Etiology of Community-Acquired Pneumonia and Antibiotic Susceptibility in Hospitalized Patients 50 Years Old and above in a Tertiary Care Hospital in Mexico City: 2010–2016

Abstract

Background. Community-acquired pneumonia (CAP) is the leading infectious cause of death among the elderly. An understanding of the local epidemiology is crucial for the formulation of initial antimicrobial regimens. Methods. From January 2010-March 2016, we conducted a bidirectional cohort study of ≥50 years old patients with CAP admitted to Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán in Mexico City. Patients with nosocomial and healthcare-associated pneumonia were excluded. During the study's prospective phase (November 2014-March 2016), etiology was assessed in blood and respiratory cultures, S. pneumoniae / L. pneumophila urinary antigen tests, and molecular methods for the identification of respiratory viruses (multiplex polymerase chain reaction assay [RespiFinder®22] and RT-PCR for influenza virus). For the retrospective phase, etiology and antibiotic susceptibility were assessed on a case-by-case basis. Results. We identified 867 episodes of CAP in 823 patients; 57% were ≥70 years old, 42.6% (369) were male and 9.7% (80/823) were immunocompromised. The median CURB-65 at admission was 2 (IQR 1-3), 21.9% (190) required intensive care, and 16.8% (146) died within 30 days. An infectious etiology was identified in 27% (234/867) of the episodes; 49.6% (116/234) had a virus and 56.1% (132/234) a bacteria. Influenza virus was found in 17.9% (42/234) cases and rhinovirus in 11.1% (26/234). S. pneumoniae was found in 21% (49/234) cases, Enterobacteriaceae in 13.2% (31/234) and S. aureus in 8.1% (19/234). A total of 42.1% (8/19) S. pneumoniae were penicillin-resistant, 15.8% (3/19) S. aureus methicillin-resistant (MRSA) and 25.8% (8/31) Enterobacteriaceae were extended-spectrum β-lactamases (ESBL) producers. Ceftriaxone was initiated in 54.8% (475) episodes, piperacillin/tazobactam in 35.3% (306), clarithromycin in 82.1% (712), and oseltamivir in 46.8% (406); 23.7% (23/97) received inappropriate empirical antimicrobial therapy and of them, 39.1% were caused by ESBL-producing Enterobacteriaceae. Conclusion. Most common causes of CAP were S. pneumoniae and Influenza virus. ESBL-Enterobacteriaceae and MRSA should be considered in the design of empirical regimens, mainly in patients with risk factors.