Antifungal resistance does not necessarily affect Candida glabrata fitness.

Although there has been an overall good coverage of Candida glabrata infections by the echinocandins, emergence of antifungal resistance during therapy has been reported. We investigated, by using an invertebrate host model, the fitness of sequential C. glabrata isolates with different echinocandins susceptibility patterns. The studied strains were isolated from a case of recurrent fungemia with a fatal outcome due to C. glabrata that developed cross-resistance to echinocandins during caspofungin therapy. The sequential strains isolated post-therapy showed a S663P mutation in the Fks2p hot spot 1. In vivo study in the invertebrate host Galleria mellonella did not suggest a fitness cost related to the acquired antifungal resistance, the three isolates displayed a similar rate of killing (P  =  0.54). We observed a clear correlation between emergence of antifungal resistance and persistence of the causal agent, probably aided by the unchanged fitness and unresponsiveness in vivo to the adopted therapy.

Experimental biofilm-related Candida infections.

AIM: We investigated the pathogenic role of biofilm and the therapeutic efficacy of anidulafungin in experimental infections of the wax moth Galleria mellonella by Candida albicans clinical strains. MATERIALS & METHODS: On the basis of the in vitro propensity to form biofilm, five biofilm-producer (BP) and four nonproducer (NP) C. albicans clinical strains were used in this study. For each strain, we assessed the virulence by infecting G. mellonella larvae and observing survival. Anidulafungin was administered 2 h after yeast inoculum at 0.6 µg, according to the therapeutic dose recommended for humans. RESULTS: Biofilm-forming ability highly influenced the larva-killing rate. A significant (p < 0.0001) survival decrease was observed in the BP group, with 80% of the infected larvae dying within 72 h. NP isolates did not reach the same killing rate, even at the end of experiments (216 h). Larval survival was enhanced (p < 0.0001) by anidulafungin administration in both groups. Survival rate at 72 h was similar in both groups (BP 78.5% and NP 87.5%); whereas there were still differences at the end of the experiments, with a higher survival in the NP group (75 vs 48%). CONCLUSION: Our data confirm the pathogenic role of biofilm in C. albicans infections. Its importance was further enhanced by a lack of contribution from extracellular enzymes, detected in both NP and BP strains. In addition, we demonstrated anidulafungin efficacy in treating biofilm-related invasive candidiasis.

Molecular picture of community- and healthcare-associated methicillin-resistant Staphylococcus aureus circulating in a teaching hospital in Milan.

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) has dramatically changed over the past 10 y with the emergence of community-associated MRSA (CA-MRSA). Recent studies have reported a frequent association of these strains with hospital outbreaks, and an incidence varying over time and by region. In order to evaluate the MRSA lineages circulating in our area of Italy, we performed a molecular characterization of CA-MRSA isolates prospectively collected from April 2006 to July 2007 at the San Paolo Hospital of Milan. We investigated the protein A-encoding gene (spa-typing), the staphylococcal chromosomal cassette SCCmec, the presence of Panton-Valentine leukocidin (PVL), and 3 adhesin genes. Twenty-five CA-MRSA isolates cultured from 25 patients were collected; an equal number of healthcare-associated (HA)-MRSA strains, from 25 patients hospitalized in various wards, were collected for comparison purposes. SCCmec type IV emerged as the most frequent genotype in both CA- and HA-MRSA. Seventeen different spa types were identified: t515 was the most common (36%), followed by t008 (20%). We detected 3 PVL-positive strains, only among the CA-MRSA. On the whole, our local MRSA epidemiology appears to be heterogeneous, with a predominant t515 spa type, only recently considered to belong to clonal EMRSA-15.

Comparative evaluation of the Vitek 2 yeast susceptibility test and CLSI broth microdilution reference method for testing antifungal susceptibility of invasive fungal isolates in Italy: the GISIA3 study.

The newly available AST-YS01 Vitek 2 cards were evaluated, and the results were compared with those obtained by the CLSI M27-A2 microdilution reference method. Clinical fungal isolates, including 614 isolates of Candida spp., 10 Cryptococcus neoformans isolates, 1 Geotrichum capitatum isolate, and 2 quality control strains, were tested for their susceptibilities to amphotericin B, fluconazole, and voriconazole using both methods. The majority of fungal isolates were susceptible to all antifungal agents tested: the MIC(90) values determined by the Vitek 2 and CLSI methods were 0.5 and 1 microg/ml, respectively, for amphotericin B; 8 and 16 microg/ml, respectively, for fluconazole; and <0.12 and 0.25 microg/ml, respectively, for voriconazole. Overall there was excellent categorical agreement (CA) between the methods (99.5% for amphotericin B, 92% for fluconazole, 98.2% for voriconazole), but discrepancies were observed within species. The CAs for fluconazole were low for Candida glabrata and Candida krusei when the results of the CLSI method at 48 h were considered. Moreover, the fully automated commercial system did not detect the susceptibility of Cryptococcus neoformans to voriconazole. The Vitek 2 system can be considered a valid support for antifungal susceptibility testing of fungi, but testing of susceptibility to agents not included in the system (e.g., echinocandins and posaconazole) should be performed with other methods.