Objective: To probe into the correlation between sputum bacterial load and disease severity in children with Chlamydia trachomatis pneumonia. Methods: C. trachomatis DNA was quantitatively detected by fluorescence quantitative polymerase chain reaction (PCR) sputum from 147 children with C. trachomatis pneumonia. The 147 cases were classified into low load group (<104/mL)

medium load group (from 104 to 106/mL) and high load group (>106/mL). Differences of clinical symptoms

results of chest radiography

duration of mechanical ventilation and length of stay were compared among different groups. Chest radiography were reviewed two weeks after discharge and compared with the results of chest radiography during hospitalization. Results: There was statistically significant difference in the time of shortness of breath among the high load group

the medium load group and the low load group (P<0.01)

yet there was no statistically significant difference between the medium load group and the low load group (P>0.05). There were statistically significant differences in the duration of fever between the high load group and the medium load group (P<0.05)

the high load group and low load group (P<0.01)

yet there was no statistically significant difference between the medium load group and the low load group (P>0.05). There was statistically significant difference in the results of chest radiography among the high load group

the medium load group and the low load group (P<0.05)

yet there was no statistically significant difference between the medium load group and the low load group (P>0.05). There was statistically significant difference in the length of stay among the high load group

the medium load group and the low load group (P<0.001)

yet there was no statistically significant difference between the medium load group and the low load group (P>0.05). There was no significant difference in the duration of mechanical ventilation and number of fever among three groups (P>0.05). After two weeks

the recovery of chest radiography was good

and there was no significant difference among three groups (P>0.05). Conclusion: There is a correlation between the sputum bacterial load of C. trachomatis pneumonia after a certain amount and the clinical characteristics of the child such as time of shortness of breath

duration of fever

severity of chest radiography

and length of hospital stay

but the prognosis is better.