The epidemiology of invasive mycoses--narrowing the gap.
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California↗
Biomedical subjects
M A Pfaller
Publications and source records attributed to M A Pfaller.
Antifungal pharmacodynamic characteristics of fluconazole and amphotericin B against Cryptococcus neoformans.
The activity of fluconazole and amphotericin B against three isolates of Cryptococcus neoformans was evaluated, with fluconazole and amphotericin B MICs of 2.0-4.0 mg/L and 1.0 mg/L respectively, using time-kill curve methods. Fluconazole was fungistatic against all isolates tested (<99.9% decrease in cfu from initial inoculum). The fungistatic activity of fluconazole was not enhanced by increasing the concentration of antifungal in solution. In contrast, amphotericin B was markedly fungicidal (> or = 99.9% decrease in cfu from initial inoculum). Both the rate and the extent of amphotericin B activity were enhanced when drug concentration was increased.
Amphotericin B↗
Antimicrobial interactions of trovafloxacin and extended-spectrum cephalosporins or azithromycin tested against clinical isolates of Pseudomonas aeruginosa and Stenotrophomonas maltophilia.
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Anti-Infective Agents↗
In-vitro activities of gatifloxacin, sparfloxacin and trovafloxacin against 103 strains of Legionella spp.
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Anti-Infective Agents↗
In vitro activities of voriconazole (UK-109,496) and four other antifungal agents against 394 clinical isolates of Candida spp.
Voriconazole (formerly UK-109,496) is a new monotriazole antifungal agent which has potent activity against Candida, Cryptococcus, and Aspergillus species. We investigated the in vitro activity of voriconazole compared to those of fluconazole, itraconazole, amphotericin B, and flucytosine (5FC) against 394 bloodstream isolates of Candida (five species) obtained from more than 30 different medical centers. MICs of all antifungal drugs were determined by the method recommended by the National Committee for Clinical Laboratory Standards using RPMI 1640 test medium. Overall, voriconazole was quite active against all the yeast isolates (MIC at which 90% of the isolates are inhibited [MIC90], < or =0.5 microg/ml). Candida albicans was the most susceptible species (MIC90, 0.06 microg/ml) and Candida glabrata and Candida krusei were the least (MIC90, 1 microg/ml). Voriconazole was more active than amphotericin B and 5FC against all species except C. glabrata and was also more active than itraconazole and fluconazole. For isolates of Candida spp. with decreased susceptibility to fluconazole and itraconazole MICs of voriconazole were also higher. Based on these results, voriconazole has promising antifungal activity and further in vitro and in vivo investigations are warranted.
Amphotericin B↗
In vitro susceptibilities of Candida bloodstream isolates to the new triazole antifungal agents BMS-207147, Sch 56592, and voriconazole.
BMS-207147, Sch 56592, and voriconazole are three new investigational triazoles with broad-spectrum antifungal activity. The in vitro activities of these three agents were compared with those of itraconazole and fluconazole against 1,300 bloodstream isolates of Candida species obtained from over 50 different medical centers in the United States. The MICs of all of the antifungal drugs were determined by broth microdilution tests performed according to the National Committee for Clinical Laboratory Standards method using RPMI 1640 as a test medium. BMS-207147, Sch 56592, and voriconazole were all quite active against all Candida sp. isolates (MICs for 90% of the isolates tested [MIC90s], 0.5, 1.0, and 0.5 microgram/ml, respectively). Candida albicans was the most susceptible species (MIC90s, 0.03, 0.06, and 0.06 microgram/ml, respectively), and C. glabrata was the least susceptible (MIC90s, 4. 0, 4.0, and 2.0 microgram/ml, respectively). BMS-207147, Sch 56592, and voriconazole were all more active than itraconazole and fluconazole against C. albicans, C. parapsilosis, C. tropicalis, and C. krusei. There existed a clear rank order of in vitro activity of the five azoles examined in this study when they were tested versus C. glabrata: voriconazole > BMS-207147 = Sch 56592 = itraconazole > fluconazole (MIC90s, 2.0, 4.0, 4.0, 4.0, and 64 microgram/ml, respectively). For isolates of Candida spp. with decreased susceptibility to both itraconazole and fluconazole, the MICs of BMS-207147, Sch 56592, and voriconazole were also elevated. These results suggest that BMS-207147, Sch 56592, and voriconazole all possess promising antifungal activity and that further in vitro and in vivo investigations are warranted to establish the clinical value of this improved potency.
