Staphylococcus aureus con resistencia múltiple a los antibióticos (MDR) en un Hospital de Maracaibo- Venezuela / Multidrug-resistant (MDR) Staphylococcus aureus in a Maracaibo’s hospital, Venezuela

Staphylococcus aureus resistente a oxacilina (SAOR) continúa siendo una causa importante de infecciones nosocomiales en todo el mundo. Se determinó la resistencia a los antibióticos de cepas intrahospitalarias, clasificándolas en multidrogo-resistentes, extensamente drogo-resistentes o pandrogo-resistentes. Las muestras biológicas fueron recolectadas entre septiembre 2013-febrero 2014 y procesadas de acuerdo a técnicas de bacteriología convencional. La resistencia a los antibióticos se determinó mediante el método de difusión con discos en agar y el gen mecA se detectó mediante reacción en cadena de la polimerasa. Se observó baja prevalencia de SAOR intrahospitalario (13,86%). La mayor resistencia fue a eritromicina (66,07%), mientras que la resistencia frente a aminoglucósidos, fluoroquinolonas, clindamicina y tetraciclina fue inferior al 25%; la resistencia frente a trimetoprim/sulfametoxazol fue muy baja y el 100% de las cepas mostraron sensibilidad a rifampicina, linezolid, vancomicina y teicoplanina. El fenotipo de resistencia a MLSB más frecuente fue el de resistencia a eritromicina y susceptibilidad a clindamicina (33,93%, fenotipo MSB). Las cepas SAOR aisladas presentaron 25 antibiotipos diferentes, siendo la mayoría de los aislamientos multidrogo-resistentes (55,36%). No se observó resistencia extensa a los antibióticos ni pandrogo-resistencia y la presencia del gen mecA se demostró en todos los aislamientos resistentes a oxacilina.

Oxacillin-resistant Staphylococcus aureus (ORSA) has remained a major cause of nosocomial infections worldwide. The antibiotic resistance of isolations was determined and we classify them in multidrug-resistant, extensively drug-resistant or pandrug-resistant. The biological samples of patients from a Maracaibo’s Hospital, during September 2013 to February 2014, were processed according to conventional techniques of bacteriology. Antibiotic resistance was determined by disk diffusion method in agar and the mecA gene was detected by polymerase chain reaction. It was observed a low prevalence of nosocomial ORSA (13.86%). The higher antibiotic resistance was observed against erythromycin (66.07%) and a resistance lower than 25% to aminoglycosides, fluoroquinolones, tetracycline and clindamycin. The isolates showed a very low resistance to trimethoprim/sulfamethoxazole and all isolates were susceptible to rifampicin, linezolid, vancomycin and teicoplanin.The majority of isolates had a MSB phenotype (33.93%), with erythromycin resistance and susceptibility to clindamycin. The ORSA isolates in this study had 25 different antibiotypes and the majority of them were multidrug-resistant (55.36%). There was not both extensively drug-resistant and pandrug-resistant isolates and the presence of the mecA gene was demonstrated in all isolates of ORSA.

Tipificación molecular y fenotípica de Staphylococcus aureus resistentes a meticilina (SAMR) en un hospital universitario / Molecular and phenotypical typification of methicillin resistant Staphylococcus aureus (MRSA) strains in a university hospital

Objective: To typify by molecular and phenotypical methods, MRSA strains, isolated from patients and nurses to establish their possible clonal origin. Materials and Methods: 50 MRSA strains isolated in a teaching hospital in Maracaibo (Venezuela) were analyzed. The typification of MRSA strains was performed by means of pulsed-field gel electrophoresis (PFGE) and antibiotyping. Results: In patients, 12 clusters (I-XII) and 19 antibiotypes were found; whereas in the health-care personnel, 6 clusters (I-VI) and two antbiotypes were detected. There was no statistically significative association between antibiotypes and band patterns obtained by PFGE (p>0.05). Conclusions: By means of detection of resistance markers and PFGE, it is feasible to discrimínate the nature of the clinical strains of MRSA. The obtained results show the possible nosocomial transmission of MRSA strains and their clonal spread in hospital departments, particularly at the ICU.

