New Delhi, Feb 14 : Despite rigorous cleaning, dangerous bacteria are lurking in hospital sink drains leading to a rise in "health-care-associated infections" (HAI), according to a study on Friday.

HAIs thrive in patients with weak immune systems, and in some hospitals due to poor adherence to hygiene protocols. These infections have become a growing problem worldwide, taking up an estimated 6 per cent of global hospital budgets, said the study.

Widely used antibiotics also contribute to the problem, selecting hardy, resistant strains of bacteria. When such resistance genes lie on mobile genetic elements, they can even jump between bacterial species, potentially leading to novel diseases.

"Here we show that hospital sink drains host bacterial populations that change over time, despite impeccable cleaning protocols in the particular hospital we looked at," said Dr. Margarita Gomila, Professor at the University of the Balearic Islands in Spain.

The study, pubished in the journal Frontiers in Microbiology, 'highlight that controlling bacterial growth in drains, and preventing colonisation by new strains of such hard-to-disinfect niches, is likely a global problem."

The team focussed on sink drains in a single modern university hospital on the island of Majorca, built in 2001 and managed by the health service of the Balearic Islands.

They found that the sinks and their drains are routinely cleaned with bleach, as well as disinfected with chemicals and pressurised steam every fortnight, or every month in non-patient areas. Once a year, drainpipes are hyperchlorinated at low temperature.

Yet they could identify 'a total of 67 different species from the drains'. "The greatest diversity occurred in general medicine and intensive care, while the fewest isolates were found in the microbiology laboratory'.

The newly opened intensive care unit also showed a high level of bacterial diversity, while six Stenotrophomonas species as well as Pseudomonas aeruginosa -- known to cause ventilator-associated pneumonia and sepsis, were found dominant across wards.

About 16 other Pseudomonas species -- also characterised by the WHO as one of the greatest threats to humans in terms of antibiotic resistance -- were also found at various times and in various wards. They were especially prominent in the short-stay ward, said the team.

Other notorious hospital-associated pathogens found repeatedly were Klebsiella pneumoniae in the general medicine ward, Acinetobacter johnsonii and Acinetobacter ursingii in general medicine and intensive care, Enterobacter mori and Enterobacter quasiroggenkampii in the short-stay ward, and Staphylococcus aureus in intensive care and haematology.

The researchers noted that as hospital drains can serve as reservoirs for both known and emerging pathogens, some of which exhibit strong antibiotic resistance, it is essential to study the source of these bacteria and their routes of transmission.

/IANS