[Methicillin resistance and vancomycin susceptibility pattern among blood isolates of Staphylococcus aureus]. / Resistencia a meticilina y susceptibilidad a vancomicina de Staphylococcus aureus aislados de sangre.

BACKGROUND: Staphylococcus aureus is capable of acquiring resistance against all antimicrobial agents. Vancomycin has been the cornerstone therapy for serious methicillin-resistant S. aureus infections. However, vancomycin treatment failures have been reported. METHODS: From March to August 2010, S. aureus blood isolates were included to determine methicillin-resistance and the vancomycin susceptibility by using a standard microdilution method. To detect methicillin-resistance, a Mueller-Hinton agar plate added with oxacillin 4 µg/mL and 2 % NaCl, and an agglutination test were used. Growth of S. aureus on the agar plate and/or reactive agglutination defined a methicillin-resistant organism. Vancomycin susceptibility was assessed by determining the minimal inhibitory concentration (MIC) in Muelller-Hinton agar plates prepared with dilutions ranging from 16 to 0.5 µg/mL. RESULTS: A total of 25 blood-isolates of S. aureus were included. A 60 % was methicillin-resistant. All isolates were vancomycin-susceptible (MIC ≤ 2 µg/mL) showing the next MICs distribution: 48 % ≤ 0.5 µg/mL; 44 % 1 µg/mL, and 8 % 2 µg/mL. CONCLUSION: The high proportion of methicillin-resistance among S. aureus and the presence of vancomycin susceptible phenotypes (MIC of 2 µg/mL) not only claim for an enforcement of standard precautions and antimicrobial control, but also for a regular surveillance of vancomycin susceptibility pattern using a reference method.

Introducción: el Staphylococcus aureus es capaz de desarrollar resistencia a todos los antimicrobianos. La vancomicina es clave para tratar infecciones graves causadas por S. aureus meticilino-resistente. Sin embargo, últimamente se reportan fallas terapéuticas. El objetivo fue establecer la resistencia a la meticilina y el perfil de susceptibilidad a la vancomicina del S. aureus. Métodos: de marzo a agosto del 2010, se determinó la meticilino-resistencia y la susceptibilidad a vancomicina de S. aureus aislados de hemocultivos, mediante el método estándar de microdilución. Para la meticilino-resistencia se utilizó una placa de agar Mueller-Hinton con 4 µg/mL de oxacilina, más NaCl al 2 % y una prueba de aglutinación. El desarrollo bacteriano o la aglutinación positiva identificaron al microorganismo meticilino-resistente. Para la susceptibilidad a vancomicina se determinó la concentración mínima inhibitoria (CMI) en placas de agar Mueller-Hinton con dilución de 16 a 0.5 µg/mL. Resultados: en total se incluyeron 25 S. aureus. El 60 % fue meticilino-resistente; el 100 % sensible a vancomicina (CMI ≤ 2 µg/mL), con las siguientes CMI: el 48 %, ≤ 0.5 µg/mL; 44 %, 1 µg/mL; y el 8 %, 2 µg/mL. Conclusión: la proporción alta de meticilino-resistencia y la evidencia de fenotipos sensibles a la vancomicina, pero asociados a falla terapéutica (CMI 2 µg/mL), demandan no solo el reforzamiento continuo de las precauciones estándar y el control de antimicrobianos sino también la vigilancia sistemática del patrón de susceptibilidad a la vancomicina con un método de referencia.

[Hospital outbreak of urinary tract infections by lubricant gel contaminated with Burkholderia cepacia]. / Infecciones urinarias nosocomiales. Contaminación de gel con Burkholderia cepacia.

BACKGROUND: Burkholderia cepacia (B. cepacia) has been the causal agent of infectious hospital outbreaks. METHODS: a case-controls study was conducted to describe an outbreak of urinary tract infection associated to lubricant-gel contaminated with B. cepacia. Patients who developed UTIsc were included in this study. Their clinical data, urine cultures, antiobiograms and the molecular bacterial analysis were analyzed. RESULTS: the urine culture was positive in 101 (55.8 %); the bacterial strains isolated were: B. cepacia 30.7 %, Escherichia coli 22.7 %, Enterococcus faecalis 9.9 %, Enterococcus spp. 8.9 %. They were 31 patients with B. cepacia isolation that was taken as the cases group and 63 with UTIsc due to another organism as control group. The Charlson comorbidity index was 5.3 ± 1.8 for cases and 4.5 ± 1.2 for controls. The factors associated with death were: heart disease, diabetes, pneumonia, bacteremia and UTIsc B. cepacia. CONCLUSIONS: the lubricant gel used for urinary catheter placement originated the outbreak. Heart disease, pneumonia, bacteremia and UTIsc B. cepacia were related to patients' death.