Diflucan
Evolution of drug resistance in experimental populations of Candida albicans.

Cowen LE, Sanglard D, Calabrese D, Sirjusingh C, Anderson JB, Kohn LM.

Department of Botany, University of Toronto, Mississauga, Ontario, Canada L5L 1C6. lcowen credit.erin.utoronto.ca

Adaptation to inhibitory concentrations of the antifungal agent fluconazole was monitored in replicated experimental populations founded from a single, drug-sensitive cell of the yeast Candida albicans and reared over 330 generations. The concentration of fluconazole was maintained at twice the MIC in six populations; no fluconazole was added to another six populations. All six replicate populations grown with fluconazole adapted to the presence of drug as indicated by an increase in MIC; none of the six populations grown without fluconazole showed any change in MIC. In all populations evolved with drug, increased fluconazole resistance was accompanied by increased resistance to ketoconazole and itraconazole; these populations contained ergosterol in their cell membranes and were amphotericin sensitive. The increase in fluconazole MIC in the six populations evolved with drug followed different trajectories, and these populations achieved different levels of resistance, with distinct overexpression patterns of four genes involved in azole resistance: the ATP-binding cassette transporter genes, CDR1 and CDR2; the gene encoding the target enzyme of the azoles in the ergosterol biosynthetic pathway, ERG11; and the major facilitator gene, MDR1. Selective sweeps in these populations were accompanied by additional genomic changes with no known relationship to drug resistance: loss of heterozygosity in two of the five marker genes assayed and alterations in DNA fingerprints and electrophoretic karyotypes. These results show that chance, in the form of mutations that confer an adaptive advantage, is a determinant in the evolution of azole drug resistance in experimental populations of C. albicans.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10692355&dopt=Abstract fluconazole Diflucan



Diflucan
Evaluation of a capacitance method for direct antifungal susceptibility testing of yeasts in positive blood cultures.

Chang HC, Chang JJ, Huang AH, Chang TC.

Institute of Medical Engineering, National Cheng Kung University, Tainan 701, Taiwan, Republic of China.

The feasibility of using a capacitance method (CM) for direct antifungal susceptibility testing of yeasts in positive blood cultures was evaluated. The CM used the same test conditions as those recommended by the National Committee for Clinical Laboratory Standards. After direct inoculation of positive culture broths into module wells (Bactometer; bioMerieux, Inc., Hazelwood, Mo.), the end-point determination was made by monitoring the capacitance change in the culture broths with Bactometer. The MIC of amphotericin B was the lowest concentration at which yeast growth was completely inhibited, while the MICs of ketoconazole, flucytosine, and fluconazole were the concentrations at which a >/=80% reduction in capacitance change was observed. The MICs of the four drugs against each blood isolate obtained on subculture plates were also determined by the macrodilution method. For 51 positive blood cultures tested, the percent agreement (+/-2 log(2) dilutions) between the CM and the macrodilution method were as follows: amphotericin B (98%), ketoconazole (92%), flucytosine (84%), and fluconazole (96%). The CM was further used for breakpoint susceptibility testing of fluconazole (8 and 64 microg/ml) and flucytosine (4 and 32 microg/ml) against yeasts in positive blood cultures. After testing of 74 specimens by the CM, flucytosine and fluconazole produced one (1.4%) major error and two (2.8%) minor errors, respectively. All yeasts that displayed resistance to flucytosine or fluconazole were detected within 24 h after direct inoculation of the positive broths into Bactometer. The CM may be useful for the rapid detection of antifungal resistance in positive blood cultures containing yeasts.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10698982&dopt=Abstract fluconazole Diflucan



Diflucan
Clonal and spontaneous origins of fluconazole resistance in Candida albicans.

Xu J, Ramos AR, Vilgalys R, Mitchell TG.

Department of Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA. jpxu acpub.duke.edu

The genotypes and susceptibilities to fluconazole of 78 strains of the human pathogenic yeast Candida albicans were compared. The strains comprised two sets of samples from Durham, N.C.: one from patients infected with the human immunodeficiency virus (HIV) and the other from healthy volunteers. For each strain, the MIC of fluconazole was determined by the standard National Committee for Clinical Laboratory Standards protocol. Genotypes were determined by PCR fingerprinting with five separate primers. The analysis revealed little evidence for genotypic clustering according to HIV status or body site. However, a small group of fluconazole-resistant strains isolated from patients infected with HIV formed a distinct cluster. In addition, two fluconazole-resistant strains were isolated from individuals who never took fluconazole, one from a patient infected with HIV and the other from a healthy person. The results suggest both clonal and spontaneous origins of fluconazole resistance in C. albicans.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10699025&dopt=Abstract fluconazole Diflucan



Diflucan
Role of yeasts as nosocomial pathogens & their susceptibility to fluconazole & amphotericin B.

