Fluconazole susceptibilities of Candida species and distribution of species recovered from blood cultures over a 5-year period

Prophylactic intravenous antifungal agents to prevent mortality and morbidity in very low birth weight infants

BACKGROUND

Invasive fungal infection is an increasingly common cause of mortality and morbidity in very low birth weight infants. As the diagnosis is often difficult, and treatment is often delayed, there is a need to assess whether antifungal prophylaxis is beneficial.

OBJECTIVES

To assess whether prophylactic intravenous antifungal therapy reduces mortality and adverse neurodevelopmental outcomes in very low birth weight infants.

SEARCH STRATEGY

We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 4, 2003), MEDLINE (1966 - October 2003), EMBASE (1980 - October 2003), conference proceedings, and previous reviews.

SELECTION CRITERIA

Randomised controlled trials that compared the effect of prophylactic intravenous antifungal therapy versus placebo, or no drug, or another antifungal agent, in very low birth weight infants.

DATA COLLECTION AND ANALYSIS

We extracted the data using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author, and synthesis of data using relative risk and risk difference. The pre-specified outcomes were death prior to hospital discharge, longer term neurodevelopment, incidence of invasive fungal infection, emergence of antifungal resistance, and adverse drug reactions.

MAIN RESULTS

We identified three eligible trials enrolling a total of 214 infants. Each of the trials compared the effect of prophylactic intravenous fluconazole versus placebo. Two of the trials reported death prior to hospital discharge as an outcome. 29 of the 203 infants recruited to these studies died. Meta-analysis revealed a statistically significantly reduced risk of death prior to hospital discharge for the infants who received fluconazole prophylaxis: typical relative risk: 0.44 (95% confidence interval 0.21, 0.91); typical risk difference: -0.11 (95% confidence interval -0.21, -0.02); number needed to treat: 9 (95% confidence interval 5, 50). None of the trials reported data on longer term outcomes.

REVIEWER'S CONCLUSIONS

We have found some evidence that prophylactic intravenous fluconazole reduces mortality prior to hospital discharge in very low birth weight infants. The meta-analysis suggests that there will be one fewer death in every nine infants treated with this intervention, but the 95% confidence interval around this estimate of effect is wide. The longer term neurodevelopmental consequences for infants exposed to this intervention remain to be determined. It will be important to identify any subgroups of very low birth weight infants that receive the most benefit from this intervention. There is also a need for further data on the effect of the intervention on the emergence of organisms with stable antifungal resistance.

The global epidemiology of invasive Candida infections—is the tide turning?

Invasive candidiasis is a condition of major medical importance. Its incidence has increased dramatically over the last 50 years, reflecting increasingly interventional standards of medical care. Candida spp. are regularly reported to be the fourth commonest cause of bloodstream infection, and it is perceived that the incidence of invasive Candida spp. infections continues to increase. The global disease burden of invasive Candida spp. infections is difficult to quantify because of wide geographic variation. Data originating from the United States indicate that mortality from candidiasis has been falling since 1989. Data from several locations have shown that the dramatic increases in Candida spp. bloodstream infections seen during the 1980s were not sustained through the 1990s. Some authors have reported a decreasing incidence. The contribution of non-albicans Candida spp. to invasive infection is rising. Invasive infections with Candida spp. continue to represent a major economic burden, increasing both mortality and morbidity in an already expensive group of hospital patients. There remains much scope for ongoing and future research into the epidemiology and basic disease processes underlying these infections.

The yeast species causing fungemia at a university hospital in Riyadh, Saudi Arabia, during a 10-year period

This study is a retrospective investigation to determine the species of yeasts causing fungemia in a university hospital in Saudi Arabia during the years 1991-2000. A total of 189 episodes of fungemia were encountered, of which 121 (64%) occurred during 1991-1995, whereas only 68 cases (36%) were found between 1996 and 2000. Overall, 50.3% episodes were due to Candida albicans including five episodes of C. dubliniensis, followed by C. tropicalis (27%), C. parapsilosis (7.9%), C. glabrata (7.4%), C. krusei (3.2%), C. famata (1.0%); 3.2% were due to other species, namely Blastoschizomyces capitatus, Hansenula anomala, Rhodotorula rubra, and Trichosporon beigelii. The percentage of episodes of fungemia caused by C. albicans ranged from 36.4% in 1991 to 71.4% in 2000, revealing an increase in recent years. The incidence of non-C. albicans fungemia decreased from 63 (33.3%) during the first 5 years (1991-1995) to 31 (16.4%) episodes during the second 5 years. Moreover, no fungemia due to C. glabrata and C. krusei were observed during the last 3 years. Overall, during the years of the study, a decreasing incidence of yeast fungemia was observed. Fungemia occurred more frequently in patients with leukemia (24%), prematurity (16%), postsurgery (10.6%), and lymphoma (9.5%). Patients with respiratory infections and preterm infants more often had C. albicans fungemia, whereas C. tropicalis predominated in patients with hepatic disorders and leukemia. The study reports for the first time the involvement of C. dubliniensis in yeast fungemia occurring in Saudi Arabia.

Routine use of a one minute trehalase and maltase test for the identification of Candida glabrata in four laboratories

AIMS

To evaluate the rapid identification of Candida glabrata using a one minute trehalase and maltase test in four clinical laboratories.

METHOD

The test was evaluated with 944 freshly isolated yeasts comprising 572 C glabrata and 372 non-C glabrata strains. These strains were isolated on one of three differential media-Candida ID, CHROMagar Candida, or Albicans ID2 medium-and all strains were fully identified using standard methods.

RESULTS

The trehalase and maltase test allowed the overall identification of 550 of 572 C glabrata strains (sensitivity, 96.2%) and only 11 of 372 isolates of other yeast species yielded a false positive result (specificity, 96.8 %). Sensitivity and specificity were consistent from one laboratory to another. Using Candida ID medium, the rapid trehalase and maltase test showed a sensitivity of 95% and specificity of 96.2%. Using CHROMagar Candida, sensitivity and specificity were 95.6% and 98.1%, respectively. Using Albicans ID2 medium (tested by two laboratories), the sensitivity was 100% and 98.5% and specificity was 98.1% and 98.2%. In 60% of cases, the test could be performed directly from the primary isolation medium, thus reducing the time for identification.

CONCLUSION

The rapid trehalase and maltase test was highly reliable for the presumptive identification of C glabrata on primary isolation using three different chromogenic media. Direct recognition of C albicans by means of their characteristic colour on chromogenic media coupled with one minute trehalase maltase testing performed only on suspect colonies of C glabrata allowed for rapid presumptive identification of the two yeast species most commonly encountered in clinical samples.

Rapid identification of Candida glabrata with a new commercial test, GLABRATA RTT

The GLABRATA RTT test (Fumouze Diagnostics, Levallois Perret, France) is based on the ability of Candida glabrata to hydrolyze trehalose but not maltose. It requires an inoculum of only four to six colonies, and the results are available within 20 min. We tested GLABRATA RTT with 330 stock isolates grown in subcultures on four different primary fungal isolation media and obtained a sensitivity of 94 to 98% (depending on the medium used) and a specificity of 97.3 to 98.6%. The false-positive results corresponded to C. tropicalis, C. famata, and C. lusitaniae. GLABRATA RTT thus offers rapid and reliable identification of C. glabrata.

