Rogelio de J. Treviño-Rangel

Aspartyl proteinase, phospholipase, esterase and hemolysin activities of clinical isolates of the Candida parapsilosis species complex

Candida parapsilosis is considered as an important emerging fungal pathogen and was recently found to be a complex that include three species, i.e., Candida parapsilosis sensu stricto, Candida orthopsilosis and Candida metapsilosis. The aim of this study was to determine the in vitro aspartyl proteinase, phospholipase, esterase and hemolysin activities of 65 clinical isolates of the C. parapsilosis complex, which had been previously identified by RFLP-BanI analysis. Of the enzymes evaluated, aspartyl proteinase was the least produced by the C. parapsilosis species complex. Phospholipase and esterase were strongly expressed by C. orthopsilosis (67% of isolates), while 10% and 13% of C. parapsilosis sensu stricto isolates were strong producers, respectively, of these two enzymes. In contrast, high production of both enzymes was not detected in C. metapsilosis. Hemolysin activity was significantly more abundant in C. orthopsilosis (87%) than C. parapsilosis sensu stricto (67%). Overall, C. orthopsilosis isolates were statistically associated with the production of hemolysins (P= 0.048) and phospholipases (P< 0.0001) compared to isolates of C. parapsilosis sensu stricto or C. metapsilosis. Furthermore, a statistical association was found between isolates recovered from blood and phospholipase production (P= 0.017). The distribution of isolates obtained from blood was 30% of C. parapsilosis sensu stricto, 67% of C. orthopsilosis and 20% of C. metapsilosis.

Molecular characterization and antifungal susceptibility of the Candida parapsilosis species complex of clinical isolates from Monterrey, Mexico

Recently, it was proposed that the opportunistic yeast pathogen Candida parapsilosis was a complex composed of the following three species: Candida parapsilosis sensu stricto, Candida orthopsilosis, and Candida metapsilosis. A set of 344 clinical isolates of Candida parapsilosis from Monterrey, Mexico was re-identified by RFLP. Their antifungal susceptibility to fluconazole, caspofungin, anidulafungin and micafungin was determined using the Clinical and Laboratory Standards Institute M27-A3 protocol. Candida parapsilosis sensu stricto was the most frequent species, and was the only one which showed resistance to antifungals.

Species distribution and antifungal susceptibility of bloodstream fungal isolates in paediatric patients in Mexico: a nationwide surveillance study

OBJECTIVES To establish the species distribution and in vitro susceptibilities of 358 bloodstream fungal isolates from paediatric patients in Mexico. METHODS Isolates were collected during a 2 year surveillance programme in 14 medical centres in 10 Mexican states. A molecular approach was used to determine the Candida parapsilosis species complex. In vitro susceptibility to amphotericin B, fluconazole, voriconazole, itraconazole, posaconazole, caspofungin, anidulafungin and micafungin was determined according to CLSI procedures. Species-specific clinical breakpoints for fluconazole, voriconazole and echinocandins were applied. RESULTS Candida spp. accounted for 98.33% of fungaemias, including 127 Candida albicans isolates, 127 C. parapsilosis complex isolates (121 C. parapsilosis sensu stricto, 4 Candida orthopsilosis and 2 Candida metapsilosis strains) and 72 Candida tropicalis isolates. C. albicans and C. parapsilosis complex were the species predominant in neonates (48 cases each; 41.02%). C. parapsilosis complex was also the predominant species in patients 1 month to <2 years of age (P = 0.007). In contrast, C. albicans was the most frequent species in patients aged 2 to <12 years (P = 0.003). Antifungal resistance was rare among the subset of isolates. Candida glabrata showed the highest resistance rate to amphotericin B (1/9 isolates), fluconazole (1/9 isolates) and itraconazole (2/9 isolates). CONCLUSIONS The species distribution differed with the age of the patients, with C. albicans and C. parapsilosis complex being the most commonly isolated species. C. glabrata showed the highest resistance rate to amphotericin B, fluconazole and itraconazole. This is the first study of fungaemia episodes in Mexican children.

Activity of sertraline against Cryptococcus neoformans: in vitro and in vivo assays.

