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P1 type 1 genotype, MLVA type 4/5/7/2 predominate CAP cases
Among patients hospitalized with community-acquired pneumonia, the P1 type 1 genotype and MLVA type 4/5/7/2 were the most prevalent, but the proportion of these types varied between pediatric and adult patients, according to recent data from the Etiology of Pneumonia in the Community, or EPIC, study.
In addition, the variation in strain types did not appear to impact clinical outcomes among patients, researchers said, and macrolide resistance was rare.
Kathryn M. Edwards, MD, of Vanderbilt University, and colleagues characterized 216 Mycoplasma pneumoniae isolates from a population of hospitalized children and adults with radiographically confirmed community-acquired pneumonia (CAP). The patients were enrolled in the EPIC study between January 2010 and June 2012 at eight hospitals in Chicago, Memphis and Nashville, Tennessee, and Salt Lake City. The researchers analyzed nasopharyngeal and oropharyngeal swabs from all patients using P1 typing, multi-locus variable-number tandem-repeat analysis (MLVA) and macrolide susceptibility genotyping.
Kathryn M. Edwards
Of the M. pneumoniae-positive specimens, 18.5% were isolated from adults; the remainder were from children. According to the researchers, the dissemination of the P1 genotypes varied between patients. Type 1 accounted for the majority of isolates, with 64.3% of detections in adult patients and 84.4% in children. Type 2 accounted for 35.7% of detections in adults and 12.9% in children (P < .01). The researchers also identified four variant strains (2.3%) among children, and P1 type distribution varied across sites.
MLVA type 4/5/7/2 was most prevalent at each site throughout the study period, except among adults in Chicago, where type 3/5/6/2 also was prevalent. Seven (3.5%) specimens exhibited a macrolide-resistant genotype; five of which were collected from patients who recently had undergone macrolide therapy.
Notably, there were no significant variations in clinical characteristics among patients with different strain types, or between macrolide-resistant vs. macrolide-sensitive M. pneumoniae.
“This study provides a deeper understanding of M. pneumoniae biology, molecular epidemiology, and macrolide resistance among patients hospitalized with CAP,” the researchers wrote. “Further investigation is warranted to understand the biological and epidemiological reasons that may explain the differences in distribution of M. pneumoniae types between adult and pediatric populations.” – by Jen Byrne
Disclosure: Edwards reports receiving grants from CDC during the conduct of the study and receiving grants from Novartis and funding for service on a data and safety monitoring board from Novartis outside the submitted work. Please see the full study for a list of all other authors’ relevant financial disclosures.