Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry azole susceptibility assessment in Candida and Aspergillus species.

BACKGROUND: Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) allows rapid pathogen identification and potentially can be used for antifungal susceptibility testing (AFST). OBJECTIVES: We evaluated the performance of the MALDI-TOF MS in assessing azole susceptibility, with reduced incubation time, by comparing the results with the reference method Broth Microdilution. METHODS: Resistant and susceptible strains of Candida (n = 15) were evaluated against fluconazole and Aspergillus (n = 15) against itraconazole and voriconazole. Strains were exposed to serial dilutions of the antifungals for 15 h. Microorganisms' protein spectra against all drug concentrations were acquired and used to generate a composite correlation index (CCI) matrix. The comparison of autocorrelations and cross-correlations between spectra facilitated by CCI was used as a similarity parameter between them, enabling the inference of a minimum profile change concentration breakpoint. Results obtained with the different AFST methods were then compared. FINDINGS: The overall agreement between methods was 91.11%. Full agreement (100%) was reached for Aspergillus against voriconazole and Candida against fluconazole, and 73.33% of agreement was obtained for Aspergillus against itraconazole. MAIN CONCLUSIONS: This study demonstrates MALDI-TOF MS' potential as a reliable and faster alternative for AFST. More studies are necessary for method optimisation and standardisation for clinical routine application.

Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry azole susceptibility assessment in Candida and Aspergillus species

BACKGROUND Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) allows rapid pathogen identification and potentially can be used for antifungal susceptibility testing (AFST). OBJECTIVES We evaluated the performance of the MALDI-TOF MS in assessing azole susceptibility, with reduced incubation time, by comparing the results with the reference method Broth Microdilution. METHODS Resistant and susceptible strains of Candida (n = 15) were evaluated against fluconazole and Aspergillus (n = 15) against itraconazole and voriconazole. Strains were exposed to serial dilutions of the antifungals for 15 h. Microorganisms' protein spectra against all drug concentrations were acquired and used to generate a composite correlation index (CCI) matrix. The comparison of autocorrelations and cross-correlations between spectra facilitated by CCI was used as a similarity parameter between them, enabling the inference of a minimum profile change concentration breakpoint. Results obtained with the different AFST methods were then compared. FINDINGS The overall agreement between methods was 91.11%. Full agreement (100%) was reached for Aspergillus against voriconazole and Candida against fluconazole, and 73.33% of agreement was obtained for Aspergillus against itraconazole. MAIN CONCLUSIONS This study demonstrates MALDI-TOF MS' potential as a reliable and faster alternative for AFST. More studies are necessary for method optimisation and standardisation for clinical routine application.

Aspergillus fumigatus Clinical Isolates Carrying CYP51A with TR34/L98H/S297T/F495I Substitutions Detected after Four-Year Retrospective Azole Resistance Screening in Brazil.

Azole antifungal resistance in Aspergillus fumigatus is a worldwide concern. As in most public hospitals in Brazil, antifungal susceptibility tests are not routinely performed for filamentous fungi at our institution. A 4-year retrospective azole antifungal resistance screening revealed two azole-resistant A. fumigatus clinical isolates carrying the CYP51A TR34 (34-bp tandem repeat)/L98H (change of L to H at position 98)/S297T/F495I resistance mechanism mutations, obtained from two unrelated patients. Broth microdilution antifungal susceptibility testing showed high MICs for itraconazole, posaconazole, and miconazole. Short tandem repeat (STR) typing analysis presented high levels of similarity between these two isolates and clinical isolates with the same mutations reported from the Netherlands, Denmark, and China, as well as environmental isolates from Taiwan. Our findings might indicate that active searching for resistant A. fumigatus is necessary. They also represent a concern considering that our hospital provides tertiary care assistance to immunocompromised patients who may be exposed to resistant environmental isolates. We also serve patients who receive prophylactic antifungal therapy or treatment for invasive fungal infections for years. In these two situations, isolates resistant to the antifungal in use may be selected within the patients themselves. We do not know the potential of this azole-resistant A. fumigatus strain to spread throughout our country. In this scenario, the impact on the epidemiology and use of antifungal drugs will significantly alter patient care, as in other parts of the world. In summary, this finding is an important contribution to alert hospital laboratories conducting routine microbiological testing to perform azole resistance surveillance and antifungal susceptibility tests of A. fumigatus isolates causing infection or colonization in patients at high risk for systemic aspergillosis.

