pH and other effects on the antifungal activity of cilofungin (LY121019)

Two groups of recent clinical isolates of Candida albicans consisting of 101 isolates for which fluconazole MICs were <0.5 g/ml (n ‫؍‬ 50) and >4.0 g/ml (n ‫؍‬ 51), respectively, were compared for their susceptibilities to fluconazole, clotrimazole, miconazole, ketoconazole, and itraconazole. Susceptibility tests were performed by a photometer-read broth microdilution method with an improved RPMI 1640 medium supplemented with 18 g of glucose per liter (RPMI-2% glucose; J. L. Rodríguez-Tudela and J. V. Martínez-Suárez, Antimicrob. Agents Chemother. 38:45-48, 1994). Preparation of drugs, basal medium, and inocula was done by the recommendations of the National Committee for Clinical Laboratory Standards. The MIC endpoint was calculated objectively from the turbidimetric data read at 24 h as the lowest drug concentration at which growth was just equal to or less than 20% of that in the positive control well (MIC 80%). In vitro susceptibility testing separated azole-susceptible strains from the strains with decreased susceptibilities to azoles if wide ranges of concentrations (20 doubling dilutions) were used for ketoconazole, miconazole, and clotrimazole. By comparison with isolates for which fluconazole MICs were <0.5 g/ml, those isolates for which fluconazole MICs were >4.0 g/ml were in general less susceptible to other azole drugs, but different patterns of decreased susceptibility were found, including uniform increases in the MICs of all azole derivatives, higher MICs of several azoles but not others, and elevated MICs of fluconazole only. On the other hand, decreased susceptibility to any other azole drug was never found among strains for which MICs of fluconazole were lower. Secondary resistance to azole antifungal agents in Candida albicans first appeared in the 1980s in patients with chronic mucocutaneous candidiasis treated with KZ for very long periods of time (25,33,36). The isolates involved had markedly reduced susceptibilities to KZ and cross-resistance to other azole drugs. More recently, resistance to the triazole FZ has been described in C. albicans strains isolated from the oral cavities of AIDS patients in different parts of the world (2, 5-8, 15, 18, 22, 24, 25, 28, 29, 32, 34, 36). The absence in most cases of comparative susceptibility data for alternative azole antifungal agents in these isolates still leaves open the question of whether cross-resistance to azole drugs in C. albicans is a general phenomenon.All of the azole antifungal agents share certain properties that makes in vitro susceptibility testing difficult, mainly partial inhibition of fungal growth that makes MIC endpoint determinations both very difficult and subjective (12,29,35). In the proposed standard of the National Committee for Clinical Laboratory Standards (NCCLS) (23), endpoints for azoles are determined visually at 48 h and the MIC is defined as the lowest drug concentration that reduces growth by 80% relative to the growth of the control (MIC 80%). We have previously shown that increased growth of C. albicans in RP...

Section: Discussionmentioning

confidence: 95%

Patterns of in vitro activity of itraconazole and imidazole antifungal agents against Candida albicans with decreased susceptibility to fluconazole from Spain

Martı́nez-Suárez

Rodríguez-Tudela

1995

“…In this report, we have analyzed the effect of changing each of several test conditions that influence test results with other antifungal agents (2,5,10,11,18,19,29 Yeasts. A group of seven yeast isolates (one each of C. albicans, Candida lusitaniae, Candida tropicalis, Candida parapsilosis, T. glabrata, C. krusei, and C. neofornans)was used for the initial studies.…”

Section: D0870(r)-2-(24-difluorophenyl)-1-(3-[(e)-4-(2233-tetrafmentioning

confidence: 99%

In vitro studies of a new antifungal triazole, D0870, against Candida albicans, Cryptococcus neoformans, and other pathogenic yeasts

Tao

Galgiani

1993

Self Cite

We investigated the effects of various assay conditions on the activity of D0870 against seven species of fungi in the broth macrodilution testing procedure proposed by the National respectively. In contrast, Candida krusei and Torulopsisglabrata had a median MIC.0 of 1.0 ,g/ml. Our studies indicate that the pathogenic yeasts C. albicans and C. neoformans are more susceptible to D0870 than other pathogenic yeasts.

“…In recent studies, we examined the relationship of endpoint results obtained by macro-and microdilution broth methods with several newer antifungal agents (8,9 Susceptibility testing. Macrodilution broth assays were performed as previously described (8,9). Briefly, twofold dilutions of the antifungal agents were prepared by standard methods (10) in media to 10 times the final concentrations, as listed below.…”

mentioning

confidence: 99%

“…Macrodilution broth assays were performed as previously described (8,9). Briefly, twofold dilutions of the antifungal agents were prepared by standard methods (10) in media to 10 times the final concentrations, as listed below.…”

mentioning

confidence: 99%

Effects of incubation temperature, inoculum size, and medium on agreement of macro- and microdilution broth susceptibility test results for yeasts

Cook

McIntyre

Galgiani

1990

Self Cite

We examined the effects of temperature and inoculum on the agreement of macro-and microdilution broth Drugs. SCH 39304 (Schering-Plough Research Corp., Bloomfield, N.J.), fluconazole (Pfizer Research, Groton, Conn.), amphotericin B (E. R. Squibb & Sons, Princeton, N.J.), and ketoconazole (Janssen Pharmaceutical, Inc., Piscataway, N.J.) were used to prepare 1-mg/ml stock solutions in 2% dimethyl sulfoxide (Sigma Chemical Co., St. Louis, Mo.) for the triazoles and 10% dimethyl sulfoxide for the other drugs. Stock solutions of flucytosine (Hoffmann-La Roche Inc., Nutley, N.J.) were prepared at a concentration of 10 mg/ml in 10% dimethyl sulfoxide. All drugs were stored at -700C.Media and buffers. Unbuffered synthetic amino acid media for fungi (SAAMF) were prepared as previously described (2, 6), except that solutions of amino acids (Irvine Scientific Sales Co., Inc., Santa Ana, Calif.) were used instead of powdered amino acids and cystine was replaced with equimolar amounts of cysteine (7). Yeast nitrogen broth (Difco), RPMI 1640 (Sigma), and high-resolution broth (kindly supplied by Peter Troke, Pfizer Inc., Sandwich, England) were prepared as specified by the manufacturers, sterilized by filtration, and stored at 4°C. On the day of use, morpholinepropanesulfonic acid (MOPS) buffer (Sigma) was added to each medium to a final concentration of 0. 165 M, the pH was adjusted to 7.0 with 10 M sodium hydroxide or 6 M hydrochloric acid, and the medium was resterilized by filtration.Susceptibility testing. Macrodilution broth assays were performed as previously described (8,9). Briefly, twofold dilutions of the antifungal agents were prepared by standard methods (10) in media to 10 times the final concentrations, as listed below. Yeast inocula were prepared by suspending 1542