May 13, 2015
2 min read

MDR gram-negative bacteria spreads within, between nursing homes

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Multidrug-resistant gram-negative bacteria in patients with severe dementia spread within and between nursing homes, according to results from the SPREAD study recently published in Infection Control and Hospital Epidemiology.

To assess the extent of MDR gram-negative bacteria in nursing home populations, researchers examined patient demographics and rectal swab cultures collected every 3 months for 1 year or death to determine the bacteria’s molecular epidemiology and characteristics. One hundred and ninety MDR gram-negative bacteria isolates collected from 152 patients across 22 nursing homes were analyzed using pulsed-field gel electrophoresis. Study participants, aged 65 years or older, had advanced dementia and were living in a nursing home for more than 30 days.

Researchers identified genetically related strains in 82% nursing homes. Mean colonization among the homes was 35%, ranging from 0% to 86%. In three nursing homes, more than half of the strains were clonally related.

“The extent of cross-transmission varied among different nursing homes,” Erika M.C. D’Agata, MD, MPH, from the division of infectious diseases at Rhode Island Hospital, and colleagues wrote. “The reasons are likely multifactorial and may include varying rates of compliance with hand hygiene, number of health care workers, and use of antimicrobials.”

Multiple colonizing strains were detected among 18.4% of patients, including 24 patients with two species and four patients with three species. The investigators wrote that this may have indicated a need to screen patients for more than a single species of MDR gram-negative bacteria.

Of the isolates, 88.4% were resistant to three antimicrobials or antimicrobial classes, 10.5% were resistant to four, and 1% were resistant to five. The most common MDR gram-negative bacteria species were Escherichia coli (42.6%)and Proteus mirabilis (32.6%).

These findings followed previously reported data that showed 46% of 362 nursing home residents with advanced dementia were colonized with least one species of MDR gram-negative bacteria, and 36% contracted at least one species within 1 year. Data from the SPREAD trial suggested that patients from different nursing homes may have contracted MDR gram-negative bacteria strains from each other during overlapping hospital stays or from health care workers visiting multiple sites, the researchers wrote.

“Ongoing efforts to curb the acquisition and spread of MDR [gram-negative bacteria] among residents of nursing homes, especially those with advanced dementia, are crucial,” D’Agata and colleagues concluded. – by Stephanie Viguers

Disclosure: The researchers report no relevant financial disclosures.