Airborne transmission of invasive fusariosis in patients with hematologic malignancies.

From 2006 to 2013, an increasing incidence of fusariosis was observed in the hematologic patients of our University Hospital. We suspected of an environmental source, and the indoor hospital air was investigated as a potential source of the fungemia. Air samplings were performed in the hematology and bone marrow transplant (BMT) wards using an air sampler with pre-defined air volumes. To study the molecular relationship among environmental and clinical isolates, 18 Fusarium spp. recovered from blood cultures were included in the study. DNA sequencing of a partial portion of TEF1α gene was performed for molecular identification. Molecular typing was carried out by multi-locus sequence typing (MLST) using a four-gene scheme: TEF1α, rDNA, RPB1 and RPB2. One hundred four isolates were recovered from the air of the hematology (n = 76) and the BMT (n = 28) wards. Fusarium isolates from the air were from five species complexes: Fusarium fujikuroi (FFSC, n = 56), Fusarium incarnatum-equiseti (FIESC, n = 24), Fusarium solani (FSSC, n = 13), Fusarium chlamydosporum (FCSC, n = 10), and Fusarium oxysporum (FOSC, n = 1). Fifteen Fusarium isolates recovered from blood belonged to FSSC, and three to FFSC. MLST identified the same sequence type (ST) in clinical and environmental isolates. ST1 was found in 5 isolates from blood and in 7 from the air, both identified as FSSC (Fusarium petroliphilum). STn1 was found in one isolate from blood and in one from the air, both identified as FFSC (Fusarium napiforme). F. napiforme was isolated from the air of the hospital room of the patient with fungemia due to F. napiforme. These findings suggested a possible clonal origin of the Fusarium spp. recovered from air and bloodcultures. In conclusion, our study found a diversity of Fusarium species in the air of our hospital, and a possible role of the air as source of systemic fusariosis in our immunocompromised patients.

Visible DNA Microarray System as an Adjunctive Molecular Test in Identification of Pathogenic Fungi Directly from a Blood Culture Bottle.

A DNA microarray platform, based on the nucleotide sequences of the internal transcribed spacer regions (ITS1 and ITS2) of the rRNA gene, was developed to identify 32 fungal pathogens at the species level. The probe sequences were spotted onto polycarbonate slides with a mini-microarray printer, and after the hybridization, the results were visible with the naked eye. The performance of the microarray platform was evaluated against the commercial automated systems (Vitek 2 and BD Phoenix systems) and DNA sequencing (gold standard). A total of 461 blood culture bottles were tested: 127 positive for fungi, 302 positive for bacteria, and 32 that were negative. Once the microorganisms were identified by automated systems, fungal DNA was extracted directly from the blood culture bottles. The DNA products were tested using the microarray platform, and DNA sequencing was performed. The results of the microarray and DNA sequencing were concordant in 96.7% of cases, and the results from the automated systems and DNA sequencing were concordant in 98.4%. Of all the nucleotide sequences contained in the microarray platform, the microarray failed to identify four fungal isolates (one Candida parapsilosis, two Candida tropicalis, and one Cryptococcus neoformans). Of note, the microarray detected Candida krusei DNA in two blood cultures from the same patient, whereas the automated system was only positive for Enterococcus faecium Our microarray system provided reliable and fast fungal identification compared to that from DNA sequencing and the automated systems. The simplicity of reading the results by the naked eye made this DNA platform a suitable method for fungal molecular diagnosis.

Surveillance for azoles resistance in Aspergillus spp. highlights a high number of amphotericin B-resistant isolates.