Detection of fluconazole-resistant isolates of Candida glabrata by using an agar screen assay

The ability of a fluconazole-containing agar screen assay to accurately detect isolates of Candida glabrata resistant to the azole antifungal agent fluconazole was evaluated on a collection of 100 clinical isolates of this organism. Results were correlated with the MIC of fluconazole for these isolates and compared with the results of a previously published disk diffusion-based fluconazole resistance screening test. Agar screen assay results were in categorical agreement with MIC-based determinations for 97% (97/100) of the isolates tested. This correlation was higher than that obtained with the disk diffusion technique, which categorized only 87% (87/100) of isolates correctly, and suggests that the agar screening approach can effectively expedite fluconazole susceptibility testing of C. glabrata isolates.

Antifungal therapy--state of the art at the beginning of the 21st century

The most relevant information on the present state of the art of antifungal chemotherapy is reviewed in this chapter. For dermatomycoses a variety of topical antifungals are available, and safe and efficacious systemic treatment, especially with the fungicidal drug terbinafine, is possible. The duration of treatment can be drastically reduced. Substantial progress in the armamentarium of drugs for invasive fungal infections has been made, and a new class of antifungals, echinocandins, is now in clinical use. The following drugs in oral and/or intravenous formulations are available: the broad spectrum polyene amphotericin B with its new "clothes"; the sterol biosynthesis inhibitors fluconazole, itraconazole, and voriconazole; the glucan synthase inhibitor caspofungin; and the combination partner flucytosine. New therapy schedules have been studied; combination therapy has found a significant place in the treatment of severely compromised patients, and the field of prevention and empiric therapy is fast moving. Guidelines exist nowadays for the treatment of various fungal diseases and maintenance therapy. New approaches interfering with host defenses or pathogenicity of fungal cells are being investigated, and molecular biologists are looking for new targets studying the genomics of pathogenic fungi.

Relationships between respiration and susceptibility to azole antifungals in Candida glabrata

Over the past two decades, the incidence of infections due to Candida glabrata, a yeast with intrinsic low susceptibility to azole antifungals, has increased markedly. Respiratory deficiency due to mutations in mitochondrial DNA (mtDNA) associated with resistance to azoles frequently occurs in vitro in this species. In order to specify the relationships between respiration and azole susceptibility, the effects of respiratory chain inhibitors on a wild-type isolate of C. glabrata were evaluated. Respiration of blastoconidia was immediately blocked after extemporaneous addition of potassium cyanide, whereas a 4-h preincubation was required for sodium azide. Antifungal susceptibility determined by a disk diffusion method on Casitone agar containing sodium azide showed a significant decrease in the susceptibility to azoles. Biweekly subculturing on Casitone agar supplemented with sodium azide was therefore performed. This resulted after 40 passages in the isolation of a respiration-deficient mutant, as suggested by its lack of growth on glycerol-containing agar. This respiratory deficiency was confirmed by flow cytometric analysis of blastoconidia stained with rhodamine 123 and by oxygraphy. Moreover, transmission electron microscopy and restriction endonuclease analysis of the mtDNA of mutant cells demonstrated the mitochondrial origin of the respiratory deficiency. Finally, this mutant exhibited cross-resistance to all the azoles tested. In conclusion, blockage of respiration in C. glabrata induces decreased susceptibility to azoles, culminating in azole resistance due to the deletion of mtDNA. This mechanism could explain the induction of petite mutations by azole antifungals which have been demonstrated to act directly on the mitochondrial respiratory chain.

Antifungal drug resistance

The increasing incidence of invasive fungal infections is the result of many factors, including an increasing number of patients with severe immunosuppression. Although new drugs have been introduced to combat this problem, the development of resistance to antifungal drugs has become increasingly apparent, especially in patients who require long-term treatment or who are receiving antifungal prophylaxis, and there is growing awareness of shifts of flora to more-resistant species. The frequency, interpretation, and, in particular, mechanism of resistance to current classes of antifungal agents, particularly the azoles (where resistance has climbed most prominently) are discussed in this review.

Secular trends of candidemia over 12 years in adult patients at a tertiary care hospital

The incidence of fungal infections has been increasing for the last 3 decades, especially among neutropenic, cancer, and critically ill patients. These infections are associated with high mortality rates. We retrospectively reviewed medical charts of adult patients with fungemia from 1989 to 2000 at our institution. The characteristics of the population groups served by the hospital were described. Of 328 patients with fungemia, we reviewed 315 (96%) medical records, and focused on those with candidemia (n = 294). The species distribution in patients with candidemia showed that the most commonly identified species were Candida albicans (66%), followed by C. glabrata (17%), and C. parapsilosis (6%). The incidence of candidemia ranged from 0.2 to 0.46 per 10,000 patient-days with the highest incidence in 1993 and the lowest in 1997. Although most studies show an increased incidence of candidemia, we observed a reduction over the study period. Furthermore, we observed no shift from C. albicans to non-albicans Candida species despite a significant increase in the use of fluconazole. The overall mortality among patients with candidemia was 44%, with the highest rate in patients over 65 years (52%). Factors independently associated with higher mortality were patient age greater than 65 years, intensive care unit admission, and underlying cancer.

Identification of Candida glabrata by a 30-second trehalase test

Rapid (30-s) trehalase tests done with material from colonies of 482 yeasts suspended in a drop of trehalose solution on a commercially supplied glucose test strip were positive for 225 (99.1%) of 227 Candida glabrata isolates grown on either of two differential media, Candida ID medium or CandiSelect medium. The test was positive for only 3 (1.2%) and 12 (4.7%) of 255 isolates of other medically important yeast species grown on the same two media, respectively. A rapid maltase test done with a subset of 255 yeast isolates was negative for all but 1 of 64 trehalase-positive C. glabrata isolates, raising the specificity of the rapid testing for C. glabrata to 98.4 to 100%, depending on the isolation medium used. Rapid trehalase and maltase tests done independently in two laboratories with 217 yeast isolates showed sensitivities of 96.0 to 98.0% and specificities of 98.2 to 99.4% for identification of C. glabrata from colonies grown on Candida ID medium. The specificity was much lower because of frequent false-positive trehalose test results when the source of colonies was Sabouraud agar formulated with 4% glucose. We conclude that direct recognition of C. albicans as blue colonies on Candida ID isolation medium coupled with the performance of the 30-s trehalase and maltase tests for C. glabrata among the white colonies on this medium will allow the rapid presumptive identification of the two yeast species most commonly encountered in clinical samples.

Prevalence of Candida spp. in hospitalized patients and their risk factors

A total of 133 Candida spp. strains originating from a group of 100 patients from Santa Casa de Misericórdia of Belo Horizonte, Brazil, between March 1995 and December 1996, were first identified and classified into six different species: Candida albicans (51%), C. tropicalis (33%), C. parapsilosis (8%), C. glabrata (5%), C. krusei (2%) and C. guilliermondii (1%). All C. albicans strains were serotyped and 55% of these were found to belong to serotype A and 45% belonging to serotype B. The medical records of each patient were examined to characterise and survey the main risk factors associated with them. Most of the patients were between 60- and 80-years-old, 53% were males and 47% were females. Most patients were from the intensive care unit (ICU). Only 10 patients were not exposed to antimicrobial agents and 72 patients were not prescribed antifungal agents. Forty patients showed no other clinical condition and all showed some underlying disease that justified hospitalization. Eighty-seven patients had undergone some invasive procedure and 31 patients had been submitted to two different procedures simultaneously.

