Detection of Aspergillus fumigatus-specific DNA, (1–3)-β-d-glucan and galactomannan in serum and bronchoalveolar lavage specimens of experimentally infected rats

Demonstration of Adventitious Sporulation in Fusarium Petroliphilum Onychomycosis

Fusarium petroliphilum is a recently described species within the Fusarium solani species complex. Some strains of Fusarium species are capable of forming yeast-like structures in tissue as well as in culture through a process known as "adventitious sporulation." Here, we describe the formation of these yeast-like reproductive structures in infected nail tissue obtained from a case of onychomycosis. These structures were also observed in culture grown on RPMI 1640 agar supplemented with 2% glucose. The isolate was resistant to azoles and echinocandins. To the best of our knowledge, this is the first report describing adventitious sporulation in F. petroliphilum and its etiologic role in onychomycosis.

First isolation of Ascotricha chartarum from bronchoalveolar lavage of two patients with pulmonary infections

Ascotricha chartarum is a rare human pathogen. We describe the isolation and characterization of A. chartarum from bronchoalveolar lavage samples of two patients with underlying pulmonary infections. The identity of both isolates was established by typical phenotypic characteristics and by sequencing of the internal transcribed spacer region and D1/D2 domains of recombinant DNA and β-tubulin gene fragment. The demonstration of branched, septate hyphae in direct microscopic examination of both the specimens and isolation of the fungus in pure cultures suggest its aetiologic role in the disease process. Because of phenotypic similarities of A. chartarum with Chaetomium spp. and other Chaetomium-like fungi, the application of molecular methods is needed for its accurate identification. Although in the absence of histopathologic evidence the aetiologic role of A. chartarum could not be established unequivocally, nonetheless, in view of the rarity of its isolation from clinical specimens and demonstration of hyphal elements in bronchoalveolar lavage sample, this report assumes considerable significance. It serves to create awareness about environmental fungi that previously have missed attention but may play a role in respiratory infections.

Allergic Fungal Sinusitis Caused by Exserohilum rostratum and Literature Review

A case of allergic fungal sinusitis (AFS) caused by Exserohilum rostratum, proven by culture and histopathology of the biopsy material, is described. The identity of the isolate was confirmed by sequencing of ITS region of rDNA. To the best of our knowledge, this is the first report of allergic E. rostratum sinusitis from Kuwait and Arabian Peninsula. Ten previously described cases of AFS have been reviewed. The report highlights the emerging importance of E. rostratum as a human pathogen in this region and role of molecular methods in its accurate identification.

Rodent Models of Invasive Aspergillosis due to Aspergillus fumigatus: Still a Long Path toward Standardization

Invasive aspergillosis has been studied in laboratory by the means of plethora of distinct animal models. They were developed to address pathophysiology, therapy, diagnosis, or miscellaneous other concerns associated. However, there are great discrepancies regarding all the experimental variables of animal models, and a thorough focus on them is needed. This systematic review completed a comprehensive bibliographic analysis specifically-based on the technical features of rodent models infected with Aspergillus fumigatus. Out the 800 articles reviewed, it was shown that mice remained the preferred model (85.8% of the referenced reports), above rats (10.8%), and guinea pigs (3.8%). Three quarters of the models involved immunocompromised status, mainly by steroids (44.4%) and/or alkylating drugs (42.9%), but only 27.7% were reported to receive antibiotic prophylaxis to prevent from bacterial infection. Injection of spores (30.0%) and inhalation/deposition into respiratory airways (66.9%) were the most used routes for experimental inoculation. Overall, more than 230 distinct A. fumigatus strains were used in models. Of all the published studies, 18.4% did not mention usage of any diagnostic tool, like histopathology or mycological culture, to control correct implementation of the disease and to measure outcome. In light of these findings, a consensus discussion should be engaged to establish a minimum standardization, although this may not be consistently suitable for addressing all the specific aspects of invasive aspergillosis.

