THERAPEUTIC FAILURE BY OS-MRSA STRAINS

The incidence of serious infections caused by Staphylococcus aureus is associated with high morbidity and mortality and may lead to an unfavorable clinical outcome. One of the factors responsible for this worse prognosis is the increased resistance of pathogens to antimicrobial agents. This fact makes the therapy of choice more difficult and limited, which contributes to the patient's clinical deterioration. Strains characterized as OS-MRSA (Oxacillin sensitive - Methicillin-resistant Staphylococcus aureus) are strains of S. aureus that are phenotypically sensitive to oxacillin but contain the mecA gene, which induces clinicians to dismantle antimicrobial treatment, resulting in therapeutic failure. The objective of this study was to characterize clinical and laboratory strains of S. aureus, obtained from clinical material, from patients hospitalized at Londrina University Hospital from 2014 to 2016. Identification of the strains, as well as their antimicrobial sensitivity profile, was performed by automated methodology, Vitek®2 system (bioMeriéux-USA). Patient hospitalization data were collected through the systematic analysis of medical records and using the AGTA Healthcare system, LABHOS® module, from the laboratory of clinical analyzes, microbiology sector, of Londrina University Hospital. The study was approved by CEP / UEL with CAAE number: 78657317.0.0000.5231. We analyzed 13 medical records of patients whose etiological agent was OS-MRSA isolates isolated from blood and culture of quantitative tracheal secretion. Of these patients, 76.92% (10/13) evolved to death, eight of them due to the infectious process. All strains identified were phenotypically sensitive to oxacillin, but attested to the presence of the mecA gene by polymerase chain reaction analysis. Data from the CDC (Centers for Disease Control and Prevention) points out that in 2011, more than 80,000 invasive infections were caused by MRSA (Methicillin-resistant Staphylococcus aureus) in the USA and that 11,285 deaths were related to the pathogen.The high frequency of complicated infections caused by multiresistant bacteria, as well as the emergence of antimicrobial resistance mechanisms, limits the options for adequate therapy and causes an unfavorable outcome in the health of the patient. In this context, this study is important to draw the attention of clinicians to the phenomenon of OS-MRSA strains, which will assist in choosing an efficient antimicrobial treatment and favor the development of effective strategies to reduce cases with unsatisfactory results.