Streptococcus pneumoniae – Aspects of the implication in human pathology, epidemiology, diagnosis, treatment and prevention of pneumococcal infections

Abstract

Streptococcus pneumoniae, part of the commensal flora of the nasopharynx, a bacterial conditioned pathogen, is the most common cause of respiratory tract infections. It is a fastidious bacterium that belongs to the family Streptococcaceae, genus Streptococcus. Pneumococcus has a number of virulence factors: endogenous (cellular components) and exogenous (enzymes, toxins), which play an important role in the pathogenesis of pneumococcal disease. Pneumococcal infections have different degrees of severity, from mild/moderate respiratory infections = non-invasive infections, which are the most common ones (otitis media, sinusitis, conjunctivitis), to very severe invasive infections (primary bacteremia, pneumonia with bacteremia, meningitis) – defined by the isolation of S. pneumoniae from a normally sterile place (blood, cerebrospinal fluid, pleural fluid etc.). Out of more than 90 pneumococcal serotypes, only 20 to 30 are responsible for the majority of invasive pneumococcal disease (IPD). These infections and their risk factors are summarized in the article. The diagnosis of pneumococcal disease is achieved through the isolation and identification of the pathogen, both by phenotypic and molecular methods. The treatment of the pneumococcal infections, mainly by antibiotherapy, is recommended depending on the location and severity of the infection, the results of antibiotic susceptibility testing and factors related to the human host. Regarding the emergence of antibiotic resistance in S. pneumoniae, it is very important to sustain the surveillance of pneumococcal disease and the prevention through vaccination, which determined a reduction in the incidence of IPD and antibiotic resistance. However, due to the limited use of pneumococcal vaccine, S. pneumoniae still remains the most common etiologic agent of severe infections. It is therefore necessary to implement a surveillance program to assess the burden of pneumococcal disease, in order to establish effective interventions, such as conjugate vaccines and antibiotic stewardship programs.