No abstract

We investigated the possible presence of DNA specific for Aspergillus species in serum samples of patients with invasive aspergillosis (IA) by the nested PCR method. Fourteen strains of fungi including 5 strains of Aspergillus species and 10 strains of common bacteria were used for examination of specificity and sensitivity of the nested PCR. Two sets of oligonucleotide primers were derived from the sequence of the variable regions V7 to V9 of the 18S rRNA genes of Aspergillus fumigatus. The specific fragment was amplified from five strains of Aspergillus species in the single and nested PCR but not from other microorganisms. Target DNA was detected by the nested PCR with as little as 50 fg of the extracted DNA of A. fumigatus. We investigated the detection of DNA specific for Aspergillus species in serum samples of a murine model of aspergillosis and 20 patients with IA. The specific fragment was detected by the nested PCR in 71% of serum samples of infected mice and 70% of serum samples of patients with IA, while galactomannan antigen was detected in 43 and 60% of samples, respectively. The high sensitivity and specificity of the nested PCR indicate that the assay can provide early diagnosis with sufficient accuracy to be clinically useful for immunocompromised patients with IA.

The G test containing factor G, fractioned from the Limulus lysate, was used to detect (1-3)-beta-D-glucan in a rat model of aspergillosis. Aspergillus fumigatus strain MF-13, 1 x 10(4) conidia, were inoculated transtracheally into rats treated with cortisone acetate (100 mg/kg) and fed a low-protein (8%) diet. Increased serum (1-3)-beta-D-glucan was found on the sixth day after inoculation in concentrations of 370 +/- 178 pg/ml (mean +/- SD) in untreated controls, and 154 +/- 43 pg/ml in rats treated with 0.5 mg/kg of amphotericin B. On day 11 (1-3)-beta-D-glucan concentrations were 2,590 +/- 2,940 pg/ml and 448 +/- 442 pg/ml, respectively. The elevation in levels of (1-3)-beta-D-glucan increased in correlation with the elevation of galactomannan antigen titers; (1-3)-beta-D-glucan is thus measurable during experimental aspergillosis in rats.

The activities of amphotericin B, miconazole, fluconazole, and itraconazole against Trichosporon beigelii were assessed in a mouse model of disseminated infection. Cyclophosphamide plus prednisolone-immunosuppressed ICR mice, intravenously challenged with a lethal inoculum of (6 × 10⁶ CFU/mouse), were assigned to receive 7 days of therapy with amphotericin B (0.5 or 2 mg/kg/day), miconazole (10 or 40 mg/kg/day), fluconazole (10 or 40 mg/kg/day), or itraconazole (10 and 40 mg/kg/day). The efficacy of a combination of amphotericin B (1 mg/kg/day) with fluconazole (10 mg/kg/day) or itraconazole (20 mg/kg/day) with that of each agent alone was also compared. Both amphotericin B and azoles improved survival and reduced the fungal counts in kidneys of infected mice in a dose-dependent pattern. In general, fluconazole was superior to amphotericin B and the other azoles, whereas the latter two drugs were as effective as amphotericin B. The activity of amphotericin B combined with fluconazole appeared to be superior to that of each agent alone, especially in reducing the organ fungal burden. The other combination (amphotericin B plus itraconazole) had a weaker effect, but no antagonism was observed. In conclusion, azoles may be an alternative to amphotericin B for the treatment of T. beigelii infection. Furthermore, their combination with amphotericin B may improve the poor outcome seen in profoundly neutropenic patients with disseminated trichosporonosis.

The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) of amphotericin B, flucytosine, miconazole, fluconazole and itraconazole against 21 isolates of Trichosporon beigelii in RPMI-1640 medium were determined using National Committee for Clinical Laboratory Standards (NCCLS) methodology in microdilution method. Most isolates were sensitive to miconazole (MIC90 0.78 microgram/ml), fluconazole (MIC90 6.25 micrograms/ml), and itraconazole (MIC90 0.19 microgram/ml), with the former being the most active agent tested (MFC90 3.12 mu/ml). Although amphotericin B inhibited most strains (MIC range, 0.78-3.12 micrograms/ml), poor fungicidal activity was observed (MFC range, 1.56-12.5 micrograms/ml) showing a pattern of relative resistance in vitro. Flucytosine showed generally poor activity against most isolates tested. These in vitro findings confirm the resistance of T.beigelii to amphotericin B and suggest that azoles may be an alternative to the former for the treatment of disseminated trichosporonosis. However, in vivo studies would better validate these in vitro findings.

