Nurses Most Likely to Spread Microbes, Says Study

If infection preventionists want to find the source of a pathogenic outbreak in a hospital setting due to poor hand hygiene compliance (HHC), look first at the nurses. According to a study in BMC Infectious Diseases nurses are much more likely to be super spreaders of microbes that are primarily spread by hand. Investigators with the University of Twente, Enschede, the Netherlands, said in so many words that nurses are more likely to be super spreaders of pathogens because they work so hard; they’re all over the place, moving from patient room to patient room and throughout wards. The study calls this the spatiotemporal method in which data are collected across space and time.

The space in this case was the University Medical Center Groningen (UMCG), a hospital in the Netherlands with more than 10,000 employees and 1400 beds. And the time was one week; between April 2 and April 8, 2018. The data were collected from wards treating patients with stomach, gut and liver problems. The method of collection was Radio Frequency Identification (RDIF), a contact tracing method that monitors the whereabouts of health care equipment, workers, and patients. The data were divided into 2 categories: data collected weekdays from 7 a.m. to 5 p.m., and data collected evenings from 5 p.m. to 7 a.m., and on the weekends.

“A guideline to identify super spreaders is to identify the 20% of the people contributing to at least 80% of the transmission potential,” the study states. “We define the transmission potential as the number of 30-s intervals (contact moment) of contact with other HCWs [health care workers] or patients. The transmission potential is estimated for all HCW occupation groups and compared to identify disproportionality and thus potential super-spreaders.”

Investigators note that the majority of health care-acquired infections (HAIs) in hospitals are Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa or Enterobacter spp. Investigators defined a contact as the physical meeting of two HCWs or a HCW and a patient. “For example, if an HCW enters a patient room, then the HCW and the patient are assumed to be in contact with each other for the time over which they co-occur in that room,” the study states.

Seven HCW categories were tracked: doctor, nurse, cleaner, department assistant, department co-assistant, consultant, and feeding assistant. “Nurses and doctors were together responsible for 81.13% and 80.19% of all contacts and time spent in contact, respectively,” the study states. “Nurses made up 70.68% and 68.06% of these percentages, five times more than the second higher HCW occupation group, doctor (10.44 and 12.13%). Therefore, a colonized nurse has a disproportionately high potential of transmitting an HMO [harmful microorganism] based on the amount of contact and time spent with HCWs or patients. For these reasons, we investigate the nurse HCW occupation group as potential super-spreaders in this study.”

They concluded that nurses are the HCWs most likely to be super spreaders because their duties require them to cover the most ground and interact with the most fellow HCWs and patients.

“The expected number of transmissions caused by a colonized nurse increases exponentially as the level of hand hygiene compliance (HHC) deteriorates or the transmission probability increases,” the study states. “These results are due to the spatiotemporal behavior and social mixing patterns of HCWs.”

It comes down to hand hygiene compliance, and investigators noticed that might depend on the workload at a particular moment, and that HHC might deteriorate from 50% to 25% during busy times. The possible transmission rates of harmful pathogens are higher weeknights and weekends, the study states according to its simulation results.

“An explanation is that HCWs spent more time with fewer HCWs or patients during weeknights and weekends but had more contact moments for every minute spent colonized,” the study states. “An increase in the time that a super-spreader navigates through the hospital ward results in an increase in the number of encountered HCWs or patients, allowing for more opportunity to transmit the HMO.”

Investigators propose that their simulation models can be used in educating nurses and other healthcare professionals about how best to maintain good hand hygiene, and also inform where best to put alcohol-based hand disinfectants.

“The performed simulations increase our insight into the consequences of varying levels of adherence to spatiotemporally specific health care policies such as hand hygiene compliance,” the study states. “The simulations further show that a change in spatiotemporal movement and social mixing patterns of health care workers will affect the expected number of transmissions in a closed health care setting.”