William G. Merz

Increase in Candida krusei Infection among Patients with Bone Marrow Transplantation and Neutropenia Treated Prophylactically with Fluconazole

BACKGROUND In early 1990 fluconazole was introduced as a prophylactic antifungal agent after bone marrow transplantation. During the same year Candida krusei emerged as the chief candida pathogen among patients with bone marrow transplants. METHODS To determine whether there was a correlation between the introduction of fluconazole and the increased incidence of C. krusei, we conducted a retrospective study based on the medical, mycologic, and autopsy records of all adult inpatients who had undergone bone marrow transplantation (n = 296) or who had leukemia (n = 167) at the study center during 1989 and 1990. RESULTS The 84 patients who received antifungal prophylaxis with fluconazole had a sevenfold greater frequency of C. krusei infection than the 335 patients who did not receive fluconazole (8.3 percent vs. 1.2 percent, P = 0.002), despite having a lower frequency of disseminated C. albicans and C. tropicalis infections (0 vs. 6.0 percent, P = 0.02). Ten of the 11 C. krusei infections were controlled by a combination of amphotericin B and flucytosine. Colonization by C. krusei was found in 40.5 percent of the patients who received fluconazole but in only 16.7 percent of those who did not receive it (P less than 0.0001). Colonization was independently associated with the prophylactic use of both fluconazole (odds ratio, 3.50; P less than 0.001) and norfloxacin (odds ratio, 2.53; P = 0.04). C. krusei was not susceptible to fluconazole in vitro. CONCLUSIONS In patients at high risk for disseminated candida infections, suppression of bacterial flora and the more common candida pathogens may permit some less pathogenic, but natively resistant candida species, such as C. krusei, to emerge as systemic pathogens.

Double-Blind Placebo-Controlled Trial of Fluconazole to Prevent Candidal Infections in Critically Ill Surgical Patients

ObjectiveTo evaluate the prophylactic use of enteral fluconazole to prevent invasive candidal infections in critically ill surgical patients. Summary Background DataInvasive fungal infections are increasingly common in the critically ill, especially in surgical patients. Although fungal prophylaxis has been proven effective in certain high-risk patients such as bone marrow transplant patients, few studies have focused on surgical patients and prevention of fungal infection. MethodsThe authors conducted a prospective, randomized, placebo-controlled trial in a single-center, tertiary care surgical intensive care unit (ICU). A total of 260 critically ill surgical patients with a length of ICU stay of at least 3 days were randomly assigned to receive either enteral fluconazole 400 mg or placebo per day during their stay in the surgical ICU at Johns Hopkins Hospital. ResultsThe primary end point was the time to occurrence of fungal infection during the surgical ICU stay, with planned secondary analysis of patients “on-therapy” and alternate definitions of fungal infections. In a time-to-event analysis, the risk of candidal infection in patients receiving fluconazole was significantly less than the risk in patients receiving placebo. After adjusting for potentially confounding effects of the Acute Physiology and Chronic Health Evaluation (APACHE) III score, days to first dose, and fungal colonization at enrollment, the risk of fungal infection was reduced by 55% in the fluconazole group. No difference in death rate was observed between patients receiving fluconazole and those receiving placebo. ConclusionsEnteral fluconazole safely and effectively decreased the incidence of fungal infections in high-risk, critically ill surgical patients.

Candida tropicalis: A Major Pathogen in Immunocompromised Patients

Of 89 consecutive patients undergoing treatment for hematologic malignancies or undergoing allogeneic bone marrow transplantation, 60 were colonized with Candida albicans and 25 with C. tropicalis. However, of the 18 disseminated infections caused by Candida species, 15 infections in 14 patients were caused by C. tropicalis and only three infections in three patients by C. albicans. The setting in which the infection occurred, skin lesions, polyarthralgias, or polymyalgias, and the unexplained deterioration of renal function were features suggestive of the diagnosis. Defervescence occurred in 10 of the 14 treated patients with C. tropicalis infections in 1 to 6 d (mean, 2.5 d) after initiation of therapy, even though all continued to be granulocytopenic. Resolution occurred in eight of the 15 C. tropicalis infections. In one case outcome was indeterminate, four patients died due to the infection, and two died from other causes but with the infection unresolved.

