University of Maryland School of Medicine researchers identify which victims of gun violence are at greater risk for infection.

A new study from researchers at the University of Maryland School of Medicine (UMSOM) found that bacterial infections develop in approximately 5 percent of adults hospitalized with firearm injuries, with most infections occurring during the initial hospitalization rather than after patients return home. The findings were published Aug. 3 in JAMA Network Open as a research letter.

Firearm injuries are a major public health concern in the United States, but relatively little research has examined the infectious complications that can occur after treatment. To better understand these risks, researchers analyzed data from 24,024 adults hospitalized with firearm injuries at 323 hospitals across the country between January 2019 and May 2021.

The study found that 1,236 patients—about 5 percent—developed a bacterial infection. Most cases occurred during the initial hospitalization, with only 1.3 percent occurring during the 90-day follow-up period. Researchers also found that patients who underwent surgeries involving the head, neck, spine, liver, or lower abdomen faced the highest risk of developing bacterial infections.

"In our study, we used a large observational dataset to understand who is more likely to develop a bacterial infection after being shot with a gun," said Jonathan D. Baghdadi, MD, PhD, senior author of the study and an Associate Professor of Epidemiology and Public Health at UMSOM. "Firearm injury is a recognized risk for bacterial infection, but no large studies have described how often they occur and which patients are most at risk."

Dr. Baghdadi and his team believe this is the largest analysis to date of bacterial infection patterns among hospitalized firearm injury patients in the United States. They also found that antibiotic exposure among patients who did not develop infections was generally low, which is reassuring and reflects current clinical recommendations to limit preventive antibiotic use in many firearm injury cases for patients without a bacterial infection.

Among patients who developed infections, the most commonly identified pathogens were Escherichia coli, Staphylococcus aureus, and enterococci.

The researchers found that patients who required surgical procedures involving the head, neck, spine, or lower abdomen were especially vulnerable to infection. At the same time, the study found that bacterial infection was not independently linked to a higher risk of death among patients who survived at least one night in the hospital.

The authors note that the research relied on administrative hospital data and that complete follow-up information may not have been available for every patient. Nonetheless, the large national dataset provided an opportunity to evaluate infection risk across a broad and diverse patient population.

"Recovery from firearm injuries can be complicated. Although our study focused on mortality, infections can impact recovery in multiple ways, contributing to long-term pain and disability." Dr. Baghdadi said. "By identifying the patients most likely to develop these complications, we hope this work contributes to more informed clinical decision-making and ultimately better outcomes for patients."

Baghdadi hopes that by developing a definition to identify patients with bacterial infection after firearm injury using observational and administrative datasets and then demonstrating how to apply it, other researchers will use the approach to run studies targeting more specific clinical questions.

"This study provides important information on the risk factors for infection amongst individuals admitted for a firearm-related injury to US hospitals. Most notably, it identifies individuals undergoing head, neck and/or spine surgery as having the highest risk of both early and late infections, underscoring the importance of close monitoring for this vulnerable population,” said study co-author Melike Harfouche, MD, MPH, Associate Professor of Surgery at UMSOM and a surgeon at the University of Maryland Medical Center.

About the University of Maryland School of Medicine

Now in its third century, the University of Maryland School of Medicine was chartered in 1807 as the first public medical school in the United States. It continues today as one of the fastest growing, top-tier biomedical research enterprises in the world, with 46 academic departments, centers, institutes, and programs, and a faculty of more than 3,000 physicians, scientists, and allied health professionals.