Development and Evaluation of a Loop-Mediated Isothermal Amplification Method for Rapid Detection of Aspergillus fumigatus

Aspergillus fumigatusis a conditional pathogen and the major cause of life-threatening invasive aspergillosis (IA) in immunocompromised patients. The early and rapid detection ofA. fumigatusinfection is still a major challenge. In this study, the new member of the fungal annexin family, annexin C4, was chosen as the target to design a loop-mediated isothermal amplification (LAMP) assay for the rapid, specific, and sensitive detection ofA. fumigatus The evaluation of the specificity of the LAMP assay that was developed showed that no false-positive results were observed for the 22 non-A. fumigatusstrains, including 5 species of theAspergillusgenus. Its detection limit was approximately 10 copies per reaction in reference plasmids, with higher sensitivity than that of real-time quantitative PCR (qPCR) at 10(2)copies for the same target. Clinical samples from a total of 69 patients with probable IA (n =14) and possible IA (n= 55) were subjected to the LAMP assay, and positive results were found for the 14 patients with probable IA (100%) and 34 patients with possible IA (61.82%). When detection using the LAMP assay was compared with that using qPCR in the 69 clinical samples, the LAMP assay demonstrated a sensitivity of 89.19% and the concordance rate for the two methods was 72.46%. Accordingly, we report that a valuable LAMP assay for the rapid, specific, and simple detection ofA. fumigatusin clinical testing has been developed.

Occurrence of triazole-resistant Aspergillus fumigatus with TR34/L98H mutations in outdoor and hospital environment in Kuwait

BACKGROUND

Invasive aspergillosis due to triazole-resistant Aspergillus fumigatus, a common airborne fungal pathogen, has emerged in some European and Asian countries, likely due to exposure to azole fungicides in the environment. This study determined the occurrence of triazole-resistant A. fumigatus in outdoor and hospital environment in Kuwait, a semi-arid desert country in Arabian Peninsula.

METHODS

Outdoor/indoor air, water and cotton swab samples were cultured on malt extract agar and A. fumigatus colonies were identified by phenotypic and molecular methods. Drug susceptibility of A. fumigatus isolates to itraconazole, posaconazole and voriconazole was carried out by an Etest and a broth microdilution method. Resistance mechanisms involving cyp51A mutations were probed by mixed-format real-time (MF-rt)-PCR assays. Triazole-resistant isolates were typed by nine-locus microsatellite analysis. A multiplex allele-specific (MAS)-PCR assay was developed for detection of L98H mutation in cyp51A.

RESULTS

Of 115 A. fumigatus isolates obtained from 362 environmental samples from across Kuwait, 8 isolates were resistant to itraconazole, posaconazole and voriconazole. All itraconazole-resistant isolates contained a 34-bp tandem repeat (TR34) in the promoter region and a L98H mutation at codon 98 (TR34/L98H) in cyp51A. These mutations were absent in all itraconazole-susceptible isolates. MAS-PCR accurately detected L98H mutation in all triazole-resistant isolates. Three microsatellite patterns were observed among resistant isolates with one pattern clustering with Indian clinical and environmental isolates.

CONCLUSIONS

Triazole-resistant A. fumigatus with TR34/L98H mutations in cyp51A is prevalent in Kuwait. Although triazole-resistant A. fumigatus has not yet been isolated from clinical specimens, its presence in the environment suggests that the possibility of susceptible individuals getting infected with such strains exists and may pose therapeutic challenges in its management.

