A study published in the Christmas edition of The BMJ reveals that healthcare workers can rest assured that coffee machines in hospitals are not responsible for the spread of diseases, and a general ban does not appear to be necessary.
To eliminate hospital-acquired (nosocomial) infections, various objects have been examined as breeding grounds for bacteria, including doctors‘ ties and even hospital Bibles.
Although hospital coffee machines are regularly touched with bare hands, the potential of hospital coffee machines as a source of infection has not been explored until now.
To address this issue, researchers in Germany examined the microbial population in healthcare coffee machines, focusing on the disease-causing pathogens classified as „ESKAPE“ by the World Health Organization (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species).
These bacteria pose an increasing threat as they are resistant to many antibiotics and can lead to deadly bloodstream or catheter-associated infections.
From October 31 to December 31, 2022, the researchers examined a total of 25 coffee machines, including fully automatic machines, capsule machines (e.g. Nespresso), and espresso machines.
Seventeen were from break rooms and offices of the Department of Anesthesiology and Intensive Care at a university hospital and the Institute of Medical Microbiology, Immunology, and Hygiene, both in Cologne. Eight more were in employees‘ homes.
All coffee machines had been in use for at least a year and none had been specifically cleaned prior to sampling. There were no current outbreaks at any of the sites at the time of sampling.
Each coffee machine was swabbed at five designated points of the machine: the drip tray, the outlet, the buttons, the water tank handle, and the inside of the water tank.
Species from cultures were identified using spectrometry. Typical pathogens were categorized as „medically relevant“ and commensals as „atypical pathogens“ and distinguished by Gram type: positive or negative (the latter have an outer membrane that supports antibiotic resistance).
Not surprisingly, microbial growth was detected on each coffee machine, and machines in hospitals were roughly three times as heavily colonized (360 strains were isolated from 72 positive swabs) as home machines (135 strains were isolated from 34 positive swabs).
The majority of detected species were commensals (bacteria living on the skin or in the intestines and pose no health threat). Only a few medically relevant and no antibiotic-resistant pathogens were identified.
Of the eight species of medically relevant gram-negative species, 81% were found in hospital coffee machines, mainly from drip trays, outlets, and water tank handles, highlighting the need to adhere to hand hygiene protocols.
Staphylococcus aureus was the only potentially gram-positive disease-causing species collected: once on the buttons of a home coffee machine and once on the inside of a water tank in the hospital, suggesting that the users‘ hands themselves unlikely parts of the machines, according to the authors‘ notice.
„To our great relief, a general ban on coffee machines does not appear necessary despite the possibility of pathogens emerging in nosocomial outbreaks,“ they write. Furthermore, the study is said to have led to extensive cleaning measures.
They add, „Our thoughts now turn to tea-drinking nations. Are tea pots, kettles, and hot water outlets similar breeding grounds for bacteria? Do the high temperatures in the pots suffice to kill off all potential pathogens? And what about the handles?“
Walker, SV, et al. (2023). Käfer im Becher: Übertragen Krankenhauskaffeemaschinen Krankheitserreger? BMJ. doi.org/10.1136/bmj.p2564.