Recent data showed that Acinetobacter baumannii and Pseudomonas aeruginosa — both of which landed the top spots on WHO’s list of “priority pathogens” in critical need of new therapies — were significantly more prevalent among patients hospitalized with carbapenem-resistant infections in the United States than the Enterobacteriaceae pathogens Escherichia coli and Klebsiella pneumoniae.
According to Bin Cai, MD, MPH, MS, PhD, senior director at Shionogi Inc., a pharmaceutical company headquartered in Osaka, Japan, and colleagues, recent infection control measures addressing the substantial increase in carbapenem-resistant (CR) infections over the past decade have largely focused on preventing the spread of CR Enterobacteriaceae (CRE). However, the researchers noted that the frequency of other CR gram-negative pathogens, A. baumannii and P. aeruginosa, has also increased in recent years. Despite this, A. baumannii and P. aeruginosa were not “well appreciated” as a source of resistance transmission until WHO recognized them as equally concerning to public health earlier this year.
During a recent study, the researchers examined data from the Premier Healthcare database to determine the prevalence of four CR organisms — E. coli, K. pneumoniae, P. aeruginosa and A. baumannii — in 206 acute-care hospitals in the United States.
“Unlike the CDC and other datasets that focus on hospital-acquired infections, the Premier Healthcare database includes both hospital-acquired and community-onset infections, many of which are health care related, thus better representing the full disease burden related to CR infections in U.S. hospitals,” the researchers wrote.
From 2009 to 2013, Cai and colleagues identified 292,742 infections caused by the four gram-negative pathogens, 4.5% (n = 13,262) of which were CR. More than 80% of these CR infections were caused by A. baumannii (22%) or P. aeruginosa (60.3%), whereas just 17.7% were caused by K. pneumoniae or E. coli.
“These data for the United States are in sharp contrast to most reports from Europe and Latin America where CREs are predominant,” the researchers noted.
Despite being more likely to receive more than one systemic antibiotic, patients with CR infections had longer hospital and ICU stays compared with patients with carbapenem-susceptible infections, except for those with respiratory infections caused by A. baumannii. In addition, in-hospital mortality was more common among most cohorts with CR infections, particularly for those with CR bloodstream (adjusted OR = 2.46) or respiratory infections (aOR = 1.27) caused by A. baumannii.
Additional analyses showed that CR rates varied by region, underscoring the importance of basing infection control measures on local epidemiology, according to the researchers. For example, CR infections caused by K. pneumoniae and E. coli (33.1%) were highest in the Middle Atlantic region. Meanwhile, the New England region reported a higher proportion of CR infections caused by P. aeruginosa (85%).
Although the study focused on the four most common gram-negative pathogens, Cai and colleagues noted that other nonfermenters such as Stenotrophomas maltophilia may represent another important source of CR infections.
“Since patients with CR infections had longer hospital and ICU stays, more antibiotic treatments and a higher mortality rate, the CR infections likely represent a higher cost burden to the health care system,” they concluded. “The development of new antibiotics should not only address CREs, but more importantly CR P. aeruginosa and A. baumannii.” – by Stephanie Viguers
Disclosure: Cai and four other authors report being full-time employees of Shionogi. Please see the study for all other authors’ relevant financial disclosures.