Detection of Circulating Candida Enolase by Immunoassay in Patients with Cancer and Invasive Candidiasis

BACKGROUND Invasive candidiasis is a major nosocomial infection that is difficult to diagnose. Few biochemically defined markers of invasive candidiasis are known. Initial findings suggested that the presence of candida enolase in the blood may be a novel marker for invasive candidiasis. METHODS We tested 170 patients at high risk for invasive candidiasis for candida enolase antigenemia. All the patients had cancer and neutropenia. We detected antigen using a double-sandwich liposomal immunoassay for candida enolase in serially collected serum samples. Invasive candidiasis was proved by finding candida species in deep nonmucosal tissue, blood cultures, or both. Antigen testing was performed with the investigator blinded to tissue or culture diagnosis. RESULTS Among 24 patients with proved invasive candidiasis, 149 serum samples were tested for enolase antigenemia; 80 were positive and 69 negative (sensitivity per sample, 54 percent). Multiple sampling improved the detection of antigenemia, which was found in 11 of 13 proved cases of deep tissue infection (85 percent) and in 7 of 11 proved cases of fungemia (64 percent). Specificity was 96 percent as measured against control groups including patients with mucosal colonization, bacteremia, and other deep mycoses. Antigenemia was detected in the absence of fungemia in 5 cases of deep tissue candidiasis, but was not detected in 6 cases of fungemia alone. CONCLUSIONS Candida enolase antigenemia is a novel marker for invasive candidiasis. It may be a useful indicator of deep infection in patients with cancer and neutropenia and may complement the diagnostic usefulness of blood cultures.

Oral norfloxacin for prevention of gram-negative bacterial infections in patients with acute leukemia and granulocytopenia. A randomized, double-blind, placebo-controlled trial

We evaluated the effect of norfloxacin, 400 mg given orally every 12 hours, on the prevention of bacterial infections in 68 adult patients who had acute leukemia throughout prolonged courses of granulocytopenia (median, 32 days). Gram-negative infections were documented in 13 of the 33 patients receiving placebo, but only in 4 of the 35 patients receiving norfloxacin; no effect on the frequency of gram-positive or fungal infections was noted. Norfloxacin administration resulted in the suppression of gastrointestinal tract colonization by aerobic bacteria without the development of norfloxacin resistance. Patients receiving norfloxacin developed first infectious fevers later than did those receiving placebo, had more rapid resolution of that fever after systemic antibiotic treatment, and spent less time febrile. Therefore, although no difference was seen in survival duration, we found that the prophylactic administration of oral norfloxacin led to decreases in overall morbidity and gram-negative infections, was well tolerated, and did not predispose to the development of multiply drug-resistant bacteria.

Interlaboratory Comparison of Results of Susceptibility Testing with Caspofungin against Candida and Aspergillus Species

ABSTRACT Seventeen laboratories participated in a study of interlaboratory reproducibility with caspofungin microdilution susceptibility testing against panels comprising 30 isolates of Candida spp. and 20 isolates of Aspergillus spp. The laboratories used materials supplied from a single source to determine the influence of growth medium (RPMI 1640 with or without glucose additions and antibiotic medium 3 [AM3]), the same incubation times (24 h and 48 h), and the same end point definition (partial or complete inhibition of growth) for the MIC of caspofungin. All tests were run in duplicate, and end points were determined both spectrophotometrically and visually. The results from almost all of the laboratories for quality control and reference Candida and Aspergillus isolates tested with fluconazole and itraconazole matched the NCCLS published values. However, considerable interlaboratory variability was seen in the results of the caspofungin tests. For Candida spp. the most consistent MIC data were generated with visual “prominent growth reduction” (MIC2) end points measured at 24 h in RPMI 1640, where 73.3% of results for the 30 isolates tested fell within a mode ± one dilution range across all 17 laboratories. MIC2 at 24 h in RPMI 1640 or AM3 also gave the best interlaboratory separation of Candida isolates of known high and low susceptibility to caspofungin. Reproducibility of MIC data was problematic for caspofungin tests with Aspergillus spp. under all conditions, but the minimal effective concentration end point, defined as the lowest caspofungin concentration yielding conspicuously aberrant hyphal growth, gave excellent reproducibility for data from 14 of the 17 participating laboratories.

An approach to intensive antileukemia therapy in patients with previous invasive aspergillosis

PURPOSE In an attempt to decrease the risk for reactivation of life-threatening invasive aspergillosis (IA) during subsequent myelosuppression in patients with previously diagnosed IA who were receiving antileukemic treatment, we evaluated the role of intensive antifungal therapy with amphotericin B and 5-fluorocytosine administered prophylactically throughout the antileukemic regimen and induced granulocytopenia to prevent IA reactivation without compromising the intensive chemotherapy. PATIENTS AND METHODS During a 30-month period, 10 patients with acute myelogenous leukemia and primary IA developing during initial antileukemia induction therapy and severe granulocytopenia (less than 100/mm3) underwent 14 subsequent courses of intensive marrow aplasia-producing chemotherapy during early complete remission or at leukemia relapse. All patients had evidence of ongoing IA healing by lung computerized tomography (CT) prior to reinstitution of intensive chemotherapy. Nine patients receiving 13 chemotherapy courses also received aggressive prophylactic anti-IA therapy with amphotericin B (1.0 mg/kg/day) and 5-fluorocytosine beginning at least 48 hours prior to antileukemia therapy institution and continued until the time of granulocyte recovery. RESULTS All nine patients receiving aggressive antifungal therapy survived without clinical evidence of IA reactivation. Transient radiographic evidence of IA reactivation during granulocytopenia was detected by lung CT during two of the 13 chemotherapy courses. In contrast, the patient who did not receive anti-IA prophylaxis had both clinical and radiographic evidence of IA reactivation during severe granulocytopenia and died. Anti-IA prophylaxis was achieved without irreversible nephrotoxicity, prolonged marrow suppression, alteration of antileukemia treatment, or negative impact on clinical outcome relative to acute leukemia. CONCLUSION This approach of antifungal prophylaxis in adults with acute leukemia and documented primary IA occurring during initial induction chemotherapy has been successful in preventing clinically significant IA reactivation during subsequent granulocytopenic courses, and allows for administration of additional intensive antileukemia therapy.

