Streptococcus pneumoniae

Drug-resistant Streptococcus pneumoniae


     To better understand how S. pneumoniae has adapted to its environment we must look at specialized abilities and morphologies it has developed over time. S. pneumoniae has a variety of abilities including a high rate of drug resistance and a very rapid genetic recombination process that allow it to thrive in our ever changing world. By examining these processes and abilities in closer detail it becomes easy to see why this very small bacteria can have a very big impact on the world.

Drug resistance

     The increase in antibiotic resistance of S. pneumoniae is seen in many parts of the world.  S. pneumoniae's ability to adapt and resist specific types of antibiotics over time is what makes combating this small enemy so difficult for doctors. A study conducted over a ten year period, concluded that there was a “striking” increase in the antibiotic resistance of the bacteria (Vasso, 2011).  The study showed that between the years 1997 and 2007 S. pneumoniae's resistance to erythromycin increased from 31% to 78%, with similar results found in the surrounding geographic regions (Vasso, 2011). S. pneumoniae is also increasing its resistance to penicillin, an antibiotic derived from Penicillium chrysogenum, at a similar rates to erythromycin. The majority of the blame for these sharp increases of resistance is due to antibiotic abuse or misuse by individual people. For example the Vasso article states that a large number of viral infections are misdiagnosed as bacterial infections, and when the uninfected individual consumes antibiotics unneeded it creates a supper bug of sorts (Vasso, 2011).

Genetic Recombination

      S. pneumoniae has an astounding ability to use genetic recombination in order to overcome obstacles it may encounter. Let’s begin by explaining what genetic recombination is. Genetic recombination is defined as the process by which an organism forms new allelic combinations in its offspring through exchanges in genetic materials such as DNA. A study conducted at University of Kaiserslautern showed that S. pneumoniae uses the process of genetic recombination in a very special way. The study concluded that S. pneumoniae is capable of using other organism’s genomic sequences for its own recombination needs (Sauerbier, 2012). This “interspecies genetic recombination” allowed the bacteria to change its resistance to penicillin by using the codons for resistance in other, closely related bacteria (Sauerbier, 2012). This is a major contributing factor as to why S. pneumoniae is such a resilient bacteria and explains its remarkable ability to evolve to resist specific types of antibiotics (Vasso, 2011).

Figure 1:Phylogenetic tree of bacteria closly related to S. pneumonia that could be potential candidates for interspecies genetic recombination. Peter Uetz 2013.

    The tree above represents the various species that are most closely related to S. pneumoniae. Though many different genre are represented in the tree above, the most likely candidates for the interspecies genetic recombination process are those found in the genus Streptococcus. The genus Streptococcus is represented above by the first blue bracket on the left. This tree is based on a combination of morphological traits and DNA links between the various specious. 

Continue to: Nutrition