Detection of a molecular biomarker for zygomycetes by quantitative PCR assays of plasma, bronchoalveolar lavage, and lung tissue in a rabbit model of experimental pulmonary zygomycosis

We developed two real-time quantitative PCR (qPCR) assays, targeting the 28S rRNA gene, for the diagnosis of zygomycosis caused by the most common, clinically significant Zygomycetes. The amplicons of the first qPCR assay (qPCR-1) from Rhizopus, Mucor, and Rhizomucor species were distinguished through melt curve analysis. The second qPCR assay (qPCR-2) detected Cunninghamella species using a different primer/probe set. For both assays, the analytic sensitivity for the detection of hyphal elements from germinating sporangiospores in bronchoalveolar lavage (BAL) fluid and lung tissue homogenates from rabbits was 1 to 10 sporangiospores/ml. Four unique and clinically applicable models of invasive pulmonary zygomycosis served as surrogates of human infections, facilitating the validation of these assays for potential diagnostic utility. For qPCR-1, 5 of 98 infarcted lung specimens were positive by qPCR and negative by quantitative culture (qCx). None were qCx positive only. Among 23 BAL fluid samples, all were positive by qPCR, while 22 were positive by qCx. qPCR-1 detected Rhizopus and Mucor DNA in 20 (39%) of 51 serial plasma samples as early as day 1 postinoculation. Similar properties were observed for qPCR-2, which showed greater sensitivity than qCx for BAL fluid (100% versus 67%; P = 0.04; n = 15). The assay detected Cunninghamella DNA in 18 (58%) of 31 serial plasma samples as early as day 1 postinoculation. These qPCR assays are sensitive and specific for the detection of Rhizopus, Mucor, Rhizomucor, and Cunninghamella species and can be used for the study and detection of infections caused by these life-threatening pathogens.

Zygomycosis in children: a systematic review and analysis of reported cases

BACKGROUND

Zygomycosis has emerged as an increasingly important infection with a high mortality especially in immunocompromised patients. No comprehensive analysis of pediatric zygomycosis cases has been published to date.

METHODS

We used a PUBMED search for English publications of pediatric (0-18 years) zygomycosis cases and references from major books as well as single case reports or case series. Individual references were reviewed for additional cases. Data were entered into Filemaker-pro database and analyzed by logistic regression analysis.

RESULTS

One hundred fifty-seven cases (64% male) were found with median age 5 years (range, 0.16-13). Underlying conditions included neutropenia (18%), prematurity (17%), diabetes mellitus (15%), ketoacidosis (10%), and no apparent underlying condition (14%). The most common patterns of zygomycosis were cutaneous (27%), gastrointestinal (21%), rhinocerebral (18%), and pulmonary (16%). Among 77 culture-confirmed cases, Rhizopus spp. (44%) and Mucor spp. (15%) were most commonly identified. Of 81 patients who were given antifungal therapy, 73% received an amphotericin B formulation only. The remaining patients received mostly amphotericin B in combination with other antifungal agents. Mortality in patients without antifungal therapy was higher than in those with therapy (88% versus 36%, P < 0.0001). Ninety-two (59%) patients underwent surgery. Cerebral, gastrointestinal, disseminated and cutaneous zygomycosis were associated with mortality rates of 100, 100, 88, and 0%, respectively. Independent risk factors for death were disseminated infection (OR: 7.18; 95% CI: 3.02-36.59) and age <1 year (OR: 3.85; 95% CI: 1.05-7.43). Antifungal therapy and particularly surgery reduced risk of death by 92% (OR: 0.07; 95% CI: 0.04-0.25) and 84% (OR: 0.16; 95% CI: 0.09-0.61), respectively.

CONCLUSIONS

Zygomycosis is a life-threatening infection in children with neutropenia, diabetes mellitus, and prematurity as common predisposing factors, and there is high mortality in untreated disease, disseminated infection, and age <1 year. Amphotericin B and surgery significantly improve outcome.

Compartmentalized intrapulmonary pharmacokinetics of amphotericin B and its lipid formulations

