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MD1 SF3 - EXAM 1 > Microbiologie: Flore normale, pathogenèse et virulence > Flashcards

Microbiologie: Flore normale, pathogenèse et virulence Flashcards

1
Q

What is colonization?

A

Presence of a microorganism in a host without necessarily causing an illness… the microorganism will still be able to replicate and be transmitted

Can be preemptive step to an infection

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2
Q

What is an infection?

A

Invasion of a host organism by a biologically active pathogen that can multiply and cause an illness (symptômes, signes cliniques, dysfonctions physiologiques, réponse immunitaire, inflammation) but may also be in sub-clinical latency or in the pre-symptomatic phase.

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3
Q

What is contamination?

A

Presence of a microorganism on nonliving things and contact with these items can lead to propagation of these infectious agents (fomites)

  • fomites: objects or materials which are likely to carry infection, such as clothes, utensils, and furniture.

Contamination in the lab: evidence of microbes that aren’t from the area that was tested

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4
Q

What does a microorganism need to do to cause an illness? (6 steps)

A
  1. penetrate organism
  2. adhere to host cells (not always)
  3. compete with normal bacteria
  4. resist immune defenses, etc…
  5. invade target tissues
  6. cause physiological dysfunction
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5
Q

What are the different kinds of reservoirs for pathogens? (STEP 1)

A

Human:

  • porteurs sains (healthy, not effected by illness)
  • porteurs latents (has been controlled by their body)
  • porteurs malades (can’t control it anyone… proliferates and can exit host and be spread)

Animals: zoonoses (ex: toxoplasma, anthrax, giardia)

Inanimés:

  • earth (tetanus)
  • water (cholera)
  • food (gastroenteritis)
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6
Q

How are microbes transmitted? (STEP 1)

A

direct contact: intimate relations, droplets/aerosol

living vectors: malaria, Zika, Nile, tularemia, Lyme, the plague, encephalitis, etc…

inanimate carrier: knives, nails, needles, thorns, STETHOSCOPE, etc…

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7
Q

What is pathogénicité? (STEP 1)

A

The ability for a microorganism to cause an infection QUALITATIVE

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8
Q

What is a primary infection?

A

illness caused in healthy individuals

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9
Q

What is an opportunistic infection?

A

causes infections in people that are immunocompromised/immunodeficient or in barriers that are already broken which make the patient more susceptible to infection

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10
Q

What is virulence? (STEP 1)

A

The degree of pathogénicité QUANTITATIVE

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11
Q

How is virulence measured?

A

taux de morbidité

taux de mortalité/LD50

(can be made worse/better by mutations… these variants can change the virulence of a microorganism over time)

  • ex: new strains of COVID
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12
Q

What are some risk factors? (STEP 1)

A

Genetics: M vs. W, deficiencies

Age: old, < 2 years old

Malnutrition, lifestyle, chronic illnesses (AIDS, CF), taking other medications (chemo), environment (weather, mosquitos?, animals?)

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13
Q

What are the two main ways microbes can enter the body? (STEP 1)

A

Muqueuses (ex: respiratory, digestive, genitals)

Skin (ex: follicles, cuts, etc.)

  • voie parentérale (lesions, pokes, cuts, bites)
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14
Q

How do microbes adhere to host cells? (STEP 2)

A

adhésine: glycoprotein or lipoprotein on the surface of the bacteria (velcro)

recepteur: sugar on host cell

LOOK AT NOTION FOR SPECIFICS

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15
Q

How do microbes compete with “flore normale”? (STEP 3)

A

Many ways specific to location in the body

Human body: 10^13 eucaryotic cells (with RBCs… 10^14) and 10^14 microbes

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16
Q

What is the microflore?

A

Ecological communities of commensal, symbiotic and pathogenic microorganisms

17
Q

What is the microbiome?

A

Microbiota + environment: genetic material of all the microbes (bacteria, fungi, protozoa and viruses) that live on and inside the human body

18
Q

What is metagenomics?

A

study of genetic material recovered directly from environmental samples

19
Q

What is the role of the “flore normale”?

A

protection, metabolism, stimulate immune response, can sometimes cause infections

20
Q

Where can the “flore normale” be found?

A

mouth, skin, digestive and respiratory systems, genitourinary system (especially in the vagina)

21
Q

What is the normal bacteria found on the skin? (STEP 3)

A

Not a very good environment for bacterial growth except for humid areas (groin, armpits, neck, etc.)

Flora here can be “résidente ou transitoire”

what are the most common ones?

staphylococcus, corynebacterium, propionibacterium (Cutibacrium acnes —> linked to acne)

22
Q

What are cutaneous staph infections?

