Growing concerns over drug-resistant bacteria spreading through hospital plumbing

When people visit hospitals, they expect treatment to improve their health, not to leave with new infections. However, healthcare-associated infections (HAIs) are an escalating global issue, accounting for approximately 6% of hospital budgets worldwide. In the European Union alone, HAIs result in over 3.5 million cases each year, leading to 2.5 million disability-adjusted life years, costing up to €24 billion, and contributing to 90,000 deaths. They are even the sixth leading cause of death in the United States.

A recent study has revealed that hospital sink drains can harbor dangerous bacteria, including antibiotic-resistant strains. Despite rigorous cleaning efforts, these bacteria persist and spread, endangering vulnerable patients. According to a SciTechDaily report, some strains are even resistant to last-resort antibiotics, making them a serious public health concern.

HAIs primarily affect patients with weakened immune systems and hospitals with insufficient hygiene measures. The excessive use of antibiotics in healthcare facilities further exacerbates the problem, encouraging the survival of resistant bacteria. These bacteria can transfer resistance genes to other species, increasing the likelihood of new and more dangerous infections.

“Hospital sink drains host bacterial populations that change over time, despite impeccable cleaning protocols,” stated Dr. Margarita Gomila, a professor at the University of the Balearic Islands in Spain and senior author of a study published in Frontiers in Microbiology.

Her research underscores the global challenge of preventing bacterial growth in drains and stopping the colonization of new, hard-to-eliminate strains.

Gomila and her team examined sink drains in a modern university hospital on the Spanish island of Mallorca, which has state-of-the-art cleaning protocols. The sinks and drains undergo regular disinfection with bleach, specialized chemicals, and pressurized steam, either every two weeks or monthly, depending on the area. Additionally, the drainpipes are hyperchlorinated annually.

Between February 2022 and February 2023, researchers collected bacterial samples from 30 drains in various wards, including intensive care, hematology, short stays, general medicine, and a microbiology lab. They cultivated bacteria from these samples and identified 1,058 isolates using DNA barcoding and mass spectrometry. Furthermore, they tested 219 isolates for antibiotic resistance.

The study identified 67 bacterial species in the drains. The diversity fluctuated over time without a clear seasonal pattern. The highest bacterial diversity was found in general medicine and intensive care, while the microbiology lab had the least. Surprisingly, a newly opened intensive care unit exhibited bacterial diversity levels comparable to older wards within a short period.

Dangerous Pathogens Identified

Among the most prevalent bacteria were six Stenotrophomonas species and Pseudomonas aeruginosa, a pathogen associated with ventilator-associated pneumonia and sepsis. The WHO classifies P. aeruginosa as one of the most concerning antibiotic-resistant threats to human health. Researchers also identified 16 other Pseudomonas species, particularly in the short-stay ward.

Other problematic hospital-associated pathogens included Klebsiella pneumoniae in general medicine, Acinetobacter johnsonii and Acinetobacter ursingii in intensive care, Enterobacter mori and Enterobacter quasiroggenkampii in the short-stay ward, and Staphylococcus aureus in hematology and intensive care.

“The bacteria found may come from multiple sources, including patients, medical staff, and the hospital environment. Once established in sink drains, they can spread, posing severe risks to immunocompromised patients,” said Gomila.

Antibiotic Resistance: A Growing Threat

Several species identified in the study belong to the ESKAPE group of bacteria, notorious for their resistance to multiple antibiotics and their ability to thrive in hospital environments.

The study found that 21% of P. aeruginosa isolates were resistant to at least one class of antibiotics. Additionally, multiple Klebsiella and Enterobacter strains exhibited resistance to third-generation cephalosporins, although they remained susceptible to carbapenems, which are commonly used against multidrug-resistant infections.

Alarmingly, the blaVIM gene, which confers resistance even to carbapenems, was detected sporadically in P. aeruginosa strains from intensive care, general medicine, and short-stay wards.

The study concludes that hospital sink drains serve as reservoirs for both known and emerging pathogens, some of which display significant antibiotic resistance.

“Regular cleaning is essential, especially in wards where controlling bacterial spread is critical. However, understanding the sources of these bacteria and their transmission pathways is crucial for effective infection control,” emphasized José Laço, a PhD student in Gomila’s laboratory.

By Nazrin Sadigova