Multicenter evaluation of the Candida albicans/Candida glabrata peptide nucleic acid fluorescent in situ hybridization method for simultaneous dual-color identification of C. albicans and C. glabrata directly from blood culture bottles

ABSTRACT We evaluated the performance of the Candida albicans/Candida glabrata peptide nucleic acid fluorescent in situ hybridization (PNA FISH) method, a rapid two-color assay for detection of C. albicans and C. glabrata, in a multicenter study. The assay is designed for use directly from positive blood culture bottles in a FISH format. Intact, fixed cells are labeled fluorescent green (C. albicans) or fluorescent red (C. glabrata) by rRNA hybridization of fluorophore-labeled PNA probes. Results are available <3 h after cultures signal positive. An evaluation of 197 routine blood culture bottles newly positive for yeast by Gram staining was performed at five hospitals. The sensitivities of detection for C. albicans, and C. glabrata were 98.7% (78/79) and 100% (37/37), respectively, and the specificity for both components of the assay was 100% (82/82). The assay was also evaluated with 70 fungal reference strains and was challenged in the BacT/ALERT microbiological detection system with spiked blood culture bottles. These results support the use of the assay for rapid, simultaneous identification of C. albicans and C. glabrata in positive blood culture bottles. This rapid assay may aid in the selection of initial antifungal drugs, leading to improved patient outcomes.

Triazole cross-resistance among Candida spp.: case report, occurrence among bloodstream isolates, and implications for antifungal therapy.

ABSTRACT Candida spp. are common causes of bloodstream infections among hospitalized patients. Fluconazole (FLC) remains a first-line therapy for candidemia; and voriconazole (VRC), an expanded-spectrum triazole, was recently approved for the treatment of candidemia in nonneutropenic patients. In vitro studies have suggested that VRC has potent activity against Candida spp. with reduced susceptibilities to FLC. We present a case report of invasive candidiasis and candidemia due to a Candida glabrata isolate that developed resistance to all currently available triazole antifungals after a course of FLC treatment. This case prompted us to determine the frequency of cross-resistance among bloodstream Candida isolates collected during a recent 12-month period at a large, academic medical center. FLC MICs were determined for 125 of 153 isolates (81.7%). Thirty of 125 isolates (24%) were resistant or showed reduced susceptibilites to FLC (MICs ≥ 16 μg/ml). When 28 of these 30 isolates were tested for their VRC susceptibilities, 9 (32%) had MICs that were ≥2 μg/ml. Five of these nine isolates were C. glabrata, two isolates were Candida tropicalis, one isolate was Candida albicans, and one isolate was Candida parapsilosis. All five Candida krusei isolates tested had VRC MICs ≤0.5 μg/ml. These data have prompted the introduction of reflexive FLC susceptibility testing of first bloodstream Candida isolates at our institution. The case report and our data also suggest that VRC should be avoided as initial therapy in unstable patients with invasive candidiasis, particularly in the setting of prior azole exposure. Studies are needed to define the clinical significance of in vitro resistance to the newer antifungal agents.

Candida albicans strain delineation.

Candida albicans is a major opportunistic pathogen causing a wide spectrum of disease in human beings. Methods for strain delineation of this species to assess or predict virulence or to conduct epidemiologic or pathogenetic investigations have been developed. Although factors associated with virulence have been identified, there is no rapid system to quantitate them in a clinical laboratory. Therefore, many typing methods are based on variable phenotypic characteristics within this species including morphotyping, serotyping, antibiogram, resistogram typing, biotyping, biotyping based on commercial carbon assimilation patterns, enzyme profiles, sensitivity to yeast killer toxins, and typing based on protein variability. Phenotypically defined strains generally do not correlate with the pathogenic potential of a strain with the exception of morphotyping. However, these methods can be useful in epidemiologic investigations; for example, they have revealed that most individuals harbor one strain and that infections are frequently due to an endogenous strain. Problems with these methods usually relate to their discriminatory power. When this is maximized, reproducibility (especially between laboratories) suffers. Recently, methods based on differences in DNA structure (genotyping) for strain delineation have been developed, including electrophoretic karyotyping and restriction enzyme fragment length polymorphisms. The development of a computer-assisted data bank and analysis for these genotypic strain delineators will open investigations into the pathogenesis of this infection and permit epidemiologic studies previously not possible with this important human pathogen.