Development of a novel inhalational model of invasive pulmonary aspergillosis in rats and comparative evaluation of three biomarkers for its diagnosis

Aspergillus fumigatus, a thermotolerant fungus, is the main causative agent of invasive pulmonary aspergillosis (IPA) in immunocompromised patients that is associated with high mortality rates. Early diagnosis of IPA is crucial for mortality reduction and improved prognosis. An experimental inhalational model of IPA was developed in rats and the efficacy of three biomarkers, namely β-D-glucan (BDG), a panfungal marker, galactomannan (GM), a genus-specific marker, and A. fumigatus DNA, a species-specific marker was evaluated in serum and bronchoalveolar lavage (BAL) specimens at different time points postinfection for early diagnosis of IPA. BDG and GM were detected by using commercial Fungitell and Platelia Aspergillus EIA kits, respectively. A. fumigatus DNA was detected by developing a sensitive, single-step PCR assay. IPA was successfully developed in immunosuppressed rats and all animals until 5 days post-infection were positive for A. fumigatus by culture and KOH-calcofluor microscopy also showed A. fumigatus in 19 of 24 (79%) lung tissue samples. Fourteen of 30 (47%) and 27 of 30 (90%) serum and BAL specimens, respectively, were positive for all three biomarkers with 100% specificity (none of sera or BAL specimens of 12 control rats was positive for biomarkers). Our data show that BAL is a superior specimen than serum and combined detection of BDG, GM and A. fumigatus DNA provide a sensitive diagnosis of IPA in an experimental animal model. Moreover, combined detection of GM and DNA in BAL and detection of either GM or DNA in serum was also positive in 27 of 30 (90%) animals. For economic reasons and considering that the positive predictive value of BDG is low, the detection of GM and/or DNA in serum and BAL samples has the potential to serve as an integral component of the diagnostic-driven strategy in high-risk patients suspected for IPA.

Aerial prevalence of Aspergillus calidoustus isolates in and around a tertiary care hospital in Kuwait and assessment of their pathogenicity

Seven Aspergillus calidoustus isolates from 486 Aspergillus spp. isolates (1.4% overall prevalence) from outdoor/indoor air samples and one isolate from the bronchoalveolar lavage fluid of a patient with pneumonia were obtained. These 8 isolates exhibited reduced susceptibility to triazoles. Preliminary pathogenicity data from BALB/c mice suggest that A. calidoustus can persist in tissues for long periods without causing mortality. Further studies using graded doses of inoculum and immunosuppression models are warranted to gain an understanding of the factors associated with its pathogenicity and virulence.

Simple, low-cost molecular assays for TR34/L98H mutations in the cyp51A gene for rapid detection of triazole-resistant Aspergillus fumigatus isolates

Simple, low-cost PCR/PCR-restriction fragment length polymorphism (RFLP) assays targeting cyp51A promoter and codon 98 regions were developed for the detection of triazole-resistant Aspergillus fumigatus strains carrying TR34/L98H mutations. The assays were evaluated using 40 itraconazole-susceptible isolates and 35 itraconazole-resistant isolates. The prevalence of TR34/L98H mutations in clinical/environmental A. fumigatus isolates may now be determined easily from resource-poor settings.

Galactomannan detection in bronchoalveolar lavage fluid for the diagnosis of invasive aspergillosis in patients with hematological diseases-the role of factors affecting assay performance

BACKGROUND

We evaluated the performance of a galactomannan (GM) assay in bronchoalveolar lavage (BAL) fluid compared to serum samples for the diagnosis of invasive pulmonary aspergillosis (IPA) in patients with hematological diseases.

METHODS

Two hundred and fifty-five bronchoscopies were performed on 230 patients. Bronchial and alveolar samples from BAL fluid as well as serum samples were analyzed in the GM assay.

RESULTS

Twenty-eight cases of IPA (11%) were diagnosed. The sensitivity, specificity, positive predictive value, and negative predictive value of the GM assay using a cut-off of 0.5 were 57.1%, 99.3%, 94.1%, and 92.5%, respectively, for the alveolar sample; 44.0%, 99.3%, 91.7%, and 91.4%, respectively, for the bronchial sample; and 60.7%, 100%, 100%, and 92.9%, respectively, for serum. The highest sensitivity (78.6%) with good specificity (98.6%) was obtained with a 'triple detection' of GM in bronchial, alveolar, and serum samples. Neutropenia and antifungal therapy for only 24h increased the sensitivity, while antifungal treatment for ≥ 2 days decreased assay performance. Moreover, a trend towards a higher volume of aspirated fluid in GM-negative BAL (p=0.092) was observed.

