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M A Pfaller

Publications and source records attributed to M A Pfaller.

At least 289 records · Page 16Linked to original sources
PubMed1996

Strain variation among and antifungal susceptibilities of isolates of Candida krusei.

Candida krusei is an emerging pathogen that is well known for its propensity to develop resistance to fluconazole and other azoles. Despite the potential clinical significance of C. krusei, little is known of its epidemiology and genetic diversity as defined by the newer DNA-based typing methods. We investigated the genotypic diversity and antifungal susceptibility of 67 clinical isolates from 44 patients and 5 health care workers from six different medical centers. Strain delineation was performed by restriction endonuclease analysis of genomic DNA (REAG) with the restriction enzyme HinfI followed by conventional electrophoresis. The susceptibility of the isolates to the antifungal agents amphotericin B, flucytosine, fluconazole, and itraconazole was determined by methods recommended by the National Committee for Clinical Laboratory Standards. The MICs at which 90% of the isolates were inhibited ranged from 1.0 microgram/ml for itraconazole to 64 micrograms/ml for fluconazole. In general, isolates from a given patient, or epidemiologically related isolates from a single institution, were identical by molecular typing methods. Epidemiologically unrelated isolates were distinctly different by the REAG typing method employed. These data document the genetic diversity and antifungal susceptibility of clinical isolates of C. krusei.

Amphotericin B↗
PubMed1996

Role of the microbiology laboratory in monitoring and identifying resistance: use of molecular biology.

Antimicrobial resistance is an increasing problem in the United States. Early detection of emerging trends in antimicrobial resistance may facilitate implementation of effective control measures. Most antimicrobial susceptibility testing is qualitative, in that it categorizes isolates as susceptible, intermediate, or resistant. This approach is relatively inexpensive and generally adequate for clinical purposes. Qualitative susceptibility testing has some limitations for monitoring for emerging resistance. Selective quantitative susceptibility testing may be useful in detecting early trends toward elevated minimal inhibitory concentrations. Molecular methods have a role also in characterizing mechanisms of resistance and in the typing of resistant strains to determine patterns of spread. Laboratory monitoring of emerging resistance must be associated with an effective infection control policy and a willingness to modify practice in a rational manner based upon the trends detected.

Drug Monitoring↗
PubMed1995

In vitro susceptibilities of clinical yeast isolates to three antifungal agents determined by the microdilution method.

A comparative evaluation of the in vitro susceptibilities of 597 clinical yeast isolates to amphotericin B, fluconazole, and 5-fluorocytosine (5FC) was conducted. The broth macrodilution reference method of the National Committee for Clinical Laboratory Standards (NCCLS, M27-P) was adapted to the microdilution method. Microdilution endpoints for amphotericin B were scored as the lowest concentration in which a score of 0 (complete absence of growth) was observed and for 5FC and fluconazole as the lowest concentration in which a score of 2 (prominent decrease in turbidity; MIC-2) was observed compared to the growth control. The MIC values were read after 24 and 48 h incubation. A broad range of MIC values was observed with each antifungal agent. Amphotericin B was very active (MIC90 < or = 1.0 microgram/ml) against all of the yeast isolates with the exception of C. lusitaniae (MIC90 > or = 2.0 micrograms/ml). Fluconazole was most active against C. parapsilosis (MIC90 of 1.0 microgram/ml) and least active against C. krusei (MIC90 of 32 micrograms/ml). 5FC was most active against C. albicans, C. parapsilosis, C. tropicalis, and T. glabrata (MIC90 < or = 1.0 microgram/ml) and was least active against C. krusei and C. lusitaniae (MIC90 > or = 16 micrograms/ml). These data indicate that the microdilution method, performed in accordance with M27-P, provides a means of testing larger numbers of yeast isolates against an array of antifungal agents and allows this to be accomplished in a reproducible and standardized manner. Given these results, it appears that the microdilution method may be a useful alternative to the macrodilution reference method for susceptibility testing of yeasts.

Amphotericin B↗
PubMed1995

Epidemiology of candidiasis.

