Bacterial co-infections cause twofold increase in mortality in COVID patients: study

Though the COVID-19 pandemic appears to be ebbing significantly in the U.S., endemic COVID-19 still poses a challenge, experts say.

Last Friday saw 31,443 new cases of COVID-19, while 344 people died from the disease, according to the Johns Hopkins Coronavirus Resource Center.

Experts continue to measure the full effects of the pandemic. A study published last week in Influenza and Other Respiratory Viruses (IORV) found that bacterial infections resulting from COVID-19 resulted in a significantly increased chance of death, according to researchers with the Centers for Disease Control and Prevention (CDC).

“After adjustment for demographic factors and co-morbidities, bacterial infections in patients with COVID-19 within seven days of admission were associated with an adjusted relative risk of death 2.3 times that of patients with negative bacterial testing,” the study said.

But although patients with COVID-19 are at risk for bacterial infection, those co-infections remain relatively uncommon when compared to co-infections tied to influenza and RSV. Bacterial coinfections with COVID-19 occur in a small subset of patients, according to the study.

Researchers looked at 250 acute care hospitals across 99 counties in 14 states for incidence of bacterial and viral co-infections among 36,490 adult patients who’d tested positive for COVID-19 from March 2020 to April 2022.

“Staphylococcus aureus and Gram-negative rods were the most frequently isolated bacterial pathogens,” the study said. “Among hospitalized adults with COVID-19, 2,766 (7.6%) were tested for seven virus groups. A non-SARS-CoV-2 virus was identified in 0.9% of tested patients.”

In addition, the study found that 6% of patients with COVID-19 also had bacterial co-infections. The authors hypothesize that more severe COVID-19 could lead to more of what the authors call “ports of entry” in ICUs, such as intravenous lines that might facilitate bacterial infection that increase deaths among those tested for bacterial infection.

“However, even after excluding those with first positive cultures two days or more after ICU admission, an increased risk for death remained,” the study said. “Further studies are needed to untangle these interactions between pathogens and host to determine the role of bacterial infections in the natural history of COVID-19 and to understand to what extent bacterial infections may drive severe COVID-19 outcomes.”

The CDC researchers noted that their findings cannot be generalizable to all hospitalized COVID-19 patients in the U.S. because testing practices differ among healthcare facilities. In addition, the number of patients tested for bacterial infection decreased during the course of the pandemic as providers became more familiar with the epidemiological characteristics of SARS-CoV-2.

“The population that had bacterial cultures performed were likely more ill or inherently different from patients with COVID-19 who did not have bacterial cultures performed which may introduce confounding by indication, limiting the generalizability of the findings to all hospitalized adults with COVID-19,” the researchers wrote. “Incidental COVID-19 admissions were included in the analysis and may contribute to observed differences.”

Though bacterial infections of patients with COVID-19 occur relatively infrequently, when they do happen they significantly increase the chance of disease severity and death, the study says.

The CDC states that Staphylococcus aureus, or staph infection, most of the time doesn’t cause harm but can sometimes be fatal in a healthcare setting. While anybody can develop staph infections, “certain groups of people are at greater risk, including people with chronic conditions such as diabetes, cancer, vascular disease, eczema, lung disease, and people who inject drugs.”

The CDC study in IORV states that “as SARS-CoV-2 continues to circulate and individuals continue to be hospitalized for COVID-19, understanding risk factors for bacterial infections and associated outcomes can help guide clinicians in providing optimal care.”