The serotypes and antimicrobial susceptibility patterns of streptococcus pneumoniae in the Cape Peninsula

Abstract

Streptococcus pneumoniae (S.pneumoniae) infections are an important cause of morbidity and mortality in adults and children worldwide. Mortality rates are highest amongst the very young and the elderly. Streptococcus pneumoniae is the most common form of community acquired bacterial pneumonia. Other diseases commonly caused by Streptococcus pneumoniae include meningitis, pericarditis, bacteraemia and septicaemia. Penicillin is today still consid3red the drug of choice when treating pneumococcal infections. The emergence of resistant pneumococcal strains has made it necessary to adapt antimicrobial regimens when treating pneumococcal infections. Hansman (1967) reported the first penicillin resistant strain, which was isolated from a woman in Australia in 1967. Since then penicillin and multi-resistant Streptococcus pneumoniae strains have been observed worldwide, including South Africa. Streptococcus pneumoniae infections may be caused by anyone of the 84 serotypes recognized to date. The distribution of serotypes varies, depending on geographical area, age and site of infection. High-level penicillin resistance and multiple resistant Streptococcus pneumoniae strains have been recognised worldwide in a few pneumococcal serotypes. Pneumococcal vaccines have been used since the seventies. These capsular polysaccharide vaccines are generally recommended for at risk population such as the elderly and immunocompromised patients. This vaccine is not effective in children under 2 years old. The current vaccine in South Africa (Pneumovax, MSD) consists of purified capsular polysaccharides of 23 pneumococcal serotypes. Conjugated polysaccharide vaccines have been developed to overcome the problems of efficacy in children < 2 years old. These vaccines consist of a capsular polysaccharide linked to a protein carrier, which makes them immunogenic in infants. Clinical trials of these vaccines are currently under way to demonstrate safety, efficacy and immunogenicity. Knowledge of serotype distribution and antimicrobial susceptibility patterns are important in relation to the treatment of pneumococcal diseases and vaccination programmes.