Aspergillus spp. are the most common invasive mould infection and are responsible for high mortality. Aspergillus fumigatus is currently of interest because resistance to azole antifungals has emerged. The Campinas University Hospital (HC-UNICAMP) receives high-risk patients susceptible to opportunistic infections but there have been no reports of resistant A. fumigatus. This study aimed to assess the susceptibility profile of Aspergillus isolates, specifically looking for azole resistance. ITS and ß-tubulin DNA sequencing was performed on 228 sequential clinical isolates. Broth microdilution susceptibility testing was performed for all isolates. A. fumigatus represented 74% of the isolates followed by Aspergillus flavus (12%). Nine A. fumigatus isolates from 9 different patients showed high MIC values to at least 1 azole, but cyp51A polymorphisms were detected in only 6 isolates and none correlated with known resistance mutations. The most troubling observation was that the minimum inhibitory concentration for amphotericin B was elevated (≥2 mg L-1 ) in 87% of patients with A. flavus isolates and 43% with Aspergillus fumigatus isolates. Given that amphotericin B is used to treat azole-resistant infections, these data highlight the need for continuous surveillance in Aspergillus for all antifungal resistance to implement correct treatment strategies for the management of these pathogens.

Detection of Pneumocystis jirovecii by nested PCR in HIV-negative patients with pulmonary disease / Detección de Pneumocystis jirovecii mediante PCR anidada en pacientes VIH negativos con enfermedad pulmonar

Background. Nested PCR can be used to determine the status of Pneumocystis jirovecii infection in other lung diseases. Aims. This study sought to detect a target DNA fragment (mitochondrial large subunit rRNA or mtL SUrRNA) of P. jirovecii in patients with lung disease who underwent bronchoscopy with collection of bronchoalveolar lavage (BAL). Methods. The results from toluidine blue staining were compared with those obtained using molecular methods that included an «in house» DNA extraction procedure, PCR and nested PCR. Results. Fifty-five BAL samples from patients with atypical chest X-rays were screened for P. jirovecii. None of the samples was positive for P. jirovecii using toluidine blue staining. In contrast, P. jirovecii DNA was detected by nested PCR in BAL samples from 36 of 55 patients (65.5%). The lung diseases in the patients included cancer, pneumonia, tuberculosis, and chronic obstructive pulmonary disease (COPD). Other chronic problems in the patients included hypertension, diabetes, smoking, and alcoholism. Conclusions. Nested PCR showed high sensitivity for detecting P. jirovecii, especially when compared with toluidine blue staining. Using this method, P. jirovecii infection was detected in HIV-negative patients with lung disease (AU)

Antecedentes. El diagnóstico de laboratorio mediante la técnica de PCR anidada permite determinar estados de infección por Pneumocystis jirovecii en otras enfermedades pulmonares. Objetivos. El objetivo de este estudio fue detectar fragmentos de ADN mitocondrial (mtLSU rRNA) de P. jirovecii en muestras de lavado broncoalveolar (LBA) de pacientes con enfermedades pulmonares, sometidos a broncoscopia. Métodos. Se compara la técnica de coloración con azul de toluidina para la microscopia, con los métodos moleculares PCR y PCR anidada; se realizó una extracción in house de ADN para las reacciones moleculares. Resultados. La presencia de P. jirovecii fue estudiada en 55 muestras de LBA de pacientes que presentaron patrones radiográficos de tórax atípicos. Ninguna de las muestras fue positiva para P. jirovecii con la técnica de coloración con azul de toluidina. Por la técnica de PCR anidada se detectó el ADN de P. jirovecii en 36 de los 55 pacientes (65,5%). Las enfermedades pulmonares de los pacientes fueron cáncer, neumonía, tuberculosis y enfermedad pulmonar obstructiva crónica (EPOC). Las otras enfermedades crónicas presentadas por los pacientes fueron hipertensión, diabetes, alcoholismo y tabaquismo. Conclusiones. La PCR anidada mostró ser altamente sensible en la detección de P. jirovecii en comparación con la coloración por azul de toluidina. Este método permite detectar infecciones por P. jirovecii en pacientes VIH negativos con enfermedades pulmonares (AU)

Comparison of DNA Microarray, Loop-Mediated Isothermal Amplification (LAMP) and Real-Time PCR with DNA Sequencing for Identification of Fusarium spp. Obtained from Patients with Hematologic Malignancies.

