A report published in CDC’s Morbidity and Mortality Weekly Report on August 4, 2023 linked a cluster of healthcare-associated infections to an Idaho hospital’s potable water system. According to the report, two patients who stayed in the same ICU room four months apart were found to be infected with carbapenemase-producing carbapenem-resistant Pseudomonas aeruginosa (CP-CRPA).
Carbapenem-resistant organisms, such as CRPA, are gram-negative bacteria resistant to the carbapenem class of antibiotics, a broad-spectrum antibiotic considered a “last resort.” Certain carbapenem-resistant organisms are resistant because they produce carbapenemase enzymes that make carbapenems ineffective. Infections from carbapenemase-producing organisms are difficult to treat and associated with high mortality. Pseudomonas aeruginosa can carry genes encoded with carbapenemases that can be transferred between strains and across bacterial species, leading to the spread of antibiotic resistance.
CP-CRPA infections are typically transmitted from person-to-person or acquired from environmental sources, like water, sink drains, and toilets.
Investigation and results
A collaborative investigation involving the Idaho Division of Public Health, the Idaho Bureau of Laboratories, the Utah Public Health Laboratory, and the CDC was undertaken to identify the cause of the infection.
The investigative team focused on the plumbing in the ICU room because Pseudomonas aeruginosa is known to persist in biofilm, a collection of microorganisms that adhere to one another and to a surface, such as a pipe. Water samples and swabs from two sinks and one toilet were collected.
CP-CRPA with the same gene type isolated in the patients was found in one of the sinks, including swab samples from the drain, p-trap (a bend in a sink drain that holds water to block sewer gases), and sink counter. Water samples from the same sink’s p-trap and a toilet also tested positive for a different strain of CP-CRPA.
Due to the genetic link between the patient isolate and sink isolate, the investigative team concluded that the most likely source of the outbreak was the ICU room sink.
Prevention and control measures
Upon identifying the sink as the likely infection source, suggested measures for prevention and control were immediately instituted. These included the application of biofilm disinfectants, a screening regimen for future patients occupying the room, and a commitment towards forwarding any CP-CRPA isolates to public health laboratories for detailed molecular profiling, prevention, and control.
On conducting a retest, no further CP-CRPA strains were detected in the environmental samples. As of December 2022, no additional CP-CRPA isolates have been reported by the hospital.
These findings underpin the important relationship between biofilm, building water systems, and healthcare-associated infections. Long-term strategies to control and prevent biofilm in plumbing systems, such as through continuous disinfection of the entire building water system, are crucial to reducing healthcare-associated infections and ensuring patient safety.
References
Centers for Disease Control and Prevention. (2023). Carbapenemase-Producing Organisms (CPO). Carbapenemase-Producing Organisms (CPO) 2023 Case Definition | CDC
Minnesota Department of Health. (2023). Carbapenem Resistant Pseudomonas aeruginosa (CRPA). Carbapenem Resistant Pseudomonas aeruginosa (CRPA) – MN Dept. of Health (state.mn.us)
Centers for Disease Control and Prevention. (2023). Cluster of Carbapenemase-Producing Carbapenem-Resistant Pseudomonas aeruginosa Among Patients in an Adult Intensive Care Unit. Morbidity and Mortality Weekly Report | CDC
