Clinical significance of different bacterial load of Mycoplasma pneumoniae in patients with Mycoplasma pneumoniae pneumonia.

OBJECTIVE This retrospective study was conducted to investigate the clinical significance of different Mycoplasma pneumoniae bacterial load in patients with M. pneumoniae pneumonia (MP) in children. METHODS Patients with MP (n=511) were identified at the Children's Hospital Affiliated to Soochow University database during an outbreak of MP between January 2012 and February 2013. RESULTS Comparing patients with high and low bacterial load those with higher loads were significantly older (p<0.01) and had fever significantly more frequently (p=0.01). Presence of wheezing at presentation was associated with low bacterial load (p=0.03). Baseline positive IgM was present in 93 (56.4%) patients with high bacterial load compared to 46 (27.8%) patients with low bacterial load (p<0.001). Co-infection with viruses was found significantly more frequent among patients with low bacterial load (24.2%) than those with high bacterial load (8.5%) [p<0.001]. Bacterial co-infection was also more frequently detected among patients with low bacterial load (22.4%) than in those with high bacterial load (12.1%) [p=0.01]. CONCLUSION M. pneumoniae at a high bacterial load could be an etiologic agent of respiratory tract disease, whereas the etiologic role of MP at a low bacterial load remains to be determined.