Cryptococcus neoformans infection is an important cause of meningitis in HIV/AIDS endemic regions. Antifungals for its management include amphotericin B, flucytosine, and fluconazole. Recently, treatment of this mycosis with sertraline has been studied with variable clinical outcomes. The aim of the study was to assess the in vitro antifungal effect of sertraline against clinical isolates of Cryptococcus spp. as well as its in vivo activity in a murine model of cryptococcal meningoencephalitis. The in vitro susceptibility to fluconazole, amphotericin B, voriconazole and sertraline of 153 Cryptococcus spp. strains were evaluated according to CLSI procedures. Fungal tissue burden, serum antigenaemia and histopathology, together with the therapeutic efficacy of amphotericin B (3 mg/kg), fluconazole (15 mg/kg), and sertraline (3, 10, and 15 mg/kg) were evaluated in mice intracranially inoculated with one isolate of Cryptococcus neoformans. All strains were susceptible to the antifungals studied and exhibited growth inhibition with sertraline at clinically relevant concentrations. Sertraline at a dose of 15 mg/kg reduced the fungal burden in the brain and spleen with an efficacy comparable to that of fluconazole. In conclusion, sertraline exhibited an excellent in vitro-in vivo anti-cryptococcal activity, representing a possible new alternative for the clinical management of meningeal cryptococcosis.

Therapeutic efficacy of posaconazole in a murine model of disseminated trichosporonosis

OBJECTIVES To study the effect of the initiation time of posaconazole treatment from 1 to 3 days after systemic infection by Trichosporon asahii in mice. METHODS BALB/c mice, 4-5 weeks old, were intravenously infected with 1 × 10(7) cfu/mouse of T. asahii. The onset of treatment varied from 1 to 3 days after infection. Orally administered posaconazole at 0.5, 1, 2, 5 or 10 mg/kg body weight/day was compared with orally administered fluconazole (at 10 mg/kg/day) and intraperitoneally administered amphotericin B (at 1 mg/kg) on alternating days. Livers, kidneys and spleens of mice that died or survived to day 25 were removed to determine fungal tissue burdens. RESULTS When therapy began 1 day after challenge, posaconazole at ≥ 1 mg/kg significantly prolonged survival of mice compared with that of the control group and considerably reduced the fungal tissue burden over the control group. On the other hand, when treatment was started 3 days after infection, regimens of 5 and 10 mg/kg posaconazole significantly prolonged mice survival over that of the control group and appreciably diminished the fungal load compared with untreated mice. In this model, as the severity of trichosporonosis increased, higher doses of posaconazole were required to achieve equivalent activity levels. Fluconazole and amphotericin B were ineffective in preventing mice death and in significantly reducing fungal tissue burden. Posaconazole displayed potent in vivo activity against the strain tested. CONCLUSIONS Posaconazole may be a suitable option in the treatment of disseminated T. asahii infection.

Cutaneous disseminated sporotrichosis: clinical experience of 24 cases

Sporotrichosis is a subcutaneous mycosis, caused by complex Sporothrix schenckii, It is the most common implantation mycoses in worldwide. It is a polymorphic disease, cutaneous-lymphatic is the most frequent (75-90%).1-3 We report our 25 years’ experience (1990-2015) in cutaneous disseminated sporotrichosis (CDS). We conducted, an open, retrospective and observational study. This article is protected by copyright. All rights reserved.

Association between Candida biofilm-forming bloodstream isolates and the clinical evolution in patients with candidemia: An observational nine-year single center study in Mexico

BACKGROUND Candidemia is one of the most common nosocomial infections globally and it is associated with considerable excess mortality and costs. Abreast, biofilm-forming strains are associated with even higher mortality rates and poor prognosis for the patient. AIMS To evaluate a possible association between the biofilm-forming capability of Candida bloodstream isolates and the clinical evolution in patients with candidemia. METHODS An observational, retrospective study was conducted at a tertiary care university hospital during 9 years (2006-2015). The biofilm quantitation of the Candida bloodstream isolates was determined by crystal violet staining and XTT reduction assay. RESULTS A total of 218 cases of candidemia had been diagnosed and 89 isolates were obtained. The mortality rate was 36% and the main risk factors were antibiotic exposure and the use of catheters. Candida tropicalis (52.8%) was the most frequent species, followed by Candida albicans (30.4%), Candida parapsilosis sensu stricto (10.1%), Candida orthopsilosis (3.4%), Candida krusei (2.2%) and Candida glabrata sensu stricto (1.1%). All the strains were biofilm producers, which is an important contribution to the patients mortality. C. tropicalis showed the highest production of biomass biofilm, whereas C. glabrata exhibited the highest metabolic activity. CONCLUSIONS This study contributes to expand the knowledge about the local epidemiology of candidemia and highlights the impact of Candida biofilm on patients outcome.

