Outbreaks of Serratia marcescens bacteriuria in a neurosurgical intensive care unit of a tertiary care teaching hospital: a clinical, epidemiologic, and laboratory perspective

Abstract

Background: Serratia marcescens is an aerobic gram-negative bacillus belonging to the family Enterobacteriacea. Infections caused by S marcescens may be difficult to treat because of their resistance to a variety of antibiotics, including beta-lactams and aminoglycosides.

Methods: This study aimed to (1) identify the risk factors associated with the development of Serratia marcescens bacteriuria in neurosurgical intensive care units (NSICU); (2) genotype the pathogens to determine the source of infection; (3) compare these results with antibiograms; and (4) determine and implement appropriate control measures. A retrospective case-control study of the epidemiologic data, the surveillance of environmental cultures, and the genotyping of strains using arbitrarily primed polymerase chain reaction (AP-PCR) were performed at a 750-bed, tertiary care teaching hospital. Seventy-four bacteriuria patients were compared with 74 age/sex-matched control patients in the NSICU between March 2002 and March 2004. The factors assessed were patient demographics; duration of hospital stay; duration of indwelling catheter use before and during stay in the NSICU; chronic underlying illnesses (diabetes mellitus, cardiovascular disease, malignancy); other sites of infection; history of trauma; exposure to a nasogastric tube; mechanical ventilation; urinary catheterization; central venous catheterization; surgical drainage; tracheostomy; brain or spine surgery; and receipt of total parenteral nutrition (TPN), antimicrobials (beta-lactams, aminoglycosides, quinolones, carbapenems, vancomycins), or steroids.

Results: Patients with S marcescens bacteriuria were more likely to have a longer NSICU stay and other sites of infection. Environmental surveillance showed the handling of urine jugs to be the point source of contamination. Genotyping and antibiograms of 14 patients were the same except for those of 2 patients.

Conclusion: The patient-related risk factors were identified, and a rapid identification of the organism was made. Heightened surveillance, infection control measures, and empiric therapy led to improved methods for handling urine jugs, which terminated the outbreak.