Determination of in vitro susceptibility of Candida species to amphotericin B by E-test and previously proposed MIC breakpoints on two different media

Alp Ş. , SANCAK B. , Arikan S.

MIKROBIYOLOJI BULTENI, vol.42, no.2, pp.293-300, 2008 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 42 Issue: 2
  • Publication Date: 2008
  • Title of Journal : MIKROBIYOLOJI BULTENI
  • Page Numbers: pp.293-300


Although much work has concentrated on defining a reliable and reproducible method for determining in vitro susceptibility of Candida species to amphotericin B, there still has been limitations of the proposed techniques. In this study, amphotericin B minimal inhibitory concentrations (MIC) and susceptibility categories of 212 Candida strains (57 C.glabrata, 53 C.lusitaniae, 51 C.krusei and 51 C.tropicalis) were determined by E-test on RPMI agar (RPG) and antibiotic medium 3 agar (AM3) both supplemented with 2% glucose. The results were interpreted according to the proposed MIC breakpoints (>= 0.38 mu g/ml on RPG, >1 mu g/ml on AM3) and discrepancies between susceptibility categories were investigated. While all Candida strains included in the study were determined to be susceptible on AM3 by amphotericin B E-test at 48h, 36.3% of the isolates were classified as resistant on RPG at 48 hours. On RPG, C.krusei strains showed the highest resistance rate (94.1% at 48 h), followed by C.tropicalis (35.3% at 48 h) and C.glabrata (17.5% at 48h). At 48h of incubation, 98.1% of C.lusitaniae isolates were found to be susceptible on RPG. The categorical agreement rates between the results obtained on two media and for C.lusitaniae and C.glabrata were 98.1% and 82.5% at 48 hours. For C.tropicalis and C.krusei, the rates of agreement were 64.7% and 5.9% at 48 hours. Conclusively, according to the previously proposed MIC breakpoints for amphotericin B E-test on RPG and AM3, discrepancies between susceptibility categories of Candida species were of remarkable significance.