The increase in infections due to Candida over the past decade is significant. This is particularly true for hospitalized patients where the rate of blood-stream infection due to Candida spp. has increased by almost 500% over the decade of the 1980s. This increase is accompanied by a significant excess mortality and a prolonged length of stay in the hospital. This trend continues into the 1990s where in the US Candida spp. remains the fourth most common blood-stream pathogen, accounting for 8% of all hospital-acquired blood-stream infections. Notably, more than one-third of candidal blood-stream infections are caused by species other than C. albicans. The majority of these infections arise from an endogenous focus of colonization; however, the documentation of nosocomial transmission or 'cross-infection' and the recognition of resistance to antifungal agents pose new and significant problems. Recent studies indicate that Candida may be isolated from the hands of 15-54% of health care workers in the intensive care unit setting and that the strain of Candida carried on the hands may be shared by infected patients. These studies are facilitated by molecular typing and careful epidemiological investigation and suggest that cross-infection is an important and preventable feature of candidal blood-stream infection. Both endogenous and exogenous sources of infection are now well-documented and such information should help direct measures to prevent infections in high risk individuals.

AIDS-Related Opportunistic Infections↗
PubMed1995

The challenge of vancomycin-resistant enterococci: a clinical and epidemiologic study.

BACKGROUND: Vancomycin-resistant enterococci have been recovered with increasing frequency from hospitalized patients. Risk factors, mode of nosocomial transmission, extent of colonization in hospitalized patients, and treatment options for these organisms have not been completely delineated. METHODS: We studied 53 patients (group A) with vancomycin-resistant enterococci isolated from various clinical specimens and also surveyed for vancomycin-resistant enterococci in stool specimens submitted for Clostridium difficile toxin assays (group B). Stool specimens submitted for identification of bacterial pathogens and stool specimens from hospital employees were also analyzed for vancomycin-resistant enterococci. RESULTS: Seventy-six isolates of vancomycin-resistant enterococci were recovered in group A. Five of these patients harbored vancomycin-resistant enterococci on admission. Fifty-three of 289 group B stool specimens submitted for C. difficile toxin assays yielded vancomycin-resistant enterococci. Cephalosporins and vancomycin were the most common antimicrobial agents received by both groups of patients. Enterococcus faecium isolates were more resistant than Enterococcus faecalis isolates to antimicrobial agents. All isolates exhibited high-level aminoglycoside resistance and were not beta-lactamase producers. There were at least 15 different molecular clones of E. faecium and three of E. faecalis. Vancomycin-resistant enterococcal bacteremia was associated with a 100% in-hospital mortality rate. CONCLUSIONS: Multidrug-resistant and vancomycin-resistant enterococci have become important nosocomial pathogens that are difficult to treat. Vancomycin-resistant enterococcal bacteremia was associated with a poor prognosis. We found a high rate of colonization in patients with suspected C. difficile toxin colitis. Judicious use of vancomycin and broad-spectrum antibiotics is recommended, and strict infection control measures must be implemented to prevent nosocomial transmission of these organisms.

Adult↗
PubMed1995

Variations in DNA subtype, antifungal susceptibility, and slime production among clinical isolates of Candida parapsilosis.

Candida parapsilosis is an important nosocomial pathogen that can proliferate in high concentrations of glucose and form biofilms on prosthetic materials. We investigated the genotypic diversity, slime production, and antifungal susceptibility among 60 isolates of C. parapsilosis from 44 patients and 10 patient care providers from five different medical centers. Molecular typing was performed using macrorestriction digest profiles with BssHII followed by pulsed-field gel electrophoresis (REAG) and by electrophoretic karyotyping (EK). Slime production was evaluated by growing the organisms in Sabouraud broth with 8% glucose and examining the walls of the tubes for the presence of an adherent slime layer. Antifungal susceptibility to amphotericin B, 5-fluorocytosine, fluconazole, and itraconazole was determined using National Committee for Clinical Laboratory Standards proposed standard methods. Overall 28 different DNA types were identified by REAG and EK methods. MIC90 values ranged from 0.12 microgram/ml for itraconazole to 1.0 microgram/ml for fluconazole and amphotericin B. Sixty-five percent of the isolates produced slime: 37% were moderately to strongly positive, 28% were weakly positive, and 35% were negative. Overall, 83% of blood and catheter isolates were slime positive versus 53% of isolates from all other sites (P < 0.05). These data underscore the genetic diversity and susceptibility of C. parapsilosis to antifungal agents. Slime production may be important in enabling C. parapsilosis to cause catheter-related bloodstream infections.