We investigated the compartmentalized intrapulmonary pharmacokinetics of amphotericin B and its lipid formulations in healthy rabbits. Cohorts of three to seven noninfected, catheterized rabbits received 1 mg of amphotericin B deoxycholate (DAMB) per kg of body weight or 5 mg of either amphotericin B colloidal dispersion (ABCD), amphotericin B lipid complex (ABLC), or liposomal amphotericin B (LAMB) per kg once daily for a total of 8 days. Following sparse serial plasma sampling, rabbits were sacrificed 24 h after the last dose, and epithelial lining fluid (ELF), pulmonary alveolar macrophages (PAM), and lung tissue were obtained. Pharmacokinetic parameters in plasma were derived by model-independent techniques, and concentrations in ELF and PAM were calculated based on the urea dilution method and macrophage cell volume, respectively. Mean amphotericin B concentrations +/- standard deviations (SD) in lung tissue and PAM were highest in ABLC-treated animals, exceeding concurrent plasma levels by 70- and 375-fold, respectively (in lung tissue, 16.24 +/- 1.62 versus 2.71 +/- 1.22, 6.29 +/- 1.17, and 6.32 +/- 0.57 microg/g for DAMB-, ABCD-, and LAMB-treated animals, respectively [P = 0.0029]; in PAM, 89.1 +/- 37.0 versus 8.92 +/- 2.89, 5.43 +/- 1.75, and 7.52 +/- 2.50 mug/ml for DAMB-, ABCD-, and LAMB-treated animals, respectively [P = 0.0246]). By comparison, drug concentrations in ELF were much lower than those achieved in lung tissue and PAM. Among the different cohorts, the highest ELF concentrations were found in LAMB-treated animals (2.28 +/- 1.43 versus 0.44 +/- 0.13, 0.68 +/- 0.27, and 0.90 +/- 0.28 microg/ml in DAMB-, ABCD-, and ABLC-treated animals, respectively [P = 0.0070]). In conclusion, amphotericin B and its lipid formulations displayed strikingly different patterns of disposition in lungs 24 h after dosing. Whereas the disposition of ABCD was overall not fundamentally different from that of DAMB, ABLC showed prominent accumulation in lung tissue and PAM, while LAMB achieved the highest concentrations in ELF.

Triazole-polyene antagonism in experimental invasive pulmonary aspergillosis: in vitro and in vivo correlation

Combination antifungal therapy is increasingly used in the treatment of invasive aspergillosis. Whether the interaction between amphotericin B and triazoles is antagonistic against invasive aspergillosis is a controversial issue that is not likely to be resolved through a randomized clinical trial. Here, we found both in vitro and in vivo antagonism between liposomal amphotericin B and ravuconazole in simultaneous treatment of experimental invasive pulmonary aspergillosis in persistently neutropenic rabbits. Bliss independence-based drug-interaction modeling showed significant antagonism in vitro and in vivo, with the observed drug effects being 20%-69% lower than would be expected if the drugs were acting independently. These in vitro and in vivo findings of antagonism were consistent with the findings from Loewe additivity-based drug-interaction modeling. No pharmacokinetic interaction was found. The combination of a triazole and polyene may be antagonistic in the treatment of invasive pulmonary aspergillosis.

Epidemiology and outcome of zygomycosis: a review of 929 reported cases

BACKGROUND

Zygomycosis is an increasingly emerging life-threatening infection. There is no single comprehensive literature review that describes the epidemiology and outcome of this disease.

METHODS

We reviewed reports of zygomycosis in the English-language literature since 1885 and analyzed 929 eligible cases. We included in the database only those cases for which the underlying condition, the pattern of infection, the surgical and antifungal treatments, and survival were described.

RESULTS

The mean age of patients was 38.8 years; 65% were male. The prevalence and overall mortality were 36% and 44%, respectively, for diabetes; 19% and 35%, respectively, for no underlying condition; and 17% and 66%, respectively, for malignancy. The most common types of infection were sinus (39%), pulmonary (24%), and cutaneous (19%). Dissemination developed in 23% of cases. Mortality varied with the site of infection: 96% of patients with disseminated disease died, 85% with gastrointestinal infection died, and 76% with pulmonary infection died. The majority of patients with malignancy (92 [60%] of 154) had pulmonary disease, whereas the majority of patients with diabetes (222 [66%] of 337) had sinus disease. Rhinocerebral disease was seen more frequently in patients with diabetes (145 [33%] of 337), compared with patients with malignancy (6 [4%] of 154). Hematogenous dissemination to skin was rare; however, 78 (44%) of 176 cutaneous infections were complicated by deep extension or dissemination. Survival was 3% (8 of 241 patients) for cases that were not treated, 61% (324 of 532) for cases treated with amphotericin B deoxycholate, 57% (51 of 90) for cases treated with surgery alone, and 70% (328 of 470) for cases treated with antifungal therapy and surgery. By multivariate analysis, infection due to Cunninghamella species and disseminated disease were independently associated with increased rates of death (odds ratios, 2.78 and 11.2, respectively).

CONCLUSIONS

Outcome from zygomycosis varies as a function of the underlying condition, site of infection, and use of antifungal therapy.