The performance of three molecular biology techniques, i.e., DNA microarray, loop-mediated isothermal amplification (LAMP), and real-time PCR were compared with DNA sequencing for properly identification of 20 isolates of Fusarium spp. obtained from blood stream as etiologic agent of invasive infections in patients with hematologic malignancies. DNA microarray, LAMP and real-time PCR identified 16 (80%) out of 20 samples as Fusarium solani species complex (FSSC) and four (20%) as Fusarium spp. The agreement among the techniques was 100%. LAMP exhibited 100% specificity, while DNA microarray, LAMP and real-time PCR showed 100% sensitivity. The three techniques had 100% agreement with DNA sequencing. Sixteen isolates were identified as FSSC by sequencing, being five Fusarium keratoplasticum, nine Fusarium petroliphilum and two Fusarium solani. On the other hand, sequencing identified four isolates as Fusarium non-solani species complex (FNSSC), being three isolates as Fusarium napiforme and one isolate as Fusarium oxysporum. Finally, LAMP proved to be faster and more accessible than DNA microarray and real-time PCR, since it does not require a thermocycler. Therefore, LAMP signalizes as emerging and promising methodology to be used in routine identification of Fusarium spp. among cases of invasive fungal infections.

Detection of Pneumocystis jirovecii by nested PCR in HIV-negative patients with pulmonary disease.

BACKGROUND: Nested PCR can be used to determine the status of Pneumocystis jirovecii infection in other lung diseases. AIMS: This study sought to detect a target DNA fragment (mitochondrial large subunit rRNA or mtL SUrRNA) of P. jirovecii in patients with lung disease who underwent bronchoscopy with collection of bronchoalveolar lavage (BAL). METHODS: The results from toluidine blue staining were compared with those obtained using molecular methods that included an "in house" DNA extraction procedure, PCR and nested PCR. RESULTS: Fifty-five BAL samples from patients with atypical chest X-rays were screened for P. jirovecii. None of the samples was positive for P. jirovecii using toluidine blue staining. In contrast, P. jirovecii DNA was detected by nested PCR in BAL samples from 36 of 55 patients (65.5%). The lung diseases in the patients included cancer, pneumonia, tuberculosis, and chronic obstructive pulmonary disease (COPD). Other chronic problems in the patients included hypertension, diabetes, smoking, and alcoholism. CONCLUSIONS: Nested PCR showed high sensitivity for detecting P. jirovecii, especially when compared with toluidine blue staining. Using this method, P. jirovecii infection was detected in HIV-negative patients with lung disease.

Resistance Surveillance in Candida albicans: A Five-Year Antifungal Susceptibility Evaluation in a Brazilian University Hospital.

