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med micro exam 3 > exam 3 > Flashcards

exam 3 Flashcards

1
Q

pathogens with animals as reservoirs

A

Yersinia, most salmonella

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2
Q

pathogens with humans as reservoirs

A

Shigella, Salmonella typhi

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3
Q

opportunistic pathogens

A

Escherichia, Klebsiella, Proteus

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4
Q

pathogens spread endogenously

A

E.coli

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5
Q

true pathogens

A

always associated with disease. Salmonella, shigella, yersinia

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6
Q

serologic group of EB based on 3 groups of antigens

A

1) Somaic O polysaccharides (LPS) - common to all EB, specific to each genus
2) K antigens (capsule) - common but different among both EB and non-EB
3) H proteins (flagella) - heat-liable, can undergo antigenic variation

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7
Q

LPS consists of three parts

A

heat-stable major cell wall antigen

1) Lipid A - fatty acids attach LPS to OM
2) Core polysaccharides - joined to lipid A, 10 sugars
2) O side chain (Oantigen) - polyssachiride chain varying in composition

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8
Q

General EB virulence factors

A

Endotoxin - lipid A of LPS released upon cell lysis
Can cause 5 things:
1-hypoglycemia
2-fever
3-reduced fever (soluble portion)
4-shock
5-DIC thrombosis (dissem interv clotting) - clotts but blood still pumping -> bleed out

Capsule - antigens prevent binding of antibodies to bacteria, poor immunogens

Antigenic phase Variation - capsular K and flagella H antigens under genetic control, protects from antibody-mediated cell death

Type III secretion system - delivers virulence factors directly into eukaryotic cells

Iron - is most important growth factor for EB

Hemolusins - lyse host cells->release iron bound in heme proteins (hemoglobin, myoglobin)

Enterobactin, aerobactin - act as competitive iron chelating compounds (lactoferrin, transferring)

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9
Q

E.coli virulence factors

A

Adhesins - clonization fator antigen (CFA/I-CFA/III)
AAF/I, AAF/III, Bfp, Ipa

Exotoxins - shiga toxins lysogenic strains only,

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10
Q

E.coli epidemiology

A

most common G- bacilli isolated from patients with sepsis, causes more than 80% of all UTis, prominent cause of gastroentericsin developing countries, most infections are endogenous(when immunocompromised)
Exceptions: neonatal meningitis, gastroenteritis

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11
Q

Septicemia

A

Originates from urinary or GI tract infections. mortality rate is 90% when immunocompromised, when primary infection is in the abdomen or CNS

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12
Q

Urinary tract infection

A

ascending infection, originate in colon->urethra->bladder->kidney or prostate, strains producingP pilli, AAFs, and Dr are the most virulent UTI strains:bind very tight to bladder and upper urinary tract - prevent elimination. Hemolysin A - lyses cells , stimulates inflammatory response.

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13
Q

Neonatal meningitis

A

CNS infections in infants less than 1 month old, primary cause by E.coli and group B streptococci,
E.coli K-1 (K1 capsular antigen) - common in G tract of pregnant women and newborns, unknown ho causes disease in infants.

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14
Q

6 groups cause gastroenteritis

A
  • Enterotoxigenic (ETEC)
  • Enteropathogenic (EPEC)
  • Enterinvasive (EIEC)
  • Enterhemmorhagic (EHEC)
  • Enteroaggregative (EAEC)
  • Diffusely adherent (DAEC)
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15
Q

ETEC

A

Enterotoxigenic E.coli - most common in developng countries, high infectious dose no perso to person spread

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16
Q

Guillain Barre Syndrome

pathogens

A

Campylobacter jejuni, Campilobacter upsaliensis

autoimmune disorder of peripheral nervous system, due to closs reactivity between oligosaccharides of campylobacter and lipids on surface of neural tissue?