Expression of genes encoding innate host defense molecules in normal human monocytes in response to Candida albicans

Little is known about the regulation and coordinated expression of genes involved in the innate host response to Candida albicans. We therefore examined the kinetic profile of gene expression of innate host defense molecules in normal human monocytes infected with C. albicans using microarray technology. Freshly isolated peripheral blood monocytes from five healthy donors were incubated with C. albicans for 0 to 18 h in parallel with time-matched uninfected control cells. RNA from monocytes was extracted and amplified for microarray analysis, using a 42,421-gene cDNA chip. Expression of genes encoding proinflammatory cytokines, including tumor necrosis factor alpha, interleukin 1 (IL-1), IL-6, and leukemia inhibitory factor, was markedly enhanced during the first 6 h and coincided with an increase in phagocytosis. Expression of these genes returned to near baseline by 18 h. Genes encoding chemokines, including IL-8; macrophage inflammatory proteins 1, 3, and 4; and monocyte chemoattractant protein 1, also were strongly up-regulated, with peak expression at 4 to 6 h, as were genes encoding chemokine receptors CCR1, CCR5, CCR7, and CXCR5. Expression of genes whose products may protect monocyte viability, such as BCL2-related protein, metallothioneins, CD71, and SOCS3, was up-regulated at 4 to 6 h and remained elevated throughout the 18-h time course. On the other hand, expression of genes encoding T-cell-regulatory molecules (e.g., IL-12, gamma interferon, and transforming growth factor beta) was not significantly affected during the 18-h incubation. Moreover, genes encoding IL-15, the IL-13 receptor (IL-13Ra1), and CD14 were suppressed during the 18-h exposure to C. albicans. Thus, C. albicans is a potent inducer of a dynamic cascade of expression of genes whose products are related to the recruitment, activation, and protection of neutrophils and monocytes.

Antifungal efficacy of caspofungin (MK-0991) in experimental pulmonary aspergillosis in persistently neutropenic rabbits: pharmacokinetics, drug disposition, and relationship to galactomannan antigenemia

The antifungal efficacy, pharmacokinetics, and safety of caspofungin (CAS) were investigated in the treatment and prophylaxis of invasive pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Antifungal therapy consisted of 1, 3, or 6 mg of CAS/kg of body weight/day (CAS1, CAS3, and CAS6, respectively) or 1 mg of deoxycholate amphotericin B (AMB)/kg/day intravenously for 12 days starting 24 h after endotracheal inoculation. Prophylaxis (CAS1) was initiated 4 days before endotracheal inoculation. Rabbits treated with CAS had significant improvement in survival and reduction in organism-mediated pulmonary injury (OMPI) measured by pulmonary infarct score and total lung weight (P < 0.01). However, animals treated with CAS demonstrated a paradoxical trend toward increased residual fungal burden (log CFU per gram) and increased serum galactomannan antigen index (GMI) despite improved survival. Rabbits receiving prophylactic CAS1 also showed significant improvement in survival and reduction in OMPI (P < 0.01), but there was no effect on residual fungal burden. In vitro tetrazolium salt hyphal damage assays and histologic studies demonstrated that CAS had concentration- and dose-dependent effects on hyphal structural integrity. In parallel with a decline in GMI, AMB significantly reduced the pulmonary tissue burden of A. fumigatus (P < or = 0.01). The CAS1, CAS3, and CAS6 dose regimens demonstrated dose-proportional exposure and maintained drug levels in plasma above the MIC for the entire 24-h dosing interval at doses that were > or =3 mg/kg/day. As serial galactomannan antigen levels may be used for therapeutic monitoring, one should be aware that profoundly neutropenic patients receiving echinocandins for aspergillosis might have persistent galactomannan antigenemia despite clinical improvement. CAS improved survival, reduced pulmonary injury, and caused dose-dependent hyphal damage but with no reduction in residual fungal burden or galactomannan antigenemia in persistently neutropenic rabbits with invasive pulmonary aspergillosis.

Dosage-dependent antifungal efficacy of V-echinocandin (LY303366) against experimental fluconazole-resistant oropharyngeal and esophageal candidiasis

V-echinocandin (VER-002; LY303366) is a semisynthetic derivative of echinocandin B and a potent inhibitor of fungal (1, 3)-beta-D-glucan synthase. We studied the antifungal efficacy, the concentrations in saliva and tissue, and the safety of VER-002 at escalating dosages against experimental oropharyngeal and esophageal candidiasis caused by fluconazole-resistant Candida albicans in immunocompromised rabbits. Study groups consisted of untreated controls, animals treated with VER-002 at 1, 2.5, and 5 mg/kg of body weight/day intravenously (i.v.), animals treated with fluconazole at 2 mg/kg/day i.v., or animals treated with amphotericin B at 0.3 mg/kg/day. VER-002-treated animals showed a significant dosage-dependent clearance of C. albicans from the tongue, oropharynx, esophagus, stomach, and duodenum in comparison to that for untreated controls. VER-002 also was superior to amphotericin B and fluconazole in clearing the organism from all sites studied. These in vivo findings are consistent with the results of in vitro time-kill assays, which demonstrated that VER-002 has concentration-dependent fungicidal activity. Esophageal tissue VER-002 concentrations were dosage proportional and exceeded the MIC at all dosages. Echinocandin concentrations in saliva were greater than or equal to the MICs at all dosages. There was no elevation of serum hepatic transaminase, alkaline phosphatase, bilirubin, potassium, or creatinine levels in VER-002-treated rabbits. In summary, the echinocandin VER-002 was well tolerated, penetrated the esophagus and salivary glands, and demonstrated dosage-dependent antifungal activity against fluconazole-resistant esophageal candidiasis in immunocompromised rabbits.

