micro - CNS, eyes, ears, and sinus infections

brain and spinal cord

the CNS consists of the _____ and _____

meninges

the inner covering of membranes in the CNS

CSF

surrounds the brain and spinal cord to provide cushioning, carry metabolites, and cleanse the tissues of waste products

CSF

found in the subarachnoid space and within cavities and canals of the brain and spinal cord, chemical and cellular changes may provide valuable information about infections within the subarachnoid space

blood brain barrier

one of the most important defense mechanisms of the CNS, this must be penetrated for the CNS to become infected

meningitis

infection within the subarachnoid space or throughout the leptomeninges

purulent meningitis

patients typically have a marked, acute inflammatory exudative CSF containing large number of PNMs

neonates

have highest infection rate of purulent meningitis; group B strep, E. coli, or L. monocytogenes

N. meningitidis

cause of meningitis in young adults

S. pneumoniae

associated with meningitis in young children and the elderly

respiratory tract

the primary portal of entry for many etiological agents of meningitis

seizures

presence of _____ is common in purulent meningitis and may assist in differentiating it from encephalitis

acute purulent meningitis

large number of inflammatory cells (PMNs), sequelae in children are common and serious

aseptic meningitis

usually viral and is characterized by an increase in lymphocytes and other mononuclear cells in the CSF, usually self limiting

encephalitis

an acute inflammation of the brain parenchyma

meningoencephalitis

concomitant meningitis with encephalitis

viral encephalitis

common in warmer months, any preceding viral illness and exposure history are important considerations in establishing a cause by clinical means

N. fowleri

a free living amoeba causes a rare but devastating meningoencephalitis

toxoplasmosis

caused by an intracellular parasite that destroys brain parenchyma

lumbar puncture (spinal tap)

one of the first steps in diagnosis

gram stain

must be performed on all CSF sediments, sample is a drop of sediment

wet preparation

amoebas are best observed as a _____ under phase contrast microscopy

india ink stain

non bloody CSF can be stained with this, large polysaccharide capsule of cryptococcus allows these organisms to be visualized

bacteria and fungi

media: chocolate agar, SBA, enrichment broth

conjunctivitis

bacterial version is pink eye, most common ocular infection

keratitis

should be considered an emergency due to corneal perforation can lead to loss of the eye within 24 hours with some organisms such as P aeruginosa and S aureus

otitis externa (external ear infections)

similar to skin and soft tissue infections

acute external otitis localized or diffuse

localized disease caused by S aureus, diffuse caused by P aeruginosa (swimmers ear)

chronic otitis externa

irritation of drainage from middle ear

otitis media

in children, S. pneumoniae and H. influenzae are usual etiologic agents

chronic otitis media

yields predominantly anaerobic flora

sinusitis

bacteria from the nose and throat make their way to the inner ear and sinuses