Antifungal drug resistance to azoles and polyenes

There is an increased awareness of the morbidity and mortality associated with fungal infections caused by resistant fungi in various groups of patients. Epidemiological studies have identified risk factors associated with antifungal drug resistance. Selection pressure due to the continuous exposure to azoles seems to have an essential role in developing resistance to fluconazole in Candida species. Haematological malignancies, especially acute leukaemia with severe and prolonged neutropenia, seem to be the main risk factors for acquiring deep-seated mycosis caused by resistant filamentous fungi, such us Fusarium species, Scedosporium prolificans, and Aspergillus terreus. The still unacceptably high mortality rate associated with some resistant mycosis indicates that alternatives to existing therapeutic options are needed. Potential measures to overcome antifungal resistance ranges from the development of new drugs with better antifungal activity to improving current therapeutic strategies with the present antifungal agents. Among the new antifungal drugs, inhibitors of beta glucan synthesis and second-generation azole and triazole derivatives have characteristics that render them potentially suitable agents against some resistant fungi. Other strategies including the use of high doses of lipid formulations of amphotericin B, combination therapy, and adjunctive immune therapy with cytokines are under investigation. In addition, antifungal control programmes to prevent extensive and inappropriate use of antifungals may be needed.

Fatal endocarditis in a neonate caused by the dematiaceous fungus Phialemonium obovatum: case report and review of the literature

Phialemonium species are grouped by most authorities among the dematiaceous fungi. Like several other darkly pigmented fungi, they appear to be an emerging cause of human disease, especially in the immunocompromised host. As numbers of immunocompromised patients increase, the trend of unusual fungi emerging as new pathogens is set to continue. Previous experience suggests that reports of rare fungal infections among selected patients often heralds the emergence of infection in a wider population of patients. We report a case of fatal endocarditis caused by Phialemonium obovatum in a premature neonate. To our knowledge this is the first documented case of native valve endocarditis due to this species, and we review the literature on invasive disease caused by the species. Unfamiliar fungal isolates are frequently misidentified or mistaken for environmental contaminants, and because of their relative rarity, data upon which to base antifungal treatment are limited. Thus, the diagnosis and treatment of unusual fungal pathogens present a significant challenge to clinicians and microbiologists alike. Early referral of such isolates to a specialist reference laboratory is advisable.

Evaluation of Etest and macrodilution broth method for antifungal susceptibility testing of Candida sp strains isolated from oral cavities of AIDS patients

A comparison of the Etest and the reference broth macrodilution susceptibility test for fluconazole, ketoconazole, itraconazole and amphotericin B was performed with 59 of Candida species isolated from the oral cavities of AIDS patients. The Etest method was performed according to the manufacturer's instructions, and the reference method was performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines. Our data showed that there was a good correlation between the MICs obtained by the Etest and broth dilution methods. When only the MIC results at +/- 2 dilutions for both methods were considered, the agreement rates were 90.4% for itraconazole, ketoconazole and amphotericin B and 84.6% for fluconazole of the C. albicans tested. In contrast, to the reference method, the Etest method classified as susceptible three fluconazole-resistant isolates and one itraconazole-resistant isolate, representing four very major errors. These results indicate that Etest could be considered useful for antifungal sensitivity evaluation of yeasts in clinical laboratories.

In vitro and in vivo antifungal activities of TAK-456, a novel oral triazole with a broad antifungal spectrum

TAK-456 is a novel oral triazole compound with potent and broad-spectrum in vitro antifungal activity and strong in vivo efficacy against Candida albicans and Aspergillus fumigatus. TAK-456 inhibited sterol synthesis of C. albicans and A. fumigatus by 50% at 3 to 11 ng/ml. TAK-456 showed strong in vitro activity against clinical isolates of Candida spp., Aspergillus spp., and Cryptococcus neoformans, except for Candida glabrata. The MICs at which 90% of the isolates tested were inhibited byTAK-456, fluconazole, itraconazole, voriconazole, and amphotericin B were 0.25, 4, 0.5, 0.13, and 0.5 microg/ml, respectively, for clinical isolates of C. albicans and 1, >64, 0.5, 0.5, and 0.5 microg/ml, respectively, for clinical isolates of A. fumigatus. Therapeutic activities of TAK-456 and reference triazoles against systemic lethal infections caused by C. albicans and A. fumigatus in mice were investigated by orally administering drugs once daily for 5 days, and efficacies of the compounds were evaluated by the prolongation of survival. In normal mice, TAK-456 and fluconazole were effective against infection caused by fluconazole-susceptible C. albicans at a dose of 1 mg/kg. In transiently neutropenic mice, therapeutic activity of TAK-456 at 1 mg/kg of body weight against infection with the same strain was stronger than those at 1 mg/kg of fluconazole. TAK-456 was effective against infections with two strains of fluconazole-resistant C. albicans at a dose of 10 mg/kg. TAK-456 also expressed activities similar to or higher than those of itraconazole against the infections caused by two strains of A. fumigatus in neutropenic mice at a dose of 10 mg/kg. These results suggest that TAK-456 is a promising candidate for development for the treatment of candidiasis and aspergillosis in humans.

Oral yeast carriage in patients with advanced cancer

The aim of this study was to investigate oral yeast carriage amongst patients with advanced cancer. Oral rinse samples were obtained from 120 subjects. Yeasts were isolated using Sabouraud's dextrose agar and CHROMagar Candida, and were identified using a combination of the API 20 C AUX yeast identification system, species-specific PCR and 26S rDNA gene sequencing. Oral yeast carriage was present in 66% of subjects. The frequency of isolation of individual species was: Candida albicans, 46%; Candida glabrata, 18%; Candida dubliniensis, 5%; others, < 5%. The increasing isolation of non-Candida albicans species is clinically important, since these species are often more resistant to antifungal drugs. Oral yeast carriage was associated with denture wearing (P = 0.006), and low stimulated whole salivary flow rate (P = 0.009). Identification of these risk factors offers new strategies for the prevention of oral candidosis in this group of patients.

Management of Candidiasis in Critically Ill Patients

Fungal infections have been increasing at an alarming rate in critically ill patients. Candida is now the fourth most common pathogen isolated from the bloodstream and is associated with significant morbidity, mortality, and economic consequences. Novel antifungals have been developed in recent years to provide alternatives to amphotericin B, which continues to be the standard therapy for most invasive fungal infections. These alternatives include lipid-based amphotericin B, ketoconazole, fluconazole, itraconazole, caspofungin, and potentially voriconazole. Optimal therapy for the various forms of candidiasis remains controversial. A standardized antifungal susceptibility testing method for Candida isolates has been developed to assist drug selection, but its clinical relevance remains to be determined. The relative susceptibility of Candida isolates can be estimated by the species. Specifically, C krusei is resistant to azoles, C glabrata may be resistant to azoles, and C lusitaniae may be resistant to amphotericin B Candida infections can affect any organ system, and the diagnosis of such infections remains difficult. The Infectious Diseases Society of America recently developed guidelines for the management of candidiasis. This review includes a brief discussion of systemically administered antifungal agents and provides a synopsis of the practice guidelines for the management of candidiasis.

Resistance of Candida species to antifungal agents: molecular mechanisms and clinical consequences

Candida albicans and related species pathogenic for man become resistant to antifungal agents, in particular triazole compounds, by expression of efflux pumps that reduce drug accumulation, alteration of the structure or concentration of antifungal target proteins, and alteration of membrane sterol composition. The clinical consequences of antifungal resistance can be seen in treatment failures in patients and in changes in the prevalences of Candida species causing disease. These effects were seen unequivocally in HIV-infected patients with oropharyngeal candida infections, but their incidence has decreased dramatically with the introduction of highly active antiretroviral therapy. The evidence for similar emergence of antifungal-resistant yeast strains and species in other types of candida infections is confounded by non-standardised susceptibility testing methods and definitions of a resistant fungal isolate. Recent large-scale surveys of yeasts isolated from blood cultures, based on standardised methodology and resistance definitions, do not support the view that antifungal resistance in pathogenic yeasts constitutes a significant or growing therapeutic problem.

