gram positive cocci
Slides in this set (5)
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- Streptococcus
- pyogenes is a gram positive cocci that causes group A streptococcal
- infections. Strep pyogenes typically produces large zones of
- beta-hemolysis and can be distinguished from other streptococcal
- organisms because it is catalase negative and bacitracin sensitive. It
- can cause a variety of disease including pyogenic infections of the
- pharynx and skin. In the pharynx, it is the classic cause of bacterial
- strep throat. In the skin, it can cause impetigo and cellulitis. This
- bacteria also causes several diseases mediated by toxins including
- scarlet fever and toxic shock like syndrome. Two of the major
- complications of group A strep infections are mediated immunologic
- mechanisms, including rheumatic fever caused by the development of
- antibodies to M protein and acute glomerulonephritis.
- https://www.youtube.com/watch?v=dg6b-lDvbC4 (Embed)
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Streptococcus pneumoniae features
- Streptococcus pneumoniae is a Gram positive “lancet-shaped” diplococci
- that is a major cause of pneumonia, meningitis, and otitis media.
- Characteristically, this bacteria is alpha hemolytic, which causes dark
- green colonies on blood agar. It is catalase dark green colonies on
- blood agar, which allows it to be distinguished from catalase positive
- Staph aureus. Strep pneumonia can be differentiated from streptococcus
- viridans using an optochin test. Strep pneumoniae is optochin sensitive
- while Strep viridans is optochin negative. The bacterium can also be
- differentiated from Strep viridans because Streptococcus pneumoniae is
- bile soluble while Strep viridans is not. This organism is encapsulated
- with a positive quellung reaction. The capsule acts as a virulence
- factor for the organism.
- https://www.youtube.com/watch?v=Qh3K_KZ9ujw (Embed)
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- Streptococcus pneumoniae, , is a gram-positive diplococci bacteria. Classically, patients can complain of coughing up rusty sputum if they have pneumonia, , which can help with clinical diagnosis. Patients who have had splenectomies are at risk forsepsis,. Those who have sickle cell anemia,
- especially children, are also at risk for sepsis, . Other
- manifestations of strep pneumo can be remembered by the mnemonic MOPS,
- This bacteria is also one of the most common causes of bacterial meningitis in adults, , and is the most common bacterial pathogen to cause otitis media, in the ear. Strep pneumonia is a very common cause of pneumonia, , and can also cause acute bacterial sinusitis,
- https://www.youtube.com/watch?v=lUwBEpBs9jQ (Embed)
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- https://www.youtube.com/watch?v=Z6BiENnal3Y (Embed)
- Staphylococcus
- epidermidis is a Gram positive cocci that is part of the human skin
- flora. This organism is usually not pathogenic but can cause infection
- in patients with compromised immune systems. Staphylococcus epidermidis
- is also a large concern with patients with catheters or other prosthetic
- devices because it is known to cause adherent biofilms that grow on the
- devices. Characteristically, it is a catalase positive, coagulase
- negative bacterium. Staphylococcus epidermidis can be differentiated
- from staphylococcus saprophyticus, which is also catalase positive,
- coagulase negative, but sensitivity to novobiocin. Because this organism
- is a component of normal skin flora, it is a common contaminate of
- blood cultures.