Serratia marcescens from a Neonatal Intensive care Unit at Siriraj Hospital : pulsotyping and antimicrobial susceptibility test

Abstract

Serratia marcescens is one of the important causative agents of nosocomial infections, particularly in critically ill neonates and immunocompromised patients. During the 4 months of specimen collection (May to August, 2000) in the Neonatal Intensive Care Unit (NICU), it was found that there were 36 out of 104 neonatal patients (34.62%) who had S. marcescens isolates in their throat swabs, tracheal secretion, urine and swabs from set of drugs mixture for inhalation. The organisms were also isolated from environments in the same patient unit. The environmental specimens included swabs from sinks, normal saline for wiping eyes/mouth and drugs mixture for inhalation. S. marcescens isolates from 10 patients admitted in the other different wards also included in this study. One hundred and twenty-five S. marcescens isolates were discriminated into 10 antimicrobial susceptibility patterns (antibiograms) and 12 pulsotypes. The isolates in NICU were in only 2 pulsotypes; A and B Except for one type B isolate, all the isolates were type A. The 10 isolates from the other different wards were 10 different pulsotypes; C, D, E, F, G, H, I, J, K, and L. The results from antimicrobial susceptility test indicated that most of the isolates were resistant to beta lactam antibiotics including third generation cephalosporins. It could be concluded that there was an outbreak of S. marcescens pulsotype A colonization in NICU during the time of study and the isolates resisted to most of the antimicrobial agents used in the treatment of the gram negative bacteria at Siriraj Hospital.