Amphotericin B↗
PubMed1995

Evidence of nosocomial spread of Candida albicans causing bloodstream infection in a neonatal intensive care unit.

Candida albicans is an increasingly important bloodstream pathogen. We investigated a cluster of bloodstream infections in the neonatal intensive care unit (NICU) to determine whether nosocomial transmission occurred. Subjects included any patient in the NICU who developed clinically significant bloodstream infection with C. albicans from January 1984 to December 1987 (N = 7). Isolates were typed by restriction fragment length polymorphism analysis using a C. albicans-specific DNA probe (27A). Four of the neonates were infected from June to August 1984 (1.4 infections per 100 admissions) (the epidemic period) versus none in the period from January to May 1984, and three in the period from September 1984 to December 1987 (0.12 infections per 100 admissions) (P = .002). Three of the four patients in the epidemic period were infected with identical strains, readily distinguished from epidemiologically unrelated strains from the NICU. We conclude that nosocomial transmission of C. albicans occurred and that neonates in intensive care units may represent one group at increased risk.

Blotting, Southern↗
PubMed1995

Electrophoretic karyotype and in vitro antifungal susceptibility of Cryptococcus neoformans isolates from AIDS patients.

Electrophoretic karyotype (EK) was used to type 13 clinical isolates of Cryptococcus neoformans from eight AIDS patients. All of the isolates were also tested for their in vitro susceptibilities to fluconazole, itraconazole, D0870, flucytosine, and amphotericin B by a broth macrodilution technique performed according to the National Committee for Clinical Laboratory Standards recommendations. Although all strains were isolated from a limited geographic area, DNA typing showed a wide genetic variation in this group of patients, yielding seven different patterns. Two patients in whom C. neoformans was isolated in the same time period shared similar EK profiles, suggesting the possibility of cross-infection. In three patients, sequential isolates were evaluated: in two of them, EK analysis showed the persistence of the same genotype throughout the infection, whereas from the third, two isolates of C. neoformans with two different DNA profiles were obtained. Despite the small number of strains considered in this study, our susceptibility data indicate that C. neoformans isolates are very susceptible to the new triazoles.

AIDS-Related Opportunistic Infections↗
PubMed1995

Control of methicillin-resistant Staphylococcus aureus in a hospital and an intensive care unit.

OBJECTIVE: To describe methicillin-resistant Staphylococcus aureus (MRSA) control in a hospital, including a surgical intensive care unit (SICU) outbreak. DESIGN: Prospective surveillance of newly identified patients with MRSA. Barrier isolation (disposable gloves for direct contact with patient or immediate environment) was used for the routine care of hospitalized MRSA patients as of October 1991. Beginning in 1992, MRSA isolates were typed by restriction endonuclease enzyme analysis of plasmid DNA (REAP) and/or pulsed-field gel electrophoresis of genomic DNA (PFGE). Surveillance information and MRSA typing were used concurrently to identify nosocomial case clustering, confirm cross-infection, and support a need for additional outbreak control interventions. SETTING: University-affiliated public hospital. PARTICIPANTS: Patients with newly identified MRSA colonization or infection from 1991 through 1993 and epidemiologically associated staff providing care to eight SICU patients in an outbreak. INTERVENTIONS: Barrier isolation for affected and unaffected patients in and admitted to the SICU institution when the outbreak was identified and cross-infection confirmed. Anterior nares cultures of staff in contact with outbreak cases for detection of MRSA colonization. RESULTS: Fifty-six hospitalized patients with community-acquired MRSA and 80 patients with nosocomial MRSA colonization or infection were identified during the 3 years. After the introduction of barrier isolation, the annual frequency of new nosocomial MRSA cases decreased and only one outbreak (eight cases in the SICU) caused by type-related isolates occurred. The other 35 nosocomial cases of MRSA during 1992 and 1993 were not epidemiologically related or were caused by isolates with different types. The SICU outbreak ended after instituting barrier isolation for all patients (with and without MRSA) in and admitted to the unit. Six colonized SICU staff were identified. All outbreak cases had identical or related MRSA types by PFGE and REAP. Staff isolates were different from case isolates by typing, and staff were not restricted and not given treatment for colonization. After more than 6 months of follow up, no further outbreaks of MRSA in the SICU or elsewhere in the hospital occurred despite returning to barrier isolation for affected patients only. CONCLUSION: MRSA in hospitals and outbreaks of MRSA in ICUs can be controlled by surveillance and minimal barrier interventions. REAP or PFGE typing of MRSA can be used to support or refute the presence of cross-transmission. Typing also may be helpful when planning and assessing the effectiveness of interventions directed at endemic, as well as outbreak, MRSA control.