Candida albicans caused 44% of the overall candidemia episodes from 2006 to 2010 in our university tertiary care hospital. As different antifungal agents are used in therapy and also immunocompromised patients receive fluconazole prophylaxis in our institution, this study aimed to perform an antifungal susceptibility surveillance with the C.albicans bloodstream isolates and to characterize the fluconazole resistance in 2 non-blood C.albicans isolates by sequencing ERG11 gene. The study included 147 C. albicans bloodstream samples and 2 fluconazole resistant isolates: one from oral cavity (LIF 12560 fluconazole MIC: 8µg/mL) and one from esophageal cavity (LIF-E10 fluconazole MIC: 64µg/mL) of two different patients previously treated with oral fluconazole. The in vitro antifungal susceptibility to amphotericin B (AMB), 5-flucytosine (5FC), fluconazole (FLC), itraconazole (ITC), voriconazole (VRC), caspofungin (CASP) was performed by broth microdilution methodology recommended by the Clinical and Laboratory Standards Institute documents (M27-A3 and M27-S4, CLSI). All blood isolates were classified as susceptible according to CLSI guidelines for all evaluated antifungal agents (MIC range: 0,125-1.00 µg/mL for AMB, ≤0.125-1.00 µg/mL for 5FC, ≤0.125-0.5 µg/mL for FLC, ≤0.015-0.125 µg/mL for ITC, ≤0.015-0.06 µg/mL for VRC and ≤0.015-0.125 µg/mL for CASP). In this study, we also amplified and sequenced the ERG11 gene of LIF 12560 and LIF-E10 C.albicans isolates. Six mutations encoding distinct amino acid substitutions were found (E116D, T128K, E266D, A298V, G448V and G464S) and these mutations were previously described as associated with fluconazole resistance. Despite the large consumption of antifungals in our institution, resistant blood isolates were not found over the trial period. Further studies should be conducted, but it may be that the very prolonged direct contact with the oral antifungal agent administered to the patient from which was isolated LIF E-10, may have contributed to the development of resistance.

Influence of the Culture Medium in Dose-Response Effect of the Chlorhexidine on Streptococcus mutans Biofilms.

The aim of this study was to evaluate the influence of culture medium on dose-response effect of chlorhexidine (CHX) on Streptococcus mutans UA159 biofilm and validate the use of the cation-adjusted-Müller-Hinton broth (MH) for the evaluation of antibacterial activity. Ultrafiltered Tryptone-Yeast Extract Broth (UTYEB) was compared against MH and MH with blood supplementation (MHS). For each medium, six groups (n = 4) were assessed: two negative control groups (baseline 48 and 120 h) and four experimental groups (0.0001, 0.001, 0.012, and 0.12% CHX). S. mutans biofilm grew on glass slides of each media containing 1% sucrose. After 48 h of growth, biofilms of baseline 48 h were collected and the other groups were treated for 1 min, twice a day, for 3 days, with their respective treatments. The media were changed daily and pH was measured. After 120 h, biofilms were collected and dry weight and viable microorganisms were determined. Results showed CHX dose-response effect being observed in all media for all the variables. However, MH and MHS showed higher sensitivity than UTYEB (p < 0.05). We can conclude that the culture medium does influence dose-response effect of CHX on Streptococcus mutans biofilm and that MH can be used for antibacterial activity.

Evaluation of antifungal combination against Cryptococcus spp.

The second cause of death among systemic mycoses, cryptococcosis treatment represents a challenge since that 5-flucytosine is not currently available in Brazil. Looking for alternatives, this study evaluated antifungal agents, alone and combined, correlating susceptibility to genotypes. Eighty Cryptococcus clinical isolates were genotyped by URA5 gene restriction fragment length polymorphism. Antifungal susceptibility was assessed following CLSI-M27A3 for amphotericin (AMB), 5-flucytosine (5FC), fluconazole (FCZ), voriconazole (VRZ), itraconazole (ITZ) and terbinafine (TRB). Drug interaction chequerboard assay evaluated: AMB + 5FC, AMB + FCZ, AMB + TRB and FCZ + TRB. Molecular typing divided isolates into 14 C. deuterogattii (VGII) and C. neoformans isolates were found to belong to genotype VNI (n = 62) and VNII (n = 4). C. neoformans VNII was significantly less susceptible than VNI (P = 0.0407) to AMB; C. deuterogattii was significantly less susceptible than VNI and VNII to VRZ (P < 0.0001). C. deuterogattii was less susceptible than C. neoformans VNI for FCZ (P = 0.0170), ITZ (P < 0.0001) and TRB (P = 0.0090). The combination FCZ + TRB showed 95.16% of synergistic effect against C. neoformans genotype VNI isolates and all combinations showed 100% of synergism against genotype VNII isolates, suggesting the relevance of cryptococcal genotyping as it is widely known that the various genotypes (now species) have significant impact in antifungal susceptibilities and clinical outcome. In difficult-to-treat cryptococcosis, terbinafine and different antifungal combinations might be alternatives to 5FC.