CONCLUSIONS

In contrast to recently published data, we found only moderate sensitivity, but high specificity and high positive predictive value of the detection of GM in BAL fluid. In addition, neutropenia, antifungal therapy, and BAL standardization affected GM assay performance.

Invasive pulmonary aspergillosis due to Aspergillus terreus: value of DNA, galactomannan and (1→3)-β-d-glucan detection in serum samples as an adjunct to diagnosis

A case of invasive pulmonary aspergillosis caused by Aspergillus terreus is described. The diagnosis was based on demonstration of branched septate hyphae in a sputum specimen and isolation of the fungus in culture. The diagnosis was further supported by detection of A. terreus-specific DNA, galactomannan (GM) and (1→3)-β-d-glucan (BDG) in consecutive serum specimens. The patient was treated for about 10 weeks with voriconazole. The decreasing levels of GM and BDG in serum samples were accompanied by symptomatic and radiological improvement. The report highlights the value of surrogate markers in the diagnosis and for monitoring the course of invasive aspergillosis during therapy.

The era of molecular and other non-culture-based methods in diagnosis of sepsis

Sepsis, a leading cause of morbidity and mortality throughout the world, is a clinical syndrome with signs and symptoms relating to an infectious event and the consequent important inflammatory response. From a clinical point of view, sepsis is a continuous process ranging from systemic inflammatory response syndrome (SIRS) to multiple-organ-dysfunction syndrome (MODS). Blood cultures are the current "gold standard" for diagnosis, and they are based on the detection of viable microorganisms present in blood. However, on some occasions, blood cultures have intrinsic limitations in terms of sensitivity and rapidity, and it is not expected that these drawbacks will be overcome by significant improvements in the near future. For these principal reasons, other approaches are therefore needed in association with blood culture to improve the overall diagnostic yield for septic patients. These considerations have represented the rationale for the development of highly sensitive and fast laboratory methods. This review addresses non-culture-based techniques for the diagnosis of sepsis, including molecular and other non-culture-based methods. In particular, the potential clinical role for the sensitive and rapid detection of bacterial and fungal DNA in the development of new diagnostic algorithms is discussed.

Invasive fungal infections in the paediatric and neonatal population: diagnostics and management issues

Invasive fungal infections in children appear to have increased over the past few decades. Especially neonates and children with primary and secondary immunodeficiencies are at risk. Candida and Aspergillus spp. are the most commonly isolated organisms. In addition, Malassezia may cause systemic infections in newborns and zygomycosis is important because of its rising incidence and high case fatality rate. Timely diagnosis and initiation of appropriate antifungal therapy is imperative for improving outcomes. However, traditional techniques are time-consuming and representative sample material, using invasive procedures, may be difficult to obtain in the paediatric setting. This review provides an overview of the advances in detection and rapid species identification, with a focus on issues relevant in these settings. Subsequently, the current antifungal treatment options for neonates and children are discussed in light of the antifungal spectrum of the available agents and the specific pharmacokinetic properties in different age groups. Although a multitude of newer antifungal compounds have become available within the last decade, further studies are necessary to clearly establish the role for each of these agents among neonates and children.

