Streptococcus pneumoniae
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Streptococcus pneumoniae
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Meningitis
Streptococcus pneumoniae p. , 134
Otitis media
Streptococcus pneumoniae p. , 134
Pneumonia p. 701
Streptococcus pneumoniae p. , 134
Streptococcus pneumoniae p. , 134
α-hemolysis p. 133
bacterial meningitis p. 725
chloramphenicol p. 189
cystic fibrosis p. 176
encapsulated bacteria p. 125
Gram-positive testing p. 132
IgA protease and p. 127
immunodeficient patients p. 116
influenza p. 166
IV drug use and p. 177
meningitis p. 177
penicillin G/V for p. 184
pneumonia p. 176, NaN
postviral infection p. 176
splenic dysfunction p. 96
transformation in p. 128
Virulence factors
Streptococcus pneumoniae p. , 134
Transcript
Streptococcus pneumoniae or Strep. pneumoniae can be broken down into strepto- which means chain, -coccus, which means round shape, and pneumoniae, which refers to the fact that it causes pneumonia - no surprises there.
So, Strep pneumoniae are round bacteria that tend to grow in chains, usually in lancet-looking pairs called diplococci.
They’re the most common cause of community-acquired pneumonia - meaning pneumonia acquired somewhere other than the hospital.
Ok now, a little bit of microbe anatomy and physiology.
Strep pneumoniae has a thick peptidoglycan cell wall, which takes in purple dye when Gram stained - so this is a gram-positive bacteria.
They’re non-motile and don’t form spores, and also, they’re facultative anaerobes, meaning that they can survive in both aerobic and anaerobic environments.
Finally, they’re catalase negative - which means they don’t produce an enzyme called catalase.
Ok, now, when cultivated on a medium called blood agar, Strep pneumoniae colonies cause alpha hemolysis, also called green hemolysis, because they produce hydrogen peroxide, which partially oxidizes initially red hemoglobin in the blood agar to green methemoglobin.
Other Streptococcus species, like Strep viridans, are also alpha hemolytic.
So, an optochin test is done to distinguish Strep pneumoniae. That’s where a few drops of optochin are added to the culture.
Strep pneumoniae are optochin sensitive, meaning the bacteria dies after adding optochin, whereas Strep viridans are optochin resistant - meaning they survive.
Now, Strep pneumoniae has a number of virulence factors, that are like assault weaponry that help it attack and destroy the host cells, and evade the immune system.
So first, Strep pneumoniae is encapsulated, meaning it’s covered by a polysaccharide layer called a capsule.
The capsule has pili and fimbriae, which are hair-like extensions that help it attach to a host cell.
Once attached to a mucosal surface like in the nasopharynx or the middle ear, Strep pneumoniae can multiply and produce biofilms.
A biofilm is basically a layer of goop-like material made of exopolysaccharides or EPS, within which Strep pneumoniae bacteria live and reproduce.
Comparing a biofilm to strawberry jam, the seeds would be the bacteria and the rest of the jam would be the EPS.
Summary
Streptococcus pneumoniae, or pneumococcus, is an encapsulated, gram-positive, and catalase-negative bacterium. It is found asymptomatically colonizing the nasal cavities and sinuses, but they can take advantage of a weakened immune system, especially in very young or very old individuals, or in those with diabetes, HIV infection, cancer, splenectomy, or those with sickle cell disease.
Streptococcus pneumoniae can cause diseases such as rhinosinusitis, otitis media, pneumonia, and meningitis. Symptoms vary depending on the type but can include fever, chills, coughing, chest pain, and difficulty breathing. The treatment of infection with Strep pneumoniae involves the use of Penicillins, but in the case of resistant strains, fluoroquinolones, third-generation cephalosporins, and vancomycin can be used.