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17
Q

Helicobacter pylori

colonization
tissue damage
evidence

A

Initial colonization:
blockage of acid production by bacterial acid-inhibitory protein. Neutralize gastric acid by ammonia, produced by urease activity

Tissue damage:
Urease byproducts-mucinase, phospholipase
Vacuolating cytotoxin - induces inflammatory response

Evidence tha H.pylori is the tiologic agent in all cases of type B gastroenteritis (ulcers)

1) a 100% association between gastritis and infection with organism
2) production of experimental infection in both animals and humans
3) histologic resolution of pathologic changes when specific therapy used to eradicate the organism

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18
Q

Proteus mirabilis and what causes stones

A

most common disease produced by this genus is UTI

Produces urease->splits urea into carbon dioxide and ammonia->increases urine pH->facilitates formation of renal/bladder stones and is toxic to uroepithelium

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19
Q

Septicemia

A

E.coli
Originates in GI and urinary tract,
90% mortal if initial infection is in abdomen or CNS

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20
Q

UTI

A

E.coli
Ascending infection, originate in colon
Strains producing P pilli, AAFs and Dr are the most virulent, bind very tightly to bladder and upper urinary tract, hemolysin A lyses cells stimulates inflammatory response

21
Q

Neonatal meningitis

A

E.coli, group B strep
CNS infections in infants <1 y.o.
E.coli K1 (K1 capsular antigen) - common in GI tract in pregnant women and newborns

22
Q

Salmonella

A

Resistant to acid environments (stomach, phagosome) - acid tolerance response gene
can colonize all animals,some do not host disease in nonhuman hosts
From contaminatexd food and fecal-oral transmission - children (fecal-oral), Adults (contaminated food)
Poultry, eggs, fecal oral
Multiply innside

23
Q

Enteritis

A

most common form of salmonelosis, from contaminated food/water, 6-48 hrs first symptoms, resolve in 2-7 days, diarrhea no blood
Salmonella

24
Q

Septicemia

A

risk is higher in immunocompromised,
osteomylytis, endocarditis and arthritis
Salmonella

25
Q

Enteric fever

A 
Typhoid - S.typhi
Paratyphoid fever - S.paratyphi
7 day fever
followed by GI symptoms after colonization of gall bladder
Salmonella
26
Q

Shigella

A

70% in childen <15
Endemic in homosexuals
Epidemic in daycares and nurseries
Transmitted by fecal oral route (contaminated hands)
Multiplies inside, replicate in phagosome unlike salmonella
move from cell to cell like lysteria
Shiga toxin

27
Q

Shigellosis

A

initial(enterotoxin) - cramps, fever, watery diarrhea
Secondary (cell destruction) - lower abdominal cramps, diarrhea with blood, pus and mucus
self limiting, but antibiotics used to decrease spread to family members

28
Q

Yersinia

A

All are zoonotic
humans are the accidental host, fleas and the vector
Y.pestis - systemic disease, high mortality
Y.enterocolitica - enteric, rarely systemic
Urban plague - rats are reservoir
Sylvatic plague - wildlife are reservoirs impossible to eliminate

29
Q

Bulbonic plague

A

Y.pestis
must be bitten by infected flea, high fever painful bubos (inflamated lymph nodes) in groin, 75% mortality rate, bacteremia rarely develops even with treatment

30
Q

Pneumonic plague

A

Y.pestis
initially fever, malaise, pulmonary signs develop within 1 day, patients are highly infectious - aerosol transmission, 90% mortality rate even when treated

31
Q

Enterocolitis

A

Y.enterocolitica
ingest contaminated food and water; diarrhea fever, abdominal pain for 2 weeks, can becaome chronic and persist for 2 months

32
Q

Bacteremia

A

Y.enterocolitica
Blood transfusions - related bacteremia
yersinia can grow at 4C

33
Q

Klebsiella

A

K.pneumoniae, community-acquired pneumonia, necrosis of alveolar spaces, cavity formation blood tinged sputum,
also causes wound, soft tissue infections and UTIs