Antifungal Agents↗
Evaluation of possible correlations between antifungal susceptibilities of filamentous fungi in vitro and antifungal treatment outcomes in animal infection models.
Nine isolates of filamentous fungi previously tested in 11 different laboratories for their susceptibilities to amphotericin B and itraconazole in vitro were injected intravenously into mice and guinea pigs, and responses to treatment with both agents were studied. The experiments were done in a single laboratory. Mean survival times, the percentages of animals surviving 12 days after infection, and culture results for samples of deep organs obtained postmortem were used as markers of antifungal efficacy. Because of variations in organism pathogenicity, interpretable test systems in vivo could not be established for Fusarium spp. in mice or guinea pigs or for Pseudallescheria boydii in mice, even with the use of immunosuppressive pretreatments. Among the infections that could be evaluated, some degree of response to the corresponding treatment in vivo was seen in animals infected with each of two Rhizopus arrhizus isolates susceptible to amphotericin B at < 0.5 microg/ml and Aspergillus spp. isolates susceptible to itraconazole at < 1.0 microg/ml. Conversely, no responses were apparent with infecting strains for which MICs were > or = 2 microg/ml (amphotericin B) or > or = 1 microg/ml (itraconazole). However, the limitations of the intravenous challenge systems studied mean that no firm conclusion relating MICs in vitro to the lowest effective doses in vivo could be drawn.
Amphotericin B↗
Influence of test conditions on antifungal time-kill curve results: proposal for standardized methods.
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 degrees C. Prior to testing, the existence of antifungal carryover was evaluated at antifungal concentrations ranging from 1x to 16x MIC by four plating methods: direct plating of 10, 30, and 100 microl of test suspension and filtration of 30 microl of test suspension through a 0.45-microm-pore-size filter. Time-kill curves were performed with each isolate at drug concentrations equal to 2 x 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 x 10(2) to 1 x 10(4), >1 x 10(4) to 1 x 10(6), and >1 x 10(6) to 1 x 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.
Antifungal Agents↗
Assessment of antifungal activities of fluconazole and amphotericin B administered alone and in combination against Candida albicans by using a dynamic in vitro mycotic infection model.
We evaluated the pharmacodynamic activities of fluconazole and amphotericin B given alone and in combination against Candida albicans by using an in vitro model of bloodstream infection that simulates human serum pharmacokinetic parameters for these antifungals. Fluconazole was administered as a bolus into the model to simulate regimens of 200 mg every 24 h (q24 h) and 400 mg q24 h. Amphotericin B was administered at doses producing the peak concentration (2.4 micrograms/ml) observed with a regimen of 1 mg/kg of body weight q24 h. A combination regimen of fluconazole (400 mg q24 h) and amphotericin B (1 mg/kg q24 h) administered simultaneously and as a staggered regimen (amphotericin B bolus given 8 h after fluconazole bolus) was also simulated in the model to characterize possible antagonism between these agents. Fluconazole alone and amphotericin B alone demonstrated fungistatic (< 99.9% reduction in numbers of CFU per milliliter from the starting inoculum) and fungicidal (> 99.9% reduction) activity, respectively. When fluconazole and amphotericin B were administered simultaneously, fungicidal activity similar to that observed with amphotericin B alone was observed. Staggered administration of fluconazole and amphotericin B, however, resulted in a substantial reduction of the fungicidal activity of amphotericin B, producing fungistatic activity similar to that observed with noncombination fluconazole regimens. These results demonstrate the usefulness of this model for comparing the in vitro pharmacodynamic characteristics of different antifungal regimens and support the theory of azole-polyene antagonism. The effects of this antagonism on the in vivo activity and clinical usefulness of combination antifungal therapy, however, remain to be determined.
