Epidemiology of extended spectrum β-lactamase producing Enterobacter bacteremia in a Brazilian hospital Epidemiologia de bacteremia causadas por Enterobacter produtores de β-lactamases de espectro estendido em um hospital brasileiro

Introduction: Enterobacter can be included in the group of extended spectrum β-lactamases (EBSL)-producing bacteria, though few studies exist evaluating risk factors associated with this microorganism. A retrospective cohort study was conducted to determine risk factors associated with ESBL-producing-Enterobacter and mortality. Methods: A retrospective cohort study with 58 bacteremia caused by ESBL-producing-Enterobacter (28 cases) and non-ESBL (30 cases). Results: Risk factors associated with ESBL-Enterobacter were trauma, length of hospitalization, admission to the intensive care unit, urinary catheter and elective surgery (p< 0.05). The survival curves were similar for ESBL and non-ESBL. Conclusions: ESBLproducing-Enterobacter bacteremia is prevalent and the survival curve was similar to non-ESBL-producing strains. Key-words: Extended spectrum β-lactamases. Enterobacter. Bacteremia. RESUMO Introdução: Enterobacter pode ser incluído no grupo de bactérias produtoras de β-lactamases de espectro estendido (ESBL), mas existem poucos estudos avaliando fatores de risco para ESBL. Nós realizamos uma coorte retrospective para determiner fatores de risco associados com Enterobacter produtores de ESBL. Métodos: Uma coorte retrospectiva com 58 bacteremias por Enterobacter ESBL (28 casos) e não-ESBL (30 casos). Resultados: Fatores de risco para ESBL-Enterobacter foram trauma, tempo de internação, admissão em UTI, sonda vesical e cirurgia eletiva (p<0.05). A mortalidade foi similar entre ESBL e não-ESBL. Conclusões: Enterobacter produtor de ESBL é prevalente e a curva de mortalidade foi semelhante com o grupo não-ESBL. Palavras-chaves: β-lactamases de espectro estendido. Enterobacter. Bacteremia. Infections caused by extended spectrum β-lactamases (ESBL) producing bacteria has increased mortality in hospitalized patients1. Invasive procedures, admission to intensive care units and previous use of antibiotics are the most common risk factors for ESBLproducing bacteria2. Enterobacter is a microorganism associated with Amp-C gene resistance that confers resistance to third generation cephalosporins. However, our group has observed a progressive decrease in susceptibility to fourth generation cephalosporin in our institution, suggesting the increase of ESBL-producing strains. Enterobacter can be included in the group of EBSL-producing bacteria, though few studies exist evaluating risk factors associated with this microorganism. Even though the treatment of infections caused by ESBL strains is the same for non-ESBL Enterobacter, we believe that certain clinical and/or laboratorial findings or previous antibiotic use could be risk factors for ESBL-producing Enterobacter. Thus, a retrospective cohort study was conducted to determine risk factors associated with ESBL strains of Enterobacter sp. The retrospective cohort study was conducted at the Hospital Universitario Evangelico de Curitiba. This center is a 660-bed tertiary hospital in Curitiba, a City located in southern Brazil. From January 2006 to January 2009, 884 bacteremia were identified (excluding coagulase negative Staphylococcus) and 58 (6.5%) were caused by Enterobacter sp. All the patients with bacteremia caused by Enterobacter were included only once using data from the first bacteremia. Only patients older than 12 years of age were evaluated. Cultures were collected according to the standard protocol used in the hospital and were processed using the BACT/Alert® (bioMerieux, Durham, USA). Enterobacter was identified using biochemical analysis3. Susceptibility testing was performed by the disk diffusion method, in accordance with CLSI guidelines, and ESBL was defined using cefepime with amoxicillin/clavulanate disk approximation method4. The following variables were evaluated for each patient: sex; age; previous hospital admission within the preceding 90 days; admission to the intensive care unit; length of hospitalization before bacteremia; use of mechanical ventilation, central venous line, urinary catheter and surgery during the current hospitalization; underlying conditions, such as diabetes mellitus, chronic renal failure, heart failure, cancer; acute renal failure trauma and previous antibiotic use during current hospitalization; previous colonization by Enterobacter. The following laboratorial results were evaluated on the day of diagnosis: hemoglobin, leukocyte, platelet counts, sodium, potassium, creatinine, urea, total billirubin and partial pressure of oxygen from arterial blood. Thirty-day and in-hospital mortality were registered. Antibiotic treatment was classified as adequate or inadequate. Treatment of each patient was considered adequate if Enterobacter was susceptible to the antibiotic used during bacteremia and treatment was initiated within the first 48 hours of bacteremia diagnosis. For ESBL strains, the only antibiotic considered adequate was carbapenem. Patients with ESBL-producing Enterobacter bacteremia were compared with patients with non-ESBL bacteremia to determine