Applications of yeast in drug discovery

The yeast Saccharomyces cerevisiae is perhaps the best-studied eukaryotic organism. Its experimental tractability, combined with the remarkable conservation of gene function throughout evolution, makes yeast the ideal model genetic organism. Yeast is a non-pathogenic model of fungal pathogens used to identify antifungal targets suitable for drug development and to elucidate mechanisms of action of antifungal agents. As a model of fundamental cellular processes and metabolic pathways of the human, yeast has improved our understanding and facilitated the molecular analysis of many disease genes. The completion of the Saccharomyces genome sequence helped launch the post-genomic era, focusing on functional analyses of whole genomes. Yeast paved the way for the systematic analysis of large and complex genomes by serving as a test bed for novel experimental approaches and technologies, tools that are fast becoming the standard in drug discovery research

Therapeutic dilemma of fluconazole prophylaxis in intensive care

OBJECTIVE

To review the data concerning the use of prophylactic fluconazole in intensive care patients who are not immunocompromised.

DATA SOURCE

Literature identified through MEDLINE (1966-March 2001) and recent abstracts of data presented at scientific meetings.

DATA SYNTHESIS

The use of fluconazole as a prophylactic antifungal agent is well documented in patients who are immunocompromised or undergoing bone marrow or solid organ transplantation, with supportive results. Recently published data suggest that the use of fluconazole in high-risk surgical patients can be safe and effective for preventing certain candida infections. However, there is growing evidence that the use of fluconazole may be contributing to the higher prevalence of fluconazole-resistant fungal infections.

CONCLUSIONS

The use of prophylactic fluconazole in nonneutropenic patients is controversial. Retrospective and surveillance studies of nosocomial fungal infections suggest that the use of fluconazole may be contributing to the shift in fungal flora causing these infections and that the isolates are more fluconazole resistant. Fluconazole prophylaxis in surgical patients may be justified in patients who are at the greatest risk of developing fungal infections, those requiring multiple intraabdominal surgeries, or those with recurrent gastrointestinal perforations or anastomotic leakages, but there is a lack of randomized controlled trials to recommend its widespread use at this time.

Trends in species causing fungaemia in a tertiary care medical centre over 12 years

Trends in the species of yeast causing fungaemia over a 12-year period at a large tertiary care medical centre were reviewed. A total of 966 unique episodes of fungaemia occurred in 898 patients. There was an overall trend toward fewer fungaemic episodes due to Candida albicans and more due to Candida glabrata and Candida parapsilosis. However, C. albicans remained the predominant species causing fungaemia, and the proportion due to other species varied from year to year. Candida glabrata was disproportionately isolated from older adults, whereas C. parapsilosis was common among neonates and infants. The trends of increasing isolation of C. glabrata and decreasing isolation of C. albicans were associated with increasing usage of fluconazole, but changes in the proportion of fungaemias due to other species appeared to have no association with fluconazole usage.

Rapid identification of yeasts in positive blood cultures by a multiplex PCR method

Yeasts are emerging as important etiological agents of nosocomial bloodstream infections. A multiplex PCR method was developed to rapidly identify clinically important yeasts that cause fungemia. The method amplified the internal transcribed spacer 1 (ITS1) region between the 18S and 5.8S rRNA genes and a specific DNA fragment within the ITS2 region of Candida albicans. With this method, C. albicans produced two amplicons, whereas other species produced only one. Through sequence analysis, the precise lengths of the PCR products were found to be as follows: C. glabrata (482 or 483 bp), C. guilliermondii (248 bp), C. parapsilosis (229 bp), C. albicans (218 or 219 and 110 bp), C. tropicalis (218 bp), Cryptococcus neoformans (201 bp), and C. krusei (182 bp). The PCR products could be effectively separated by disk polyacrylamide gel electrophoresis. The method was used to test 249 positive blood cultures (255 isolates), from which the following species (strain number) were isolated: C. albicans (128), C. tropicalis (51), C. glabrata (28), C. parapsilosis (23), C. neoformans (9), C. krusei (5), C. guilliermondii (3), and other, minor species (8). The test sensitivity of the method was 96.9% (247 of 255 isolates). The eight minor species were either misidentified (one strain) or not identified (seven strains). From the time at which a positive bottle was found, the multiplex PCR could be completed within 8 h; the present method is simpler than any previously reported molecular method for the identification of blood yeasts.

Antifungal resistance among Candida species

Isolation of Candida sp less susceptible to traditional therapies and recovery of increasingly resistant isolates during antifungal therapy are growing problems. It is important for clinicians to be aware of trends and mechanisms responsible for the expression of resistance.

In vitro antifungal susceptibility testing

With the rising frequency of fungal infections, as well as increasing reports of resistance to antifungal agents, it is imperative that clinically applicable antifungal susceptibility testing be available. In 1997 the National Committee for Clinical Laboratory Standards published standard guidelines for antifungal susceptibility testing of Candida sp and Cryptococcus neoformans with amphotericin B, flucytosine, fluconazole, itraconazole, and ketoconazole. Although the methods are standard, they are time consuming, can be difficult to interpret, and are approved only for testing limited organisms and drugs. Modifications to the methods and alternative approaches have been proposed to make these tests more convenient and efficient, applicable to a greater number of species, and appropriate for performing in the clinical laboratory.

Fungal infection of the diabetic foot: two distinct syndromes

AIMS

Fungal infection of diabetic foot ulcers has not been described. We analysed the features of 17 patients with diabetic foot ulcers probably infected with fungi.

METHODS

Seventeen patients were identified with clinically infected foot ulcers, (i) which had failed to heal despite prolonged antibiotic therapy and intensive podiatric care, (ii) from which Candida spp. was isolated or hyphae +/- yeasts were visualized in material from ulcers or surrounding skin.

RESULTS

Multiple ulcers arising simultaneously were present in 10 patients (59%), preceded by blistering in seven cases. Single ulcers with markedly ulcerated margins were present in seven (41%) patients and were preceded by blisters in two. All 17 cases had neuropathy and 15 (88%) had severe peripheral vascular disease. All ulcers responded to antifungal therapy.

CONCLUSIONS

Candida spp. is associated with two distinctive patterns of protracted ulceration in diabetic feet which improve following systemic antifungal therapy. Diabet. Med. 18, 567-572 (2001)

Outbreak of Pichia anomala infection in the pediatric service of a tertiary-care center in Northern India

An outbreak of nosocomial fungemia due to the unusual yeast, Pichia anomala occurred in the pediatric wards of our hospital over a period of 23 months (April 1996 to February 1998). A total of 379 neonates and children (4.2% admissions) were infected. The probable index case was admitted to the pediatric emergency ward, with subsequent transmission to the premature nursery, pediatric intensive care units, and other children wards. Carriage on the hands of health care personnel was likely to be responsible for dissemination of the fungus. The outbreak could only be controlled after a health education campaign to improve hand-washing practices was instituted and after nystatin-fluconazole prophylaxis to all premature neonates and high-risk infants was introduced. In a case-control study, we identified a lower gestational age, a very low birth weight (<1,500 g), and a longer duration of hospital stay as significant risk factors associated with P. anomala fungemia in premature neonates. We conducted a culture prevalence survey of 50 consecutive premature neonates and found that 28% were colonized with P. anomala at a skin or mucosal site on the date of delivery and that 20% of these neonates subsequently developed P. anomala fungemia. We performed multilocus enzyme electrophoresis on 40 P. anomala outbreak isolates (including patient and health care workers' hand isolates), and the results suggested that these isolates were identical. Our study highlights the importance of P. anomala as an emerging nosocomial fungal pathogen.

