Bacterial Co-infection Rates in Mycoplasma Pneumoniae Community-Acquired Pneumonia
Bacterial co-infection occurs in approximately 2-10% of patients with Mycoplasma pneumoniae community-acquired pneumonia, with Streptococcus pneumoniae being the predominant co-pathogen.
Co-infection Prevalence
The frequency of bacterial co-infection with Mycoplasma pneumoniae varies based on diagnostic methods and population studied:
In hospitalized children, bacterial co-infection with M. pneumoniae pneumonia occurs in approximately 2% of cases based on a large retrospective study of 8,612 children, with S. pneumoniae identified in 56.2% of these co-infections 1
In adult populations, the American Thoracic Society guidelines report that atypical pathogen co-infection (including M. pneumoniae with bacterial pathogens) ranges from 3% to 40% depending on diagnostic criteria used, though the clinical significance of serologic diagnoses remains uncertain 2
European guidelines indicate that mixed infections involving bacteria with atypical organisms occur in 29% of polymicrobial CAP cases, with the most frequent combination being S. pneumoniae with C. pneumoniae (15%), though specific M. pneumoniae co-infection rates are lower 2
Most Common Co-pathogens
When bacterial co-infection does occur with M. pneumoniae:
S. pneumoniae is the predominant bacterial co-pathogen, accounting for 56-63% of identified bacterial co-infections 1, 2
H. influenzae represents the second most common co-pathogen 2
Mixed viral-bacterial infections with M. pneumoniae occur in approximately 10% of polymicrobial cases 2
Important Clinical Caveats
Diagnostic limitations significantly affect reported rates:
Most co-infection data derives from serologic testing showing fourfold titer rises, which may not represent true concurrent infection versus sequential infection or cross-reactivity 2
The distinction between M. pneumoniae causing initial infection that predisposes to secondary bacterial infection versus true simultaneous co-infection remains uncertain 2
Blood cultures are positive in only 13.6% of bacterial pneumonia cases, limiting definitive bacterial diagnosis 3
Age-related patterns:
In children aged 5 years and older, M. pneumoniae accounts for 4-39% of CAP cases, with co-infection rates appearing lower in pediatric populations compared to mixed bacterial-viral infections 2
In adults, M. pneumoniae represents 13-37% of outpatient CAP when serologic testing is performed, with the highest co-infection rates (up to 10.2%) reported in Chinese adult populations 2, 4
The conservative clinical estimate for true bacterial co-infection with M. pneumoniae pneumonia is 2-10%, though this likely underestimates the actual rate due to diagnostic limitations 1, 2.