Air conditioning and the ultra-sterile environment in places like hospitals may actually contribute to infections, say experts. Friendly bacteria found outdoors could be recruited to fend off the potentially deadly microbes that cause hospital-acquired infections, according to Jack Gilbert of Argonne National Laboratory in Chicago and head of the Earth Microbiome Project, a global database of microbial species, The Independent reported Monday. He said the idea is supported by a study showing that open windows influence the composition of microbial communities found on handles and surfaces, but did not increase the numbers of dangerous pathogens - the sort of antibiotic-resistant superbugs which infect patients. ‘Open windows let bacteria in from outside and you will either dilute out the pathogens, or you are not allowing the pathogens to establish themselves because there is too much competition for the nutrients and energy that the bacteria need to survive,’ Gilbert told the American Association for the Advancement of Science. ‘There’s a good bacterial community living in hospitals and if you try to wipe out that good bacterial community with sterilisation agents and excessive antibiotic use, you actually lay waste to this green field of protective layer and these bad bacteria can just jump in and start causing hospital-borne infections.’ Hospitals need to be clean but too much sterilisation may be counter-productive, which may explain why hospital infections can recur even under the most sterile circumstances, the newspaper quoted Gilbert as saying.