Macrolides Still Best Choice for Treating Mycoplasma pneumoniae

The large majority of cases of Mycoplasma pneumoniae infection in the United States remain sensitive to macrolide antibiotics, but resistance may be increasingly common, according to data from an epidemiologic study published online July 15 and in the August issue of Emerging Infectious Diseases.

Macrolide-resistant M. pneumoniae (MRMP) has become prevalent in Asia and is now also being reported in Europe. It was first identified in North America in 2008, but its prevalence is unclear, as there is no ongoing organized surveillance.

Investigators led by Xiaotian Zheng, MD, PhD, associate professor of Pathology at the Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, Illinois, studied 91 M. pneumoniae–positive specimens collected between 2012 and 2014 in six US cities (Chicago, Illinois; Kansas City, Missouri; Hackensack, New Jersey; New York City; Seattle, Washington; and Birmingham, Alabama). The specimens came from patients aged 10 months to 66 years, although most were aged 18 years or younger.

Polymerase chain reaction assays, subculturing, and DNA sequencing to identify point mutations known to confer macrolide resistance showed that 13.2% of the specimens had a high level of resistance to these antimicrobial agents. This prevalence of MRMP exceeds the 8% to 12% prevalence reported in North America in earlier years.

Neither patient age nor type of specimen was significantly correlated with macrolide resistance.

Antimicrobial susceptibility testing confirmed that macrolide-resistant isolates had a high erythromycin minimal inhibitory concentration, whereas macrolide-susceptible isolates had a low one. In contrast, all isolates had low minimal inhibitory concentrations when tested with tetracycline and with levofloxacin.

"Although our study has confirmed MRMP in 6 geographically diverse US states, macrolides should remain the drugs of choice in children with M. pneumoniae respiratory infections," the investigators recommend. "Clinicians should be vigilant for macrolide treatment failures and consider using alternative drugs if necessary."

They continue, "Given the common use of macrolides in the United States to treat pediatric respiratory infections, judicious use of antimicrobial drugs should be emphasized. Reevaluation of existing classes and investigation of new classes of antimicrobial agents may be prudent to have additional treatment alternatives for MRMP infections beyond tetracyclines and fluoroquinolones. Surveillance for this resistance in the United States will help monitor the trend."

Additional study findings showed that in a third of the 80 respiratory specimens having data on coinfections, a viral pathogen was detected along with M. pneumoniae. "A viral co-infection rate >30% supports the use of multiplex testing for viral and bacterial pathogens in children with respiratory infections of uncertain etiology," the investigators maintain.

The authors have disclosed no relevant financial relationships.

Emerg Infect Dis. Published online July 15, 2015. Full text

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