Abstract
Thirty-three clinical isolates of Streptococcus pneumoniae were tested for susceptibility to penicillin and ampicillin by a standard agar dilution method. Results were compared to those obtained using a micro-broth dilution technique in which Mueller-Hinton broth was supplemented with 5% difibrinated whole sheep blood. Among the 33 strains, 2 were resistant (minimal inhibitory concentration, 8 micrograms/ml), 10 were relatively resistant (minimal inhibitory concentration, 0.12 to 0.5 micrograms/ml), and 20 were susceptible (minimal inhibitory concentration, less than or equal to 0.06 micrograms/ml) to penicillin by both methods. Only one stain showed a two-dilutional-step difference by micro-broth and agar dilution testing resulting in categorization as relatively resistant by the former method but susceptible by the latter. A 1-microgram oxacillin disk correctly identified 11 of the 12 resistant strains. The micro-broth dilution technique is a reliable, simple method for penicillin or ampicillin susceptibility testing of pneumococci and economically feasibile to perform manually or with a semiautomated system.
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Selected References
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- Appelbaum P. C., Bhamjee A., Scragg J. N., Hallett A. F., Bowen A. J., Cooper R. C. Streptococcus pneumoniae resistant to penicillin and chloramphenicol. Lancet. 1977 Nov 12;2(8046):995–997. doi: 10.1016/s0140-6736(77)92892-6. [DOI] [PubMed] [Google Scholar]
- Dixon J. M., Lipinski A. E., Graham M. E. Detection and prevalence of pneumococci with increased resistance to penicillin. Can Med Assoc J. 1977 Nov 19;117(10):1159–1161. [PMC free article] [PubMed] [Google Scholar]
- Jacobs M. R., Gaspar M. N., Robins-Browne R. M., Koornhof H. J. Antimicrobial susceptibility testing of pneumococci. 2. Determination of optimal disc diffusion test for detection of penicillin G resistance. J Antimicrob Chemother. 1980 Jan;6(1):53–64. doi: 10.1093/jac/6.1.53. [DOI] [PubMed] [Google Scholar]
- Maki D. G., Helstad A. G., Kimball J. L. Penicillin susceptibility of Streptococcus pneumoniae in 1978. Screening for resistance by disk testing. Am J Clin Pathol. 1980 Feb;73(2):177–182. doi: 10.1093/ajcp/73.2.177. [DOI] [PubMed] [Google Scholar]
- Naraqi S., Kirkpatrick G. P., Kabins S. Relapsing pneumococcal meningitis: isolation of an organism with decreased susceptibility to penicillin G. J Pediatr. 1974 Nov;85(5):671–673. doi: 10.1016/s0022-3476(74)80513-5. [DOI] [PubMed] [Google Scholar]
- O'Callaghan C. H., Morris A., Kirby S. M., Shingler A. H. Novel method for detection of beta-lactamases by using a chromogenic cephalosporin substrate. Antimicrob Agents Chemother. 1972 Apr;1(4):283–288. doi: 10.1128/aac.1.4.283. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Paredes A., Taber L. H., Yow M. D., Clark D., Nathan W. Prolonged pneumococcal meningitis due to an organism with increased resistance to penicillin. Pediatrics. 1976 Sep;58(3):378–381. [PubMed] [Google Scholar]
- Tarpay M. Importance of antimicrobial susceptibility testing of Streptococcus pneumoniae. Antimicrob Agents Chemother. 1978 Oct;14(4):628–629. doi: 10.1128/aac.14.4.628. [DOI] [PMC free article] [PubMed] [Google Scholar]