A new study of nursing home residents suggests that recent exposure to hospital-based antibiotics is associated with multidrug-resistant organism (MDRO) colonization and room contamination.
The study, published this week in JAMA Network Open, found that nearly 60% of 642 nursing home patients had received an antibiotic during hospitalization prior to study enrollment. In addition, many of these patients were prescribed an antibiotic that posed an increased risk for Clostridioides difficile infection (CDI), antibiotic resistance, or adverse events.
Those who had received antibiotics were more than 1.5 times as likely to be colonized with an MDRO or have an MDRO-contaminated room compared with patients who hadn't received antibiotics.
The study authors say the findings highlight high-risk antibiotic prescribing in nursing home residents as a target for antibiotic stewardship.
High-risk antibiotic exposure
In the study, which was a secondary analysis of data from a parent study of patients at six nursing homes in Michigan, researchers from the University of Michigan Medical School and the Veterans Affairs (VA) Ann Arbor Healthcare System collected data on antibiotic exposures prior to the parent study that were either associated with a hospitalization or were initiated during the patients' nursing home stay. The parent study was a longitudinal assessment of MDRO colonization in newly admitted nursing home patients.
The researchers defined antibiotics as high-risk if they predisposed patients to increased risk of CDI or if they fell into the "watch" or "reserve" antibiotic categories developed under the World Health Organization (WHO) AWaRe (Access, Watch, and Reserve) framework. Watch antibiotics are broad-spectrum, high-priority antibiotics with toxic effects or antibiotic resistance concerns, and reserve antibiotics are last-resort treatments for MDRO infections.
Using data from the parent study, the researchers then looked at MDRO colonization among patients and contamination of high-touch patient room environment sites within the nursing homes. To determine if pre-enrollment exposure to high-risk hospital antibiotics was associated with MDRO colonization and room contamination, the researchers conducted a multivariable logistic regression analysis.
Of the 642 patients in the study with data on antibiotic exposure (median age, 74.7 years, 57.5% female), 422 (65.7%) had antibiotic exposure prior to enrollment: 368 (57.3%) received 971 hospital-associated antibiotic prescriptions, and 119 (18.5%) received 198 nursing home-associated prescriptions. For antibiotics with documented indications, the most common indications were urinary tract infections (25.1%), skin and skin-structure infections (19.7%), and respiratory tract infections (16.1%).
Analysis of antibiotic classification showed that 283 patients (44.1%) received an antibiotic that increased the risk for CDI, and 322 (50.2%) received at least one watch or reserve antibiotic. High-risk, C diffogenic antibiotics and watch and reserve antibiotics were more prevalent among the hospital-associated prescriptions than the nursing home prescriptions.
Overall, 364 patients (56.7%) were colonized with an MDRO, and 437 (68.1%) patient room environments were contaminated with an MDRO upon enrollment in the study. The most common MDROs were vancomycin-resistant enterococci (VRE), resistant gram-negative bacilli (R-GNB), and methicillin-resistant Staphylococcus aureus (MRSA).
In multivariable analysis, pre-study enrollment exposure to antibiotics was positively associated with MDRO baseline colonization (odds ratio [OR], 1.70; 95% confidence interval [CI], 1.22 to 2.38) and MDRO environmental contamination (OR, 1.67; 95% CI, 1.17 to 2.39) compared with patients who had not been exposed to antibiotics.
In an exploratory analysis, the researchers found that exposure to a C diffogenic agent increased the risk for MDRO colonization (OR, 1.99; 95% CI, 1.33 to 2.96) and environmental contamination (OR, 1.86; 95% CI, 1.24 to 2.79). Similarly, exposure to watch or reserve antibiotics increased the effect size (MDRO colonization: OR, 2.32; 95% CI, 1.61 to 3.63; MDRO environmental contamination: OR, 1.86; 95% CI, 1.26 to 2.75)
Downstream impact on nursing homes
While high rates of antibiotic use in nursing home patients—and the risks it poses—are well established, the authors of the study say the results add to an emerging body of evidence that exposure to hospital antibiotics in this population can have a downstream impact on the burden of MDROs in nursing homes.
This is important because nursing home patients are often treated at multiple healthcare facilities and are commonly re-hospitalized, and they frequently receive antibiotics before being discharged back to nursing homes. That antibiotic exposure, the study suggests, increases the risk of these patients bringing dangerous pathogens back into the nursing homes and shedding those pathogens into the environment, where they can spread to other patients. Furthermore, certain types of antibiotics can exacerbate that risk.
"These findings support previous research demonstrating that antibiotics have both short- and long-term effects on the intestinal microbiota, which can lead to increased susceptibility to CDI, sepsis, colonization, and intestinal dominance with VRE and patient shedding onto their proximal environment," they wrote. "Furthermore, our work complements research illustrating that specific antibiotics may predispose patients to a heightened risk for adverse events, such as patient colonization, shedding, and infection."
The authors say these observations underscore the potential value of integrating hospital and nursing home antibiotic stewardship programs.