Objetivo: Tipificar por métodos moleculares y fenotípicos, las cepas SAMR aisladas de pacientes y personal de enfermería para establecer su posible origen clonal. Materiales y Métodos: Se analizaron 50 cepas SAMR aisladas en un Hospital Universitario de Maracaibo (Venezuela). La tipificación se efectuó mediante electroforesis en gel de campo pulsado (EGCP) y antibiotipia. Resultados: Entre pacientes, se obtuvieron 19 antibiotipos y 12 grupos (I-XII); mientras que, en el personal de salud, por EGCP se detectaron seis grupos (I-VI) y dos antibiotipos. No se encontró asociación estadísticamente significativa entre los antibiotipos y patrones de bandas obtenidos por EGCP (p > 0,05). Conclusiones: Por medio de la detección de marcadores de resistencia y mediante la EGCP, es factible diferenciar la naturaleza de las cepas SAMR de origen clínico. Los resultados obtenidos demuestran la posible transmisión intrahospitalaria de cepas SAMR; así como, su diseminación clonal en los servicios del hospital, particularmente en la UCI, durante el período estudiado.

Pulsed-Field Gel Electrophoresis (PFGE) Patterns and Antibiotypes for Sequential Isolates of Staphylococcus epidermidis from Blood Cultures / 감염과화학요법

BACKGROUND: The significance of Staphylococcus epidermidis positive blood cultures is difficult to determine, but repeated isolation of the same organism with the same genotype is suggestive of true bacteremia. MATERIALS AND METHODS: Two sequential isolates of S. epidermidis from blood cultures of the same twelve patients were genotyped by PFGE. The results were compared with those of antibiotyping and isolation time intervals between the two strains. RESULTS: The two sequential strains from each patient had identical PFGE patterns in 66.6% (8 of 12) of the patients and two different types in 33.3% (4 of 12) of the patients. Antibiotypes of the two isolates from the same patient were different in all 4 patients whose isolates had different PFGE patterns, and they were the same in 7 of 8 patients whose isolates had identical PFGE patterns:the PFGE results were in agreement with the antibiotyping for 91.7% (11/12) of patients. The isolation time interval between the two strains was or =5 days. CONCLUSION: These data showed that two consecutive isolates of S. epidermidis from blood cultures had different PFGE patterns in 33% of patients, suggesting a high prevalence of contamination. In the absence of genotyping measures, both antibiotype and isolation time interval can be alternative and useful tools for determining strain relatedness of sequential isolates of S. epidermidis from blood cultures.

Pulsed-Field Gel Electrophoresis (PFGE) Patterns and Antibiotypes for Sequential Isolates of Staphylococcus epidermidis from Blood Cultures / 감염과화학요법

BACKGROUND: The significance of Staphylococcus epidermidis positive blood cultures is difficult to determine, but repeated isolation of the same organism with the same genotype is suggestive of true bacteremia. MATERIALS AND METHODS: Two sequential isolates of S. epidermidis from blood cultures of the same twelve patients were genotyped by PFGE. The results were compared with those of antibiotyping and isolation time intervals between the two strains. RESULTS: The two sequential strains from each patient had identical PFGE patterns in 66.6% (8 of 12) of the patients and two different types in 33.3% (4 of 12) of the patients. Antibiotypes of the two isolates from the same patient were different in all 4 patients whose isolates had different PFGE patterns, and they were the same in 7 of 8 patients whose isolates had identical PFGE patterns:the PFGE results were in agreement with the antibiotyping for 91.7% (11/12) of patients. The isolation time interval between the two strains was or =5 days. CONCLUSION: These data showed that two consecutive isolates of S. epidermidis from blood cultures had different PFGE patterns in 33% of patients, suggesting a high prevalence of contamination. In the absence of genotyping measures, both antibiotype and isolation time interval can be alternative and useful tools for determining strain relatedness of sequential isolates of S. epidermidis from blood cultures.