exam 3 Flashcards
pathogens with animals as reservoirs
Yersinia, most salmonella
pathogens with humans as reservoirs
Shigella, Salmonella typhi
opportunistic pathogens
Escherichia, Klebsiella, Proteus
pathogens spread endogenously
E.coli
true pathogens
always associated with disease. Salmonella, shigella, yersinia
serologic group of EB based on 3 groups of antigens
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
LPS consists of three parts
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
General EB virulence factors
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)
E.coli virulence factors
Adhesins - clonization fator antigen (CFA/I-CFA/III)
AAF/I, AAF/III, Bfp, Ipa
Exotoxins - shiga toxins lysogenic strains only,
E.coli epidemiology
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
Septicemia
Originates from urinary or GI tract infections. mortality rate is 90% when immunocompromised, when primary infection is in the abdomen or CNS
Urinary tract infection
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.
Neonatal meningitis
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.
6 groups cause gastroenteritis
- Enterotoxigenic (ETEC)
- Enteropathogenic (EPEC)
- Enterinvasive (EIEC)
- Enterhemmorhagic (EHEC)
- Enteroaggregative (EAEC)
- Diffusely adherent (DAEC)
ETEC
Enterotoxigenic E.coli - most common in developng countries, high infectious dose no perso to person spread
Guillain Barre Syndrome
pathogens
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?
Helicobacter pylori
colonization
tissue damage
evidence
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
Proteus mirabilis and what causes stones
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
Septicemia
E.coli
Originates in GI and urinary tract,
90% mortal if initial infection is in abdomen or CNS
UTI
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
Neonatal meningitis
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
Salmonella
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
Enteritis
most common form of salmonelosis, from contaminated food/water, 6-48 hrs first symptoms, resolve in 2-7 days, diarrhea no blood
Salmonella
Septicemia
risk is higher in immunocompromised,
osteomylytis, endocarditis and arthritis
Salmonella
Enteric fever
Typhoid - S.typhi Paratyphoid fever - S.paratyphi 7 day fever followed by GI symptoms after colonization of gall bladder Salmonella
Shigella
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
Shigellosis
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
Yersinia
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
Bulbonic plague
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
Pneumonic plague
Y.pestis
initially fever, malaise, pulmonary signs develop within 1 day, patients are highly infectious - aerosol transmission, 90% mortality rate even when treated
Enterocolitis
Y.enterocolitica
ingest contaminated food and water; diarrhea fever, abdominal pain for 2 weeks, can becaome chronic and persist for 2 months
Bacteremia
Y.enterocolitica
Blood transfusions - related bacteremia
yersinia can grow at 4C
Klebsiella
K.pneumoniae, community-acquired pneumonia, necrosis of alveolar spaces, cavity formation blood tinged sputum,
also causes wound, soft tissue infections and UTIs
Proteus
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
EB treatment and prevention
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
Vibrio cholerae
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
Vibrio parahaemolyticus
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
Vibrio vulfinicus
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
Aeromonas
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
Plesiomonas shigelloides
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
Pseudomonas
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
Pseuomonas pulmonary infections
lower respiratory tract colonization in 100% patients with cystic fibrosis and chronic lung disease
pseudomonas primary skin infections (burns)
predisposing factors for infection, moist surface of the burn, lack of immune response to invasion, topical ab has little success
Pseudomonas primary skin infections (folliculitis)
results from immersion in contaminated water, hot tubs, swimming pools,
secondary folliculitis infections in people with bad acne
Pseudomonas UTI and ear infections
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
Pseudomonas eye infections
occur after truma to cornea then exposure to organism in contaminated water - contact lense abraison, scratch - corneal ulcers, eye-threatening disease
Campylobacter jejuni
most common cause of bacterial gastroenteritis in US
Campylobacter coli
2-5% of campylobacter associated gastroenteritis
Campylobacter fetus
systemic infections - bacteremia, arthritis, meningitis
