Some nursing home facilities prescribe antibiotics more often than others, which is tied to increased health risks, even for residents who don’t receive the medications, according to a new study.

About two-thirds of nursing home residents receive antibiotic treatment of some kind each year. Prescribing the drugs inappropriately increases the risk of medication reactions, allergies, diarrhea and infections by antibiotic-resistant bacteria, the authors write in JAMA Internal Medicine.

“Wherever antibiotic prescriptions have been systematically audited, be it in acute care hospitals, long term care settings or in community clinics, there has been a consistent finding that one-third to one-half of antibiotic treatments are unnecessary or inappropriate,” said lead author Dr. Nick Daneman of the Sunnybrook Health Sciences Center at the University of Toronto.

“Appropriate antibiotic prescribing may be a particular challenge in the nursing home, though, because histories are difficult to obtain from patients with cognitive impairment, elderly patients often have infection with atypical symptoms such as absence of fever, and there is less access to on-site doctors and laboratory testing,” Daneman told Reuters Health by email.

The researchers used population-level administrative databases in Ontario to link antibiotic prescriptions among all users of Ontario’s universal single-payer health care system with a registry of continuing care residents, a drug benefit program database, health insurance plan database and emergency room visit and hospitalization databases.

Between 2010 and 2011, more than 110,000 people over age 66 lived in an Ontario nursing home. Multiplying the number of residents by the number of days the study covered, the researchers found that for every 1,000 days each resident spent in a nursing home, they were prescribed antibiotics on 55 of those days, on average.

That number varied by facility from 20 days to almost 193 days per 1,000 resident-days.

The researchers divided the 607 total nursing home facilities into three groups: low use, medium use and high use, based on how often they prescribed antibiotics.

High-use facilities tended to be smaller, more rural and more often had for-profit ownership.

Among residents who received the antibiotics, 14 percent of those in high-use facilities experienced an adverse reaction like allergy or diarrhea, compared to 13.5 percent in medium-use facilities and 12.9 percent in low-use facilities.

Those who did not receive the antibiotics were also at a higher risk for antibiotic-resistant infections such as Clostridium difficile, or “C. diff,” in high-use facilities.

Most often, residents were prescribed penicillin, which can treat Listeria or Staph infections, or fluoroquinolones, which are often prescribed to treat hospital-acquired infections that may be resistant to other treatment.

“It is fascinating that this risk extends both to the residents treated with antibiotics, but also to the residents that never directly received an antibiotic during the study,” Daneman said. “This makes sense, though, because many of the harms of antibiotics can be transmitted to neighbouring and future patients.”

Antibiotic stewardship programs - multidisciplinary teams working to optimize antibiotic treatment to maximize the benefits of these medications while limiting their harms - are becoming more common in acute care hospitals, but are still rare in nursing homes, he said.

Older people are particularly high risk because of frailty and less ability to “bounce back” from an adverse event, he added.

Infections can also be harder to diagnose among older adults, as they present with different symptoms than in younger people.

“The easy solution is then to just give a prescription,” said Dr. Lona Mody of the University of Michigan Medical School in Ann Arbor, who coauthored an editorial accompanying the study.

“Second, early evaluation is often performed by front line staff followed by a telephone conversation with the prescriber who is often off-site and unable to personally evaluate the elderly patient before prescribing antibiotics,” Mody told Reuters Health by email.

Urinary tract infections are the most overdiagnosed infection, Mody said.

“Antibiotic stewardship should be a shared concern of not only healthcare workers but also patients and their families,” Daneman said. “Family members and patients should be aware that more antibiotic use is not always better, and should ask their doctor to make sure the treatments are needed, chosen appropriately, and prescribed for the necessary length of time.”