Assessing risk factors for systemic fungal infections

The incidence of invasive fungal infection has increased in recent years. Most infections are caused by Candida albicans and Aspergillus spp. but the emergence of other fungal infections is changing the spectrum of disease. Immunosuppression and breakdown of anatomical barriers such as the skin are the major risk factors for fungal infections. Health care workers encounter at-risk patients in various settings, including AIDS clinics and intensive care, transplantation and oncology units. Patients with prolonged and deep neutropenia (haematological malignancy patients) are most at risk and are therefore most likely to receive prophylactic therapy. Practical measures can be taken to avoid exposing the patient to fungi (air filtration, regular hand washing, avoiding plants and flowers) and antifungal agents can be administered to prevent systemic fungal infection. Most fungal infections have non-specific symptoms; this makes recognition of the signs and symptoms of the disease important but also makes diagnosis difficult and empirical treatment necessary. Some antifungal agents have limitations but new formulations will improve therapy and play a key role in future antifungal strategies.

Trends in frequency and susceptibilities of Candida glabrata bloodstream isolates at a university hospital

The frequency of isolation and antifungal susceptibility patterns to fluconazole and itraconazole were determined for 166 Candida glabrata isolates causing bloodstream infection at a single institution from 1995-2000. Findings demonstrated a trend of increasing resistance to itraconazole among the isolates, but no trend in resistance to fluconazole. The frequency of C. glabrata isolates among all blood culture isolates of Candida spp. causing bloodstream infection remained stable during the study period and ranged from 18-31%.

Fluconazole for prophylaxis against candidal rectal colonization in the very low birth weight infant

BACKGROUND

Candidal infections are an important cause of morbidity and mortality in the very low birth weight (VLBW) infant. Current intervention focuses on treatment once candidal septicemia is either suspected or diagnosed. Studies have suggested that colonization with candidal species is an important risk factor for subsequent infection.

OBJECTIVE

To determine whether prophylactic fluconazole for the first 28 days of life results in a decreased incidence of candidal colonization in the VLBW infant.

RESEARCH DESIGN

Prospective, randomized, controlled, intention-to-treat design comparing prophylaxis with fluconazole versus placebo for the first 28 days of life.

SETTING

A tertiary level intensive care nursery in a major teaching hospital in Charleston, South Carolina.

PATIENTS

One hundred three infants with a birth weight of <1500 g, either inborn or outborn, who were admitted to the intensive care nursery between January 1998 and February 1999.

METHODS

Infants were enrolled within 72 hours of life with rectal cultures performed on the day of randomization (DOR), as well as day of life (DOL) 7, 14, and 28. Those infants with a birth weight of <1250 g had additional cultures on DOL 35, 49, and 56. Cultures were plated on selective media for isolation of candidal organisms. Infants were randomized to receive either fluconazole (6 mg/kg) or placebo on the DOR. Subsequent doses were given every 72 hours until DOL 7 and then every 24 hours until DOL 28. Medication was given either intravenously or by feeding tube once the infant had been gavage feeding for a 48-hour period without feeding intolerance. Aspartate aminotransferase and alanine aminotransferase levels were obtained on DOR and DOL 7, 14, and 28 to assess for fluconazole toxicity. The minimal inhibitory concentration to fluconazole was determined for all positive cultures to assess the development of resistance.

RESULTS

The infants who received fluconazole (n = 53) and placebo (n = 50) had no statistical difference in the major risk factors known to increase the chances of candidal septicemia in the VLBW infant. Rectal colonization by candidal species was detected in 8 of the 53 fluconazole-treated patients (15.1%) and in 23 of the 50 infants treated with placebo (46%). Fluconazole significantly reduced rectal colonization from DOL 14 through DOL 56 in all infants with a birth weight of <1250 g, and from DOL 14 through DOL 56 in all infants with a birth weight of 1250 to 1500 g. Alanine aminotransferase levels were higher in the fluconazole versus the placebo-treated group on DOL 14 (18.1 IU/L vs 15 IU/L), but no clinically significant abnormalities were observed. Candida albicans was the most common species isolated. There was no increase in species of Candida noted for their intrinsic resistance to fluconazole, and there was no statistically significant difference in the minimal inhibitory concentrations to fluconazole for all C albicans isolates in either group at any period.

CONCLUSION

Prophylactic administration of fluconazole to the VLBW infant for the first 28 days of life is safe and results in a decreased risk of rectal colonization by candidal species. Larger studies to determine the effect of prophylaxis on candidal septicemia and development of resistance in such a selective high-risk group are warranted before initiation of routine prophylaxis.fluconazole, very low birth weight infant, prophylaxis, candidal sepsis, sensitivities to fluconazole.

In vitro activity of a new echinocandin, LY303366, and comparison with fluconazole, flucytosine and amphotericin B against Candida species

OBJECTIVE

To investigate the in vitro activity of LY303366 (LY) against Candida isolates comprising nine different species and comparison with fluconazole (FLU), flucytosine (5FC) and amphotericin B (AMB).

METHODS

The method used was a microtitre modification of the NCCLS M27-A accepted standard using either RPMI-1640 with 2% glucose (5FC and FLU) or antibiotic medium 3 with 2% glucose (LY and AMB). The minimum inhibitory concentration (MIC) was the lowest drug concentration that reduced growth by 80% compared with the drug-free control. Minimum fungicidal concentrations (MFCs; 99% kill) were also determined for all isolates for LY and AMB.

RESULTS

Overall, 58 of 105 (55.2%) isolates were resistant to FLU (MIC < or = 16 mg/L). There was no relationship between FLU and LY MICs for C. albicans or non-albicans species. For all isolates, geometric mean (GM) MIC values and ranges (in mg/L) were: LY 0.011 and < or = 0.001-16, FLU 8.72 and < or = 0.125- > 128, 5FC 0.393 and < or = 0.03- > 32, AMB 0.046 and 0.008-0.125. Differences in susceptibility to LY were seen: C. parapsilosis (n = 12, GM 0.4 and range 0.125-16) and C. guilliermondii (n = 8, GM 0.46 and range 0.25-1) were both found to be significantly less susceptible to LY than all other species (P < or = 0.05). For all isolates, geometric mean MFC values and ranges (in mg/L) were: LY 0.032 and 0.002-16, AMB 0.143 and 0.03-2. The MFC value was the same as or only one drug dilution higher than the MIC value for 69.5% and 48.6% of isolates tested for LY and AMB, respectively. Tolerance was described in 13.3% and 5.7% of isolates for LY and AMB, respectively. A reproducibility study performed on 20% of the isolates showed that 90.5%, 100%, 95.2% and 100% of isolates retested were the same or within one well of the original MIC value for LY, FLU, 5FC and AMB, respectively.

CONCLUSIONS

LY303366 shows promising antifungal activity in vitro and warrants further in vivo investigation.

