Microbiology Chapter 20

Yersinia pestis - caused the black death of the middle ages - pandemics

1) Small gram negative rod, rodent reservoir, and insect vector.

2) Rats, small rodents, ground squirrels

3) Humans acquire it from fleas

d. Disease starts at site of bite, and the organisms enter blood stream where the bacteria are phagocytized, grow in phagocyte and the organisms proliferate to infect lymph nodes (form bulbous swellings – buboes (619) – thus bubonic plague)

e. Can spread to lungs – pneumonic form and can be spread by respiratory droplets – very serious form of disease and can often be fatal

f. Septicemia is also seen

g. Now found in the us west and seem to be more cases (people and rodents are coming together more often) – endemic in rodents

h. Antibiotics – streptomycin and tetracycline are effective if caught early enough – vaccine is available

Francisella tularensis – 90% acquired by handling wild rabbits (skinning), can be transmitted by ticks, even infected wild meat – streptomycin, gentamycin drugs of choice – so infective in such small doses that researchers have to be extra careful.

Brucella species - undulant fever

small gram (-) rod, fastidious, cattle, sheep, goats, wild animals like elk

a. Brucellosis usually mild, self limiting disease, fever rises and peaks at night – thus undulant fever

b. Used to be passed to humans through unpasteurized milk

c. With current vaccination programs and pasteurization occurs infrequently

Borrelia burgdorferi (pg. 625 life cycle)

spirochete transmitted by tick bite, deer tick in Texas - probably the most common tick borne disease in the us

a. Circular rash (bulls eye) at site of bite (pg 624)

b. Systemic progression of disease – aches, pains, fever, fatigue, chronic arthritis symptoms

c. Caught early, antibiotics are useful, in later stages, large doses are required

d. Lyme county Conn. – first described in 1970

small gram – obligate intracellular parasites

a. Rocky mountain spotted fever – tick borne

b. Typhus – lice or fleas

c. Systemic diseases, caught early then antibiotics are
effective

hemorrhagic viral diseases, spread by mosquitos.

a. Panama canal was halted because of yellow fever – a serious infection with a high mortality rate

b. US finished it after Walter Reed discovered a vaccine for yellow fever

c. Dengue fever similar to yellow fever, break bone fever – so painful, person feels bones are breaking.

Infectious mononucleosis – large enveloped DNA virus that can survive outside host. Infects the lymphatic system and can last for weeks

Malaria – mosquito born-look at our lab manual – complex life cycle (see page 633 for life cycle) chloraquinone is drug used to treat it, now have resistant strains, old quinine treatment had lots of side effects

See page 627, checkpoint 20.7

a. Marburg – filament virus, from monkeys imported from Africa to Marburg germany

b. Ebola – another filo virus, 90% mortality rate, shepherds crook

c. Lassa fever African disease, rodents involved see

pg 641 these bugs make good thriller movies

protozoan with complex life cycle. Transmitted to humans usually by cats. Particularly a problem with fetus, organism can cross placenta. HIV patients are at higher risk

Trematode helminth -- Flukes