Pneumococcal pneumonia in adults national gas average 2012

Of the approximately four million cases of pneumonia each year in the United States, pneumococcus ( Streptococcus pneumoniae) is the most common agent leading to hospitalization in all age groups [ 1]. (See "Epidemiology, pathogenesis, and microbiology of community-acquired pneumonia in adults".)

A general overview of pneumococcal pneumonia will be presented here. The epidemiology, microbiology, diagnosis, and treatment of community-acquired pneumonia are discussed separately. (See "Diagnostic approach to community-acquired pneumonia in adults" and "Epidemiology, pathogenesis, and microbiology of community-acquired pneumonia in adults" and "Treatment of community-acquired pneumonia in adults in the outpatient setting" and "Treatment of community-acquired pneumonia in adults who require hospitalization".)

Prevalence in community-acquired pneumonia — S. pneumoniae has traditionally been the most common cause of community-acquired pneumonia (CAP). In the preantibiotic era, S. pneumoniae was responsible for >75 percent of cases of pneumonia [ 2-4]. However, more recent studies have isolated the organism in only 5 to 15 percent of cases in the United States [ 5-9] but in a higher proportion of cases in some other countries [ 2,10-12]. Factors that are likely to have contributed to the decline in S. pneumoniae as a cause of CAP in the United States include the use of pneumococcal vaccines in adults, the universal use of pneumococcal conjugate vaccines in children (leading to herd immunity), and a reduction in cigarette smoking [ 2,13]. The impact of pneumococcal vaccination on the incidence of pneumonia is discussed in greater detail separately. (See "Pneumococcal vaccination in adults".)

It is important to note that the rate of isolation increases when more invasive methods are used for obtaining specimens, such as transtracheal aspiration, which eliminates contaminating oropharyngeal flora; this method was used in the past but is no longer used. It is believed that many culture-negative cases are caused by pneumococcus. One factor arguing for the predominance of S. pneumoniae as a cause of CAP is that, in patients with CAP who have positive blood cultures, 58 to 81 percent of bloodstream isolates are S. pneumoniae [ 1,14]; however, only 7 to 10 percent of patients with CAP have positive blood cultures [ 1,6,14]. One group has estimated that, for every case of bacteremic pneumococcal pneumonia, there are at least three additional cases of nonbacteremic pneumococcal pneumonia [ 15].

Influenza infection — Influenza infection greatly predisposes to secondary pneumococcal pneumonia [ 16]. This is discussed in detail separately. (See "Clinical manifestations of seasonal influenza in adults", section on ‘Secondary bacterial pneumonia’.)

• File TM Jr, Low DE, Eckburg PB, et al. Integrated analysis of FOCUS 1 and FOCUS 2: randomized, doubled-blinded, multicenter phase 3 trials of the efficacy and safety of ceftaroline fosamil versus ceftriaxone in patients with community-acquired pneumonia. Clin Infect Dis 2010; 51:1395.

• Harboe ZB, Larsen MV, Ladelund S, et al. Incidence and risk factors for invasive pneumococcal disease in HIV-infected and non-HIV-infected individuals before and after the introduction of combination antiretroviral therapy: persistent high risk among HIV-infected injecting drug users. Clin Infect Dis 2014; 59:1168.

• Meiring S, Cohen C, Quan V, et al. HIV Infection and the Epidemiology of Invasive Pneumococcal Disease (IPD) in South African Adults and Older Children Prior to the Introduction of a Pneumococcal Conjugate Vaccine (PCV). PLoS One 2016; 11:e0149104.

• Weiser JN, Pan N, McGowan KL, et al. Phosphorylcholine on the lipopolysaccharide of Haemophilus influenzae contributes to persistence in the respiratory tract and sensitivity to serum killing mediated by C-reactive protein. J Exp Med 1998; 187:631.

• Marrie TJ, Low DE, De Carolis E, Canadian Community-Acquired Pneumonia Investigators. A comparison of bacteremic pneumococcal pneumonia with nonbacteremic community-acquired pneumonia of any etiology–results from a Canadian multicentre study. Can Respir J 2003; 10:368.

• Gutiérrez F, Masiá M, Rodríguez JC, et al. Evaluation of the immunochromatographic Binax NOW assay for detection of Streptococcus pneumoniae urinary antigen in a prospective study of community-acquired pneumonia in Spain. Clin Infect Dis 2003; 36:286.

• Martínez JA, Horcajada JP, Almela M, et al. Addition of a macrolide to a beta-lactam-based empirical antibiotic regimen is associated with lower in-hospital mortality for patients with bacteremic pneumococcal pneumonia. Clin Infect Dis 2003; 36:389.