Identification and phylogenetic relationship of the most common pathogenic Candida species inferred from mitochondrial cytochrome b gene sequences

We sequenced a 396-bp region of the mitochondrial cytochrome b gene of the most common clinically important Candida species: Candida albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. krusei, and C. lusitaniae. The recently described species of Candida, C. dubliniensis, associated with mucosal candidiasis in human immunodeficiency virus-infected individuals, was also included. Two to five strains of each species were examined. Some species represented intraspecies variation, which was not more than 1.8% (DNA). However, interspecies variations were more than 10 and 7%, respectively, for DNA and amino acid sequences. Multiple alignments of nucleotide and deduced amino acid sequences revealed species-specific nucleotides and amino acids. Nucleotide- and amino acid-based phylogenetic trees were constructed and are discussed. Using the database, it is possible to identify presumptive Candida species within a working day.

Vaginal yeasts in the era of "over the counter" antifungals

OBJECTIVE

To establish whether there has been any rise in the prevalence of non-albicans Candida species isolated from vaginal swabs since the introduction of "over the counter" antifungal treatments.

METHOD

A retrospective review looking at all positive vaginal yeast isolates collected from women attending one genitourinary medicine clinic during the 6 year period from 1993 to 1998 inclusive. All positive vaginal yeast isolates were included, regardless of whether or not the patients were symptomatic. Isolates from HIV positive women were excluded from the analysis.

RESULTS

No increase in non-albicans vaginal yeast isolates was shown during the period studied. The proportion of non-albicans yeasts remained constant at approximately 5% of the total yeasts isolated. The most common non-albicans yeast isolated was C glabrata.

CONCLUSION

There is no evidence from this study to suggest that the increasing use of "over the counter" antifungal treatment has selected for atypical, possibly inherently azole resistant, strains of vaginal yeasts in HIV seronegative women.

Management of Infections Caused by Candida glabrata

Candida glabrata infections undoubtedly have become more frequent, and are now common. They appear to be the consequence of widespread and often indiscriminate use of azoles, especially fluconazole. This species constitutes the Achilles heel of all available azoles, including newer ones in the pipeline. Even when amphotericin B is used, higher dosages are now required. Little is known about the epidemiology of and risk factors for this troublesome species; even less about its virulence factors. However, studying the resistance mechanisms of this haploid organism may provide answers in developing new fungicidal agents.

The ins and outs of DNA fingerprinting the infectious fungi

DNA fingerprinting methods have evolved as major tools in fungal epidemiology. However, no single method has emerged as the method of choice, and some methods perform better than others at different levels of resolution. In this review, requirements for an effective DNA fingerprinting method are proposed and procedures are described for testing the efficacy of a method. In light of the proposed requirements, the most common methods now being used to DNA fingerprint the infectious fungi are described and assessed. These methods include restriction fragment length polymorphisms (RFLP), RFLP with hybridization probes, randomly amplified polymorphic DNA and other PCR-based methods, electrophoretic karyotyping, and sequencing-based methods. Procedures for computing similarity coefficients, generating phylogenetic trees, and testing the stability of clusters are then described. To facilitate the analysis of DNA fingerprinting data, computer-assisted methods are described. Finally, the problems inherent in the collection of test and control isolates are considered, and DNA fingerprinting studies of strain maintenance during persistent or recurrent infections, microevolution in infecting strains, and the origin of nosocomial infections are assessed in light of the preceding discussion of the ins and outs of DNA fingerprinting. The intent of this review is to generate an awareness of the need to verify the efficacy of each DNA fingerprinting method for the level of genetic relatedness necessary to answer the epidemiological question posed, to use quantitative methods to analyze DNA fingerprint data, to use computer-assisted DNA fingerprint analysis systems to analyze data, and to file data in a form that can be used in the future for retrospective and comparative studies.

Evaluation of the VITEK 2 system for rapid identification of yeasts and yeast-like organisms

The new VITEK 2 system is a fully automated system dedicated to the identification and susceptibility testing of microorganisms. In conjunction with the VITEK ID-YST card the VITEK 2 system allows the identification of clinically important yeasts and yeast-like organisms in 15 h due to a sensitive fluorescence-based technology. The ID-YST card consists of 47 biochemical reactions. The database comprises 51 taxa, including newly described species. In this study we evaluated the reliability of the VITEK ID-YST card for the identification of yeasts and yeast-like organisms encountered in a clinical microbiology laboratory. A total of 241 strains representing 21 species were studied. The strains were isolated from clinical samples within a period of 60 days prior to the identification. The tests were performed using 24-h to 55-h subcultures on Sabouraud-gentamicin-chloramphenicol agar. Each strain was tested in parallel using the ID 32C strip as a comparison method combined with microscopic morphology and an agglutination test for C. krusei. Overall, 222 strains (92.1%) were unequivocally identified including 11 isolates (4.6%) identified with low discrimination resolved by simple additional tests. Ten strains (4. 1%) for which results were given with low discrimination could not be unequivocally identified with supplemental tests, 4 strains (1. 7%) were misidentified and 5 strains (2.1%) could not be identified. In conclusion, we found that the VITEK 2 system is a rapid and accurate method for the identification of medically important yeasts and yeast-like organisms.

In vitro activity of A-192411.29, a novel antifungal lipopeptide

A-192411.29 is a novel antifungal agent derived from the structural template of the natural product echinocandin. The in vitro activity of A-192411.29 against common pathogenic yeasts was assessed by National Committee for Clinical Laboratory Standards method M27-A. It demonstrated broad-spectrum, fungicidal activity and was active against the most clinically relevant yeasts, such as Candida albicans, Candida tropicalis, and Candida glabrata, as well as less commonly encountered Candida species; in general, its potency on a weight basis was comparable to that of amphotericin B. It maintained potent in vitro activity against Candida strains with reduced susceptibilities to fluconazole and amphotericin B. The in vitro activity of A-192411.29 against Cryptococcus neoformans was comparable to its activity against Candida spp. However, A-192411.29 did not demonstrate complete growth inhibition of Aspergillus fumigatus by the broth microdilution method used. A-192411.29 possesses an antifungal profile comparable to or better than those of fluconazole and amphotericin B against pathogenic yeasts, including strains resistant to fluconazole or amphotericin B, suggesting that it may be a therapeutically useful new antifungal drug.

Nosocomial fungaemia: a 2-year prospective study

Eighty-six consecutive patients with fungaemia were studied during a period of 2 years, 81% had two or more positive blood cultures. Gastrointestinal tract (28%) and haematological diseases (17%) were the most common underlying conditions. The majority of cases had received vancomycin and/or imipenem (87%) and a central venous catheter (78%). Candida albicans (50%) and Candida parapsilosis (17%) were the most frequent isolates. Overall mortality was 41%, and for patients with Candida tropicalis was 71%. There was not significant difference in survival with gender, age and days of treatment with antifungal drugs. Haematological diseases, neutropenia and a higher number of positive blood cultures were associated with poor outcome.

The ins and outs of DNA fingerprinting the infectious fungi

DNA fingerprinting methods have evolved as major tools in fungal epidemiology. However, no single method has emerged as the method of choice, and some methods perform better than others at different levels of resolution. In this review, requirements for an effective DNA fingerprinting method are proposed and procedures are described for testing the efficacy of a method. In light of the proposed requirements, the most common methods now being used to DNA fingerprint the infectious fungi are described and assessed. These methods include restriction fragment length polymorphisms (RFLP), RFLP with hybridization probes, randomly amplified polymorphic DNA and other PCR-based methods, electrophoretic karyotyping, and sequencing-based methods. Procedures for computing similarity coefficients, generating phylogenetic trees, and testing the stability of clusters are then described. To facilitate the analysis of DNA fingerprinting data, computer-assisted methods are described. Finally, the problems inherent in the collection of test and control isolates are considered, and DNA fingerprinting studies of strain maintenance during persistent or recurrent infections, microevolution in infecting strains, and the origin of nosocomial infections are assessed in light of the preceding discussion of the ins and outs of DNA fingerprinting. The intent of this review is to generate an awareness of the need to verify the efficacy of each DNA fingerprinting method for the level of genetic relatedness necessary to answer the epidemiological question posed, to use quantitative methods to analyze DNA fingerprint data, to use computer-assisted DNA fingerprint analysis systems to analyze data, and to file data in a form that can be used in the future for retrospective and comparative studies.

