Mecanismo de resistencia a antibióticos ß-lactámicos en Staphylococcus aureus / Mechanisms of resistance to ß-lactam antibiotics in Staphylococcus aureus

S. aureus ha demostrado un gran poder de adaptación a los agentes antimicrobianos, adquiriendo paso a paso resistencia a todos los antibióticos disponibles para el tratamiento de las infecciones que ocasiona. Existen tres mecanismos de resistencia a los antibióticos ß-lactámicos en S. aureus: resistencia mediada por enzimas (penicilinasas o ß-lactamasas) las cuales desactivan al antibiótico; resistencia intrínseca, que no es debida a la inactivación de drogas y es responsable dela resistencia a meticilina; y la modificación de las proteínas de unión a penicilinas (PBPs). Además, S. aureus puede expresar el fenómeno de tolerancia, en el que ocurre una disociación de las acciones inhibitoria y bactericida de los antibióticos ß-lactámicos. De éstos, el mecanismo más importante, es la resistencia intrínseca que es probablemente más compleja, debido a que varios factores pueden afectar también su expresión

S. aureus has shown a great power of adaptation to antimicrobial agents, acquiring, step-bystep, resistance to all available antibiotics for treatment of the infections it causes. S. aureus has three major mechanisms of resistance to ß-lactam antibiotics: enzyme mediated (penicillinase or ß-lactamase) by which the antibiotic is inactivated; intrinsic resistance, which is not due to drug inactivation and accounts for methicillin resistance; and modifications of penicillin-binding proteins (PBPs). Additionally, S. aureus can express the tolerance phenomenon, in which there is a dissociation of the inhibitory and killing actions of ß-lactam antibiotics. Of these, the most important mechanism is intrinsic resistance, which is probably more complex because several factors can affect its expression

[Evaluation of ultrasound waves effect on antibiotic resistance Pseudomonas aeruginosa and Staphylococcus aureus isolated from hospital and their comparison with standard species]

Pseudomonas aeruginosa and Staphylococcus aureus are important pathogens that produce wide spread infections. Purpose of this study was to evaluate the antimicrobial effect of ultrasonic irradiation [US] alone and in combination with antibiotic on antibiotic resistance Pseudomonas aeruginosa and Staphylococcus aureus. In this study ultrasonic irradiation [US] in a laboratory-scale batch sonoreactor with low frequency [42 kHz] plate type transducer at 170W of acoustic power was used. The Water samples, were taken from different wards of the 3 teaching hospitals which were affiliated to the Kurdistan University of Medical Sciences to isolate Pseudomonas aeruginosa and Staphylococcus aureus and also to determine their antimicrobial susceptibility pattern. Our results showed that Pseudomonas aeruginosa and Staphylococcus aureus were affected by the ultrasound and the bactericidal effect increased with time. It was found that P. aeruginosa was more susceptible to the ultrasonic treatment than S. aureus. The combination of US with an antibiotic [amoxicillin] enhanced killing of both bacteria over the use of US alone. There were no differences in resistance to ultrasound between isolated strains and standard strains from Persian type culture collection