Haemophilus, Neisseria and Fastidious gram-Negatives: Meningitis and Bites Flashcards
name two bacteria that can cause meningitis?
haemophilus influenzae and neisseria meningitidis
define meninges
three connective tissue layers in the CNS. pia mater, arachnoid, and dura mater. support blood vessels and contain CSF mostly in subarachnoid space
define meningitis. is it always due to infection?
inflammation of the meninges. usually but not always, can also have malignant or neoplastic meningitis and autoimmune
what two other disease are associated with meningitis?
meningoencephalitis (parenchymal involvement) and encephalitis (predominantly disease of brain tissue)
describe the pathogenesis of meningitis
bacteria in CNS and bacterial products leads to an inflammatory response of neutrophils and cytokine release. these result in injury to the BBB which leads to edema, elevated ICP, metabolic and toxic disturbances. immune response also leads to vaso-dilation and constriction which leads to more edema, elevated ICP, local ischemia, necrosis, and hydrocephalus
name some symptoms of meningitis
systemic-fever, vomiting
local-headache stiff neck
organ related-photophobia, confusion, coma, somnolence, seizures.
name some signs of meningitis
systemic-fever
local- meningismus (meniges are sensitive to stretch) i.e. headache, stiff neck, positive Kernig and Brudzinski signs
organ related- cranial nerve abnormal findings, signs of elevated CNS pressure, altered mental status
describe 3 cases in which the typical signs and symptoms of meningitis may not be seen
newborns, older patients (no fever, just acute altered mental status), neutropenic and other immunocompromised patients.
what factors will cause you to perform or not perform a STAT lumbar puncture with a clinical suspicion of meningitis? 7
immunocompromise, history of CNS disease, new-onset seizure, papilledema, altered state of consciousness, focal neurologic deficit (i.e. paresis, weakness in left or right arm), delay in performance of diagnostic lumbar puncture.
What CSF lab results indicate a high risk for bacteria meningitis?
high leukocytes >1000, high neutrophils >85-95%, high protein count >100-150, low glucose serum <40%, 85% smear-positive
describe the microbiology of bac meningitis in newborns, infants, children, and adults
1-group B streptococci, E. coli, Listeria
2-Neisseria meningitidis, Haemophilus influenzae, streptococcus pneumoniae
3-N. meningitidis, S. pneumoniae
4- S. pneumoniae, N. meningitidis
name the sequelae of meningitis
hearing loss, vision loss, ataxia, stroke or spinal infection, hemi or quadraparesis, diabetes insipisus, hydrocephalus, intellectual and behavioral deficits
Describe the biology of Haemophilus Influenzae
gram-negative coccobacilli, blood loving, requires X (heme) and V (NAD) factors for growth.
which strain of H. influenzae is a major invasive human pathogen? what diseases can it cause? (5)
capsule type b (polyribitol ribose phosphate, PRP) strains. meningitis, epiglottitis, pneumonia and empyema (suppurative infection of sleural space), cellulitis, septic arthritis
what is a bacterial capsule?
polysaccharide or polypeptide layer outside cell wall, usually has antiphagocytic and or other immunomodulatory properties
what diseases can non-encapsulated H. influenzae cause?
otitis media, pneumonia, sinusitis, exacerbation of COPD
describe the epidemiology of H. influenzae. where is it found? when is carriage common, genetic history
it’s found in humans only, carriage occurs a few days after birth, group b is clonal (i.e. derived from a single ancestor)
What type of vaccine is H. Influenzae group b (Hib)
is a conjugate to protein antigen; because polysaccharide weren’t had beneficial for children the higher risk group.
what is the drug of choice for H. influenzae infections. What abt for PCN-allergic? what else is used for decreasing sequelae?
ceftriaxone; chloramphenicol if PCN-allergic; dexamethasone
describe the biology of neiserria meningitidis
aka meningococcus, gram-negative diplococci (slightly flattened, kidney bean shape), grows on chocolate (aka blood+RBC content) agar, prefers CO2
What should be kept in mind when obtaining a Neisseria meningitidis?
specimen is highly susceptible to cold, high pH, and drying, must get to lab quickly.
which portion of the immune system is important in immunity against Neiserria meningitidis?
complement
describe the epidemiology of N. meningitidis. how does it spread, carrier, is it seasonal, rate in children and developing countries,
respiratory pathogen (spread via aerosol route), carrier state is frequent, highest in Feb-Mar, lowest in Sept, rate is 10x higher in children <2 y/o (day care is risk factor), higher rates in less-well developed nations (i.e. African meningitis belt).
Name some diseases caused by meningococcus 3
meningitis and acute meningococcemia, chronic meningococcemia (fever, petechiae, dermatitis, artritis), note: pneumonia is unusual. also not primary cause of pharyngitis
describe the pace, severity, and triad seen in meningococcal meningitis seen with acute septicemia.
- rapid (symptoms seen 12-15 hrs after disease onset)
- vry high mortality
- headache, confusion, and stiff neck in less than half of patients
what are some other things to look for in meningococcal meningitis?
upper respiratory symptoms, myagias, petechial and purpuric rashes (>50%), shock, DIC, waterhouse-friderichsen syndrome
what vaccines are available for meningococcal diseases? which group is not covered under this vaccine?
polysaccharide vaccine (ages 2-10 and >55) conjugate vaccine (for everyone else) does work with serogroup B
what drug is used for chemoprophylaxis treatment of meningococcal meningitis?
rifampin 1st; ciprofloxacin, ceftriaxone
give within 24hrs of contact
name common bacteria found in cat, dog, and human bites
cats/dogs-pasteurella multocida (agressive cellulitis and sepsis)
human-eikenella corrodens
dogs- capnocytophaga canimorsus-sepsis in P. with liver disease and asplenia
