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Pseudomonas in the sinks in an intensive care unit: relation to patients
Abstract:
Sink drains in a medical-surgical intensive care unit (ICU) were cultured during six consecutive weeks as part of a seven month prospective study of acquisition of Pseudomonas aeruginosa by ICU patients. Isolates were typed serologically and by aminoglycoside and chlorhexidine susceptibility patterns. All 11 sinks contained multiple strains of P aeruginosa; some strains persisted for weeks while others were isolated once. Of the sink isolates 56% had high level resistance to gentamicin and tobramycin whereas none of the strains found in patients. In sink isolates chlorhexidine resistance correlated with aminoglycoside resistance and with the presence of a chlorhexidine dispenser at a sink. The sequence of recovery of phenotypically similar isolates suggested that sinks were the source of at most two acquisitions of P aeruginosa by patients during the six weeks. Our study confirms that sinks may be reservoirs for large numbers of highly resistant P aeruginosa but are rarely the source of organisms colonising patients in our ICU.
Insights
Hospital sink drains rarely transmit Pseudomonas aeruginosa to patients in intensive care units (ICUs). While sinks harbor resistant strains, they are not a common source of patient infections.
Area of Science:
- Infectious Diseases
- Microbiology
- Hospital Epidemiology
Background:
- Sink drains in intensive care units (ICUs) can potentially harbor and disseminate microorganisms.
- Pseudomonas aeruginosa is an opportunistic pathogen frequently associated with healthcare-associated infections.
Purpose of the Study:
- To investigate the role of sink drains as a reservoir for Pseudomonas aeruginosa acquisition by patients in a medical-surgical ICU.
- To determine the prevalence and characteristics of P. aeruginosa strains isolated from sink drains and compare them to patient isolates.
Main Methods:
- Prospective study over seven months, with sink drain cultures performed weekly for six consecutive weeks.
- Isolates were characterized using serological typing and antimicrobial susceptibility testing (gentamicin, tobramycin, chlorhexidine).
- Phenotypic similarity and recovery sequences were analyzed to infer potential transmission events.
Main Results:
- All 11 sinks cultured yielded multiple P. aeruginosa strains, with some persisting for weeks.
- 56% of sink isolates exhibited high-level resistance to gentamicin and tobramycin, unlike patient strains.
- Chlorhexidine resistance in sink isolates correlated with aminoglycoside resistance and the presence of chlorhexidine dispensers.
- Sink drains were implicated as the source of at most two P. aeruginosa acquisitions by patients during the six-week sampling period.
Conclusions:
- Sink drains can serve as reservoirs for a high number of multidrug-resistant P. aeruginosa.
- Despite harboring resistant strains, sink drains are an infrequent source of P. aeruginosa colonization in ICU patients.
- Environmental cleaning and antimicrobial stewardship are crucial for controlling P. aeruginosa in ICUs.