Joint research by Wageningen University Department Animal Sciences and Central Veterinary Institute shows that transmission of pathogens can occur over short distances without direct contact between the hosts.
It was deduced that it takes the bacteria several days to bridge this short distance. Thus creating the opportunity to interrupt this transmission by repeated cleaning of the environment.
In an experiment with broilers inoculated with the bacteria Campylobacter jejuni and Escherichia coli, it became clear that these bacteria could be transported over short distances to spatially separated susceptible recipients. However, it was observed that it took several days before birds in the separated group got infected.
A large difference was seen between the two bacterium species in the time needed to bridge a small distance of 75 cm: 15 days for Campylobacter jejuni and 4 days for Escherichia coli. This difference occurred although both bacteria started at the same time from the same source. The researchers were able to show that the difference in bridging time is caused by the difference in mortality during the transport in the environment. From these calculations it was also possible to obtain the traveling time of the bacteria in the environment.
For disease control measures against indirect transmission it is important to take into account that the pathogens are already in the environment for days before they cause infection. Regular cleaning of the direct environment of infected and recipient individuals should therefore be effective to prevent new infections.
With the help of groups working on human infections from Chicago and Utrecht the calculation method was then applied to data obtained from the transmission of vancomycin-resistant enterococci in an intensive care unit. It was clear that also in this case the time needed to bridge a short distance played a role in the transmission of the bacteria. The effect of this indirect transmission over a short distance disappeared when the environment was cleaned repeatedly.
These results suggest that the calculation method developed can be an important instrument to study the effect of cleaning the environment in order to control infections.