Mycoplasma pneumoniae immunoglobulin M (IgM) antibody-secreting cells (ASCs) were successfully used to differentiate patients with M pneumoniae infection from carriers in a pediatric population, according to study results published in The American Journal of Respiratory and Critical Care Medicine.

Pharyngeal swabs and whole blood from pediatric patients with community-acquired pneumonia (CAP) were compared with swabs and blood from controls including both siblings of patients with CAP, because of their higher chance of being asymptomatic carriers, and healthy children. M pneumoniae-DNA from pharyngeal swabs was analyzed by polymerase chain reaction (PCR), while blood was analyzed for M pneumoniae-IgM-ASCs by enzyme-linked immunospot (ELISpot) assay.

The study cohort consisted of 152 patients with CAP and 156 controls. M pneumoniae-DNA was detected by PCR in 29% of patients with CAP and in 8% of controls (P <.001).

In a subgroup of patients with CAP, M pneumoniae-DNA was detected by PCR in 51%, 46% of whom showed positive responses in the M pneumoniae-IgM-ASC ELISpot assay (P <.722). Among controls, M pneumoniae-DNA was detected by PCR in 48% of children. However, all of these tested negative for M pneumoniae-IgM-ASCs (P <.001).

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“In this longitudinal observational study, the measurement of [M pneumoniae]-IgM-ASCs by ELISpot assay allowed a differentiation between infection and carriage,” the researchers wrote. “The inclusion of asymptomatic carriers in our study was essential to assess the usefulness of [M pneumoniae]-IgM-ASC detection as a diagnostic test that can distinguish between carriage and infection.”

Reference

Meyer Sauteur PM, Seiler M, Trück J, et al. Diagnosis of Mycoplasma pneumoniae pneumonia with measurement of specific antibody-secreting cells [published online June 28, 2019]. Am J Respir Crit Care Med. doi:10.1164/rccm.201904-0860LE