Prasad KN, Agarwal J, Dixit AK, Tiwari DP, Dhole TN, Ayyagari A.

Department of Microbiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow.

A total of 213 and 208 yeasts were isolated as nosocomial pathogens from various infected specimens during 1996 and 1997 respectively. Yeasts ranked fifth among uropathogens in both the years and from eighth to eleventh in other specimens. Increasing trend in nosocomial urinary tract yeast infection (11.9 in 1996 to 12.6 in 1997) and decreasing trend in wound and other infections (5.1 in 1996 to 2.9 in 1997) per 1000 patients' discharges were observed; blood stream infection remained unchanged (2/1000 discharges) in both the years. Eighty two (41 from each year) randomly selected yeasts were identified to species level following standard protocol and tested for antifungal susceptibility against fluconazole and amphotericin B by reference broth macrodilution technique and agar dilution (AD) method. The frequency of various yeast species identified was Candida albicans 39 (47.6%), C.tropicalis 29 (35.4%), C. krusei 4 (4.9%), C. glabrata 3 (3.7%), C. zeylanoides 2 (2.4%), C. guilliermondii 2 (2.4%), one strain (1.2%) each of C. kefyr, C. parapsilosis, and Trichosporon beigelii. Resistance to fluconazole (MIC > or = 64 micrograms/ml) as per NCCLS criteria was observed in 2 Candida sp. (2.4%). Significantly higher number of non-albicans Candida sp. (8/43; 18.6%) had MIC > 8 micrograms/ml as compared to C. albicans (2/39; 5.1%) (P < 0.05). Only one strain of C. tropicalis had MIC 8 micrograms/ml to amphotericin B and none had MIC > 8 micrograms/ml. Agreement between the reference and the AD methods for fluconazole was 88 per cent and for amphotericin B was 94 per cent. The present study indicates that Candida sp. are emerging as important nosocomial pathogens and the tendency of yeasts to develop resistance to antifungal agents appears to be a challenge for patient management.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10709333&dopt=Abstract fluconazole Diflucan



Diflucan
Pharmacodynamics of fluconazole, itraconazole, and amphotericin B against Candida albicans.

Burgess DS, Hastings RW, Summers KK, Hardin TC, Rinaldi MG.

College of Pharmacy, The University of Texas at Austin, USA. burgessd uthscsa.edu

The objective of this study was to evaluate the pharmacodynamic activity of fluconazole, itraconazole, and amphotericin B against Candida albicans. Susceptibilities were determined according to the NCCLS guidelines (M27). Time-kill studies were performed using antifungal concentrations of 0.25-32 x MIC. Samples were withdrawn at predetermined timepoints, then plated using a spiral plater. Colony counts were determined after incubation at 35 degrees C for 24 h. The AUKC(0-48) was plotted against the concentration/MIC ratio. Candida isolates (95-2672, 96-15, and 95-2542) were classified as susceptible, susceptible-dose dependent, and resistant to fluconazole and itraconazole (MIC = 0.25 and 0.03 microg/mL, 32 and 0.5 microg/mL, 64 and 1 microg/mL; respectively). All three isolates were susceptible to amphotericin B (MIC = 0.13 microg/mL). Fluconazole inhibited the growth of the susceptible and S-DD isolates and was ineffective at all concentrations against the resistant isolate. Itraconazole, on the other hand, inhibited growth of the susceptible isolate, but was ineffective for the S-DD and resistant isolates. Maximal effectiveness was noted at the concentration 8 x MIC and 2 x MIC for fluconazole and itraconazole, respectively. Amphotericin B demonstrated concentration-dependent antifungal activity. The times necessary for the colony counts to fall below the limit of quantification were inversely related to increasing concentrations of amphotericin B. The maximal effect for amphotericin B was recorded at 2 x MIC. In summary, the triazoles inhibit growth of susceptible C. albicans; however, careful consideration should be given to the MIC for S-DD isolates because itraconazole may not be active if the MIC is reported in the higher susceptible-dose dependency range. In reference to amphotericin B, optimal activity may be achieved by maximizing the peak drug concentration/MIC ratio.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10744363&dopt=Abstract fluconazole Diflucan



Diflucan
Histamine release induced by antimicrobial agents and effects of antimicrobial agents on vancomycin-induced histamine release from rat peritoneal mast cells.

