This study was designed to examine the effects of antifungal carryover, agitation, and starting inoculum on the results of time-kill tests conducted with various Candida species. Two isolates each of Candida albicans , Candida tropicalis , and Candida glabrata were utilized. Test antifungal agents included fluconazole, amphotericin B, and LY303366. Time-kill tests were conducted in RPMI 1640 medium buffered with morpholinepropanesulfonic acid (MOPS) to a pH of 7.0 and incubated at 35°C. Prior to testing, the existence of antifungal carryover was evaluated at antifungal concentrations ranging from 1× to 16× MIC by four plating methods: direct plating of 10, 30, and 100 μl of test suspension and filtration of 30 μl of test suspension through a 0.45-μm-pore-size filter. Time-kill curves were performed with each isolate at drug concentrations equal to 2× MIC, using a starting inoculum of approximately 10 ⁵ CFU/ml, and incubated with or without agitation. Last, inoculum experiments were conducted over three ranges of starting inocula: 5 × 10 ² to 1 × 10 ⁴ , >1 × 10 ⁴ to 1 × 10 ⁶ , and >1 × 10 ⁶ to 1 × 10 ⁸ CFU/ml. Significant antifungal carryover (>25% reduction in CFU/milliliter from the control value) was observed with amphotericin B and fluconazole; however, carryover was eliminated with filtration. Agitation did not appreciably affect results. The starting inoculum did not significantly affect the activity of fluconazole or amphotericin B; however, the activity of LY303366 may be influenced by the starting inoculum. Before antifungal time-kill curve methods are routinely employed by investigators, methodology should be scrutinized and standardized procedures should be developed.

We assessed resistance rates and trends for important antimicrobial-resistant pathogens (oxacillin-resistant Staphylococcus aureus [ORSA], vancomycin-resistant Enterococcus species [VRE], ceftazidime-resistant Klebsiella species [K-ESBL], and ciprofloxacin-resistant Escherichia coli [QREC]), the frequency of outbreaks of infection with these resistant pathogens, and the measures taken to control resistance in a stratified national sample of 670 hospitals. Four hundred ninety-four (74%) of 670 surveys were returned. Resistance rates were highest for ORSA (36%), followed by VRE (10%), QREC (6%), and K-ESBL (5%). Two-thirds of hospitals reported increasing ORSA rates, whereas only 4% reported decreasing rates, and 24% reported ORSA outbreaks within the previous year. Most hospitals (87%) reported having implemented measures to rapidly detect resistance, but only ∼50% reported having provided appropriate resources for antimicrobial resistance prevention (53%) or having implemented antimicrobial use guidelines (60%). The most common resistant pathogen in US hospitals is ORSA, which accounts for many recognized outbreaks and is increasing in frequency in most facilities. Current practices to prevent and control antimicrobial resistance are inadequate.

The postantifungal effect (PAFE) of fluconazole, MK-0991, LY303366, and amphotericin B was determined against isolates of Candida albicans and Cryptococcus neoformans . Concentrations ranging from 0.125 to 4 times the MIC were tested following exposure to the antifungal for 0.25 to 1 h. Combinations of azole and echinocandin antifungals (MK-0991 and LY303366) were tested against C. neoformans . Fluconazole displayed no measurable PAFE against Candida albicans or Cryptococcus neoformans , either alone or in combination with either echinocandin antifungal. MK-0991, LY303366, and amphotericin B displayed a prolonged PAFE of greater than 12 h against Candida spp. when tested at concentrations above the MIC for the organism and 0 to 2 h when tested at concentrations below the MIC for the organism.

We evaluated the in vitro activity of the new echinocandin antifungal micafungin against Candida spp. using microdilution and time-kill methods. Additionally, we examined the postantifungal effect (PAFE) of micafungin. Finally, we evaluated the effect of the addition of serum and plasma on the MIC of micafungin. Four Candida albicans isolates and two isolates of each Candida glabrata , Candida krusei , and Candida tropicalis were selected for testing. The MICs of micafungin were determined in RPMI 1640 medium buffered with morpholinepropanesulfonic acid alone and with the addition of 10, 20, and 50% human serum and plasma. MICs were determined by using two endpoints: a prominent reduction in growth (the MIC at which 80% of isolates are inhibited [MIC ₈₀ ]) and complete visual inhibition of growth (MIC ₁₀₀ ). The minimum fungicidal concentration (MFC) of micafungin for each isolate was also determined. Time-kill curves were determined for each isolate in RPMI 1640 medium with micafungin at concentrations ranging from 0.125 to 16 times the MIC ₈₀ to assess the correlation between MIC ₈₀ and fungicidal activity. PAFE studies were conducted with each isolate by using concentrations ranging between 0.25 and 4 times the MIC ₈₀ . The MIC ₈₀ s for the test isolates ranged from 0.0039 to 0.25 μg/ml. Overall, the addition of serum or plasma increased the MIC 6 to 7 doubling dilutions for C. albicans and 3 to 4 doubling dilutions for C. krusei and C. tropicalis . Micafungin time-kill studies demonstrated fungicidal activity at concentrations ranging from 4 to 16 times the MIC ₈₀ . Micafungin is very potent agent against a variety of Candida spp., producing fungicidal activity against 7 of 10 isolates tested. A PAFE was observed against all isolates. The PAFE was influenced by the drug concentration, with the highest concentration resulting in the longest observed PAFE in each case. The highest concentration tested, four times the MIC, resulted in a PAFE of more than 9.8 h for 5 of 10 isolates tested (range, 0.9 to ≥20.1 h).

The risk of opportunistic infections is greatly increased in patients who are immunocompromised due to AIDS, cancer chemotherapy and organ or bone marrow transplantation. Candida albicans is often associated with serious systemic fungal infections, however other Candida species such as Candida krusei, Candida tropicalis and Candida glabrata, as well as Cryptococcus neoformans and filamentous fungi such as Aspergillus, have also emerged as clinically significant fungal pathogens. Two triazole antifungal agents, fluconazole and itraconazole, were introduced over a decade ago and since then have been used extensively for the prophylaxis and treatment of a variety of fungal infections. Although both drugs are effective and have their place in therapy, limitations regarding the utility of these agents do exist. For example, fluconazole is not effective for the prophylaxis or treatment of Aspergillus species and has limited activity against C. krusei and C. glabrata. The use of itraconazole has been limited sec...