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Determinación del gen aac(6´)-aph(2´´) asociado con resistencia a aminoglucósidos en cepas de staphylococcus coagulasa negativa en una unidad neonatal en Bogotá
Detection of gene aac(6')-aph(2") in associated with aminoglucosides resistance in Staphylococcus coagulase-negative strains isolates from one neonatal unit in Bogota.
Palabras clave:
enzimas, infecciones estafilocócicas, Staphylococcus epidermidis, recién nacido, farmacorresistencia bacteriana (es)enzymes, staphylococcal infections, Staphylococcus epidermidis, infant, newborn, drug resistance, bacterial (en)
Antecedentes. La causa más común de resistencia a antibióticos aminoglucósidos en bacterias Gram positivas, especialmente en S. epidermidis, es la enzima modificante AAC(6')-APH(2"), capaz de acetilar y fosforilar un amplio rango de antibióticos.
Objetivo. Determinar la presencia del gen aac(6')-aph(2") en cepas de Staphylococcus coagulasa negativa aisladas en infecciones neonatales, e investigar la concordancia con las pruebas de sensibilidad in-vitro.
Material y métodos. Se determinó la presencia del gen aac(6')-aph(2") en 63 cepas de estafilococos coagulasa negativa provenientes de hemocultivos y puntas de catéter, de la Unidad de Neonatología del Instituto Materno Infantil, en Bogotá.
Resultados. Staphylococcus epidermidis fue el germen más frecuente y el gen aac(6')-aph(2") estaba presente en 55 (87,3%) cepas; de éstas, 42 (73,4%) cepas provenían de hemocultivos y 13 (23,6%) cepas de punta de catéter. La susceptibilidad a gentamicina se determinó mediante concentración inhibitoria mínima y para amikacina por difusión en disco. No se encontró asociación estadísticamente significativa entre la presencia del gen aac(6')-aph(2") y la resistencia a gentamicina y amikacina.
Conclusión. La presencia del gen aac(6')-aph(2") de resistencia a aminoglucósidos es muy alta en cepas de Staphylococcus epidermidis. Diferencias en la expresión del gen pueden explicar parcialmente la falta de consistencia con las pruebas de susceptibilidad utilizadas en la clínica.
Background. The most common cause of resistance to aminoglucosides is the acetilation and phosphorilation of the antibiotic by the enzyme AAC(6')APH(2").
Objetive. To determine the presence of the gene aac(6')-aph(2") in strains of coagulase-negative Staphylococci isolated from infected neonates and to investigate the concordance with the susceptibility tests in-vitro.
Materials and methods. the aac(6')-aph(2") gene was determined in 63 coagulase-negative Staphylococci strains isolated from blood cultures and catheter tips obtained from the neonatal care unit at the Instituto Materno Infantil in Bogotá, Colombia.
Results. Staphylococcus epidermidis was the most frequently identified microorganism. The aac(6')-aph(2") gene was detected in 55 out of 63 strains (73,43%), 42 strains (87,5%) isolated from blood cultures, and 13 strains (23,6%) isolated from catheter tips. Susceptibility to gentamycin was determined by minimum inhibitory concentration, and susceptibility to amikacin by the disk diffusion antibiotic sensitivity test. There was no a significant statistical association between the presence of the gene and the microbial susceptibility to either gentamycin or amikacin.
Conclusion. The presence of the aac(6')-aph(2") gene in strains of Staphylococcus epidermidis is very high. Differences in the expression of the gene might explain some cases of inconsistency with the susceptibility tests.
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