Amphotericin B↗
Evaluation of endpoints for antifungal susceptibility determinations with LY303366.
We have previously reported poor correlation between the in vitro fungicidal activity of LY303366 and MIC results in RPMI medium based upon the manufacturer's suggested susceptibility endpoint, lack of visual growth. Additionally, we have noted a significant trailing effect with LY303366 when MICs are determined in RPMI medium. These observations have led us to evaluate an alternative susceptibility endpoint for LY303366, an 80% reduction in growth compared with control (similar to that utilized for azoles). Two isolates each of Candida albicans, Candida glabrata, and Candida tropicalis were selected for testing. MICs were determined for LY303366 in RPMI 1640 medium buffered with morpholinepropanesulfonic acid. MICs were determined with suggested (MIC100) and experimental (MIC80) endpoints. The minimal fungicidal concentration (MFC) of LY303366 for each isolate was also determined. Time-kill curves were determined in RPMI medium with each isolate at concentrations of LY303366 ranging from 0.125 to 16x MIC80 to assess the correlation between MIC80 and fungicidal activity. Lastly, fungi exposed to LY303366 were examined via scanning electron microscope (SEM) for evidence of drug-induced ultrastructure change. MIC80s for test isolates ranged from 0.015 to 0.12 microgram/ml and were consistently three to five wells less than MIC100s. Good correlation was observed between fungicidal activity, as assessed by kill curves, and the MIC80. SEM data revealed significant ultrastructure changes induced by LY303366 even at sub-MIC80s. Based on our results demonstrating better correlation between MIC80 and fungicidal activity, i.e., time-kill curves and MFCs, we suggest that 80% reduction in visible growth be utilized as the endpoint for susceptibility determinations with LY303366 in RPMI medium.
Anidulafungin↗
Bacterial pathogens isolated from patients with bloodstream infection: frequencies of occurrence and antimicrobial susceptibility patterns from the SENTRY antimicrobial surveillance program (United States and Canada, 1997).
The SENTRY Program was established in January 1997 to measure the predominant pathogens and antimicrobial resistance patterns of nosocomial and community-acquired infections over a broad network of sentinel hospitals in the United States (30 sites), Canada (8 sites), South America (10 sites), and Europe (24 sites). During the first 6-month study period (January to June 1997), a total of 5,058 bloodstream infections (BSI) were reported by North American SENTRY participants (4,119 from the United States and 939 from Canada). In both the United States and Canada, Staphylococcus aureus and Escherichia coli were the most common BSI isolates, followed by coagulase-negative staphylococci and enterococci. Klebsiella spp., Enterobacter spp., Pseudomonas aeruginosa, Streptococcus pneumoniae, and beta-hemolytic streptococci were also among the 10 most frequently reported species in both the United States and Canada. Although the rank orders of pathogens in the United States and Canada were similar, distinct differences were noted in the antimicrobial susceptibilities of several pathogens. Overall, U.S. isolates were considerably more resistant than those from Canada. The differences in the proportions of oxacillin-resistant S. aureus isolates (26.2 versus 2.7% for U.S. and Canadian isolates, respectively), vancomycin-resistant enterococcal isolates (17.7 versus 0% for U.S. and Canadian isolates, respectively), and ceftazidime-resistant Enterobacter sp. isolates (30.6 versus 6.2% for U.S. and Canadian isolates, respectively) dramatically emphasize the relative lack of specific antimicrobial resistance genes (mecA, vanA, and vanB) in the Canadian microbial population. Among U.S. isolates, resistance to oxacillin among staphylococci, to vancomycin among enterococci, to penicillin among pneumococci, and to ceftazidime among Enterobacter spp. was observed in both nosocomial and community-acquired pathogens, although in almost every instance the proportion of resistant strains was higher among nosocomial isolates. Antimicrobial resistance continues to increase, and ongoing surveillance of microbial pathogens and resistance profiles is essential on national and international scales.