A

coagulase positive or negative:

  • 90% of the flora found on the skin originates from the nose
  • S. epidermidis Is the most common —> not a pathogen but S. aureus can be a pathogen
    • 90% of S. aureus are resistant to penicillin
  • can cause folliculitis, furuncles (boil), impetigo
  • infections nosocomiales: SARM (resistant to meticillin)
23
Q

What is acne?

A

most frequent skin disease

genetic and hormonal influence that favours sebum production and leads to the eventual blockage of openings of pilosebaceous units which leads to the accumulation of sebum

Cutibacterium acnes hydrolyzes glycerol and produces fatty acids which attract inflammatory cells —> apparition of papules and pustules

24
Q

What is the normal bacteria found in the mouth? (STEP 3)

A

oral mucosa: Streptococcus salivarius, Bacteroides, yeast

teeth: Streptococcus mutans —> **caries **

25
Q

What is the normal bacteria found in GI tract? (STEP 3)

A

Stomach:

  • H. pylori –> ulcers
  • pH of 2

​​Duodenum:

  • Lactobacilli (acido-resistants)

Jejunum:

  • pH 4-5
  • Streptococci, lactobacilli

Ilium and colon:

  • colon pH: 7
  • so much bacteria
26
Q

What happens when you take antibiotics?

A

flora is disrupted and the loss of ecological niches can favour the proliferation of C. difficile —> diarrhea in patients

  • if antibiotics don’t work to treat the C. difficile.. you can resort to a fecal transplant
27
Q

What is the normal bacteria found in respiratory system? (STEP 3)

A

Nose: Staphylococcus, streptococcus, Haemophilus

Throat and nasopharynx: similar to saliva

Trachea, bronchi, lungs: once considered to be sterile

28
Q

What is the normal bacteria found in genitourinary tract? (STEP 3)

A

kidneys and bladder: usually sterile

ureters: staphylococcus, streptococcus, enterococcus, anaerobic bacilla
vagin: very complex

  • adult: vaginal epithelium —> glycogen —> Lactobacillus —> lactic acid —> acidic pH (3.8-4.5)
  • before puberty and after ménopause: no glycogen —> no Lactobacillus —> **no lactic acid —> alkaline pH (≥ 7)
29
Q

What are some of the ways in which microbes can resist the immune system? (STEP 4)

A

Hide their vulnerable components, protect from phagocytosis, survive inside leukocytes, secrete enzymes that destroy leucocytes, interfere with antibodies and the compliment

30
Q

What extracellular enzymes (4 kinds) can be secreted to help invade host tissue? (STEP 5)

A
  1. cytolysines: break cellular components (collagénase, phospholipases)
  2. hémolysines: destroy RBCs, alpha and beta hémolyses, strep B-hémolytiques groupes A, B, C
  3. coagulases et fibrinolysines: provoque formation of caillots or prevent coagulation
  4. leucocidines: destroy leucocytes by perforating them
31
Q

What are the different types of toxins? (STEP 6)

A

Endotoxins and exotonins

32
Q

How to endotoxins work?

A

naturally in gram - cell, released when it starts being attacked by WBCs/antibiotics

  • Bacteremia —> sepsis —> septic shock —> dead
  • Endotoxin —> inflammatory mediators, cytokines —> fever, cellular toxicity
  • Endotoxin —> vasoactive mediators —> vascular problems and hypotension
  • Heart/lung/kidney failure —> high mortality rate without antibiotics
33
Q

How does the inflammatory reaction started by endotoxins work?

A

Redness, swelling, heat, pain

  • can be localized or systemic, chronic or acute
  • médiateurs protéiques: cytokines, chimiokines
  • médiateurs lipidiques: prostaglandines, leucotriènes
    • TNF-alpha and interleukine-1 (PRO INFLAMMATORY)
  • Other mediators: nitric oxide
  • Involves adhesion molecules, receptors, etc. and interaction with systems
34
Q

What exotoxins are secreted?

A

proteins, poisons (sub-unit A and B), cytotoxins (all cells), neurotoxins (nervous system), enterotoxins (attack cells lining GI tract)

35
Q

What is a good thing about exotoxins?

A

most exotoxins can be inactivated by heat into completely safe anatoxins

36
Q

What are some examples of diseases caused by exotoxins? (10)

A
37
Q

What is tetanus?

A
  • Clostridium tetani in contaminated soil from fecal matter
  • Can stay in the ground for a long time (spores)
  • Secretes a potent exotoxin (neurotoxin) which blocks nerve impulse and stops cells from relaxing leading to severe full-body spasms, paralysis, and death
  • Vaccine: TDAP… booster every 10 ish years
38
Q

What is botulism?

A
  • alimentary intoxication caused by Clostridium botulinum that secretes toxine botulinique (poison)
  • causes facial paralysis and cardiorespiratory problems
  • without treatment: 70% mortality rate
  • thankfully, it is inactivated by heat

MD1 SF3 - EXAM 1 (11 decks)

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