Bacterial Typing Techniques↗
PubMed1995

DNA subtypes and fluconazole susceptibilities of Candida albicans isolates from the oral cavities of patients with AIDS.

Sixty-two Candida albicans isolates from the oral cavities of 28 patients with AIDS who were receiving fluconazole therapy were typed by restriction endonuclease analysis followed by pulsed-field gel electrophoresis; these isolates were then tested for fluconazole susceptibility by a standard broth dilution method. Sequential isolates (range, 2-4) were evaluated for 22 patients; only one isolate was evaluated for six patients. DNA subtyping revealed a total of 37 different DNA subtypes. Twelve (54.5%) of 22 patients with multiple episodes of oropharyngeal candidiasis were infected with a single DNA subtype throughout the observation period. Ten (45.5%) of 22 patients with multiple episodes of oropharyngeal candidiasis were infected with two or three DNA subtypes during the observation period. In vitro susceptibility tests revealed that MICs of fluconazole ranged from < or = 0.125 microgram/mL to 64 micrograms/mL, with an MIC50 of 0.5 microgram/mL and an MIC90 of 4 micrograms/mL. A significant increase in the MICs (fourfold or greater) of fluconazole for sequential C. albicans isolates was found for 66.6% of the patients infected with a single DNA subtype and for 50% of the patients infected with multiple DNA subtypes. Despite a limited number of patients and isolates, our data suggest that C. albicans isolates that are susceptible to fluconazole at MICs of > or = 8 micrograms/mL in vitro will be less susceptible in vivo to standard doses (100-200 mg/d) of this drug.

AIDS-Related Opportunistic Infections↗
PubMed1995

Vancomycin-resistant Enterococcus faecium bacteremia: risk factors for infection.

We describe an outbreak of vancomycin-resistant Enterococcus faecium (vanA phenotype) bacteremia on the oncology ward of a tertiary care community hospital. In 10 of the 11 cases the patients had leukemia and were neutropenic (median duration of neutropenia, 21 days) at the time of bacteremia. On average, patients received six antibiotic agents for a total of 61 agent-days prior to development of vancomycin-resistant E. faecium bacteremia. The mortality rate was 73%. Molecular typing of 22 isolates revealed that the majority (83%) represented a common strain, indicating nosocomial spread. When the 11 cases were compared to 22 matched control patients, gastrointestinal colonization with vancomycin-resistant E. faecium (odds ratio [denominator, 0] infinity, P = .005) and the use of antimicrobial agents with significant activity against anaerobes (metronidazole, clindamycin, and imipenem; odds ratio infinity, P = .02) were found to be risk factors for the development of vancomycin-resistant E. faecium bacteremia. Since no proven therapy for such infection exists, there is an urgent need to identify effective measures to prevent and control the development of vancomycin-resistant E. faecium bacteremia.

Adult↗
PubMed1995

Epidemiology of fungal infections: the promise of molecular typing.

As the incidence of invasive fungal disease-particularly nosocomial candidal infection-has increased significantly over the past two decades, molecular typing has become increasingly important for the development of rational infection-control measures and therapeutic strategies. Numerous molecular methods have been used to subtype Candida species, including restriction endonuclease analysis of genomic DNA, Southern hybridization analysis, pulsed-field gel electrophoresis, and polymerase chain reaction-based approaches. Increasingly, typing techniques are being applied to other fungal organisms as well. Although an ideal epidemiological typing technique applicable to a wide range of fungal pathogens is not yet available, several molecular-typing methods may permit rapid, simple, and sensitive discrimination of specific strains among the most clinically important species of fungi.

Aspergillus↗
PubMed1995

Familial carriage of methicillin-resistant Staphylococcus aureus and subsequent infection in a premature neonate.