In vitro antifungal susceptibility of clinical isolates of Candida spp. from hospitalized patients

A total of 122 Candida spp. strains, isolated from a group of 100 patients hospitalized in the Santa Casa de Misericordia of Belo Horizonte were assayed for in vitro susceptibility to amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine using a microbroth technique proposed by the National Committee for Clinical Laboratory Standards. In this study large variations were observed among minimum inhibitory concentration values depending on the species tested. The statistical analysis (Kruskal-Wallis test) showed that itraconazole and flucytosine were the more efficient antifungal drugs for most of species, and amphotericin B and fluconazole were the least efficient.

Bloodstream infections due to Candida species: SENTRY antimicrobial surveillance program in North America and Latin America, 1997-1998

An international program of surveillance of bloodstream infections (BSI) in the United States, Canada, and Latin America detected 306 episodes of candidemia in 34 medical centers (22 in the United States, 6 in Canada, and 6 in Latin America) in 1997 and 328 episodes in 34 medical centers (22 in the United States, 5 in Canada, and 7 in Latin America) in 1998. Of the 634 BSI, 54.3% were due to Candida albicans, 16.4% were due to C. glabrata, 14.9% were due to C. parapsilosis, 8.2% were due to C. tropicalis, 1.6% were due to C. krusei, and 4.6% were due to other Candida spp. The percentage of BSI due to C. albicans decreased very slightly in the United States between 1997 and 1998 (56.2 to 54.4%; P = 0.68) and increased in both Canada (52.6 to 70.1%; P = 0.05) and Latin America (40.5 to 44. 6%; P = 0.67). C. glabrata was the second most common species observed overall, and the percentage of BSI due to C. glabrata increased in all three geographic areas between 1997 and 1998. C. parapsilosis was the third most prevalent BSI isolate in both Canada and Latin America, accounting for 7.0 and 18.5% of BSI, respectively. Resistance to fluconazole (MIC, >/=64 microgram/ml) and itraconazole (MIC, >/=1.0 microgram/ml) was observed infrequently in both 1997 (2.3 and 8.5%, respectively) and 1998 (1.5 and 7.6%, respectively). Among the different species of Candida, resistance to fluconazole and itraconazole was observed in C. glabrata and C. krusei, whereas isolates of C. albicans, C. parapsilosis, and C. tropicalis were all highly susceptible to both fluconazole (98.9 to 100% susceptible) and itraconazole (96.4 to 100% susceptible). Isolates from Canada and Latin America were generally more susceptible to both triazoles than U.S. isolates were. Continued surveillance appears necessary to detect these important changes.

Potential role of phospholipases in virulence and fungal pathogenesis

Microbial pathogens use a number of genetic strategies to invade the host and cause infection. These common themes are found throughout microbial systems. Secretion of enzymes, such as phospholipase, has been proposed as one of these themes that are used by bacteria, parasites, and pathogenic fungi. The role of extracellular phospholipase as a potential virulence factor in pathogenic fungi, including Candida albicans, Cryptococcus neoformans, and Aspergillus, has gained credence recently. In this review, data implicating phospholipase as a virulence factor in C. albicans, Candida glabrata, C. neoformans, and A. fumigatus are presented. A detailed description of the molecular and biochemical approaches used to more definitively delineate the role of phospholipase in the virulence of C. albicans is also covered. These approaches resulted in cloning of three genes encoding candidal phospholipases (caPLP1, caPLB2, and PLD). By using targeted gene disruption, C. albicans null mutants that failed to secrete phospholipase B, encoded by caPLB1, were constructed. When these isogenic strain pairs were tested in two clinically relevant murine models of candidiasis, deletion of caPLB1 was shown to lead to attenuation of candidal virulence. Importantly, immunogold electron microscopy studies showed that C. albicans secretes this enzyme during the infectious process. These data indicate that phospholipase B is essential for candidal virulence. Although the mechanism(s) through which phospholipase modulates fungal virulence is still under investigations, early data suggest that direct host cell damage and lysis are the main mechanisms contributing to fungal virulence. Since the importance of phospholipases in fungal virulence is already known, the next challenge will be to utilize these lytic enzymes as therapeutic and diagnostic targets.

Antibiotic-Resistant Organism Infection

Bacteria possess a remarkable number of ways to become resistant to antibiotics. Antibiotic resistance has become a major problem in the treatment of Gram-positive infections. Resistance to methicillin and vancomycin in staphylococci and enterococci has resulted in organisms that are resistant to all known antibiotics. Although it is important to continue to search for newer and more effective antibiotics, it is imperative that we develop a surgical mindset of appropriate antibiotic stewardship. The use of single-dose prophylactic regimens, using narrow-spectrum agents when possible for therapeutic indications, limiting the duration of therapeutic agents appropriately, avoiding the use of vancomycin except when necessary, and adhering to strict infection control measures are all steps that will limit the spread and development of resistant organisms.

Potential role of phospholipases in virulence and fungal pathogenesis

Microbial pathogens use a number of genetic strategies to invade the host and cause infection. These common themes are found throughout microbial systems. Secretion of enzymes, such as phospholipase, has been proposed as one of these themes that are used by bacteria, parasites, and pathogenic fungi. The role of extracellular phospholipase as a potential virulence factor in pathogenic fungi, including Candida albicans, Cryptococcus neoformans, and Aspergillus, has gained credence recently. In this review, data implicating phospholipase as a virulence factor in C. albicans, Candida glabrata, C. neoformans, and A. fumigatus are presented. A detailed description of the molecular and biochemical approaches used to more definitively delineate the role of phospholipase in the virulence of C. albicans is also covered. These approaches resulted in cloning of three genes encoding candidal phospholipases (caPLP1, caPLB2, and PLD). By using targeted gene disruption, C. albicans null mutants that failed to secrete phospholipase B, encoded by caPLB1, were constructed. When these isogenic strain pairs were tested in two clinically relevant murine models of candidiasis, deletion of caPLB1 was shown to lead to attenuation of candidal virulence. Importantly, immunogold electron microscopy studies showed that C. albicans secretes this enzyme during the infectious process. These data indicate that phospholipase B is essential for candidal virulence. Although the mechanism(s) through which phospholipase modulates fungal virulence is still under investigations, early data suggest that direct host cell damage and lysis are the main mechanisms contributing to fungal virulence. Since the importance of phospholipases in fungal virulence is already known, the next challenge will be to utilize these lytic enzymes as therapeutic and diagnostic targets.