Fusarium napiforme systemic infection: case report with molecular characterization and antifungal susceptibility tests.

INTRODUCTION: During the last decades, Fusarium spp. has been reported as a significant cause of disease in humans, especially in immunocompromised patients, who have high risk of invasive life-threatening disease. Fusarium species usually reported as cause of human disease are F. solani, F. oxysporum and F. verticillioides. CASE DESCRIPTION: We describe the second case in the literature of disseminated fusariosis caused by Fusarium napiforme, that occurred in a 60-year-old woman with multiple myeloma after subsequent cycles of chemotherapy. DISCUSSION AND EVALUATION: We identified the F. napiforme not only by standard morphologic criteria by macroscopic and microscopic characteristics, but also confirmed by molecular biology methods, including sequencing. The antifungal susceptibility of the F. napiforme isolates were tested to seven antifungal drugs; the azoles were the most active drug against all the isolates tested. CONCLUSIONS: Fusarium spp. are of relevance in medical mycology, and their profiles of low susceptibility to antifungal drugs highlight the importance for faster and more accurate diagnostic tests, what can contribute to an earlier and precise diagnosis and treatment.

Visual analysis of DNA microarray data for accurate molecular identification of non-albicans Candida isolates from patients with candidemia episodes.

The performance of a visual slide-based DNA microarray for the identification of non-albicans Candida spp. was evaluated. Among 167 isolates that had previously been identified by Vitek 2, the agreement between DNA microarray and sequencing results was 97.6%. This DNA microarray platform showed excellent performance.

Is the incidence of candidemia caused by Candida glabrata increasing in Brazil? Five-year surveillance of Candida bloodstream infection in a university reference hospital in southeast Brazil.

From 2006 to 2010, a retrospective study was conducted in a university referral tertiary care hospital to study the frequency and distribution of Candida species in different medical specialties. The use of mechanical ventilation, central venous catheter, and urinary catheter were recorded per 1,000 patient-days and the use of antifungals was calculated using defined daily dose (DDD). A total of 313 episodes were identified and the overall incidence was 0.54 (0.41-0.71) episodes per 1,000 patient-days. Candida albicans caused 44% of the overall episodes, followed by C. tropicalis (21.7%), C. parapsilosis (14.4%), C. glabrata (11.2%), and C. krusei (3.5%). The incidence of C. glabrata significantly increased from 2006-2010 (range: 4.8-23.5%) (P = 0.024). Candida glabrata was associated with malignancies (P = 0.004) and C. krusei with hematologic malignancies (P < 0.0001). The use of antifungals was higher in the hematology/bone marrow transplant units and represented 40% of all fluconazole prescription in the hospital. There was no correlation with the use of fluconazole and the increasing ratio of C. glabrata (r = 0.60). The use of invasive devices was significantly higher in the intensive care units (ICUs) than the medical and surgical emergencies units (P < 0.001). In contrast, the emergencies had higher incidence of candidemia (2-2.1 episodes/1,000 patient-days) than the ICUs (1.6 episodes 1,000 patient-days). Candida glabrata candidemia showed a significant increase in contrast to the current national literature where C. parapsilosis remained the most important non-C. albicans Candida species in Brazilian hospitals. Our findings suggested that the increasing incidence of C. glabrata was not associated with use of fluconazole and other risk factors might play an important role.

Susceptibility testing of terbinafine alone and in combination with amphotericin B, itraconazole, or voriconazole against conidia and hyphae of dematiaceous molds.

