Microbio lecture 1

Question 1

Initiation of infectious disease is known as what, and what happens after?

Answer 1

Colonization -> 1.) elimination of microbe , no effect on host
2.) infectious disease (tissue dmg from organism)
3.).transient/prolonged carrier state.

Question 2

3 common shapes of typical bacteria and names

Name for no distinct shape

Answer 2

Bacillus: Rod
Coccus: sphere
spirillus: spiral

Pleomorphic = no shape

Question 3

gram positive bacteria

Answer 3

Thick peptidoglycan layer
1 membrane

Question 4

Gram negative bacteria

Answer 4

Contains LPS (Lipopolysaccharide). Synonymous with endotoxin.
thin peptidoglycan layer, between 2 membranes.

Question 5

Fungi Characteristics

Answer 5

Eukaryotic
Some unicellular (yeasts) or multicellular (molds,mushrooms)
Reproduction asexual/sexual/both
Produce spores
Generally saprophytic (feed on dead/decaying matter)
Non-photosynthetic

Tend to target lungs

Question 6

Medically important fungi : Infection site

Answer 6

Candida albicans: Vagina, mouth
Cryptococcus neoformans: Lungs, Meninges, Wound/Skin
Histoplasma capsulatum: Lungs
Aspergillus niger: Lungs
Blastomyces dermatitidis: Lungs

Question 7

Protozoa characteristics

Answer 7

Eukaryotic
Unicellular
Non-photosynthetic
Many free living, but parasitic to humans
Can be intracellular / extracellular parasites in blood, urogenital region, intestine

Question 8

Medically important protozoa

Answer 8

Giardia lamblia -> causes STD
Trichomoniasis vaginalis -> causes STD
Trypanosoma species
Leishmania species

Question 9

Helminths Characteristics, and 3 main groups

Answer 9

Eukaryotic
Multicellular
Worms
Parasitic

3 Groups:
1.) Nematodes (Roundworms)
2.) Cestodes (Tapeworms)
3.) Trematodes (Flukes)

Question 10

Most common Helminth in US, causes, Characteristics

Answer 10

Enterobius vermicularis (pinworm) is the most common helminth infection in USA
Causes anal itching

Characteristics:
Elongated
NON-SEGMENTED
Tapered at both ends
**HAVE A COMPLETE DIGESTIVE SYSTEM UNLIKE OTHERS*

Question 11

Characteristics of Cestodes

Answer 11

Ribbon-like
Segmented
Absorb nutrients (lack digestive system)

Question 12

Characteristics of Flukes

Answer 12

Flat
Leaf-like
Absorbs nutrients (lack digestive system)
Use freshwater snails as intermediate host

Question 13

Viruses Characteristics

Answer 13

Obligate intracellular parasites
Cannot replicate without a host cell
Has no cellular structure
Contains DNA or RNA
Surrounded by protein coat (capsid)
May have envelope from cell membrane of host cell
Virus particle called virion

Question 14

Human microbiome definition

Answer 14

The human microbiome is the total number and diversity of microbes in and on the human body.

Question 15

Most common sites of body inhabited by normal microbiota

Answer 15

Gut (intestinal tract, has the most amount of microbiota)
Skin
Mouth (oral cavity)
Nose
Eye

Question 16

Microbiota in the Skin

Answer 16

Staphylococcus epidermis (90% of skin aerobes)
- Can colonize plastic catheters and medical devices that penetrate the skin. (This is why you must clean area well when you puncture skin).

Staphylococcus aureus
- skin infections

Propionibacterium acnes
- anaerobic
- Major player in causing pimples, feed on sebum.

Question 17

Microbiota in Mouth / Nose

Answer 17

Streptococcus mutans
- colonize the teeth / gingival tissue
- can travel from oral cavity to heart following dental surgery, colonize in damaged heart valves which leads to endocarditis (fatal).

Streptococcus pneumonia
- can cause pneumonia.

Question 18

Microbiota in Intestinal tract

Answer 18

H. Pylori can survive enzyme of stomache. Urea -> ammonia (basic) cloud surrounds H. Pylori, neutralizing acid.

Gut microbiota has the largest number of bacteria and the greatest number of species compared to other areas of the body.

Question 19

Beneficial functions of normal microbiota

Answer 19

Competition. Competes with pathogenic microbiota
Some produce antimicrobial substances
Can stimulate development of immune system in the young
Can make vitamins (e coli makes vit. k)

Question 20

Harmful effects of normal microbiota

Answer 20

Displacement from normal site to abnormal site causes problems
Diminishing population bad due to competition importance
Ingested food substances converting to carcinogenic derivatives
Normal microbiota overgrow / become pathogenic

Question 21

Opportunistic definition

Answer 21

Opportunistic - Some microbes cause disease only under certain conditions

Question 22

All terms of Microbiota

Answer 22

Subclinical - no symptoms
Latent - potential to become active
Opportunistic
Primary - Can cause other disease manifestations
Secondary - Reactivation of latent infection/ second stage of infection
Mixed - 2 + bacteria infecting same tissue
** Pyogenic - pus forming
** Pyrogenic - fever / heat inducing
Fulminant - Infections occur suddenly and intensely

Question 23

Bacterial pathogenesis (pathway)

Answer 23

1.) Entry
2.) Adhesion
3.) Invasion
4.) Propagation
5.) Damage
6.) Progression/Resolution

Question 24

Virulence factors and how it is quantified by.

