- Article
Comparison of Typical and Atypical Community Acquired Pneumonia Cases in Hospitalized Patients in Two Tertiary Centers in Riyadh, Saudi Arabia
- Abdullah Almufleh,
- Abdulrahman Altuwayjiri and
- Abdulmalik Alshehri
- + 3 authors
Background/Objectives: Community-acquired pneumonia (CAP) is classified into typical and atypical forms, with Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila being the most common atypical pathogens and Streptococcus pneumoniae and Haemophilus influenzae the most common typical organisms. This study aimed to compare the prevalence, demographics, and clinical outcomes of hospitalized typical and atypical CAP patients. Methods: A cross-sectional study was conducted from January 2016 to June 2022 at two tertiary hospitals in Riyadh, Saudi Arabia. All inpatients diagnosed with CAP by imaging and clinical findings were included, excluding viral cases. Outcomes measured included pathogen testing and identification, hospitalization duration, ICU stay, and in-hospital mortality. Results: Among 1238 CAP hospitalizations, 65% underwent molecular testing, with atypical pathogens detected in 17 cases (2.09%). Mycoplasma pneumoniae was the most common organism. The cases had an almost equal male-to-female ratio. Mean hospitalization was 12 days overall versus 4 days for atypical pneumonia. Of 265 ICU admissions, none tested positive for atypical CAP. Overall mortality was 6.94%, with no deaths in atypical pneumonia positive patients. Conclusions: PCR molecular testing was performed in 65% of patients hospitalized with CAP, and atypical pneumonia organisms were uncommon in these patients, with Mycoplasma pneumoniae being the most common. Clinical outcomes were more favorable for these patients. Expanding molecular testing may improve pathogen detection and guide target management.
13 December 2025