Anti-Bacterial Agents↗
Fluconazole susceptibility testing of Cryptococcus neoformans: comparison of two broth microdilution methods and clinical correlates among isolates from Ugandan AIDS patients.
We compared the yeast nitrogen base (YNB) broth microdilution method with the National Committee for Clinical Laboratory Standards (NCCLS) M27-A microdilution reference method for measuring the in vitro susceptibility of Cryptococcus neoformans isolates to fluconazole. A total of 149 isolates of C. neoformans var. neoformans from Ugandan AIDS patients was tested by both methods. An overall agreement of 88% between the two microdilution methods was observed. All isolates grew well in both RPMI 1640 and YNB media, and MICs could be read after 48 h of incubation by both methods. The range of fluconazole MICs obtained with the YNB method was broader than that obtained with the NCCLS method. The extended range of MICs provided by the YNB method may be of clinical value, as it appears that the clinical outcome may be better among patients infected with strains inhibited by lower concentrations of fluconazole as determined by the YNB method. The YNB method appears to be a viable option for testing C. neoformans against fluconazole.
AIDS-Related Opportunistic Infections↗
Use of molecular and reference susceptibility testing methods in a multicenter evaluation of MicroScan dried overnight gram-positive MIC panels for detection of vancomycin and high-level aminoglycoside resistances in enterococci.
Modified MicroScan gram-positive MIC no. 8 panels (PM-8) were analyzed for their improved ability to detect vancomycin resistance (VR) and high-level aminoglycoside resistance (HLAR) in enterococci. A validation study design that utilized selected challenge strains, recent clinical isolates, and reproducibility experiments in a multicenter format was selected. Three independent medical centers compared the commercial panels to reference broth microdilution panels (RBM) and Synergy Quad Agar (QA). Resistance was verified by demonstration of VR and HLAR genes by PCR tests. The study was conducted in three phases. (i) In the challenge phase (CP), two well-characterized sets of enterococci were obtained from the Centers for Disease Control and Prevention; one set contained 50 isolates for VR testing and one contained 48 isolates for HLAR testing. In addition, a set of 47 well-characterized isolates representing diverse geographic areas, obtained from earlier national surveillance studies, was tested at the University of Iowa College of Medicine (UICM). (ii) In the efficacy phase (EP), each laboratory tested 50 recent, unique clinical isolates by all methods. (iii) In the reproducibility Phase (RP), each laboratory tested the same 10 strains by all methods in triplicate on three separate days. All isolates from the EP were sent to the UICM for molecular characterization of vanA, -B, -C1, -C2-3, and HLAR genes. In the CP, the ranking of test methods by error rates (in parentheses; very major and major errors combined, versus PCR results) were as follows: for high-level streptomycin resistance (HLSR), QA (12.0%) > PM-8 (5.2%) > RBM (1.6%); for high-level gentamicin resistance (HLGR), RBM (3.7%) > PM-8 (3.1%) > QA (2.6%); and for VR, RBM = QA (3.0%) > PM-8 (1.2%). In the EP, agreement between all methods and the reference PCR result was 98.0% for HLSR, 99.3% for HLGR, and 98. 6% for VR. In the RP, the percentages of results +/- 1 log2 dilution of the all-participant mode were as follows: for VR, 100% (PM-8), 98.9% (QA), and 90.0% (RBM); for HLSR, 99.6% (RBM), 98.5% (PM-8), and 82.2% (QA); and for HLGR, 99.6% (RBM), 99.3% (PM-8), and 98.1% (QA). The ability of the PM-8 to detect VR and HLAR in enterococci was comparable to those for reference susceptibility and molecular PCR methods and was considered acceptable for routine clinical laboratory use.
