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Multidrug-resistant Serratia marcescens bacteriuria related to urologic instrumentation
Abstract:
An outbreak of urinary tract infections caused by multidrug-resistant Serratia marcescens lasted for 12 months and was found to be related to urologic instrumentation. Thirty-four patients had primary infections; four had cross-infections. Only six patients had indwelling bladder catheters. The median interval between instrumentation and initial isolation of Serratia was six days. Seventy-three percent of patients were symptomatic, two were bacteremic. No common instruments, personnel, or wards were identified, and environmental cultures failed to reveal the epidemic strain of Serratia. The outbreak ended when the instrument disinfectant was changed. Serotyping was identical in nine of ten isolates. Intraspecies conjugation demonstrated resistance transfer of gentamicin, tobramycin, carbenicillin, chloramphenicol, and co-trimoxazole. The enzyme 6'-N-acetyl transferase was responsible for gentamicin-inactivation in patient isolates and a transconjugate. Although no significant spread of this multidrug-resistance plasmid to other Enterobacteriaceae occurred in the hospital, two instances of apparent in vivo transfer to other bladder organisms occurred.
Insights
A 12-month outbreak of multidrug-resistant Serratia marcescens urinary tract infections linked to urologic instrumentation ended after changing instrument disinfectant. Resistance genes were transferable, highlighting infection control challenges.
Area of Science:
- Infectious Diseases
- Microbiology
- Hospital Epidemiology
Background:
- Urinary tract infections (UTIs) pose a significant healthcare challenge, particularly when caused by multidrug-resistant organisms.
- Serratia marcescens is an opportunistic pathogen frequently associated with healthcare-associated infections.
- Urologic instrumentation is a known risk factor for UTIs.
Purpose of the Study:
- To investigate a prolonged outbreak of multidrug-resistant Serratia marcescens UTIs.
- To identify the source and transmission dynamics of the outbreak.
- To understand the mechanisms of multidrug resistance in the epidemic strain.
Main Methods:
- Retrospective analysis of patient data during a 12-month outbreak.
- Microbiological investigation including cultures and serotyping of Serratia marcescens isolates.
- Plasmid analysis and conjugation experiments to assess resistance transfer.
Main Results:
- Thirty-eight patients were infected with multidrug-resistant Serratia marcescens, primarily associated with urologic instrumentation.
- The outbreak ceased following a change in the instrument disinfectant.
- Serotyping confirmed the clonal nature of the outbreak isolates, and conjugation studies demonstrated the transferability of resistance genes, including those for gentamicin, tobramycin, carbenicillin, chloramphenicol, and co-trimoxazole.
Conclusions:
- Urologic instrumentation was the likely source of the multidrug-resistant Serratia marcescens outbreak.
- Changes in instrument disinfectant protocols are crucial for controlling such outbreaks.
- The transferable nature of resistance genes underscores the need for vigilant infection control measures against multidrug-resistant bacteria.