Background: Adult community-acquired pneumonia is the most common cause of hospitalization and a leading cause of death. Identification of microorganisms causing community-acquired pneumonia.
Materials and Methods: A cross-sectional design was used. Information on adults hospitalized due to pneumonia in the cold seasons of 2018 and 2019 was collected. Results of microbiologic tests, other than serology and urinary antigen, were reviewed
Results: 205 patients had eligible criteria. The mean age was 52.4 and 62% were male. Microorganisms were identified in 117 (57%) patients. The most common etiologic agents were Influenza H1N1 2009 (n=39, 33.4%), Tuberculosis (n=21, 17.9%), Non-Albicans Candida Yeast (n=9, 7.8%), Methicillin Resistant Staphylococcus Epidermis (n=7, 6%) and Klebsiella Pneumonia (n=5, 4.3%). Streptococcus Pneumoniae had the 6^th rank (n=3, 2.6%). A higher body mass index was associated with superimposed infections.  10 of 18 (56%) patients who died in hospital, got definite microbiologic diagnoses. The maximum mortality was due to staphylococci, with methicillin-resistant strains of Staphylococcus aureus (n=2, 66%) and Staphylococcus epidermis (n=2, 29%).
Conclusion: H1N1 2009 was the first cause. Tuberculosis with rising incidence could cause acute pneumonia. Pneumococcal incidence had declined. Community-acquired staphylococcal pneumonia is the most dangerous; hence, specific protocol-based treatments should be applied promptly. Community-acquired Staphylococcus epidermis and Tuberculosis must be included in differential diagnosis of the disease. Antibiotics need to be individualized in managing the obese patients. A special focus on the epidemiology of virulence factors of Klebsiella pneumoniae is needed as it is common, severe, and lethal.