Susceptibility profile of yeast-like organisms isolated from HIV/AIDS patients; using NCCLs macrodiltion method compared with agar diffusion technique

CA Enwuru, A Ogunledun, N Idaka, NV Enwuru



Yeast like opportunistic fungal infection has been reported globally amongst HIV/AIDS patients, particularly as the etiologic agent of oral thrush. Fluconazole antibiotic has been most popularly employed in treating cases of oral thrush in HIV/AIDS patients. Recent reports have recorded antifungal drug resistance amongst immunocompromised subjects. This constitutes a big problem in the management of opportunistic candidiasis. The NCCLS micro/macrodilusion sensitivity testing procedure is expensive, cumbersome and requires a level of sophistication. This study was designed to compare NCCLS M-27-A macrodilution method (expensive) with agar diffusion technique (cheap and simple), to provide a reliable rapid alternative to the new pressing need for antifungal routine sensitivity testing. Sputum specimens from 213(108 females and 105 males) HIV positive patients were plated onto SDA. The isolates were identified by morphotyping, microscopy and speciated using germ tube test, and battery of biochemical sugar fermentation; and assimilation tests. Fluconazole agar diffusion susceptibility testing was carried out on each isolate, compared with the NCCLS macrodilution sensitivity assay standard.
Of the 74 isolates tested for fluconazole sensitivity, 59(79.7%) were sensitive (zone diameter > 19mm, mean diameter 28mm), 6(8.1%) were Sensitive Dose Dependent (S-DD) (zone diameter 13-18mm, mean diameter 16mm), while 9(12.2%) were resistant (zone diameter < 12mm) using agar diffusion method, matched with 58(78.4%) sensitive MIC < 8μg/ml, 9 (12.2%) S-DD MIC 16-32μg/ml and 7(9.5%) resistant MIC >64μg/ml profile, using the NCCLS macrodilution assay. The differences between the test method (Agar diffusion) and the control standard method (NCCLS-M 27-A broth Macrodilution MICS) were not statistically significant using t-test (two tail) (t = 4.302656, P=1.0). Among the C. albicans isolates, 26(86.7%) were sensitive to fluconazole. The rank of susceptibility was C. albicans > C. tropicalis > C. krusei.
It is concluded that broncho-oro-pharyngeal Candida and other yeast-like species existed in about one third of the HIV and AIDS patients studied; in which C. albicans was the most prevalent, while about ten percent of all the Candida isolates were resistant to fluconazole. The reliability of germ tube production as a confirmatory test for Candida albicans in HIV infection was as high as 96.7% and is therefore, recommended for continued use. Agar diffusion compared favourably with the NCCLS macrodilution technique, hence it is recommended for routine antifungal sensitivity test on all isolates of yeast-like cells from HIV and AIDS subjects.

Keywords: HIV/AIDS, oral thrush, yeast-like cells, fluconazole resistance, NCCLS vs agar diffusion technique.

African Journal of Clinical and Experimental Microbiology Vol. 9 (2) 2008 pp. 88-96