title: Carbapenemase-producingEnterobacteriaceae: Risk factors for infection and impact of resistance on outcomes.
abstract: BACKGROUND
  Carbapenemase-producingEnterobacteriaceae(CPE) have increased in recent years leading to limitations of treatment options. The present study was undertaken to detect CPE, risk factors for acquiring them and their impact on clinical outcomes.
  
  
  METHODS
  This retrospective observational study included 111 clinically significantEnterobacteriaceaeresistant to cephalosporins subclass III and exhibiting a positive modified Hodge test. Screening for carbapenemase production was done by phenotypic methods, and polymerase chain reaction was performed to detect genes encoding them. Retrospectively, the medical records of the patients were perused to assess risk factors for infections with CPE and their impact. The data collected were duration of hospital stay, Intensive Care Unit (ICU) stay, use of invasive devices, mechanical ventilation, the presence of comorbidities, and antimicrobial therapy. The outcome was followed up. Univariate and multivariate analysis of the data were performed using SPSS software.
  
  
  RESULTS
  Carbapenemase-encoding genes were detected in 67 isolates. The genes detected were New Delhi metallo-β-lactamase, Verona integron-encoded metallo-β-lactamase, and oxacillinase-181.Although univariate analysis identified risk factors associated with acquiring CPE infections as ICU stay (P= 0.021), mechanical ventilation (P= 0.013), indwelling device (P= 0.011), diabetes mellitus (P= 0.036), usage of multiple antimicrobial agents (P= 0.007), administration of carbapenems (P= 0.042), presence of focal infection or sepsis (P= 0.013), and surgical interventions (P= 0.016), multivariate analysis revealed that all these factors were insignificant. Mortality rate was 56.7% in patients with CPE infections. By both univariate and multivariate analysis of impact of the variables on mortality in these patients, the significant factors were mechanical ventilation (odds ratio [OR]: 0.141, 95% confidence interval [CI]: 0.024-0.812) and presence of indwelling invasive device (OR: 8.034; 95% CI: 2.060-31.335).
  
  
  CONCLUSIONS
  In this study, no specific factor was identified as an independent risk for acquisition of CPE infection. However, as it is evident by multivariate analysis, there is an increased risk of mortality in patients with CPE infections when they are ventilated and are supported by indwelling devices.
authors.affiliation: Department of Microbiology, Sri Ramachandra Medical College and Research Institute, Sri Ramachandra University, Porur, Chennai, India.
authors.forename: Shanthi
authors.initials: S
authors.lastname: Mariappan
authors.affiliation: Department of Microbiology, Sri Ramachandra Medical College and Research Institute, Sri Ramachandra University, Porur, Chennai, India.
authors.forename: Uma
authors.initials: U
authors.lastname: Sekar
authors.affiliation: Department of Molecular Biology, Central Leprosy Teaching and Research Institute, Chengalpattu, Tamil Nadu, India.
authors.forename: Arunagiri
authors.initials: A
authors.lastname: Kamalanathan
keywords: Carbapenemase; Enterobacteriaceae; outcomes; risk factors