Streptococcus pneumoniae Flashcards
What are the major virulence factors of s. pneumoniae?
PPPPLANCCH (four P's two C's) polysaccharide capsule pneumolysin pili peptidoglycan lipoproteins autolysin neuraminidase competence protein choline binding protein hyaluronidase
What diseases are commonly caused by S. pneumoniae?
pneumonia, meningitis, otitis media, sinusitis, sepsis
What shape are S. pneumoniae?
lancet-shaped, diplococcus
Is S. pneumoniae Gram - or +?
Gram positive
What is the most common cause of CAP (community acquired pneumonia)?
S. pneumoniae
What are commensal microbiota and is S. pneumoniae one of them?
Commensal bacteria are those that asymptomatically colonize a large percentage of the population. S. pneumoniae colonizes up to 60% of children and 30% of adults
What is the primary vector for transmission of S. pneumoniae to vulnerable populations?
children
What is the most important virulance factor of S. pneumoniae? What defense does the body have against it?
polysaccharide capsule that has antiphagocytic effects. There are anti-capsule antibodies that are opsonic.
What is pneumolysin?
pore-forming toxin (hemolysin) that binds to cholesterol in host cell membranes and makes a pore, lysing the cell. Causes recruitment of neutros, T and B cells, increasing inflammation.
Is S. pneumoniae hemolytic? If so what type?
alpha hemolytic. Green appearance on blood agar
What is hyaluronidase?
aids spread of bacteria in hyaluronic acid containing tissues
What is neuraminidase?
clips N-acetylneuraminic acid from cell surface, causing damage and opening sites for pneumococci binding. Specifically this leads to spread of pneumococci along the Eustachian tubes towards the middle ear.
What functions do pili serve in S. pneumoniae?
aid in pneumococcal adhesion to epithelial cells
What are the main cell wall components of S. pneumoniae?
peptidoglycan and teichoic acid
What are high levels of CRP correlated with in S. pneumoniae infections?
high risk for heart disease. It is released by the liver as an acute phase reactant during inflammation
What are the two forms of teichoic acid?
Wall teichoic acid (WTA) and lipoteichoic acid (LTA)
What are choline-binding proteins (CBPs)?
achored to cell surface via repeate domains that bind to choline in the cell wall (on WTA or LTA). Some are hydrolytic enzymes that release cell wall fragments to stimulate inflammation. Some (PspA and PspC bind to complement factor H to inhibit phagocytosis.
What is competence protein?
enables pneumococci to acquire DNA form the environment
What is autolysin, LytA?
allows cocci to disrupt cell wall formation at the site where peptide crossbridgesa re attached. Important in cell wall remodeling and can release fragments to stimulate inflammation and immune response.
Where is the primary site of S. pneumoniae colonization?
nasal cavity
What can PMNs do to S. pneumoniae?
Nothing at first because of the heavy capsules. If there are opsonic antibodies then they can phagocytose them and kill.
Aside from smoking, alcohol, immunosuppression, what are significant predisposing factors to S. pneumoniae infection?
COPD, diabetes, and “striking association with viral infections in both children and adults”
What are the main diseases s. pneumoniae causes?
meningitis, pneumonia, otitis, media, sinusistis and sepsis
What predisposing factors make sepsis more likely after s. pneumoniae infection?
asplenia, spenectomy, recent surgery and other immunocompromised states.
How do you diagnose S. pneumoniae in a patient with pneumonia?
look for rust colored sputum. Positive gram stain. Lancet-shaped diplococci.
Is S. pneumoniae catalase + or -?
catalase negative.
What is the treatment for otitis media and sinusistis caused by s. pneumonaie?
amoxicillin and clavulanic acid. OR for outpatients macrolides and doxycycline
What is the treatment for meningitis caused by s. pneumoniae?
penicllin or ceftriaxone
What are the preventive measures against s. pneumoniae?
pneumovax and prevnar 13 vaccines.
What time of year are s. pneumoniae infections most common?
mid winter
What is the quellung reaction?
when treated with capsule specific antiserum, there is capsule stabiliaztion that looks like swelling.
