Bacterial Pathogenesis Flashcards

Question

Invasion of the bacterial pathogen

Answer 1

1. Can be active penetration into host cells -ex. Type 3 secretion system: inject bacterial proteins into the host cell, can zombifies the actin cytoskeleton of the host cell, the host cell start to rearrange all its action to engulf the salmonella and bring it inside the host cell 2. Can be active penetration between host cells Ex. Secrete factors or other ways to chew up these tight junctions and the bacteria can slip in between cells 3. Can be passive -not related to pathogen itself Ex. Skin lesions, insect bites, wounds -can use existing host pathways of internalization Ex. Phagocytosis

Answer 2

Occurs when pathogen finds appropriate environment within host Important factors include: access to nutrients, pH, temperature, redox potential, protection from host “attack” Different bacterial pathogens have evolved to survive and multiply within different environments within the host Intracellular/extracellular pathogens Some bacteria invade specific cells and have adapted strategies to live inside Ex. Mycobacteria growing inside a macrophage

Answer 3

mechanisms to resist host defenses such as complement system, phagocytosis, and specific immune responses

Answer 4

Composed of chemicals not recognized as foreign Slippery and difficult for phagocytes to engulf

Answer 5

Most bacteria leave by passive mechanisms – in feces, urine, droplets, saliva, or desquamated (sloughed) cells Many symptoms of disease aid in this process – Sneezing, coughing, runny nose, diarrhea

Answer 6

Commensal E. coli strains rarely cause disease Different pathogenic strains cause different diseases

Answer 7

1. Colonization or invasion of the host 2. Ability to multiply and complete life cycles on or in host 3. Ability to evade host defenses 4. Ability to leave host and enter new host

Answer 8

1. Gene is present in strains of bacteria that cause the disease 2. Not present in avirulent strains 3. Disrupting the gene reduces virulence 4. Re-introduction of gene restores virulence. 5. The gene is expressed during infection 6. Specific immune response to the gene protects

Answer 9

E.coli with type 1 fimbriae, which bind with oligomannosides, small molecule mannoside inhibitors can bind with fimbriae, therefore prevent the bind with host cell

Answer 10

Outside the cell wall Usually polysaccharide, can be other Can protect from phagocytosis by host cells Streptococcus pneumoniae: – With capsule: kills mice – No capsule: no disease

Answer 11

Different types of (3, 4, 6)

Answer 12

- Encoded by approximately 20 genes - Present in Gram-negative pathogens (Salmonella, Shigella, Yersinia…) -Injects bacterial proteins directly into host cells “Syringe” genes: similar between the different species Injected proteins and cellular effects: vary between the different bacteria Related to the flagella’s basal body (evolution)

Answer 13

Salmonella: T3SS induces uptake into host cells Yersinia: T3SS blocks uptake into host cells

Answer 14

Endotoxin - part of the bacterial cell Exotoxins – secreted

Answer 15

LPS of Gram-negative bacteria Structural component of Gram –ve OM •released when bacteria lyses •released during bacterial multiplication Toxic component is Lipid A Heat stable Toxic only at high doses

Answer 16

Indirectly -No **enzymatic activity** on host -Interaction with host cells through binding of a receptor complex -Induced transcriptional response in the host cell -Increased production of host cell proteins which produce severe host-mediated inflammatory response -In the case of sepsis: fever, increased heart rate, increased breathing rate, low blood pressure…

Answer 17

Botulinum toxin (Clostridium botulinum) -the most poisonous naturally occurring substance in the world -One of the greatest threats for biological warfare -**Cleaves a protein involved in neurotransmission from motor neurons to muscles**

Answer 18

Double vision/blurred vision Droopy eyelids Slurred speech Difficulty swallowing Muscle weakness Injection of minute amounts leads to localized paralysis

Answer 19

Usually easily inactivated (eg by heat) inactivated toxin can be used to elicit immune response Toxin-specific antiserum can be used to treat disease Antitoxin= antibody used to neutralize a specific toxin

Answer 20

• AB exotoxins – A subunit has **enzyme activity** – B subunit mediates **cell binding/entry** – Both activity and binding can vary depending on specific toxin • membrane-disrupting exotoxins – Attack host cell membranes – E.g. hemolysins, phospholipases • Superantigens – Stimulates T cells —> exaggerated immune response • Can also be categorized by site of action: neurotoxin, enterotoxin etc.

Answer 21

Different AB toxins have: • Different receptors on host cells • Different enzymatic activities • Different biological effects • Similar overall organization

Answer 22

Pore-forming and phospholipases

Answer 23

-Does not require entry of bacteria into host or bacterial replication in host to cause disease -diseases that result from entry of a specific pre-formed toxin into host -Usually very fast onset: e.g. 30 min- 6 h

Answer 24

Bacillus cereus • Spore forming bacteria found in the soil and several foods • Produces a toxin that causes vomiting • Contamination and improper storage of food-> growth • Ingestion of toxin pre-formed in food-> vomiting • Onset within 1–5 hours of ingestion • Recovery usually within 6–24 hours

Answer 25

Cattle are asymptomatic carriers (reservoir) Outbreaks commonly associated with ground beef, manure-contaminated produce Infectious dose may be as few as 10 organisms

Answer 26

• Diarrhea which can become bloody (hemorrhagic colitis) • 0-20% of patients: hemolytic uremic syndrome (HUS): – Hemolytic anemia – Platelet deficiency – Kidney failure • 50% of HUS patients: chronic renal problems • 25% of HUS patients: neurological symptoms (seizures, stroke, coma) • Fatality of HUS: 3-5%

Answer 27

Inject Tir into host cell : a protein inserts into the host cell membrane and becomes areceptor for EHEC on the host cell ~30 other proteins which dissociate tight junctions between intestinal epithelial cells, block host phagocytic pathways and interfere with the host immune response

Answer 28

• AB toxin • Encoded by bacteriophages which have integrated into the chromosome (“prophage”) • B subunit binds specific glycolipids on host cells (**Gb3**) • A subunit inhibits protein synthesis by **modifying the 60S subunit of the ribosome**

Answer 29

• Present in intestinal epithelium ->bloody diarrhea • Present in high amounts in kidney-> kidney problems • Present in neurons-> neurological complications • Absent in cow intestine -> asymptomatic carriers

Answer 30

• Supportive care and monitoring for the development of complications • Antibiotic therapy NOT recommended: lyses of EHEC will release more toxin (increased risk of HUS) • Antiperistaltic agents (eg imodium) not: help EHEC to gather and attach recommended (increased risk of HUS) • HUS: treat the symptoms, watch and wait – Fluid administration – Platelet, RBC transfusion – Kidney dialysis

Answer 31

• Handwashing • Thorough cooking of beef • Keep raw/cooked utensils separate • Pasteurization for milk, juice