Antifungal efficacy, safety, and single-dose pharmacokinetics of LY303366, a novel echinocandin B, in experimental pulmonary aspergillosis in persistently neutropenic rabbits

LY303366 is a novel semisynthetic derivative of echinocandin B and a potent inhibitor of fungal (1,3)-beta-D-glucan synthase. The antifungal efficacy and safety of LY303366 were investigated in treatment and prophylaxis of primary pulmonary aspergillosis due to Aspergillus fumigatus in persistently neutropenic rabbits. Treatment study groups were either not treated (controls) or treated with amphotericin B (AmB) at 1 mg/kg of body weight per day or with LY303366 at 1, 5, 10, and 20 mg/kg/day. In rabbits treated with LY303366, there was a significant improvement in survival and a reduction in organism-mediated pulmonary injury measured by the number of infarcts, total lung weight, and ultrafast computerized tomography scan pulmonary lesion score. Rabbits receiving prophylactic LY303366 also demonstrated significant improvement in survival and reduction in organism-mediated pulmonary injury. AmB and LY303366 had comparable therapeutic efficacies by all parameters with the exception of reduction in tissue burden of A. fumigatus, where AmB was superior to LY303366. LY303366 demonstrated a dose-dependent effect on hyphal injury with progressive truncation, swelling, and vacuolization. LY303366 administered in single doses of 1, 5, 10, and 20 mg/kg demonstrated dose-proportional increases in the maximum concentration of drug in plasma and the area under the concentration-time curve from 0 to 72 h with no changes in plasma drug clearance. The 1-mg/kg dosage maintained plasma drug levels above the MIC for 18 h, and dosages of >/=5 mg/kg maintained plasma drug levels above the MIC for the entire 24-h dosing interval. There was no significant elevation of the concentrations of hepatic transaminases or creatinine in serum in LY303366-treated rabbits. In summary, LY303366 improved survival and decreased pulmonary injury with no apparent toxicity in the treatment and prevention of invasive pulmonary aspergillosis in persistently neutropenic rabbits.

Quantitative urine cultures do not reliably detect renal candidiasis in rabbits

The significance of quantitative urine cultures in patients at risk for hematogenous disseminated candidiasis is controversial. While various concentrations of Candida spp. in urine have been suggested as critical cutoff points in the diagnosis of renal candidiasis, other investigators consider quantitative cultures less critical in diagnosing upper tract infections. To determine the significance of quantitative urine cultures in renal candidiasis, we studied serial quantitative urinary cultures of Candida albicans in a rabbit model of hematogenous infection. Of 197 urine samples from 34 infected animals, 144 were culture positive, with a sensitivity of 73.1% for urine cultures and a lower limit of detection of 10 CFU/ml. The yield of urine cultures varied according to severity and duration of infection. The mean renal and urinary concentrations of C. albicans from rabbits with subacute candidiasis differed significantly from those from rabbits with acute candidiasis (P = 0.013 and P < or = 0.001, respectively). During the first 4 days of subacute renal candidiasis, more than one-half of all urine cultures were negative for C. albicans. Only 12 (8.1%) of 148 urine cultures in animals with subacute renal candidiasis had concentrations of > 10(3) CFU/ml, 2.7% had concentrations of > 10(4) CFU/ml, and none were > or = 10(5) CFU/ml. By comparison, all urine cultures from the animals with lethal acute renal candidiasis had higher concentrations of C. albicans and were positive throughout the course of infection. Urinary concentrations of C. albicans were not predictive of the amount of Candida in the kidney (r < or = 0.49) and did not correlate with survival (r = 0.0232). However, the renal concentration of C. albicans (in CFU/gram) inversely correlated with the duration of survival (in days) of rabbits with renal candidiasis (r = 0.76; P < 0.001). These findings indicate that a negative urine culture in rabbits does not preclude the presence of renal candidiasis. The interpretation of a urine culture positive at any concentration, on the other hand, must involve an analysis of the risk factors for renal candidiasis, for any urinary concentration of C. albicans may reflect kidney infection.