Severity of Lower Respiratory Tract Infections in School-age Children is Associated with Mycoplasma Pneumoniae Genotype

Background: Mycoplasma pneumoniae (MP) can be categorized into two genotypes, P1 type 1 (MP1) and P1 type 2 (MP2), based on the DNA sequence of the P1 adhesion protein. It remains unknown if clinical manifestations of lower respiratory tract infections (LRTI) in children differ between the two genotypes.

Objective: To determine if MP genotype is associated with disease severity of LRTI in preschool and school-age children.

Methods: Medical charts of children (≤ 15 years-old) with signs of LRTI who tested positive for MP by PCR from pharyngeal swabs in 2014 were analysed. We used a culture and pyrosequencing approach for genotyping PCR-positive samples. We compared epidemiological and clinical data of children infected with either MP1 or MP2 divided in two age groups, ≤ 5 year-olds and 5-15 year-olds.

Results: Among 5-15 year-olds, 208 patients were infected with MP1 (mean age 8.6 yrs, 46% boys) and 69 with MP2 (mean age 8.3 yrs, 59% boys). MP2 infected children presented with higher median baseline CRP level (16 vs 28 mg/L, p=.006) and were admitted to the hospital more often (22.6% vs 34.8%, p=0.045). There was no difference in the requirement for oxygen treatment (40.4% vs. 33.3%) or in the average duration of hospital stay (2.7 days vs 2.3 days) between hospitalised patients. No intensive care treatment was required in either group. No group differences in clinical data were observed among ≤ 5 year-olds.

Conclusion: In contrast to previous smaller studies, the data from our large cohort indicate that MP genotype could influence the severity of LRTI in school-age children. Patients infected with MP2 in this age group presented with a higher median baseline CRP level and a higher rate of hospital admission.