Rapid molecular differentiation and genotypic heterogeneity among Candida parapsilosis and Candida orthopsilosis strains isolated from clinical specimens in Kuwait

Recent molecular studies have led to the recognition of three distinct species within the Candida parapsilosis complex, namely Candida parapsilosis, Candida orthopsilosis and Candida metapsilosis. As currently available yeast identification systems fail to differentiate these species, there is a paucity of information on their occurrence in different geographical regions. This study describes a simple PCR-based protocol for rapid discrimination among C. parapsilosis, C. orthopsilosis and C. metapsilosis strains by using primers derived from unique sequences within the internally transcribed spacer 1 (ITS1)-5.8 rRNA-ITS2 region. Retrospective analysis of 114 C. parapsilosis-complex isolates recovered from clinical specimens in Kuwait identified 109 as C. parapsilosis, five as C. orthopsilosis and none as C. metapsilosis. The results were further validated by PCR-RFLP patterns of the secondary alcohol dehydrogenase gene fragment. DNA sequencing of the ITS region and the D1/D2 regions of the 28S rRNA gene confirmed the species-specific identification of all five C. orthopsilosis strains. The amplicon length of the intergenic spacer between the 28S and 5S rRNA genes (IGS1) was also species-specific, and PCR-RFLP analyses of the IGS1 region identified two distinct genotypes among the five C. orthopsilosis strains, which corresponded with the ITS region sequence data. The three bloodstream C. orthopsilosis strains were confined to a single genotype. Among 81 randomly selected C. parapsilosis strains, two genotypes were detected by IGS1 region analyses, indicating limited genotypic heterogeneity among C. parapsilosis sensu stricto strains. As far as is known, this is the first report on the identification of C. orthopsilosis from a bloodstream infection in the Arabian Gulf region.

Invasive aspergillosis: diagnosis, prophylaxis and treatment

PURPOSE OF REVIEW

Invasive aspergillosis is a common cause of morbidity and mortality in hematopoietic stem cells transplant recipients. Owing to its intrinsic high mortality rate, early diagnosis and treatment are critical. This review will therefore address the most important recent advances in diagnosing, preventing and treating invasive aspergillosis in hematopoietic stem cells transplant.

RECENT FINDINGS

The present review will focus on therapeutic and prophylactic aspects, with particular regard to clinical use of drugs other than voriconazole (which has a well known and consolidated role for first-line therapy), combination therapy and prophylactic regimens, particularly with posaconazole. This review will also briefly deal with the clinical role of diagnostic tests such as the detection of galactomannan in body fluids other than blood, beta-D-glucan in serum and fungal DNA by PCR in body fluids.

SUMMARY

Galactomannan antigen detection is a rather reliable diagnostic test for invasive aspergillosis, particularly when a lower threshold of sensitivity is used. PCR is still to be validated. Liposomal amphotericin B at 3 mg/kg per day showed a similar efficacy in invasive aspergillosis as reported for voriconazole. Therapeutic drug monitoring of Aspergillus-active azoles should be implemented whenever possible in order to maximize the antifungal effect and minimize toxicity. Posaconazole showed to be active in prophylaxis, though its effectiveness in the global patient population is still controversial.

Strain-dependent variation in 18S ribosomal DNA Copy numbers in Aspergillus fumigatus

Enumerating Aspergillus fumigatus CFU can be challenging since CFU determination by plate count can be difficult. CFU determination by quantitative real-time PCR (qPCR), however, is becoming increasingly common and usually relies on detecting one of the subunits of the multicopy rRNA genes. This study was undertaken to determine if ribosomal DNA (rDNA) copy number was constant or variable among different A. fumigatus isolates. FKS1 was used as a single-copy control gene and was validated against single-copy (pyrG and ARG4) and multicopy (arsC) controls. The copy numbers of the 18S rDNA subunit were then determined for a variety of isolates and were found to vary with the strain, from 38 to 91 copies per genome. Investigation of the stability of the 18S rDNA copy number after exposure to a number of different environmental and growth conditions revealed that the copy number was stable, varying less than one copy across all conditions, including in isolates recovered from an animal model. These results suggest that while the ribosomal genes are excellent targets for enumeration by qPCR, the copy number should be determined prior to using them as targets for quantitative analysis.