Association of doxycycline treatment with time to first documented MP-RNA negative conversion in pediatric Mycoplasma pneumoniae pneumonia: a retrospective cohort study.

BACKGROUND

Macrolide-resistant Mycoplasma pneumoniae (MRMP) complicates the treatment of pediatric M. pneumoniae pneumonia (MPP). We evaluated whether treatment with doxycycline, compared with azithromycin, was associated with faster first documented negative conversion of M. pneumoniae RNA (MP-RNA) and clinical recovery during a period of high macrolide resistance prevalence.

METHODS

This retrospective cohort study included 137 children hospitalized with MPP between October 2023 and January 2025 who received azithromycin (n = 90) or doxycycline (n = 47) monotherapy initiated on admission. MP-RNA was monitored using simultaneous amplification and testing. The primary endpoint was the time from the first antibiotic dose to first documented MP-RNA negative conversion. Multivariable Cox regression, propensity score overlap weighting, and an approximate interval-censored Weibull accelerated failure time model were used.

RESULTS

The doxycycline group was older and had greater baseline disease severity. The median time to first documented MP-RNA negative conversion was shorter with doxycycline than with azithromycin (6.0 vs. 10.0 days; P < 0.001). Doxycycline use was associated with faster negative conversion in the multivariable Cox model (summary HR 9.28, 95% CI 5.02-17.17; P < 0.001). After overlap weighting, 19 of 20 covariates met the balance threshold, although residual age imbalance remained (absolute SMD = 0.164); the association persisted (summary HR 8.08, 95% CI 4.27-15.31; P < 0.001). The interval-censored model yielded a time ratio of 0.60 (95% CI 0.53-0.67; P < 0.001). The 24-hour rapid defervescence rate was 89.4% with doxycycline and 37.8% with azithromycin (risk difference 51.6%, 95% CI 36.3%-63.4%). No severe treatment-limiting adverse events were documented. Among 24 doxycycline-treated children aged < 8 years, no tooth discoloration or enamel hypoplasia was reported during follow-up, although dental assessment was not standardized.

CONCLUSIONS

Doxycycline use was associated with faster first documented MP-RNA negative conversion and clinical recovery than azithromycin. These retrospective, nonrandomized findings do not establish causal superiority. Doxycycline may be considered when macrolide resistance is confirmed or strongly suspected, but prospective multicenter studies are required.