Molecular and immunologic tests promise better, faster laboratory diagnosis of aspergillosis, but microscopy and culture remain commonly used and essential tools. Procedural changes, as well as adequate training of laboratory professionals, can enhance the value of these traditional tools. Using Blankophor or Calcofluor for microscopic examinations; improving recognition of morphologic characteristics of opportunistic fungi in stained smears of specimens; maximizing the growth rate and production of conidia by Aspergillus spp. in culture; and recognizing atypical variants of common aspergilli can improve the laboratory's contribution to rapid diagnosis. Surveys indicate that the number of laboratory professionals is declining as the demand for healthcare is rising. Effective recruitment, retention, and training of personnel must be concurrent with advances in technology.
Molecular strain typing by restriction fragment length polymorphism analysis was used to demonstrate that two clusters ofMycobacterium tuberculosis cultures involving six patients resulted from cross-contamination in the mycobacteriology laboratory. Contaminated cultures were processed by the decontamination procedure and were read on the BACTEC instrument following acid-fast bacillus smear-positive specimens from patients with active tuberculosis. Investigation of these episodes suggested opportunities for modification of laboratory procedures to minimize cross-contamination and confirmed the adverse medical and public health consequences of false-positive cultures. Strain-typing results were used in decisions regarding patient care, including the curtailment of unnecessary treatment in one patient. Molecular strain typing appears to be a valuable means of identifying false-positive cultures of M. tuberculosis in selected settings.
It is not uncommon to see amphotericin B treatment failure in patients with systemic infection caused by Candida lusitaniae. We report a patient with stage IV ovarian carcinoma and C. lusitaniae sepsis whose treatment with amphotericin B failed. The initial blood isolate was susceptible to amphotericin B in vitro; however, the MIC for a blood isolate recovered 7 weeks after treatment began showed a fourfold increase. Direct subculture of two positive blood samples obtained within a week of the patient's death showed the coexistence of two distinct colony color variants on CHROMagar Candida (CAC). One variant was susceptible to amphotericin B, and one was resistant. These results emphasize the importance of repeat amphotericin B susceptibility testing for patients with persistent C. lusitaniae infection. The presence of colony variants on CAC may signal the emergence of amphotericin B resistance in C. lusitaniae and should be investigated.Candida lusitaniae is considered an opportunistic pathogen, causing infection primarily in immunocompromised patients (1)(2)(3)(4)(5)17). Recent studies have shown that the incidence of serious infection caused by C. lusitaniae is increasing. Clinical management of systemic infection by this organism is challenging because of innate amphotericin B resistance in some isolates (3, 10, 16). Moreover, some isolates of C. lusitaniae may develop amphotericin B resistance in vivo, a finding which is supported by in vitro studies (14). Recently, Yoon et al. reported high-frequency, reversible, in vitro switching of isolates from being amphotericin B susceptible to amphotericin B resistant after exposure to the drug (18). Here we report a case of fatal systemic infection caused by C. lusitaniae with amphotericin B treatment failure. Blood cultures obtained during therapy yielded colonies with distinct differences in color on CHROMagar Candida (CAC) between amphotericin B-susceptible and amphotericin B-resistant strains. CASE REPORTA 69-year-old woman with stage IV metastatic ovarian carcinoma had fever for 5 days, respiratory distress, and metabolic acidosis despite metronidazole and imipenem therapy for 2 weeks. The culture of a central venous pressure catheter tip and three Isolator (Wampole Laboratories, Cranbury, N.J.) blood cultures drawn 2 days later were positive for C. lusitaniae. The catheter line was removed, and empiric treatment with fluconazole was started on day 1 (Table 1). The treatment was switched to amphotericin B at 35 mg (0.7 mg/kg of body weight) four times a day on day 6 and then to lipid complex amphotericin B (Abelcet) at 350 mg (7 mg/kg) four times a day on day 10 because of persistent fungemia, which was confirmed by another positive blood culture. The patient's symptoms improved, and after approximately 5 weeks of hospitalization, she was discharged on continuing treatment with lipid complex amphotericin B. Seven days after discharge, she experienced shortness of breath and was readmitted. She denied having fever, chills, or nausea. A pleural effusion prompted...
In a recent report, Schaenman and colleagues (5) describe a case of a Scedosporium apiospermum soft tissue infection in an immunocompromised patient successfully treated with voriconazole. The article focuses on one of the hottest topics in current medical mycology, the emergence of antimycotic-resistant fungal isolates (3). Indeed, Scedosporium apiospermum is, also in our direct experience, one of the emerging fungal pathogens frequently endowed with resistance against drugs used as first-line agents (i.e., amphotericin B and fluconazole) (2). Therefore, we agree to the general message of the paper regarding the need of a prompt and well designed antifungal therapy. However, we would like to address a major point on how this could be achieved. In fact, we disagree that presumptive fungal identification based on aspecific morphological aspects is sufficient to take into account a new drug such as voriconazole as a first-line agent in the management of fungal infections. As admitted by the authors and clearly shown in Fig. 2 of their case report, many fungal genera feature morphological characteristics difficult to discriminate and the identification is not straightforward, especially if specific structures are not usually evident, as may be the case upon direct examination of clinical samples. A clinician making the same assumption as the authors might feel free to treat critically ill patients with voriconazole in the majority of cases, thus putting the whole community at risk for the emergence of new resistances to this valuable drug, as has already and inevitably happened for narrow-spectrum triazoles. Moreover it is still far from being proven that the toxicity profile of the new extended-spectrum triazoles is really safer than that of narrow-spectrum drugs, with severe side effects reported in up to 10% of patients receiving voriconazole (1). We think that a rapid and precise identification, at least at the genus level, is crucial for the prescription of a well designed empirical therapy, but we are convinced that it should be based on objective data. Recently, we addressed the diagnosis of mycotic keratitis using, in parallel with cultural methodologies, a molecular approach based on direct amplification from the biological sample and sequencing, by means of universal fungal primers (4, 6), of genus-and species-specific targets on the fungal genome. In our opinion this molecular approach allowing unequivocal identification of a fungal pathogen, at least at the genus level, in only one day is, together with a more thorough understanding of mechanisms of drug resistance, a real improvement of the conventional mycological diagnosis and represents a correct answer to the clinical questions posed by the availability of multiple classes of antifungal agents.
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