ml, whereas resistant strains had minimal inhibitory concentrations of 8 μg or greater per ml. This medium can be used for either disk diffusion, tube dilution, or agar plate dilution methods of susceptibility testing. It has the practical advantage of simplicity of preparation and retains the light color and transparency of Mueller-Hinton medium. This medium can also be used for preparation of an inoculum suspension that can be adjusted to a standardized turbidity.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bauer A. W., Kirby W. M., Sherris J. C., Turck M. Antibiotic susceptibility testing by a standardized single disk method. Am J Clin Pathol. 1966 Apr;45(4):493–496. [PubMed] [Google Scholar]
- Ericsson H. M., Sherris J. C. Antibiotic sensitivity testing. Report of an international collaborative study. Acta Pathol Microbiol Scand B Microbiol Immunol. 1971;217(Suppl):1+–1+. [PubMed] [Google Scholar]
- Khan W., Ross S., Rodriguez W., Controni G., Saz A. K. Haemophilus influenzae type B resistant to ampicillin. A report of two cases. JAMA. 1974 Jul 15;229(3):298–301. [PubMed] [Google Scholar]
- McLinn S. E., Nelson J. D., Haltalin K. C. Antimicrobial susceptibility of Hemophilus influenzae. Pediatrics. 1970 May;45(5):827–838. [PubMed] [Google Scholar]
- Nelson J. D. Editorial: Should ampicillin be abandoned for treatment of Haemophilus influenzae disease? JAMA. 1974 Jul 15;229(3):322–324. [PubMed] [Google Scholar]
- Neter E. Yeast Autolysate: A Culture Medium for Hemophilus influenzae. Science. 1947 Oct 10;106(2754):350–352. doi: 10.1126/science.106.2754.350-a. [DOI] [PubMed] [Google Scholar]
- Sherris J. C., Rashad A. L., Lighthart G. A. Laboratory determination of antibiotic susceptibility to ampicillin and cephalothin. Ann N Y Acad Sci. 1967 Sep 27;145(2):248–267. doi: 10.1111/j.1749-6632.1967.tb50223.x. [DOI] [PubMed] [Google Scholar]
- Tomeh M. O., Starr S. E., McGowan J. E., Jr, Terry P. M., Nahmias A. J. Ampicillin-resistant Haemophilus influenzae type B infection. JAMA. 1974 Jul 15;229(3):295–297. [PubMed] [Google Scholar]
- Wood S. H. In vitro sensitivity studies of Hemophilus infuenzae--typable and non-typable strains. Pediatrics. 1967 Feb;39(2):214–219. [PubMed] [Google Scholar]