Study Finds Concerns Regarding Macrolide-resistant S. Pneumoniae

A recent study found that approximately 40% of Streptococcus pneumoniae (S. pneumoniae) infections in the United States are macrolide-resistant strains.

The analysis included isolates from 3626 patients with S. pneumoniae blood or respiratory infections between October 2018 and September 2019 from 329 US health care facilities.

The study, published in Open Forum Infectious Diseases, found that macrolide resistance varied by region; however it was greater than 25% in most areas and 39.5% overall. The research also found resistance was more common in ambulatory patients (45.3%) than inpatients (37.8%) and in respiratory isolates (47.3%) than blood isolates (29.5%).

The Infectious Diseases Society of American and the American Thoracic Society recommends that macrolide antibiotics are only used to treat community-acquired bacterial pneumonia (CABP) if macrolide resistance is less than 25%. The CDC has designated drug-resistant S. pneumoniae as a serious threat.

“Our data support the need for ongoing surveillance of CAP epidemiology and resistance profiles. These efforts are particularly important given changes in azithromycin prescriptions during the coronavirus disease 2019 pandemic,” the study authors wrote.

Regions of the United States with the highest rates of macrolide resistance were the West North Central Region (54.2%) and the South Atlantic (48%). Regions with macrolide resistances rates less than 25% were Mountain (13.9%), New England (18.2%), and Pacific (18.3%); however, resistance in respiratory isolates was 25% or greater in all of those regions.

The study results were “neither new nor surprising, but very much deserve repeating,” Daniel M. Musher, MD, FIDSA, of Baylor College of Medicine and the Michael E. DeBakey Veterans Affairs Medical Center in Houston, wrote in an associated commentary.

Musher recommended amoxicillin for healthy adults and amoxicillin/clavulanic acid in older adults with comorbid conditions and noted that 2 new drugs, lefamulin and omadacycline have been approved.

Lefamulin was approved in August 2019 and is the first systemic pleuromutilin antibiotic available for human use. Omadacycline is a tetracycline that was approved in October 2018.

“In summary, Gupta et al give us good reason not to treat outpatient pneumonia empirically with a macrolide,” Musher wrote. “My choice remains a beta-lactam, but fluoroquinolones are effective, and two new drugs are now available for consideration.”

The study authors concluded that surveillance is vital to track ongoing macrolide resistance.

“Our findings document the high rates of macrolide-resistant S. pneumoniae throughout the United States and suggest that, in most parts of the country, clinicians should consider alternatives to macrolide monotherapy as empiric therapy for suspected CAP. Ongoing surveillance efforts are required to track trends in resistance,” the study authors wrote.