Chapter 22 Microbial Diseases of the Ne

Central nervous system consists of

brain and spinal cord

CNS

central nervous system

PNS

peripheral nervous system

peripheral nervous system

nerves that branch from the CNS

Meninges

3 layers of membranes that cover and protect the brain and spinal cord

dura mater layer

outer layer

arachnoid layer

middle layer

pia mater layer

innermost layer

what contains cerebrospinal fluid (CSF)

subarachnoid

CSF

cerebrospinal fluid

blood brain barrier

network of blood vessels that acts as a filter and carries blood to brain and spinal cord tissue

Meningitis

inflammation of the meninges

encephalitis

inflammation of the brain

Meningoencephalitis

inflammation of the brain and meninges

Bacterial meningitis

fever headache and stiff neck, followed by nausea and vomiting, can turn into convulsions and coma; death from organ shock due to endotoxin from gram negatives and cell wall fragments from gram positives

Meningitis: Haemopilus influenzae type b

G- aerobic, normal throat microbiota, can enter bloodstream, pathogenicity due to capsule antigen Type b, occurs mostly in children and is prevented by the Hib vaccine

Pneumococcal Meningitis: Streptococcus pneumoniae

G+ encapsulated diplococcus, 70% population healthy carriers, causes pneumonia and otitis media, most common in children, main cause of bacterial meningitis, prevented by conjugate vaccine

main cause of bacterial meningitis

Streptococcus pneumoniae

Meningococcal meningitis: Neisseria meningitidis

G- aerobic diplococcus, capsule, droplet/aerosol/secretion contact transmission, 40% are healthy carriers, throat infection spreads to blood then to meninges, 10-15% mortality

Diagnosis types for bacterial meningitis

Sample CSF via spinal tap or lumbar puncture, gram stain of CSF, culture CSF, latex agglutination tests

Treatment types for bacterial meningitis

chemotherapy initiated before diagnosis, broad-spectrum 3rd generation cephalosporins

Listeriosis: Listeria monocytigenes

G+ rod, usually foodborne, can grow at fridge temperatures, can cause sepsis, red produces in phagocytes, can cause meningitis, treatment is penicillin

Tetanus: Clostridium tetani

G+, endospores forming, obligate anaerobe, found in soil, grows in deep wounds, tetanospasmin neurotoxin released from dead cells enters CNS and causes muscle spasms, death via respiratory muscle spasms, prevented by tetanus toxoid (DTaP) vaccine

Botulism: Clostridium botulinum

G+, endospore forming, obligate anaerobe, found in soil and aquatic sediments, specific for synaptic end of nerve causing flaccid paralysis, death by respiratory or cardiac failure, foodborne/infant botulism due to lack of intestinal microbiota/wound botulism

Leprosy: Mycobacterium leprae

“Hansen’s disease”, acid fast rod, 30°C ideal temp, 12 day generation time, grows in peripheral nerves and skin cells, transmission via prolonged contact or inhaling secretions, incubates for years

Leprosy types

Tuberculoid (neural) form and Lepromatous (progressive) form

Leprosy: Tuberculoid form

neural, loss of sensation in skin areas

Leprosy: Lepromatous form

progressive, disfiguring nodules on body, affects mucous membrane, diagnosed via skin biopsy/skin smear/blood test, acid-fast stain of skin scrapings, treatment of antibiotics for 6-24 months

Polio/Poliomyelitis: Poliovirus

transmitted by ingesting feces-containing water, mostly mild or asymptomatic cases, sore throat and nausea, may lead to viremia or entering the CNS

How many serotypes of poliovirus

3

Salk vaccine

inactivated injectable vaccine for poliovirus

Sabin vaccine

attenuated oral vaccine for poliovirus, risk of reversion due to virulence

Rabies: Lyssavirus

bullet shaped, single stranded RNA, transmitted via saliva, 1-6 human cases in the U.S. annually, causes encephalitis, muscle spasms and hydrophobia, forms negri bodies in the brain system, 30-50 day incubation

Furious rabies

classical rabies, animals restless, then highly excitable, aggressive biting, paralysis, then death in several days

Paralytic rabies

dumb/numb rabies, animals seem unaware of surroundings, minimally excitable

Arboviral encephalitis

arbovirus, arthropod-borne virus, several families of viruses, caused by mosquito-borne viruses with seasonal incidence

Eastern equine encephalitis (EEE) and western equine encephalitis (WEE)

EEE has 30% mortality in humans, brian damage/deafness/neurologica

West nile virus (WNV)

bird-mosquito-bird cycle, culex mosquitoes are the vector, most cases subclinical and mild, can cause polio-like paralysis and fatal encephalitis

Zika virus disease

vector is Aedes spp. mosquito, can be transmitted sexually/mother to fetus/blood transfusions, 20% cases are mild, infection during pregnancy creates risk of microcephaly in infants

Meningitis: Cryptococcus neoformans

soil fungus, transmitted via respiratory route, spreads thru blood via CNS in immunocompromised, 30% mortality, treatment with amphotericin B and flucytosine

African Trypanosomiasis: sleeping sickness

flagellated protozoans, humans are the only reservoir for Trypanosoma brucei gambiense, fever/headache/deterioration of CNS, transmitted by tsetse flies, parasite evades antibodies by antigenic variation

Amoebic Meningeocephalitis

Naegleria fowleri is protozoan, causes primary amoebic meningoencephalitis (PAM), infects nasal mucosa/penetrates brain/feeds on brain tissue, 100% mortality

Scrapie

prion, TSE in sheep

TSE

transmissible spongiform encephalopathies

Creutzfeldt-Jakob disease (CJD)

TSE in humans

Bovine spongiform encephalopathy (BSE)

mad cow disease, may be caused by cattle eating feed containing bone meal from scrapie-infected sheep

Prion sterilization

extended autoclaving at 134°C and using NaOH, no PrPSc detection exists for live animals

Congenital infections

mother to fetus, vertical transmission

Congenital virus infections

Zika, neonatal herpes, rubella

Congenital bacterial infections

Listeria monocytogenes, Group B Streptococcus

Congenital protozoan infections

Toxoplasma gondii

TORCH test

screen tests pregnant women for congenital diseases; Toxoplasmosis, other, Rubella, Cytomegalovirus, Herpes