Bacterial pathogens causing community–acquired pneumonia in hospitalized adult patients with and without chronic obstructive pulmonary disease

Background: Community-acquired pneumonia (CAP) is a common infection that often occurs in older adults who may have chronic obstructive pulmonary disease (COPD), a common respiratory condition characterized by airflow limitation. Chronic obstructive pulmonary disease and community-acquired pneumonia usually cause the same symptoms as respiratory tract infections, but they have potential differences in microbial etiology. This study aimed to assess the potential of bacterial pathogens in hospitalized CAP patients with and without COPD as well as bacterial combinations and to examine different rates of bacterial pathogens causing CAP between patients with and without COPD. Methods: This is a multicenter study conducted on hospitalized adult patients with community-acquired pneumonia with and without chronic obstructive pulmonary disease at the Respiratory Department of Nguyen Tri Phuong Hospital, Nhan Dan Gia Dinh Hospital and University Medical Center from 04/2021 to 03/2023. Collected sputum samples that were assessed as reliable (according to the Bartlett scale) were included in the study. The sputum samples were transported to Nam Khoa Company’s laboratory to carry out multiplex real-time PCR with King Fisher FLEX as the nucleic acid extraction instrument and CFX 96TM of Bio-Rad as the real-time PCR system. For statistical analysis, data collection was solved by SPSS 20.0 software and Microsoft Excel 2020. Results: Among 341 CAP patients, there were 91 patients (26.7%) with COPD, in which 89 patients were detected with a bacterial infection. The positive rates were 97.8% in CAP patients with COPD and 54.0% in CAP patients without COPD (p<0.001). Bacterial pathogens that caused CAP in patients with and without COPD extended to gram-negative bacilli. The top 5 bacterial pathogens in CAP patients with and without COPD were Acinetobacter baumannii (25.3% & 14.4%), Haemophilus influenzae (23.1% & 10.8%), Klebsiella pneumoniae (22.0% & 17.2%), Streptococcus pneumoniae (20.9% & 14.8%) and Escherichia coli (13.2% & 8.4%), in which the different percentages of Acinetobacter baumannii and Haemophilus influenzae were statistically significant (p<0.05). Pseudomonas aeruginosa was found at a low frequency (1.1% & 5.6%). Atypical bacteria were detected for only Mycoplasma at low frequencies (4.4% & 6.8%) and often occurred as a combined bacterium. Klebsiella pneumoniae and Escherichia coli in CAP with COPD and Acinetobacter baumannii and Escherichia coli in CAP without COPD were not often defined as the primary bacteria alone. More than one bacterial pathogen was commonly found in the sputum of CAP patients with and without COPD. Conclusions: CAP patients with COPD occur at a rate of 26.7%. Bacterial pathogens were detected in 97.8% of CAP patients with COPD and 54.0% of CAP patients without COPD (p<0.001), and they extended to gram-negative bacilli. The top 5 bacterial pathogens in the two groups were the same with different rates, in which the different rates of Acinetobacter baumannii and Haemophilus influenzae were statistically significant (p<0,05). Pseudomonas aeruginosa is found less commonly, although it is important because of its critical antibiotic resistance and mortality. Atypical bacteria are detected for only Mycoplasma in low frequency, and it often occurs as a combined bacterium. Klebsiella pneumoniae and Escherichia coli in CAP with and without COPD are rarely or not defined as the primary bacteria alone. More than one bacterial pathogen is commonly found in the sputum of CAP patients with and without COPD.