Anti-Bacterial Agents↗
Comparison of genomic methods for differentiating strains of Enterococcus faecium: assessment using clinical epidemiologic data.
Genomic DNA extracted from 45 vancomycin-resistant Enterococcus faecium (VRE) isolates was cleaved with HindIII and HaeIII and subjected to agarose gel electrophoresis. The ability of this method (restriction endonuclease analysis [REA]) to distinguish strains at the subspecies level was compared with results previously determined by pulsed-field gel electrophoresis (PFGE). Chart reviews were performed to provide a clinical correlation of possible epidemiologic relatedness. A likely clinical association was found for 29 patients as part of two outbreaks. REA found 21 of 21 isolates were the same type in the first outbreak, with PFGE calling 19 strains the same type. In the second outbreak with eight patient isolates, HindIII found six were the same type and two were unique types. HaeIII found three strains were the same type, two strains were a separate type, and three more strains were unique types, while PFGE found three were the same type and five were unique types. No single "ideal" method can be used without clinical epidemiologic investigation, but any of these techniques is helpful in providing focus to infection control practitioners assessing possible outbreaks of nosocomial infection.
Anti-Bacterial Agents↗
Variation in electrophoretic karyotype and antifungal susceptibility of clinical isolates of Cryptococcus neoformans at a university-affiliated teaching hospital from 1987 to 1994.
Ninety-eight isolates of Cryptococcus neoformans were collected from 30 patients at the University of Iowa Hospitals and Clinics from December 1987 through December 1994. The susceptibility of each isolate was determined against fluconazole, itraconazole, amphotericin B, and flucytosine. Of the 98 isolates, 53 were recovered from blood, 19 were recovered from cerebrospinal fluid (CSF), and 26 were recovered from other sources. Although the strains were isolated from the same institution, DNA typing by electrophoretic karyotype (EK) revealed wide genetic variation. Overall, 23 different EK profiles were identified by computer-aided analysis. An isolate exhibiting a single EK was isolated from 24 of 30 patients (80%), whereas multiple strains with unique EKs were isolated from 6 of 30 (20%) patients. Of the six patients who had multiple strains recovered, only one individual had two strains isolated from unique body sites, one strain from the blood and the other from the CSF. Six strains were isolated from multiple patients. Nine patients had multiple sequential isolates recovered over periods of time ranging from 3 days to 4 months. EK analysis revealed persistence of the same genotype in six of the cases. Three patients, however, appeared to have an isolate with a second distinct EK emerge during therapy. Of the patients with sequential positive cultures, an increase in the MICs for test agents was observed in only one case. C. neoformans isolates were collected over a period of 7 years, during which time MICs at our institution remained stable.
Cryptococcus neoformans↗
Hospital specificity, region specificity, and fluconazole resistance of Candida albicans bloodstream isolates.
In a survey of bloodstream infection (BSI) isolates across the continental United States, 162 Candida albicans isolates were fingerprinted with the species-specific probe Ca3 and the patterns were analyzed for relatedness with a computer-assisted system. The results demonstrate that particular BSI strains are more highly concentrated in particular geographic locales and that established BSI strains are endemic in some, but not all, hospitals in the study and undergo microevolution in hospital settings. The results, however, indicate no close genetic relationship among fluconazole-resistant BSI isolates in the collection, either from the same geographic locale or the same hospital. This study represents the first of three fingerprinting studies designed to analyze the origin, genetic relatedness, and drug resistance of Candida isolates responsible for BSI.
Antifungal Agents↗
International surveillance of bloodstream infections due to Candida species: frequency of occurrence and antifungal susceptibilities of isolates collected in 1997 in the United States, Canada, and South America for the SENTRY Program. The SENTRY Participant Group.