Toyoguchi T, Ebihara M, Ojima F, Hosoya J, Shoji T, Nakagawa Y.

Department of Pharmacy, Yamagata University Hospital, Japan.

Vancomycin and certain fungicides may cause anaphylactoid reactions. We investigated the effects of vancomycin, miconazole and fluconazole on histamine release in rat peritoneal mast cells. Vancomycin and miconazole provoked histamine release in a dose-dependent manner. In contrast, fluconazole did not provoke histamine release at concentrations of 3 x 10(-6)-3 x 10(-3) M. Vancomycin is efficacious in the treatment of gram-positive bacterial infections; patients presenting themselves with mixed infections require concomitant therapy with a second antimicrobial agent. We investigated the effect of fosfomycin sodium, cilastatin sodium or fluconazole on vancomycin-induced histamine release. Fosfomycin sodium inhibited vancomycin-induced histamine release but neither cilastatin sodium nor fluconazole inhibited it in the mole ratios of daily doses used in humans. These results suggest that vancomycin and miconazole provoke histamine release in rat mast cells, but that fluconazole probably does not, while fosfomycin sodium may inhibit vancomycin-induced histamine release.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10757422&dopt=Abstract fluconazole Diflucan



Diflucan
Variation in morphotype, karyotype and DNA type of fluconazole resistant Candida albicans from an AIDS patient.

Takasuka T, Baily GG, Birch M, Anderson MJ, Law D, Denning DW.

Department of Medicine, University of Manchester School of Medicine, UK.

Azole-resistant oropharyngeal and oesophageal candidiasis is a recent phenomenon observed in patients with AIDS usually previously treated with fluconazole. Some variation has been observed in antifungal susceptibility testing among separate colonies of Candida albicans from the same patient. This raises the question of whether there are multiple clones present or simply phenotypic variation in expression of azole resistance. To address this question we took 18 isolates grown from multiple swabs taken before and after experimental azole therapy from a single HIV-positive individual with fluconazole-resistant oral candidiasis and compared morphotype, karyotype, PCR-based DNA typing and azole susceptibility. Ten of the isolates were from a single 2-day period. Amongst these 10 there were seven morphotypes, five karyotypes and four polymerase chain reaction (PCR) types. Three further morphotypes, one karyotype and two PCR types were found amongst the eight isolates obtained during the subsequent 4 months. Limited variation in susceptibility to two azoles--fluconazole and D0870--was also seen. This work emphasizes both the large genotype and phenotypic variability of C. albicans isolates in the mouth of AIDS patients with fluconazole resistance, and the difficulties in interpretation of present typing methods.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9515670&dopt=Abstract fluconazole Diflucan



Diflucan
Comparison of fluconazole pharmacokinetics in serum, aqueous humor, vitreous humor, and cerebrospinal fluid following a single dose and at steady state.

Mian UK, Mayers M, Garg Y, Liu QF, Newcomer G, Madu C, Liu W, Louie A, Miller MH.

Department of Ophthalmology, Montefiore Medical Center-Albert Einstein College of Medicine, Bronx, New York, USA.

The objective of this study was to characterize the pharmacokinetic parameters and penetration of fluconazole following a single dose in the serum, aqueous humor, vitreous humor and cerebrospinal fluid (CSF) of non pigmented rabbits using serial sampling techniques and to determine if the pharmacokinetic parameters in the eye and CSF are similar. Twenty healthy male rabbits received intravenous fluconazole 20 mg/kg as a single dose or 20 mg/kg every 12 hours for 4 doses. Serum, aqueous humor, vitreous humor and CSF samples were taken 15 minutes after the initial intravenous injection and hourly thereafter for six hours. Fluconazole concentrations were determined by microbiological assay. Pharmacokinetic analyses were performed using a nonlinear least-square regression program. Fluconazole's penetration in all anatomical compartments was > 70% than in the serum. Similar elimination half-lives and time to reach maximum concentrations were noted in all compartments. While mean concentrations in each anatomical compartment were similar in animals receiving a single dose or among those at serum steady state, the mean concentrations achieved in the serum, aqueous and vitreous humors and CSF were between 1.82 and 2.17 times higher at serum steady state than following a single dose. At serum concentrations that are comparable to those in humans, the penetration of fluconazole into the noninflamed aqueous and vitreous humors and CSF were > or = 70%. The CSF and ocular pharmacokinetic parameters closely resembled each other, so that either could be used as a surrogate for the other.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9811235&dopt=Abstract fluconazole Diflucan