Also known as: Pneumococcus
Industry of Interest: Healthcare
Microbiology: Streptococcus pneumoniae is a Gram-positive coccus that commonly exists as chains of cells. S. pneumoniae produces haemolysin, a compound that breaks down the haemoglobin present in red blood cells. When S. pneumoniae is grown on blood agar the effect of haemolysin can be visualised. The haemolysin released by S. pneumoniae oxidises the red blood cells in the media leaving haemolysed regions a “greenish” colour; this process is known as -haemolysis (Mitchell and Mitchell, 2010).
Habitat and transmission: S. pneumoniae is a common commensal microorganism and is present in the nasopharynx of around 60% of all pre-school children (Henriques-Normark and Normark, 2010). The organism is often coated in a polysaccharide layer called a capsule, which is anti-phagocytic and allows adherence and antimicrobial resistance. It also utilises pili, surface proteins, enzymes and the toxin pneumolysin (PLY) to establish an infection (Mitchell and Mitchell, 2010). S. pneumoniae uses a wide variety of means to evade the immune system and establish an infection.
Disease and symptoms: It is one of the most significant causes of fatal bacterial pneumonia in the under fives worldwide and has been known to be an important cause of pneumonia in the elderly population. Persons with underlying diseases such as asthma, HIV, cancer, viral infection (particularly Influenza) and those suffering from alcoholism and immunodeficiency diseases are particularly susceptible to S. pneumoniae infections (Henriques-Normark and Normark, 2010). S. pneumoniae causes not only pneumonia but can lead to infections such as otitis media, bronchitis, sinusitis, bacteraemia and meningitis (Liñares et al., 2010; Mitchell and Mitchell, 2010).
Treatment and Antibiotic resistance: Prior to 1967 S. pneumoniae was susceptible to penicillin and most other antimicrobials. However, with overuse of broad-spectrum antibiotics, S. pneumoniae strains are becoming increasingly resistant to the effects of antibiotics. S. pneumoniae has a very efficient transformation system that allows high frequency horizontal gene transfer between pneumococcal strains and other streptococci. This allows S. pneumoniae to acquire and share antibiotic resistance genes (Henriques-Normark and Normark, 2010).
Prevention and control: A vaccine called the seven-valent pneumococcal conjugate vaccine (PCV7) was introduced for administration to children in the 2000’s, against the serotypes 4, 6B, 9V, 14, 18C, 19F and 23F (Liñares et al., 2010). Since its introduction there has been a decrease in invasive pneumococcal disease amongst children under five in several countries, however there has recently been an increase in multiresistant serotypes (Liñares et al., 2010).
Henriques-Normark B. and Normark S. (2010) Commensal pathogens, with a focus on Streptococcus pneumoniae, and interactions with the human host. Exp Cell Res. 316(8):1408-1414.
Liñares J., Ardanuy C., Pallares R. and Fenoll A. (2010) Changes in antimicrobial resistance, serotypes and genotypes in Streptococcus pneumoniae over a 30-year period. Clin Microbiol Infect. 16(5): 402-410.
Mitchell A.M. and Mitchell T.J. (2010) Streptococcus pneumoniae: virulence factors and variation. Clin Microbiol Infect. 16(5): 411-418.