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51 Cards in this Set
- Front
- Back
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What does the virulence factor of shigellae do?
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Subvert nomal host cell functions so as to benefit the invading bacterium, such as the ability to acquire iron, adhere to host cells or invade them.
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How many proteins does shigella comprise of?
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20 to 30 different proteins. Some protein form needlelike structure connected to a basal body.
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What protein do Shigella uses for structual component like the needle?
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Spa protein.
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What is Ipa B proteins in shigellae used for?
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Ipa B protein appears to be used to invade the host - homologous with many pore forming toxins.
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What does the needlelike structure in shigellae do?
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The needle penetrates the targe cell membrane and deliver other proteins through it.
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What is the incubation period for shigellae?
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Incubation ranges from 1-3 days; through organisms are shed over a period of 1-2 weeks.
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How is shigellae diagnosed?
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Identification of isolates is based on biochemical characteristic and serology.
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How long does shigellosis last?
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The disease is normally self-limiting in adults and last an average of 4-7 days.
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Why is shigellosis fatal to infant and young children?
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It can lead to neurological complications and kidney failure.
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What is the sufficient treatment for shigellosis?
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Fluid and electrolyte replacement.
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When necessary, what is the treatment for shigellosis?
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trimethoprim-sulfamethoxazole or flouroquinolones
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How can we prevent shigellosis?
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Good personal hygiene and maintenance of clean water supply.
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What causes Staphylococcal food poisoning?
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Ingestion of improperly stored or cooked food - hams, processed meats, chicken salad pastries, ice cream and hollandaise sauce, in which Staphylococcus aureus has grown.
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What is S. aureus?
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Gram-positie coccus that is very resistant to heat,drying, and radiation.
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Where can we find S. aureus?
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Nasal passages and on the skin of humans and other mammals worldwide - from these sources they can readily enter food.
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What's going to happen if S. aureus are allowed to incubate in certain food?
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They produce heat-stable enterotoxins that render the food dangerous even though it appears normal.
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Is there going to intoxication in S. aureus even if the food has been thoroughly cooked?
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Yes. Once the bacteria have produced the toxin, the food can be extensively and properly cooked, killing the bacteria without destroying the toxin.
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How many enterotoxins have been identified for S. aureus
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13 different enterotoxins - A, B, C1, C2, D, and E are the most common, A & B are superantigens.
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How does these enterotoxins act? (S. aureus)
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Act as neurotoxin that stimulate vomiting through the vagus nerve.
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What are the symptoms for staphylococcal food poisoning?
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Abdominal pain, cramps, diarrhea, nausea, and vomiting.
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What is the onset of staphylococcal food poisoning?
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usually 1 to 8 hours - usually less than 24 hours.
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How is staphylococcal food poisoning being diagnosed?
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Diagnosis based on symptoms or laboratory identification of bacteria from the food.
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How is enterotoxins detected from staphylococcal food poisoning?
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Enterotoxins may be detected from animal toxicity tests or antibody-based methods.
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What is the treatment for staphylococcal food poisoning?
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Fluid and electrolyte replacement.
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How can we preven and control staphylococcal food poisoning?
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Avoidance of food contamination, and control of personnel responsible for food preparation and distribution.
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What is the major agent for Traveller's diarrhea?
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E. coli
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Why does E. coli doesn't cause any problem in the resident population?
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Immunity to previous exposure.
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What are the major categories or strains of diarrheagenic E. coli?
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1. Enterotoxegenic E. coli (ETEC) 2. Enteroinvasive E. coli (EIEC) 3.Enteropathogenic E. coli (EPEC) 4. Enterohemorrhagic E. coli (EHEC) 5. Enteroaggregative E. coli (EAggEC) 6. Diffusely adhering E. coli (DAEC)
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What is Enterotoxigenic E. coli (ETEC)?
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Strains produce one or both of two distinct enterotoxins, which are responsible for diarrhea and distinguished by their heat stability: heat stable (ST), and heat labile enterotoxin (LT)
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Where does ETEC ST and LT acquired from?
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The genes for ST and LT production and for colonization factors are usually plasmid-borne and acquired by horizontal gene transfer.
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What does ETEC ST do?
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ST binds to glycoprotein receptor that is coupled to guanylate cyclase on the surface of the intestinal epithelial cells.
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What does guanylate cycle do?
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Activation of guanylate cyclase stimulates the production of cyclic guanine monophospate (cGMP), which leads to the secretion of electrolytes and water into the lumen of the small intestine, manifested as watery diarrhea characteritic of ETEC infection.
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What is the characteristic of ETEC infection.
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watery diarrhea
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What does LT do?
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LT binds to specific gangliosides on the epithelial cells and activates the membrane bound andenyclate cyclase.
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What does the activation of adenyclate cyclase do?
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It increases the production of cyclic adenosine monophospate (cAMP) through the same mechanism employed by cholera toxin. Result is hypersecretion of electrolytes and water in the intestinal lument.
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What is Enteroinvasive E. coli (EIEC)?
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Strains causes diarrhea by penetraing and multiplying within the intestinal epithelial cells.
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How does EIEC invade epithelial cells?
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The ability to invade epithelial cells is associated with the presence of large plasmid; EIEC may also produce cytotoxin and enterotoxin.
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What is Enteropathogenic E. coli (EPEC)?
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Strains attach to the brush border of intestinal epitheilial cell and cause a specific type of cell damage - effacing lesions.
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What is effacing lesions?
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Is also called attaching-effacing (AE) lesions represent destruction of brush border microvilli adjacent to adhering bacteria.
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What is the important cause of diarrhea in children residing in developing countries?
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AE E. coli - EPEC
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What is enterohemorrhagic E. coli (EHEC)?
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Strains carry the bacteriophage-encoded genetic determinants for shiga-like toxin (Stx-1 and Stx-2 proteins)
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EHEC produces what to the body?
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Produces AE lesions causing hemorrhagic colitis with severe abdominal pain and cramps followed by bloody diarrhea.
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Stx-1 and Stx-2 is implicated in what kind of disease?
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Extraintestinal disease
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What is hemolytic uremic syndrome?
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Severe hemolytic anemia that leads to kidney failure?
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What is the major type EHEC?
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E. coli O157:H7
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What is enteroaggregative E. coli (EAggEC)?
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Strains adhere to epithelial cells in localized regions, forming clumps of bacteria with a "stacked brick" appearance.
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What is diffusely adhering E. coli (DAEC)?
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Strains adhere over the entire surface of the epithelial cells and usually cause diseasse in immunoligically naive or malnourished children.
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How do you diagnose traveller's diarrhea?
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caused by E. coli based on past travel history and symptoms.
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What is the laboratory diagnosis for traveller's diarrhea?
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Laboratory diagnosis is by isolation of the specific type of E. coli from feces and identification using DNA probes, the determination of virulence factors,and the polymerase chain reaction.
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What is the treatment for traveller's diarrhea?
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Treatment is with fluid and electrolytes plus doxycycline and trimetroprim-sulfamethoxazole.
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How can traveller's diarrhea be prevented and controlled?
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Avoid contaminated food and water.
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