We compared PCR, galactomannan detection assay using a latex agglutination test and (1→3)-β-D-glucan detection assay in detecting infection in rats experimentally infected with Aspergillus fumigatus. On day 2 after inoculation, (1→3)-β-D-glucan and nested PCR were positive for 80%, while galactomannan detection assay was positive for 60%. In addition, the positive result of nested PCR (87.5%) was higher than those of galactomannan detection assay (75%) and (1→3)β-D-glucan (71.4%) on day 3 after inoculation. The sensitivity of nested PCR was superior to those of galactomannan detection assay and (1→3)-β-D-glucan detection assay. The three diagnostic tests were compared with histopathological findings, and the sensitivity of three diagnostic tests was correlated with histopathological changes. In addition, the elevated levels of (1→3)-β-D-glucan paralleled the development and progression of pulmonary aspergillosis. Our results indicate that a combination of two or three of these tests seems to provide a rapid diagnosis of invasive aspergillosis and assist in the evaluation of the development and severity of invasive aspergillosis.

Deep-seated trichosporonosis is a lethal opportunistic infection that disseminates rapidly and widely in immunocompromised patients, and early diagnosis is crucial for the treatment of this infection. We developed a novel nested-PCR assay that detects DNA specific for clinically important strains of Trichosporon in serum samples from patients with disseminated trichosporonosis. In this assay, two sets of oligonucleotide primers were derived from the sequence of 26S rRNA genes of Trichosporon asahii. The specific fragment was amplified from T. asahii and T. mucoides, but not from other microorganisms, including some other basidiomycetous fungi (Cryptococcus, Malassezia,Rhodotorula, and Sporobolomyces). Target DNA was detected by the nested PCR with as little as 5 fg of the extracted DNA of T. asahii. In a study using 11 clinical samples, the specific fragment was detected by the nested PCR in 64% (7 of 11) of sera from patients with histologically diagnosed disseminated trichosporonosis, while glucuronoxylomannan antigen was detected in only 54% (6 of 11) of the samples. Our new nested-PCR assay using serum samples can be performed repeatedly throughout the course of the disease. In addition, not only can it be used for early diagnosis of trichosporonosis, but it may also be beneficial for monitoring its progress or response to therapy.

Pulmonary aspergillosis is classified into invasive, saprophytic, and allergic forms. In this study, we evaluated the usefulness of PCR for differentiating between different forms of aspergillosis or in monitoring disease activity during treatment by detecting DNA specific for Aspergillus species in the serum. Nested PCR was used to detect Aspergillus DNA in the sera of 30 patients with various forms of pulmonary aspergillosis. The results were compared with those of latex agglutination tests for detecting galactomannan antigen. We also examined the serial changes in the results of nested PCR during and after treatment of a subgroup of patients with invasive pulmonary aspergillosis with amphotericin B. The highest proportion of positive nested PCR results were in patients with invasive aspergillosis (10 of 12; 83%), while patients with pulmonary aspergilloma had the lowest frequency of positive tests (1 of 9; 11%). These results suggested that the sensitivity of the nested PCR depends on the extent of invasion by Aspergillus species. Serial assays showed that the results of nested PCR became negative shortly after commencement of antifungal treatment and that such changes did not correlate with clinical responsiveness to treatment. Our results indicate the potential usefulness of nested PCR with serum samples for the diagnosis of invasive aspergillosis and the detection of a shift in the status of infection from a noninvasive type to invasive aspergillosis. However, the results of the nested PCR did not correlate with the response to antifungal treatment.