Bug in a Mug: Are Hospital Coffee Machines Transmitting Pathogens?

Coffee is a popular stimulant among healthcare workers, and coffee machines in break rooms and homes are frequently touched by bare hands. The World Health Organization recommends eliminating any potential vector in the transmission of nosocomial infections, and the search for hazards within hospitals is ongoing. Personal objects and doctors’ attire have been investigated as transmission sources for pathogenic bacteria, leading to the nationwide ban on wearing ties in UK hospitals. However, the coffee maker, household appliances, and hospital staff’s hands are known sources of spreading pathogens, increasing risks for nosocomial outbreaks, increased morbidity and mortality, and financial burden on the healthcare system. A study assessed the microbial population in healthcare-associated coffee machines, focusing on WHO’s high priority “ESKAPE” pathogens, which pose an increasing threat due to possible nosocomial transmission and infections, such as fatal bloodstream or catheter-associated infections.

From October to December 2022, 25 coffee makers were swabbed with their owners’ consent, spanning a range of fully automatic, capsule, and espresso machines. Seventeen were from break rooms and offices at a university hospital’s department of anaesthesiology and intensive care medicine and the Institute for Medical Microbiology, Immunology, and Hygiene in Cologne, Germany, while eight were in staff members’ homes. All coffee makers had been in use for at least a year, and none was specially cleaned before sampling.

The study found 360 strains of micro-organisms isolated from 72 positive swabs from the drip tray, outlet, buttons, handle of the water tank, and inside of the water tank. The micro-organisms were classified into two categories: “medically relevant/typical pathogens,” consisting of species on WHO’s high priority list plus typical pathogens responsible for most nosocomial infections; and “atypical pathogens/commensals.” All species defined as high risk pathogens were tested for antimicrobial susceptibility.

Among the eight genera of “medically relevant” Gram negative species detected, 81% were found in coffee makers at the hospital. In total, 72% of all cultivated Gram negative isolates (148/209)—“medically relevant” and “commensals” combined—derived from hospital-based coffee makers.

Microbial growth was detected on every coffee machine, but few medically relevant and no multiresistant pathogens were identified, excluding any potential resistance against standard antibiotics used to treat severe infections. The majority of cultivated species were commensals or atypical pathogens. Hospital-based machines were about three times as heavily colonised by bacterial species as those at home, reflecting transmission from the hands operating these machines—and only family members at home.

Gram negative pathogens and commensal species were common, with potential medically relevant Gram negative species predominantly detected on the drip tray and water tank handle. However, only one isolate of each of those pathogens—E coli, K pneumoniae, and P aeruginosa—was cultivated, even though they are the predominant Gram negative nosocomial pathogens. S aureus was cultivated only twice, indicating either impeded colonisation on coffee makers or consistent compliance with hand disinfection protocols.

To our great relief, despite their potential for pathogen origins in nosocomial outbreaks, a general ban on coffee makers doesn’t seem necessary. Commensal species—the majority of detected species—are of no concern and are expected. The finding of medically relevant species emphasizes the necessity of following WHO’s Five Moments for Hand Hygiene, which considerably reduces the risk of transmission.

Read More @ BMJ

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