Abstract
A dye reduction method for determining a definitive endpoint with agar dilution susceptibility testing has been developed. Bacterial growth was determined by applying to the inoculum spot a dye solution containing 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride and phenazine methosulfate. Viable colonies reduced the tetrazolium salt to a visible red color within 3 to 5 min. The minimum inhibitory concentrations of six antimicrobial agents tested against 167 clinical streptococcal isolates were recorded before and after the addition of the tetrazolium-phenazine methosulfate solution. A total of 252 discrepancies (25%) were observed, and of these, 30 (12%) differed by more than one tested antibiotic concentration. Endpoint reproducibility of the dye procedure was assessed by four technologists in a double-blind study. A 2.7-fold reduction in disagreement was observed when the dye was used. Use of the tetrazolium-phenazine methosulfate solution involves little deviation from standard antimicrobial susceptibility test procedures and yields more accurate, as well as reproducible, susceptibility results.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bartlett R. C., Mazens M. F. Rapid antimicrobial susceptibility test using tetrazolium reduction. Antimicrob Agents Chemother. 1979 Jun;15(6):769–774. doi: 10.1128/aac.15.6.769. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bartlett R. C., Mazens M., Greenfield B. Acceleration of tetrazolium reduction by bacteria. J Clin Microbiol. 1976 Mar;3(3):327–329. doi: 10.1128/jcm.3.3.327-329.1976. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Boyle V. J., Fancher M. E., Ross R. W., Jr Rapid, modified Kirby-Bauer susceptibility test with single, high-concentration antimicrobial disks. Antimicrob Agents Chemother. 1973 Mar;3(3):418–424. doi: 10.1128/aac.3.3.418. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Istre G. R., Humphreys J. T., Albrecht K. D., Thornsberry C., Swenson J. M., Hopkins R. S. Chloramphenicol and penicillin resistance in pneumococci isolated from blood and cerebrospinal fluid: a prevalence study in metropolitan Denver. J Clin Microbiol. 1983 Mar;17(3):472–475. doi: 10.1128/jcm.17.3.472-475.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Liñares J., Garau J., Domínguez C., Pérez J. L. Antibiotic resistance and serotypes of Streptococcus pneumoniae from patients with community-acquired pneumococcal disease. Antimicrob Agents Chemother. 1983 Apr;23(4):545–547. doi: 10.1128/aac.23.4.545. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McCarthy V. P., Cho C. T., Diehl A. M., Ramsey B. W. Bacterial endocarditis due to penicillin-resistant Streptococcus viridans. Clin Pediatr (Phila) 1979 May;18(5):263–266. doi: 10.1177/000992287901800501. [DOI] [PubMed] [Google Scholar]