Increased MDR Gram-Negative Bacteria Prevalence in US Nursing Homes Highlights Need to Enhance Infection Control

Researchers from Columbia University recently conducted a systematic review and meta-analysis to investigate the prevalence of multidrug-resistant organisms in US nursing homes. Their findings were published in the American Journal of Infection Control.

According to Nimalie Stone, MD, MS, Team Lead, LTC, Division of Healthcare Quality Promotion at the Centers for Disease Control and Prevention (CDC), many infrastructure gaps exist in US nursing homes, which has affected the quality of infection prevention and control in these facilities.

Now, researchers from Columbia University School of Nursing and the Department of Epidemiology at Mailman School of Public Health at Columbia University, and led by Sainfer Aliyu, MPhil, MSEd, MHPM, BSN, RN, analyzed the prevalence of multidrug-resistant gram-negative bacteria in nursing home residents across the country. According to the researchers, “To our knowledge, this is the first systematic review and meta-analysis to estimate the prevalence of [multidrug-resistant gram-negative bacteria] colonization among [nursing home] residents.”

Aliyu and colleagues used multiple databases to extract data collected between January 1, 2005 and February 28, 2016. The researchers chose to limit the review to studies published after 2005 “given the emergence of [multidrug-resistant gram-negative bacteria] in recent years.”

A total of 12 peer-reviewed studies were included in the systematic review (3 retrospective studies, 1 case-control study, 4 cross-sectional studies, and 4 prospective studies). The studies were limited to those which reported on adult patients and which were published in English in indexed journals. Criteria for inclusion focused on outcome measures, such as colonization and infection rates with multidrug-resistant gram-negative bacteria, as well as mortality rates associated with these infections. Patients were classified as “colonized” if swab samples from rectal, nasal, skin, throat, oropharyngeal, inguinal swabs, or wounds tested positive, while “infection” was characterized by positive samples collected from sputum, blood, and urine. Of the 12 studies included in the review, 1 “reported sputum and urine [samples] as both infection and colonization.”

The majority of the 12 studies were conducted within the United States, while the rest were from Korea, Italy, Singapore, and Germany. Eight of the reviewed studies reported on cases in more than 1 nursing home

No standard definition for multidrug-resistant gram-negative bacteria was provided across all 12 studies included in the systematic review. Eight of the 12 studies only included information on nursing home residents, while the rest included information on nursing home residents and other patients.

Among the reviewed studies, colonization prevalence of multidrug-resistant gram-negative bacteria “ranged from 11.2% to 59.1%,” with Escherichia coli “account[ing] for the highest proportion of isolates.”

Nine of the studies identified risk factors that were “previously shown to be associated with increased [multidrug-resistant gram-negative bacteria] colonization.” These included the following:

• Age and Gender
• Comorbid chronic diseases
• Advanced dementia
• History of recurrent hospitalization
• Frequent exposure to antimicrobials
• Delayed initiation of effective antibiotic therapy
• Residency in long-term-care facility

A total of 8 studies included in the systematic review were “eligible for meta-analysis… [which] represented data from 2720 [nursing home] residents.” The researchers found colonization prevalence to be 27% among all nursing home residents included in the meta-analysis. In addition, the researchers found a greater prevalence of colonization among those studies conducted within the United States as opposed to those conducted in Germany and Korea.

“Although study duration, study location, and sample size varied considerably among studies and might have contributed to differences between groups, the review provides important insights and meaningful themes [on the prevalence of multidrug-resistant organisms in US nursing homes],” the authors concluded.

Because of the high prevalence of colonization, the researchers believe that this “emphasizes the need to enhance policies for infection control and prevention in [nursing homes].” By identifying the prevalence of multidrug-resistant gram-negative bacteria in US nursing homes, these researchers are giving infection preventionists the means to “tailor efforts and stem future contaminations.”