During routine surveillance of patients in a Neonatal Intensive Care Unit (NICU), an alert infection-control practitioner confirmed the relationship of the index patient (sibling 3) who had a methicillin-resistant Staphylococcus aureus (MRSA) infection to an infant sibling (sibling 2) who had been admitted to the hospital 7 months previously with an MRSA infection. Cultures of nasal specimens obtained from the index patient's parents and two other siblings also yielded MRSA for two of the family members, the mother and sibling 1. The strains were typed by antibiogram, plasmid analysis, and genomic DNA typing. The isolates from sibling 1, sibling 2, the mother, and one isolate from sibling 3 were found to be identical by all techniques. The other isolates from sibling 3 shared the same genomic type but had no detectable plasmids. These findings suggest that transmission of this strain occurred at least three times within this family and that at least one family member was colonized with the same strain for 7 months or more. Recognition that family members may serve as reservoirs for nosocomial infections with MRSA raises important issues for infection control.

Adult↗
PubMed1995

Transmission of fluconazole-resistant Candida albicans between patients with AIDS and oropharyngeal candidiasis documented by pulsed-field gel electrophoresis.

Electrophoretic karyotype and restriction endonuclease analysis of genomic DNA were used for the typing of nine isolates of Candida albicans from the oral cavities of two patients with AIDS--a husband and wife--whose infections became resistant to treatment with fluconazole (400 mg/d). The in vitro susceptibilities of sequential isolates to fluconazole and two other triazoles, itraconazole and the investigational drug D0870, were also evaluated. DNA analysis showed that the isolates responsible for fluconazole-resistant episodes of oropharyngeal candidiasis in the two patients were genetically related. In vitro susceptibility to fluconazole correlated well with clinical outcome. Although the minimal inhibitory concentrations of itraconazole and D0870 for fluconazole-resistant isolates were higher than those for fluconazole-susceptible isolates, both of the former triazoles exhibited good in vitro activity against the isolates tested.

AIDS-Related Opportunistic Infections↗
PubMed1995

Relapse of catheter-related Flavobacterium meningosepticum bacteremia demonstrated by DNA macrorestriction analysis.

A 6-year-old boy with non-Hodgkin's lymphoma presented because of recurrent episodes (on 13 September 1993 and 12 January 1994) of possibly catheter-related bacteremia. The strains isolated during both episodes and seven epidemiologically unrelated control strains were typed by pulsed-field gel electrophoresis (PFGE) of chromosomal DNA. The similarity of the PFGE patterns of the two isolates suggests that both episodes of bacteremia were caused by the same strain. The antimicrobial susceptibility of the nine strains was tested against 32 antimicrobial agents. The antimicrobial susceptibility patterns of the two isolates from the referred case were identical and differed from those of other clinical isolates. The best in vitro activity (associated with 100% susceptibility) was demonstrated by ofloxacin, clinafloxacin, minocycline, and rifampin.

Bacteremia↗
PubMed1995

Strain variation and antifungal susceptibility among bloodstream isolates of Candida species from 21 different medical institutions.

Variation in the DNA profile and antifungal susceptibility of 271 bloodstream isolates of Candida species was evaluated. The isolates were obtained from 152 nonneutropenic patients hospitalized in 21 different medical centers. In general, each patient was infected with their own distinct DNA type of Candida, and in those cases in which multiple cultures were positive, the same strain was isolated repeatedly over time. Minimum inhibitory concentrations of fluconazole or amphotericin B did not increase over time among the strains isolated repeatedly from individual patients.

Amphotericin B↗
PubMed1995

Comparison of expression of virulence factors by Escherichia coli causing cystitis and E. coli colonizing the periurethra of healthy girls.

The prevalence of virulence factors possessed by Escherichia coli colonizing the periurethra was examined and compared with that of E. coli causing urinary tract infection. One hundred two E. coli isolates obtained from the periurethra and urine of 7 non-sexually active girls at risk for cystitis were characterized for genetic relatedness and examined for expression of six virulence factors. Expression of virulence factors in colonizing clones of E. coli were compared with expression in clones from symptomatic infection. All virulence factors except P adhesin were commonly expressed by colonizing clones of E. coli that did not go on to infect the urinary tract. Although P adhesin-expressing E. coli were commonly isolated from episodes of cystitis, the presence of P adhesin on periurethral E. coli did not usually predict subsequent infection. By itself, expression of virulence factors on periurethral E. coli is not enough to predict subsequent infection.

Agglutination Tests↗