Microbiologie: Flore normale, pathogenèse et virulence

Question 1

What is colonization?

Answer 1

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

Question 2

What is an infection?

Answer 2

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.

Question 3

What is contamination?

Answer 3

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

Question 4

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

Answer 4

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

Question 5

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

Answer 5

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)

Question 6

How are microbes transmitted? (STEP 1)

Answer 6

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…

Question 7

What is pathogénicité? (STEP 1)

Answer 7

The ability for a microorganism to cause an infection QUALITATIVE

Question 8

What is a primary infection?

Answer 8

illness caused in healthy individuals

Question 9

What is an opportunistic infection?

Answer 9

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

Question 10

What is virulence? (STEP 1)

Answer 10

The degree of pathogénicité QUANTITATIVE

Question 11

How is virulence measured?

Answer 11

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

Question 12

What are some risk factors? (STEP 1)

Answer 12

Genetics: M vs. W, deficiencies

Age: old, < 2 years old

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

Question 13

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

Answer 13

Muqueuses (ex: respiratory, digestive, genitals)

Skin (ex: follicles, cuts, etc.)

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

Question 14

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

Answer 14

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

recepteur: sugar on host cell

LOOK AT NOTION FOR SPECIFICS

Question 15

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

Answer 15

Many ways specific to location in the body

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

Question 16

What is the microflore?

Answer 16

Ecological communities of commensal, symbiotic and pathogenic microorganisms

Question 17

What is the microbiome?

Answer 17

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

Question 18

What is metagenomics?

Answer 18

study of genetic material recovered directly from environmental samples

Question 19

What is the role of the “flore normale”?

Answer 19

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

Question 20

Where can the “flore normale” be found?

Answer 20

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

Question 21

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

Answer 21

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)

Question 22

What are cutaneous staph infections?

Answer 22

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)

Question 23

What is acne?

Answer 23

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

Question 24

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

Answer 24

oral mucosa: Streptococcus salivarius, Bacteroides, yeast

teeth: Streptococcus mutans —> **caries **

Question 25

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

Answer 25

**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

Question 26

What happens when you take antibiotics?

Answer 26

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

Question 27

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

Answer 27

**Nose**: Staphylococcus, streptococcus, Haemophilus **Throat and nasopharynx**: similar to saliva **Trachea, bronchi, lungs**: once considered to be sterile

Question 28

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

Answer 28

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)

Question 29

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

Answer 29

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

Question 30

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

Answer 30

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

Question 31

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

Answer 31

Endotoxins and exotonins

Question 32

How to endotoxins work?

Answer 32

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

Question 33

How does the inflammatory reaction started by endotoxins work?

Answer 33

**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

Question 34

What exotoxins are secreted?

Answer 34

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

Question 35

What is a good thing about exotoxins?

Answer 35

most exotoxins can be inactivated by heat into completely safe anatoxins

Question 36

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

Answer 36

Question 37

What is tetanus?

Answer 37

* *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

Question 38

What is botulism?

Answer 38

* 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