Studies have demonstrated excellent in vivo efficacy of terbinafine combined with other antifungal agents against dematiaceous molds; however, there is a lack of in vitro studies. Most studies evaluated conidia inocula, but susceptibility testing of hyphae could mimic the fungal status in infected tissues and might reflect the therapeutic potential of the agent. We investigated the in vitro susceptibility of terbinafine alone and in combination with amphotericin B, itraconazole, or voriconazole against conidia by microdilution and dynamic measurement of hyphae growth of dematiaceous molds. The MIC values for hyphae were, until 3 dilutions, below the MIC obtained for conidia. The results indicated 100% synergistic interactions between terbinafine and azoles or amphotericin B in all tests, but lower MICs for hyphae. In conclusion, our findings allow us to say that the hyphal form of tested dematiaceous molds showed high susceptibility to all antifungal agents evaluated, alone and in combination with terbinafine.

In vitro evaluation of the type of interaction obtained by the combination of terbinafine and itraconazole, voriconazole, or amphotericin B against dematiaceous molds.

In vitro associations using the checkerboard microdilution method indicated lower MIC ranges and MIC median values for each drug (terbinafine, itraconazole, voriconazole, and amphotericin B) in association than those obtained for each single drug. Fractional inhibitory concentration index (FIC) results showed 100% synergism in the association of terbinafine with voriconazole, 96.5% in the association of terbinafine with amphotericin B, and 75.9% in the association of terbinafine with itraconazole. Drug combinations may be useful for treatment of dematiaceous mold infections as an alternative treatment to enhance the effectiveness of each drug.

Standardization of hyphal growth inhibition rate as a means of evaluating Microsporum spp. in vitro susceptibility to terbinafine, griseofulvin, and ciclopiroxolamine.

Reference methods for antifungal susceptibility tests recommend the use of conidia as inoculum. However, some isolates produce few conidia, while the invasive form of filamentous fungi in general is hyphae making susceptibility tests infeaseble. These facts suggest that other than conidia broth dilution method is required for susceptibility tests. The aim of this study was to clarify if the hyphal growth inhibition rate could be used as a method of determining the antifungal susceptibility of genus Microsporum. For this reason, a method which traces hyphal tips automatically and measures their growth rate was standardized for Microsporum spp. Control growth curves and test growth curves obtained by real-time observation of the hyphae groups responses to different concentrations of terbinafine, griseofulvin, and ciclopiroxolamine were used to compare with minimum inhibitory concentrations (MICs) obtained by conidia broth microdilution method. A visible reduction in the growth inhibition rate was observed when hyphal activity was evaluated using the third or fourth serial two-fold dilution below the MIC determined by broth microdilution for terbinafine and ciclopiroxolamine. For griseofulvin, this reduction occurred after the fifth dilution below the MIC. This study highlights the importance of the inoculum type used to determine the in vitro susceptibility of Microsporum strains. We conclude that measurement of hyphal growth inhibition, despite being time consuming, could be a suitable method for evaluating antifungal susceptibility, particularly for fungi as Microsporum spp. that produce a small (or not at all) number of conidia.

Preanalytical conditions for broth microdilution antifungal susceptibility of Microsporum spp.

Dermatophytoses caused by the genus Microsporum require a long-duration therapy compared to infections caused by other genera. Treatment of these cutaneous infections includes topical and systemic antifungal agents. Tinea capitis and tinea unguium caused by M. canis and M. gypseum are the most difficult-to-treat dermatophytoses. There are few specific studies about corresponding antifungal susceptibility in vitro. Recently, the Clinical and Laboratory Standards Institute proposed the M38A document as standard to determine the minimum inhibitory concentrations (MICs) of several antifungal agents against conidium-forming filamentous fungi; however, dermatophytes were not included in this document. This study aimed to contribute to continuing investigations concerning the optimal antifungal susceptibility testing conditions of Microsporum spp. to terbinafine, ciclopiroxolamine and griseofulvin. The results pointed out potato dextrose agar as the best culture medium for inducing conidia sporulation, inoculum density amounting to 1 x 10(3) conidia ml(-1), containing only microconidia, with an incubation time of 7 days at 28 degrees C and 100% growth inhibition serving as an endpoint. The minimum fungicidal concentration values were in accordance with the MICs values, showing a fungicidal activity of these drugs towards the tested strains. According to our results, in general, terbinafine was more active than griseofulvin and ciclopiroxolamine.