Community-acquired pneumonia (CAP) remains a hot topic in the medical literature. This is not surprising, as it is the most common infectious complication leading to hospital admission and is still associated with a considerable mortality. In addition, new challenges are emerging, in view of a growing population of elderly, not infrequently severely disabled patients who are particularly prone to pneumonia. The growing list of acronyms, such as NHAP (nursing-home associated pneumonia), HCAP (health-care–associated pneumonia), HAP (hospital-acquired pneumonia), forming a "pneumonia soup," clearly hint at the need to address new issues related to pneumonia in the immunocompetent host. These include adequate treatment settings, pathogen patterns, development of resistance, assessment of individual risk factors, and empiric initial antimicrobial treatment.
In this issue of Hot Topics in Respiratory Medicine, four most important aspects of CAP are highlighted in comprehensive reviews. These include the etiology and epidemiology of CAP, the economic impact of CAP, a critical review of CAP guidelines, and treatment failure. The reader may admit a few comments on these topics.
It is most evident that the etiology of CAP depends on the host. The epidemiological fact that CAP is mainly a condition of the elderly raises many questions as regards the impact of age on pathogen and resistance patterns. There is a need to address other factors such as geographical area, season, residence, comorbidity, pretreatment, and severity as well as the methodological approach in order to avoid bias in our view about the pathogen and resistance patterns we have to expect in the elderly.
The economic impact of CAP is enormous and definitely will increase in the years to follow. The main cost driver is hospitalization, not antimicrobial drugs, and therefore, much attention should be dedicated to the appropriate assessment of severity. Although the Pneumonia Severity Index and CURB-65 and its modifications have been named as powerful tools to identify low-risk patients, many questions regarding the need for hospitalization in the elderly population residing in nursing homes remain to be settled.
The guidelines for CAP provided by the British Thoracic Society, the European Respiratory Society, and the Infectious Diseases Society of America in cooperation with the American Thoracic Society consensus have gained much attention. Although these guidelines converge on many important issues, there is significant disagreement in the selection of initial antimicrobial treatment, particularly in patients with mild pneumonia, which cannot exclusively be explained by differing etiologies in America and Europe. Moreover, the American HCAP concept, which disrupts the classical pneumonia triad of CAP, HAP, and pneumonia in the immunosuppressed host, has not yet been adopted by European guidelines.
Finally, treatment failure is a complex and difficult clinical situation, and attending physicians are in need of detailed advice in order to select the appropriate approach to these patients. Whereas many clinicians believe, and some studies suggest, that microbial resistance is the main clue to explaining treatment failures, it appears that this is a less frequent cause of treatment failure. Instead, host and pathogen factors, inappropriate assessment of risk factors, and pneumonia mimics account for the majority of treatment failures.
The authors of the four topics provide a most comprehensive and differentiated framework to deal with these challenges. It is hoped that these reviews result in both useful clinical advice as well as stimulate investigational efforts.