Is Streptococcus pneumoniae a nosocomially acquired pathogen?

ABSTRACT Streptococcus pneumoniae is primarily a major cause of community-acquired infections of the respiratory tract, central nervous system, and bloodstream, but an increasing interest results from its role in the epidemiology of hospital-acquired infections. Penicillin-resistant pneumococcal strains appeared three decades ago and now are present worldwide with the adjunctive feature of multiple resistance supported by antibiotic selective pressure. Horizontal spread can cause either sporadic cases or hospital outbreaks, primarily in younger children and elderly patients. Pneumococcal transmission from one patient to another can be documented by PCR technique or pulsed gel electrophoresis typing. Nosocomial acquisition of infection along with pediatric age, previous hospitalization, and previous beta-lactam therapy are the main risk factors significantly associated with penicillin-resistant pneumococcal infections. Nosocomial acquisition is also associated with higher mortality from pneumococcal disease. The importance of penicillin resistance as a risk factor significantly associated with higher mortality from pneumococcal infection is confirmed by some studies and denied by other ones. Mortality from pneumococcal pneumonia is approximately the same for HIV-infected, non-AIDS patients as for HIV-negative subjects, but it is significantly higher in AIDS patients. Penicillin-resistant strains are involved in the vast majority of hospital outbreaks, whether these cause a clinically manifest infection or a simple colonization. Pneumococcal vaccination is universally recommended in order to lower the incidence of invasive infection, although a number of problems can limit its effectiveness.