New carbapenem-nonsusceptible Acinetobacter baumannii infections occur “almost exclusively” in patients who have stayed at least 1 night in a health care facility or have an indwelling device, according findings from a 4-year multisite surveillance project published in Emerging Infectious Diseases.
Findings from the Emerging Infections Program (EIP), a collaboration between the CDC and state health departments, also showed that carbapenem-resistant A. baumannii infections “might have plateaued,” researchers wrote.
According to the CDC, infections caused by Acinetobacter bacteria — ranging from pneumonia to serious blood or wound infections — are often resistant to common antibiotics and can cause outbreaks in ICUs and other health care settings where seriously ill patients are being treated, but rarely in the community.
baumannii is the most common bacterium in the genus, accounting for about 80% of all Acinetobacter infections, according to the CDC. Carbapenem-resistant A. baumannii, which landed a top spot on WHO’s first priority pathogens list, has been associated with death rates as high as 52%, researchers noted in the new study.
Using data from eight metropolitan surveillance sites in eight U.S. states from 2012 through 2015, the EIP researchers established an annual incidence of 1.2 cases of carbapenem-nonsusceptible A. baumannii infections per 100,000 people, which they described as “low.” In fact, incidence rates for carbapenem-nonsusceptible A. baumannii infections during the study were lower than those reported for carbapenem-resistant Enterobacteriaceae (CRE) in the same EIP catchment areas, and “substantially lower” than rates reported for MRSA and Clostridium difficile, although the reasons were unclear.
According to the researchers, yearly adjusted incidence rates for carbapenem-nonsusceptible A. baumannii infections “did not change significantly” from 2013 to 2015, and the percentage of Acinetobacter species that were resistant or nonsusceptible to carbapenems also declined, in contrast to reported increases before 2012.
“These data, along with data from the National Healthcare Safety Network, provide early evidence that carbapenem resistance among A. baumannii isolates might have plateaued, although additional years of surveillance in both systems are needed to confirm this observation,” the researchers wrote.
Among 598 cases that were analyzed from the eight sites in Colorado, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon and Tennessee, 98.7% of infections with carbapenem-resistant A. baumannii occurred in patients with overnight stays in a hospital during the preceding year, and 84.6% of infected patients had an indwelling device, such as a catheter. The researchers estimated the crude mortality rate at 17.9% — approximately double that for patients with CRE.
“For most cases, samples for culture were collected outside of short-stay acute-care hospitals, indicating that efforts to prevent transmission should include a variety of health care settings,” the researchers wrote. “These unique data, which include clinical data and isolate reports from a variety of health care settings and patients, highlight potential opportunities to reduce transmission.”
“Despite a currently low population-based incidence,” they concluded, “the medical complexity of carbapenem-nonsusceptible A. baumannii, along with treatment challenges posed by high levels of resistance to noncarbapenem antimicrobial drugs and high death rates, highlight the need for additional work in health care settings to contain carbapenem-nonsusceptible A. baumannii spread.” – by Gerard Gallagher
Disclosures: The authors report no relevant financial disclosures.