Evaluación de la susceptibilidad a glicopéptidos en cepas de Staphylococcus aureus resistentes a oxacilina / Evaluation of susceptibility to glycopeptides in oxacillin resistant Staphylococcus aureus strains

Candida albicans y Candida dubliniensis presentan una estrecha relación filogenética. La similitud de estas especies puede hacer que en un laboratorio microbiológico se identifique en forma errónea C. dubliniensis como C. albicans. El objetivo de esta investigación fue evaluar diversos métodos fenotípicos para la diferenciación entre Candida dubliniensis y Candida albicans. Se utilizaron 6 cepas control de C. dubliniensis y una de C. albicans, provenientes de colecciones reconocidas y sometidas a genotipificación. También se utilizaron 70 aislados identificados como posibles C. albicans utilizando el medio CHROMagar Candida y el medio de bilis agar Feo. Los métodos evaluados fueron: agar Sabouraud dextrosa a 45°C, agar Sabouraud con NaCl al 6,5%, agar Tween 80, agar tabaco, agar Pal’s, agar tomate-zanahoria y aglutinación con partículas de látex (Bichro-Dubli Fumouze®). Encontramos que las técnicas más confiables para realizar la diferenciación fenotípica entre estas dos especies fueron: el agar tomate-zanahoria, el agar Pal’s, el agar tabaco y la aglutinación con partículas de látex (Bichro-Dubli Fumouze®). Además en este estudio, de los 70 aislados considerados como C. albicans, encontramos 1 (1.4%) posible Candida dubliniensis. Sin embargo, las pruebas de biología molecular son las más adecuadas para el diagnóstico certero de estas dos especies.

Candida albicans and Candida dubliniensis have a close phylogenetic relationship. The similarity between these species can cause a microbiology laboratory to identify C. dubliniensis erroneously as C. albicans. The objective of this research was to evaluate diverse phenotypic methods for differentiating between Candida dubliniensis and Candida albicans. Six control strains of C. dubliniensis and one of C. albicans from recognized collections were used and submitted to genotypification. Also, 70 isolates were used, identified as possible C. albicans utilizing CHROMagar Candida and bilis agar Feo mediums. The methods evaluated were: Sabouraud dextrosa agar at 45°C, Sabouraud agar with NaCl at 6.5%, Tween 80 agar, tobacco agar, Pal’s agar, tomato-carrot agar and agglutination with latex particles (Bichro-Dubli Fumouze®). It was found that the most reliable techniques for performing phenotype differentiation between these two species were tomato-carrot agar, Pal’s agar, tobacco agar and agglutination with latex particles (Bichro-Dubli Fumouze®). Of the 70 isolates considered to be C. albicans, one (1.4%) possible Candida dubliniensis was found. Nevertheless, molecular biology tests are the most appropriate means for achieving an accurate diagnosis of these two species.

Oxacilin-resistant Coagulase-negative staphylococci (CoNS) bacteremia in a general hospital at São Paulo city, Brasil / Bacteremias por Staphylococcus coagulase negativos oxacilina resistentes em um hospital na cidade de São Paulo, Brasil

In the last decades, coagulase-negative staphylococci (CoNS), especially Staphylococcus epidermidis have become an important cause of bloodstream infections. In addition, rates of methicillin-resistance among CoNS have increased substantially, leading to the use of glicopeptides for therapy. The objective of this study was to evaluate eleven consecutives clinically relevant cases of oxacillin-resistant CoNS bacteremia in a general hospital localized in São Paulo city, Brazil. Five different species were identified by different phenotypic methods, including S. epidermidis (5), S. haemolyticus (3), S. hominis (1), S. warneri (1) and S. cohnii subsp urealyticus (1). A variety of Pulsed Field Gel Electrophoresis profiles was observed by macrorestriction DNA analysis in S. epidermidis isolates, but two of three S. haemolyticus isolates presented the same profile. These data indicated the heterogeneity of the CoNS isolates, suggesting that horizontal dissemination of these microorganisms in the investigated hospital was not frequent. One S. epidermidis and one S. haemolyticus isolates were resistant to teicoplanin and susceptible to vancomycin. The selective pressure due to the use of teicoplanin in this hospital is relevant.

Staphylococcus coagulase negativos (SCoN), especialmente Staphylococcus epidermidis tem se tornado causa importante de infecções da corrente circulatória nas últimas décadas. Além disso, percentuais de resistência a meticilina entre os SCoN têm aumentado significativamente, levando ao uso de glicopeptídeos nestes pacientes. O objetivo deste estudo foi avaliar onze casos consecutivos de bacteremia clinicamente relevantes por SCoN oxacilina resistentes em um hospital localizado na cidade de São Paulo, Brasil. Cinco diferentes espécies foram identificadas por diferentes métodos fenotípicos, incluindo S. epidermidis (5), S. haemolyticus (3), S. hominis (1), S. warneri (1) e S. cohnii subsp urealyticus (1). Diferentes perfis eletroforéticos obtidos pela técnica de "Pulsed Field Gel Electrophoresis" foram observados na análise da macrorestrição do DNA nos isolados de S. epidermidis, mas dois dos três isolados de S. haemolyticus apresentaram o mesmo perfil. Esses dados indicam uma heterogeneidade nos isolados SCoN, sugerindo que a disseminação horizontal no hospital investigado não é freqüente. Um isolado de S. epidermidis e um de S. haemolyticus foram resistentes à teicoplanina e sensíveis à vancomicina. Observa-se a relevância da pressão seletiva pelo uso de teicoplanina nos pacientes deste hospital.

The recent evolution of therapeutic weapons against resistant Gram-positive microorganisms

Multiresistant Gram-positive cocci, including Staphylococcus aureus, the group of coagulase-negative staphylococci, Enterococcus faecalis and Enterococcus faecium, as well as Streptococcus pneumoniae and other streptococci, represent emerging pathogens. This issue is especially concerning in the setting of immunocompromised, hospitalized patients, in particular when surgery, invasive procedures, or prosthetic implants are carried out, patients are admitted in intensive care units, or underlying chronic disorders and immunodeficiency are of concern, and broad-spectrum antibiotics are widely used in the environment; moreover, a community spread of resistant Gram-positive cocci has been recognized during recent years. The spectrum of antimicrobials available for an effective management of these relevant infections is significantly threatened by the emerging of methicillin-resistant and more recently glycopeptide-resistant strains. The streptogramine association represented by quinupristin/dalfopristin, the oxazolidinone derivative linezolid, and the recently licensed daptomycin and tigecycline, together with a number of glycopeptides, fluoroquinolones, cephalosporins, and other experimental compounds, represent an effective response. It is due to the innovative mechanisms of action of these compounds, their maintained or enhanced activity against multiresistant pathogens, their effective pharmacokinetic/pharmacodynamic properties, their frequent possibility of synergistic activity with other compounds effective against Gram-positive pathogens, and a diffuse potential for a safe and easy administration, also to compromised patients.