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Acute respiratory infections cause 18% of all deaths worldwide among children younger than 5 years old (1). In 2005, Bartlett defined that community-acquired pneumonia (CAP) pathogens are identified in less than 10% of cases in current medical practice in adults, and a literature review from North America showed that Streptococcus pneumoniae (Sp) represents the first cause of CAP in 20% to 60% of isolates, and it also explains 66% of deaths with this condition in 2011 (2,3). It has been concluded that Sp continues to be a leading cause of morbidity and mortality with a peak incidence in children younger than 2 years old and adults older than 65 (4). Currently, 93 different serotypes of this bacterium have been identified, and certain have proved to be more virulent than others, being able to produce different clinical conditions: bacteremia or sepsis, pneumonia, meningitis, sinusitis, mastoiditis, otitis media, conjunctivitis, arthritis, endocarditis, pericarditis, etc. (4).The rapid development of antibiotic resistance (macrolides, clindamycin, amoxicillin, tetracyclines, penicillin, trimethoprim-sulfamethoxazole, and chloramphenicol) has explained that prevention should be more effective than treatment for pneumococcal disease (4).
Children very commonly carry different serotypes of Sp. Adults have a prevalence of 6% with no children at home, but it increases to 29% when children are present at home (4,5). Daycare Centers are important tools to explain the transmission of this microorganism (4).
Vergison published in 2010 a vicious cycle between the increased use or abuse of antibiotics especially in crowded populations and the appearance of antibiotic –resistant Sp (6). It is necessary to summarize the risk factors for a pneumococcal condition: young age or very old, Alaskan Native children, Navajo and Apache populations, African American children, peak incidence between December to February, lack of breast-feeding, crowding, sickle cell disease, immunocompromising conditions, malignancies, asthma, diabetes, neurologic disorders like seizures, and muscular dystrophies, malnutrition, tuberculosis, and exposition to second-hand smoke (4, 7). There is a very important synergism between the Influenza A virus and Sp following studies during the 1918 influenza pandemic and recent data obtained during the 2009 H1N1 influenza pandemic (4).
Prevention of Sp conditions starts with the interruption of the risk factors and the adequate immunoprophylaxis. The administration of polysaccharides from different Sp serotypes initiated the active immunization, inducing antibody production primarily by T-cell independent mechanisms that are not fully developed in infants and toddlers. But currently, there is another type: Conjugated capsular polysaccharide vaccine (PCV) that is able to produce the adequate recruiting of T-cells that both amplify the B-cell response and create memory B-cells. The goals of this new type of vaccines are to prevent invasive pneumococcal disease and mucosal infections, and to reduce the nasopharyngeal colonization (4). PCV13 contains 13 serotypes and it started to be analyzed in 2010. It has reduced bacteremia, meningitis, and pneumonia produced by this microorganism. There is a new PCV 15 (15 serotypes) in clinical trials at this time.
In conclusion: Sp continues to be a threatening agent and because its antimicrobial-resistant serotypes and the replacement of nasopharyngeal colonization by vaccine serotypes with non-vaccine, new active immunoprophylaxis will be necessary to counterbalance its uninterrupted attack with 93 different serotypes.