34
Q

Proteus

A

P.mirabilis
UTI - most common

!!! Produces urease-splits urea into carbon dioxide and ammonia - increases urine pH - facilitates formation of renal/bladder stones and is toxic to uroepithelium

35
Q

EB treatment and prevention

A

Antibiotics cannot be used for E.coli and Salmonella gastroenteritis due to increased risk of secondary inf. and prolonged fecal carriage

Cannot prevent endogenous infections due to most organism being normal microbiota

Can prevent exogenous -

  • Salmonella - proper preparation and storage of poultry products
  • Shigella - proper hygene, especially in children

Y.pestis - vaccines

36
Q

Vibrio cholerae

A

serotypes based on O antigen (LPS)
V.cholerae O1 and O139 cause classic epidemic and pandemic cholerae, other cause cholera but not epidemic/pandemic
grow naturally in water enviroments worldwide (increased salinity low temperatures, high numbers in water with shellfish
asymptomatically infected humans serve as reservoir
initially sporadic and endemic disease spread during war

Spread by contaminated food and water, requires high infectious dose with normal gastric acidity pH 2.0-2.5

Gastric acidity decreases, ID decreases

signs begin 2-3 days after ingestion. increased flui loss, colorless odorless feces, no protein, mucus - rice water stools
death in 60% of untreated

37
Q

Vibrio parahaemolyticus

A

Consumption of improperly cooked oysters,
Self limiting diarrhea to mild cholera-like illness
develops 24 hrs after consumption - explosive watery diarrhea no blood or mucus, most recover in 72 hrs
can cause wound infections in people exposed to contaminated seawater

38
Q

Vibrio vulfinicus

A

Rapidly progressive wound infections after exposure to contaminated seawater
initiall swelling, pain; development of vesicles; tissue necrosis, systemic signs fever and chills
50% mortality rate once systemic even with treatment

39
Q

Aeromonas

A

Ubiquitous in water,
GI carriage in 30% increases during warmer months

  • Opportunistic systemic disease - in immunocompromised
  • Diarrheal disease - in immunocompetent, acute and severe in children resembling shigelosis
40
Q

Plesiomonas shigelloides

A

Taxonomically related to Proteus, serologically to Shigella
Infected from contact with contaminated water, seafood or exposure to amphibians or reptiles
Self limited gastroenteritis with 48hrs onset
susceptibility is a must

41
Q

Pseudomonas

A

Ubiquitous in water, soil, vegetation
Found throughout hospital (food, cut flowers, sinks, toilets
Normal microbiota in hospitalized and immunocompromised, opportunistic infections. P. aerogenosa most common

42
Q

Pseuomonas pulmonary infections

A

lower respiratory tract colonization in 100% patients with cystic fibrosis and chronic lung disease

43
Q

pseudomonas primary skin infections (burns)

A

predisposing factors for infection, moist surface of the burn, lack of immune response to invasion, topical ab has little success

44
Q

Pseudomonas primary skin infections (folliculitis)

A

results from immersion in contaminated water, hot tubs, swimming pools,
secondary folliculitis infections in people with bad acne

45
Q

Pseudomonas UTI and ear infections

A

UTI - primarily in patients with long term indwelling urinary catheters treated with range of AB

Ear infections - Otitis extrna media - swimmers ear
malignant external otitis - in diabetics, elderly - damage cranial nerves and bone, surgery required

46
Q

Pseudomonas eye infections

A

occur after truma to cornea then exposure to organism in contaminated water - contact lense abraison, scratch - corneal ulcers, eye-threatening disease

47
Q

Campylobacter jejuni

A

most common cause of bacterial gastroenteritis in US

48
Q

Campylobacter coli

A

2-5% of campylobacter associated gastroenteritis

49
Q

Campylobacter fetus

A

systemic infections - bacteremia, arthritis, meningitis

med micro exam 3 (1 decks)

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