Nucleic acid sequence-based amplification (NASBA) detection of medically important Candida species

Nucleic Acid Sequence Based Amplification (iNASBA), an isothermal amplification technique for nucleic acids, was evaluated for the identification of medically important Candida species using primers selected from 18S rRNA sequences conserved in fungi. An RNA fragment of 257 nucleotides was amplified for Candida albicans. Nineteen different fungi were tested for rRNA amplification with the NASBA. All were positive when analyzed on agarose gel, whereas human RNA was negative. For the identification of Candida species, NASBA amplification products were analyzed in an enzyme bead-based detection format, using species-specific biotinylated probes and a generic Candida HRPO probe or a membrane-based system using biotinylated probes and avidin-HPRO. Discrimination of the major human pathogenic Candida spp. was based on a panel of biotinylated probes for C. krusei, C. tropicalis, C. albicans, C. glabrata, and C. lusitaniae. Using rRNA dilutions obtained from pure cultures of C. albicans, the combination of NASBA and the enzymatic bead-based detection yielded a sensitivity equivalent to 0.01 CFU. In a model system using 1 ml of artificially contaminated blood as few as 1-10 CFU of C. albicans could be detected. Testing of 68 clinical blood samples from patients suspected of candidemia showed that eight samples were positive for C. albicans and one for C. glabrata. Testing of 13 clinical plasma samples from patients suspected of fungemia identified the presence of C. albicans in two specimens. The whole procedure of sample preparation, amplification and identification by hybridization can be performed in 1 day. This speed and the observed sensitivity of the assay make the NASBA a good alternative to PCR for the detection of candidemia.

Nosocomial fungal infections: candidemia

Candida species are frequently encountered as part of the human commensal flora. Colonization mostly precedes candidemia and is an independent risk factor for the development of candidemia. Genotyping methods showed the similarity between colonizing and infecting strains, thus making endogenous origin likely, though exogenous sources like total parenteral nutrition also have been described. Health care workers (HCWs) play an important role in the transmission of yeasts. Candida species are frequently isolated from the hands of HCWs and can be transmitted from hands to patients. Granulocytopenia and damage of the mucosal lining resulting from intensive chemotherapy due to cancer, the increasing use of broad spectrum antibiotics, and the use of intravenous catheters are other important risk factors for the development of candidemia. Candidemia is associated with a high mortality and prolonged hospitalization. Therefore, and because of the high frequency of dissemination, all candidemias should be treated. Amphotericin B was considered the standard drug for the systemic treatment of candidemia. Fluconazole has been shown to be an effective and safe alternative in non-neutropenic patients. 5-Fluorocytosine has been used in combination with amphotericin B in the treatment of deep-seated infections. Liposomal formulations of amphotericin B and other new antifungal drugs currently are under investigation. C. albicans is the most frequently isolated Candida species, although the proportion of infections caused by non-C. albicans species is increasing. Also, there are reports of development of resistance to amphotericin B. C. lusitaniae is known for primary resistance and the development of resistance to amphotericin B. Development of resistance to fluconazole is mainly seen in AIDS patients with recurrent oropharyngeal candidiasis who receive longer courses of therapy.

Fluconazole susceptibilities of bloodstream Candida sp. isolates as determined by National Committee for Clinical Laboratory Standards method M27-A and two other methods

The in vitro activity of fluconazole against 143 Candida spp. obtained from the bloodstreams of 143 hospitalized patients from 1995 to 1997 was studied. Susceptibility tests were carried out by two macrodilution methods, the M27-A and a modified M27-A method (0. 165 M, pH 7/morpholinepropanesulfonic acid-buffered RPMI 1640 medium supplemented with 20 g of D-dextrose per liter), and by the agar diffusion method (with 15-microg fluconazole [Neo-Sensitab] tablets). With 2 microg of fluconazole per ml, 96.92% of 65 C. albicans isolates, 86.2% of 58 C. parapsilosis isolates 7 of 8 C. tropicalis isolates, and 1 of 6 C. glabrata isolates were inhibited. Only one strain of C. albicans and one strain of C. tropicalis were resistant. The agreement between the two macrodilution methods was greater than 90% within +/-2 log2 dilutions for all strains except C. glabrata (83.3%) and C. tropicalis (87.5%). Generally, MICs were 1 log2 dilution lower in glucose-supplemented RPMI 1640 medium. No correlation between zone sizes and MICs was found. All strains susceptible by the diffusion test were susceptible by the dilution method, but the converse was not necessarily true. Interestingly, inhibition zones were smaller for C. albicans, for which the geometric mean MIC was 0.29 microg/ml and the mean inhibition zone diameter was 25.7 mm, while for C. parapsilosis the geometric mean MIC was 0.96 microg/ml and the mean inhibition zone diameter was 31. 52 mm. In conclusion, the two macrodilution methods give similar results. The modified M27-A method with 2% dextrose has the advantage of shortening the incubation time and simplifying the endpoint determination.

Fluconazole prophylaxis prevents intra-abdominal candidiasis in high-risk surgical patients

OBJECTIVE

To evaluate the efficacy and safety of intravenous fluconazole for the prevention of intra-abdominal Candida infections in high-risk surgical patients.

DESIGN

Randomized, prospective, double-blind, placebo-controlled study.

SETTING

Two university-affiliated hospitals in Switzerland.

PATIENTS

Forty-nine surgical patients with recurrent gastrointestinal perforations or anastomotic leakages.

INTERVENTIONS

Prophylaxis with intravenous fluconazole (400 mg per day) or placebo continued until resolution of the underlying surgical condition.

MEASUREMENTS AND MAIN RESULTS

Patients were evaluated daily, and specimens for culture were obtained three times per week during prophylaxis. The primary study end points were the frequency of and the time to intra-abdominal Candida infections. Secondary end points were the frequency of candidiasis (intra-abdominal and extra-abdominal) and the emergence or persistence of Candida colonization. Among patients who were not colonized at study entry, Candida was isolated from surveillance cultures during prophylaxis in 15% of the patients in the fluconazole group and in 62% of the patients in the placebo group (relative risk, 0.25; 95% confidence interval, 0.07 to 0.96; p = .04). Candida peritonitis occurred in one of 23 patients (4%) who received fluconazole and in seven of 20 patients (35%) who received placebo (relative risk, 0.12; 95% confidence interval, 0.02 to 0.93; p = .02). In addition, one catheter-related Candida albicans sepsis occurred in a fluconazole-treated patient. Thus, overall, candidiasis developed in two fluconazole patients and seven placebo patients (relative risk, 0.25; 95% confidence interval, 0.06 to 1.06; p = .06). C. albicans accounted for 87% of the Candida species isolated before or during prophylaxis, and all C. albicans strains were susceptible to fluconazole. Fluconazole was well tolerated, and adverse events occurred at similar frequencies in both treatment groups.

CONCLUSIONS

Fluconazole prophylaxis prevents colonization and invasive intra-abdominal Candida infections in high-risk surgical patients.

Rapid identification of fungi by using the ITS2 genetic region and an automated fluorescent capillary electrophoresis system

Invasive fungal disease often plays an important role in the morbidity and mortality of immunocompromised patients. The poor sensitivity of current fungal blood culture and histological practices has led to the development of highly sensitive and specific molecular techniques, such as the PCR. Sequence variability of the internal transcribed spacer 2 (ITS2) region of fungi is potentially useful in rapid and accurate diagnosis of clinical fungal isolates. PCR with fungus-specific primers targeted toward conserved sequences of the 5.8S and 28S ribosomal DNA (rDNA) results in amplification of the species-specific ITS2 regions, which are variable in amplicon length. We have made use of the ABI PRISM 310 genetic analyzer and the ABI PRISM 310 GeneScan analysis software for the determination of variable size differences of the ITS2 region of clinically important fungi, including Candida and non-Candida yeasts, Aspergillus species, and a variety of dermatophytes. No cross-reaction occurred when samples were tested against human and bacterial genomic DNA. We have found that most clinically significant fungal isolates can be differentiated by this method, and it therefore serves to be a promising tool for the rapid (<7 h) diagnosis of fungemia and other invasive fungal infections.