Answer 24

These are characteristics of a bacterium that enhance its pathogenicity

Can be quantified by
1.) Infection Dose (ID 50): How many organisms are required to cause disease in 50% of those exposed
2.) Lethal Dose (LD 50): How organisms kill 50% of test animals.

Question 25

Target question:

What is the role of the capsule?

Answer 25

When an organism has a capsule on, it is harder for it to be phagocytized. (It is antiphagocytic)

Question 26

Virulence factors

Answer 26

Capsule
Surface adhesion molecule
Bacterial enzymes (collagenase / hyaluronidase) These breakdown ECM.
Iron binding proteins
Bacterial toxins.

Question 27

Bacterial toxins

Answer 27

Exotoxins: Secreted. More toxic. (remember, lipopolysaccharide LPS used synonymously with exotoxins).
Endotoxins: not secreted, but can be released by bacterial lysis.

Question 28

Host-mediated pathogenesis

Answer 28

Pathogenesis caused by host response rather than the bacterial factors.

Classic Question: Inflammatory cytokines are an example. Host immune response is so intense that host tissues are destroyed.

Question 29

Viral infections can lead to:

Answer 29

Cell death
Transformation (Normal cell -> cancer cell) Example: HPV
Cell fusion (large giant cells)
Cytopathic effect (Visible changes, cell disintegration)

Question 30

Symptoms and Indication for physical examinations

Answer 30

Bullseye skin lesion: Lyme disease
Chills, Fever, cardiovascular instability: Bacteremia
Pulmonary consolidation (fluid in lung): Pneumonia
Stupor (near unconsciousness) / stiff neck: Meninges

Question 31

Common techniques: Gram stain

Answer 31

Trying to differentiate between gram positive / negative organisms.

CIAS : Crystal violet, iodine, acetone, safranin solution. Do this in order.

1.) Add first stain, crystal violet.
2.) Use iodine to trap stain. Fix it.
3.) Acetone decolorizes sample. Wash it out.
4.) If gram positive, crystal violet will be trapped. Will be purple.
5.) If gram negative, will be pink. (thin peptidoglycan layer, so the Crystal violet washes out).

Question 32

Acid-fast stain

Answer 32

Purpose: try to find mycobacterium. These contain large amounts of mycolic acids (FAs)

When cell wall has a lot of fatty acids, gram stain does not work well.

Stain pink when positive. Negative = blue.

Question 33

India Ink

Answer 33

Look for capsule. Stains background so capsule is visible.

Question 34

Oxygen requirement terminologies

Answer 34

Obligate aerobes: requires oxygen for growth
Obligate anaerobes: requires anaerobic environment for growth
Facultative anaerobes: have ability to grow anaerobically, but better with oxygen
Aerotolerant anaerobes: Do not use oxygen but can tolerate it.
Microaerophiles: Requires oxygen concentrations lower than O2 found in
air.

Question 35

Solid / liquid medium

Answer 35

Solid medium : nutrient agar. Used for isolation of bacterium

Liquid medium : nutrient broth. Used to grow larger quantities of bacteria.

Question 36

Types of media : Characteristics

Answer 36

Defined : Contains known quantities
Undefined: Unknown quantities
Enriched: Support wide growth of organisms. *** Examples: Blood agar, chocolate agar.
Selective: growth of selected microorganisms
Differential: Differentiate organisms
Reducing: Growth of obligate anaerobes.

Question 37

Catalase Test

Answer 37

Enzyme that degrades hydrogen peroxide. Looking to see if it has catalase.

U just add h2o2. If it bubbles its positive. (cuz h2o and o2 released)

**staphylococci = positive
**streptococci = negative

Question 38

Oxidase Test

Answer 38

Looking to see if it has cytochrome c oxidase. (complex 4 of ETC). If you have this, oxidation occurs.

Question 39

Coagulase Test

Answer 39

Clot formation = positive test result.

Used to differentiate staphylococcus aureus (positive) from other staphylococci (negative).

Question 40

Urease test

Answer 40

Expose urea. urea broken down to ammonia. check pH levels. (alkaline side)

Question 41

Quelling reaction

Answer 41

Looking for organisms with capsules.

Question 42

Latex Agglutination Test

Answer 42

Unknown antigen exposure to bound antibody (or other way around) Agglutination occurs.

Question 43

Complement fixation

Answer 43

Detect patient’s serum antibody by the ability of the antibody to bind complement.

Solution pink if negative.

Question 44

ELISA

Answer 44

Direct assay: one primary antibody conjugate.
Indirect Assay: Using 2 antibody conjugates.

Question 45

Fluorescent Antibody Test

Answer 45

No fluorescence = no virus present

Fluorescence = virus present

Question 46

Nucleic Acid-based techniques (NAT) (NAAT)

Answer 46

Detect / amplify nucleic acid of pathogen

Question 47

Susceptibility Tests

Answer 47

Do this when you don’t know which antibiotic to use. DO this when you want to know which one is affected.