In vivo pathogenicity of Trichosporon asahii isolates with different in vitro enzymatic profiles in an immunocompetent murine model of systemic trichosporonosis

Trichosporon asahii is an opportunistic yeastlike fungus that colonizes the gastrointestinal and respiratory tracts and human skin. Although it is an important cause of disseminated infections by non-Candida species, there are a few reports related to its virulence factors and their possible role in in vivo pathogenicity. We developed a murine model of disseminated trichosporonosis in immunocompetent mice for the evaluation of the in vivo pathogenicity of 6 T. asahii isolates with different in vitro virulence factor profiles. Tissue fungal burden was determined on days 1, 3, 7, 15, and 25 post-challenge. Overall, the largest fungal load was detected in the kidney on the 5 experimental days, while brain, spleen, and liver displayed a comparatively low fungal count. We observed a fungal burden decrease in most experimental groups from day 15. Histological analysis showed the presence of T. asahii in tissue and a generalized inflammatory infiltrate of polymorphonuclear cells in the kidney, liver, red pulp of the spleen, and the hippocampus. Even though our isolates showed different in vitro virulence factors profiles, we did not detect relevant differences when assayed in vivo, except for a higher persistence of a protease- and biofilm-producing strain in kidney, liver, and brain.

Molecular Identification, Antifungal Susceptibility, and Geographic Origin of Clinical Strains of Sporothrix schenckii Complex in Mexico

Sporotrichosis is a subcutaneous mycosis caused by Sporothrix schenckii complex. The disease has been reported worldwide. However, the incidence of the etiological agent varies in its geographic distribution. We studied 39 clinical isolates of Sporothrix schenckii from diverse regions in Mexico, collected from 1998 to 2016. Molecular identification was performed by sequence analysis of the partial calmodulin gene. In vitro antifungal susceptibility to amphotericin B (AMB), itraconazole (ITC), voriconazole (VRC), posaconazole (PSC), fluconazole (FLC), terbinafine (TRB), caspofungin (CSF), anidulafungin (ANF), and micafungin (MCF) was evaluated. Thirty-eight isolates of S. schenckii complex were divided into five supported clades in a phylogenetic tree. The predominant clinical form was lymphocutaneous (92.3%), fixed cutaneous (5.1%), and disseminated (2.5%). Terbinafine exhibited the best in vitro antifungal activity, while fluconazole was ineffective against Sporothrix schenckii complex. Our results showed diverse geographic distribution of clinical isolates in eight states; definitive identification was done by CAL gen PCR-sequencing. In Mexico, S. schenckii is considered to be an etiological agent of human sporotrichosis cases, and lymphocutaneous is the most prevalent form of the disease. This study revealed four clades of S. schenckii sensu stricto by phylogenetic analysis. Furthermore, we report one case of S. globosa isolated from human origin from the North of Mexico.

Biofilm formation and antifungal susceptibility of Trichosporon asahii isolates from Mexican patients

BACKGROUND Trichosporon asahii is a yeast-like fungus that has recently gained importance as a cause of opportunistic systemic infections. The pathogenicity and virulence factors of T. asahii remain largely unknown. Because of the association between invasive infections and the use of catheters and related devices, the ability of the microorganism to adhere and form biofilms may play an important role in the pathogenicity during a trichosporonosis. AIMS The aim of this study is to identify an association between biofilm formation by T. asahii isolates and their genotype and/or clinical source. METHODS The biofilm production of 49 T. asahii strains isolated from Mexican patients was measured using the crystal violet stain method, and a comparison made with different adhesion phase incubation times. Antifungal susceptibility testing was performed using a modified CLSI protocol coupled with the quantification of the viable cells with the XTT reduction method. RESULTS All the T. asahii isolates assayed were able to produce biofilm in vitro, with an intraspecific variability being observed. Overall, increased biofilm production was found when extending the adhesion phase incubation time from 2 to 4h. No association could be established between the biofilm-producing phenotype and either the genotype or clinical source. Higher antifungal resistance to amphotericin B and fluconazole was linked to increased biofilm production by T. asahii. CONCLUSIONS All clinical isolates tested were able to produce biofilm. No association could be established between biofilm formation and genotype or clinical source.