Impacto da introdução do sistema microbiológico automatizado Phoenix na evolução clínica das infecções de corrente sanguínea hospitalares por Enterobacteriaceae / Impact of the introduction of the Phoenix automated microbiology system on clinical outcomes of nosocomial bloodstream infections caused by Enterobacteriaceae

Luciana Azevedo Callefi

The family Enterobacteriaceae is an important cause of bloodstream infections (BSI). The increasing antimicrobial resistance is a complicating factor in treating these infections, thus the minimum inhibitory concentration (MIC) plays a key role in the analysis of susceptibility. Until August 2007, the antimicrobial susceptibility testing (AST) of blood cultures for Enterobacteriaceae were performed by disk diffusion method at Hospital Sao Paulo - UNIFESP. As of this date, the AST began to be performed through the Phoenix. automated microbiology system, which provides an approximated MIC by microdilution. Although the importance of MIC is well documented in studies with methicillin-resistant Staphylococcus aureus (MRSA), there is no study analyzing the impact of automated systems on clinical outcomes of these infections. Objectives: To compare the clinical outcomes of nosocomial BSI caused by Enterobacteriaceae during the non-automated versus automated period; to determine the prevalence of Enterobacteriaceae species causing BSI during the study period and analyze the factors associated with 14-day mortality. Method: This is a retrospective cohort study that evaluated nosocomial BSIs caused by Enterobacteriaceae in the periods non-automated (August 2006 to July 2007) and automated (August 2008 to July 2009) at Hospital Sao Paulo - UNIFESP. In the second part of the study, patients were realocated and divided into deaths and survivors within 14 days of diagnosis of infection to analyze the predictors of mortality. Results: We evaluated 90 and 106 patients in non-automated and automated periods, respectively. There was a male prevalence and the average age was 60 years in both periods. During the automated period, patients had higher APACHE II score (p <0.001), higher use of immunosuppressive drugs (p <0.001) and there was a greater incidence of central venous catheter-related BSI (p = 0.002). Klebsiella spp (36.6% and 43.3%) and Proteus spp (13.3% and 18.8%) respectively, during the non-automated and automated period were the most prevalent Enterobacteriaceae species. There was no significant difference regarding the adequacy of treatment (p = 0.45), clinical response (p = 0.75) and death . 7 days (p = 0.79), . 14 days (p = 0.94) and . 28 days (p = 0.12) between the periods. The predictors independently associated with mortality were septic shock (OR = 7.04; IC 95%= 2,92 . 17,01; p <0.001) and use of immunosuppressive therapy (OR = 2.23; IC 95%= 1,01 . 4,93; p = 0.01). Conclusion: The introduction of Phoenix. automated microbiology system showed no impact on clinical outcomes of bloodstream infections caused by Enterobacteriaceae. Klebsiella spp and Proteus spp were the most prevalent pathogens in both periods. Septic shock and the use of immunosuppressive drugs were the only factors associated with 14-day mortality among those patients.

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