meningitis Flashcards
describe each cause of meningitis
viral
- common, mostly benign
- spontaneously improves
- influenza (mainly A), enterovirus
bacterial
- common, serious
- N. meningitis or S. pneumoniae
- (M. TB = rarer)
- illness preceded by nasopharynx colonisation
fungi
- rare
- usually only in AIDs
presentation
- headache
- sometimes photophobia
- neck stiffness
- drowsiness
- also systemic systems = fever, septic shock, rash
diagnosis of meningitis
- clinical suspicion (signs appear late)
- samples = CSF, blood culture, throat swab, blood to detect bacterial DNA by PCR
kernigs sign
lift legs up, bending at the hips, if headache worsens = meningitis
streptococcal antigen test
shows if S. pneumoniae is present. Colour change when antigen binds to card
lumbar puncture
- take CSF between L4/5 spinous process. fluid drawn from subarachnoid space
what difference will viral vs bacterial CSF have
Bacterial
- increased protein
- decreased glucose
- increased neutrophils
- increased WBC
viral
- normal glucose
- increased or normal protein
- increased WBC
- increased lymphocytes
describe PCR testing
- amplifies a single coy or a few copies of a segment of DNA
- tests for nucleic acid (tests S. pneumoniae DNA in CSF)
- doesn’t require live bacteria
- used when pathogens can’t be cultivated easily
n meningitidis
characteristic rash, transforming into large petechiae (however no rash doesn’t exclude)
CSF gram stain negative = single layer peptidoglycan
pathogenic mechanisms of N. meningitidis
- polysaccharide capsule prevents opsonisation and phagocytosis
- protein binds factor H (down-regulates complement)
- bacteria produces lipopolysaccharides to release in bloodstream (avoids complement)
- C4 binding protein prevents cleavage of C3
development of shock
- when bacteria load is very high neutrophils commit suicide
- release their DNA into capillaries
- DNA forms nets in capillaries, trapping circulating bacteria & immune cells
- decreases BF to organs causing shock
treatment for bacterial
- give IV antibiotics (penicillin)
- resuscitate
- take blood culture when IV inserted
- transfer to hospital
- investigations
- pain relief, fluids, IV antibiotics
treatment for viral
- reassurance
- analgesia
- can usually recover at home
treatment for patients in shock
maintain organ perfusion
- IV fluids, oxygen
resolve infection
- antibiotics, surgery
early recognition important
cephalosporins
- derived from mould acremonium
- works in the same way as penicillin but with an extra carbon ring
- 3rd generation = ceftriaxone