An international program of surveillance of bloodstream infections (BSIs) in the United States, Canada, and South America between January and December 1997 detected 306 episodes of candidemia in 34 medical centers (22 in the United States, 6 in Canada, and 6 in South America). Eighty percent of the BSIs were nosocomial and 50% occurred in patients hospitalized in an intensive care unit. Overall, 53.3% of the BSIs were due to Candida albicans, 15.7% were due to C. parapsilosis, 15.0% were due to C. glabrata, 7.8% were due to C. tropicalis, 2.0% were due to C. krusei, 0.7% were due to C. guilliermondii, and 5.8% were due to Candida spp. However, the distribution of species varied markedly by country. In the United States, 43.8% of BSIs were due to non-C. albicans species. C. glabrata was the most common non-C. albicans species in the United States. The proportion of non-C. albicans BSIs was slightly higher in Canada (47.5%), where C. parapsilosis, not C. glabrata, was the most common non-C. albicans species. C. albicans accounted for 40.5% of all BSIs in South America, followed by C. parapsilosis (38.1%) and C. tropicalis (11.9%). Only one BSI due to C. glabrata was observed in South American hospitals. Among the different species of Candida, resistance to fluconazole (MIC, > or = 64 microg/ml) and itraconazole (MIC, > or = 1.0 microg/ml) was observed with C. glabrata and C. krusei and was observed more rarely among other species. Isolates of C. albicans, C. parapsilosis, C. tropicalis, and C. guilliermondii were all highly susceptible to both fluconazole (99.4 to 100% susceptibility) and itraconazole (95.8 to 100% susceptibility). In contrast, 8.7% of C. glabrata isolates (MIC at which 90% of isolates are inhibited [MIC90], 32 microg/ml) and 100% of C. krusei isolates were resistant to fluconazole, and 36.9% of C. glabrata isolates (MIC90, 2.0 microg/ml) and 66.6% of C. krusei isolates were resistant to itraconazole. Within each species there were no geographic differences in susceptibility to fluconazole or itraconazole.
Antifungal Agents↗
Evaluation of the Etest method for determining fluconazole susceptibilities of 402 clinical yeast isolates by using three different agar media.
The performance of the Etest for fluconazole susceptibility testing of 402 yeast isolates was assessed against the National Committee for Clinical Laboratory Standards (NCCLS) microdilution broth method. The NCCLS method employed RPMI 1640 broth medium, and MICs were read after incubation for 48 h at 35 degrees C. Etest MICs were determined with RPMI agar containing 2% glucose (RPG), Casitone agar (CAS), and Mueller-Hinton agar (MHA) and were read after incubation for 48 h at 35 degrees C. The yeast isolates included Candida albicans (n = 161), Candida glabrata (n = 41), Candida tropicalis (n = 35), Candida parapsilosis (n = 29), Candida krusei (n = 32), Candida lusitaniae (n = 31), Candida species (n = 19), Cryptococcus neoformans (n = 40), and miscellaneous yeast species (n = 14). The Etest results correlated well with reference MICs. Overall agreement was 94% with RPG, 97% with CAS, and 53% with MHA. When RPG was used, agreement ranged from 89% for Candida spp. to 100% for C. krusei. When CAS was utilized, agreement ranged from 93% for Cryptococcus neoformans to 100% for C. tropicalis, C. parapsilosis, C. lusitaniae, Candida spp., and miscellaneous yeast species. With MHA, agreement ranged from 17% for C. parapsilosis to 90% for C. krusei. Both RPG and CAS supported growth of all yeast species, whereas growth on MHA was comparatively weaker. Etest results were somewhat easier to read on CAS. The Etest method using either RPG or CAS, but not MHA, appears to be a viable alternative to the NCCLS reference method for determining fluconazole susceptibilities of yeasts.
Agar↗