[Pay attention to new evolution trends in the etiology of community-acquired pneumonia in adults].

Over the past two to three decades, the emergence and re-emergence of new infectious diseases, advances in molecular detection techniques of pathogens, antibiotic resistance, changes in population lifestyle and immune status (including vaccination), and other factors have led to new evolutions in the etiology of community-acquired pneumonia (CAP). (1) Although remains a common pathogen of CAP, it is no longer the leading cause in China and the United States. According to the results of 2 multicenter studies in China in the early 21st century, accounted for 10.3% and 12.0% of adult CAP pathogens, respectively, ranking second. A study on key pathogens of adult CAP in nine cities in mainland China from 2014 to 2019 using real-time quantitative PCR and conventional culture on respiratory and blood specimens showed an overall prevalence of of 7.43%, ranking sixth. However, its ranking varied from third to seventh among the nine cities. (2) Challenges and concerns about viruses have increased. National surveillance of acute respiratory tract infections and epidemiology in China from 2009 to 2019 indicated that the positivity rates for viral infections in adult pneumonia was 20.5%. These rates were similar to the results of the CDC's CAP pathogen study in the United States, although the rankings were different (viruses ranked second in China and first in the United States). Over the past 20 years, the emergence of new viral respiratory infections caused by mutant strains or zoonotic strains has significantly increased the challenges and threats posed by viral respiratory infections. (3) The role of () in adult CAP and the need for routine empirical antibiotic coverage are controversial. In addition to the influence of epidemic cycles, the prevalence of is influenced by factors such as age, season, study design, and detection methods, and geographical distribution is also an important influencing factor. Although ranks first among CAP pathogens in mainland China (11.05%), there are significant regional differences. In Beijing, Xi'an, and Changchun ranks first, while in Harbin, Nanjing, and Fuzhou it ranks second to sixth. In Wuhan, Shenzhen, and Chengdu ranks after the tenth position. Available evidence supports the notion that routine coverage of is not necessary for empirical treatment of CAP, except in severe cases. In regions with a high prevalence of , the decision to cover atypical pathogens in patients with mild to moderate CAP should be based on local data and individualized. (4) CAP caused by multidrug-resistant bacteria, especially multidrug-resistant Gram-negative bacilli (GNB), has become a concern. According to a systematic review of Chinese literature, accounted for 8.12% of adult CAP patients, ranking fifth, and accounted for 4.7% (ninth). The China Antimicrobial Resistance Surveillance System (CARSS) reported an average resistance rate of 27.7% for to third-generation cephalosporins and a resistance rate of 10.0% to carbapenems in 2021. The average resistance rate of to carbapenems was 16.6%. Early empirical treatment should consider predicting the resistance profile using a "locally validated risk factor" scoring system. (5) Co-infections are common but under-reported. The development of non-culture detection techniques over the past 40 years has significantly increased the detection rate of respiratory pathogens, especially viruses, leading to an increasing number of reports of bacterial-viral co-infections in CAP. It has been reported that co-infections account for 39% of severe CAP cases on ventilators in the ICU. Currently, there is inconsistency and confusion regarding the definition and concept of co-infection, the choice of detection techniques, and the differentiation between co-detection and co-infection. Many reports of co-infections in COVID-19 lacked pathogenic evidence, and some even listed "effective antibiotic treatment" as one of the diagnostic criteria for viral-bacterial co-infections, suggesting to some extent an overuse of antibiotics in COVID-19. Due to the diverse etiological spectrum of CAP between regions in the recent years, it is challenging to develop unified guidelines for the management of CAP in large countries. This article provides recommendations for the development of local guidelines for the diagnosis and treatment of CAP.