First reported nosocomial outbreak of Serratia marcescens harboring blaIMP-4 and blaVIM-2 in a neonatal intensive care unit in Cairo, Egypt

Abstract

Introduction: Serratia marcescens is a significant hospital-acquired pathogen, and many outbreaks of S. marcescens infection have been reported in neonates. We report a sudden breakout of S. marcescens harboring the blaIMP-4 and blaVIM-2 metallo-β-lactamase (MBL) genes that occurred from March to August 2015 in the neonatal intensive care unit of Cairo University Hospital, Cairo, Egypt. Methods: During the study period, 40 nonduplicate clinical isolates of S. marcescens were collected from blood culture samples. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to identify each isolate. Then, minimum inhibitory concentrations of different antibiotics were assessed by the Vitek 2 compact system. Screening of the MBL genes blaIMP, blaVIM, blaSIM-1, blaSPM-1, and blaGIM-1 as well as the carbapenemase genes KPC, NDM, OXA-48, SME-1, and SME-2 were evaluated. Pulsed field gel electrophoresis was preformed to detect the genetic relationship of the isolates. Results: Analysis showed that 37.5% of the S. marcescens clinical isolates were resistant to meropenem (minimum inhibitory concentrations ≥ 2 µg/mL), and blaIMP-4 and blaVIM-2 were the most prevalent MBL genes (42.5% and 37.5%, respectively). None of the other investigated genes were observed. Pulsed field gel electrophoresis typing revealed two discrete clones; 33/40 (82.5%) were pulsotype A and 7/40 (17.5%) were pulsotype B. Conclusion: Here, we report for the first time the detection of MBL-producing S. marcescens isolates, particularly IMP-4 and VIM-2 recovered from inpatients with bacteremias from the intensive care unit at Cairo University Hospital.