Etiology and antibiotic resistance patterns in adults with severe community-acquired pneumonia in Russia

Background: Severe community-acquired pneumonia (SCAP) is distinguished by high mortality and socio-economic burden. Both etiology and antimicrobial resistance (AMR) are essential for appropriate antibiotic choice. We aimed to study etiology of SCAP in adults and determine AMR among common pathogens. Materials and Methods: A prospective cohort study recruited adults with SCAP admitted to multi-ward hospitals in 2014-2018. Etiology was confirmed by blood, respiratory culture, urinary antigen tests (L.pneumophila, S.pneumoniae);PCR for identification of M.pneumoniae, C.pneumoniae and 15 respiratory viruses was applied. AMR was determined according to national guidelines. Results: Altogether 109 patients (60.6% male; mean age 50.8 ± 18.0 years old) were enrolled. Etiological agent was identified in 70/109 (64%) patients. S.pneumoniae, Rhinovirus, Influenza A virus, S.aureus and K.pneumoniae were most commonly isolated pathogens (29.4, 11.9, 9.2, 8.3 and 6.4% of patients, respectively). Co-infection was revealed in 38.6% of cases. Bacteriemia was seen in 18.5% of patients with confirmed etiology of SCAP. Proportion of S.pneumoniae isolates non-susceptible to ampicillin, ceftriaxone, erythromycin, levofloxacin, vancomycin, tetracycline and co-trimoxazole was as follows: 6, 6, 11, 0, 0, 22 and 17%. All S.aureus stains were susceptible to methicillin. Conclusions: S.pneumoniae, respiratory viruses and S.aureus were the most common pathogens in adults with SCAP. The majority of S.pneumoniae strains remain susceptible to beta-lactams; high resistance to tetracycline and co-trimoxazole require limiting their use for SCAP.