Microbiology Exam 2 Based on Study Guide

Antonie van Leeukwenhoek

Who discovered animalcules using early microscopy?

in rainwater

Where were the first observations of microscopic living creatures?

Viruses

Bacteria

Fungi

Parasites

What are the categories of microbes?

1. One organism, one disease

2. One organism, multiple disease manifestations

3. Multiple organisms, same disease

What are the microbial disease patterns?

one organism, one disease

Clostridium tetani causes tetanus is an example of?

One organism, multiple disease manifestations

Staphylococcus aureus causes skin infections, pneumonia, endocarditis, and osteomyelitis is an example of?

Multiple organisms, same disease

Meningitis can be caused by viruses, bacteria, fungi, and parasites is an example of?

3.9 × 10^13 colonizing microbes in human body

3.0 × 10^13 human cells

In the human microbiome, what is the number of microbes vs human cells?

microbes

Are there more human cells or more microbes in the human microbiome?

Skin and adjacent mucous membranes

Respiratory tract

Gastrointestinal tract ("Mouthville" - oral cavity)

Outer opening of urethra

External genitalia and vagina

External ear canal

External eye

Possibly blood

Where are the sites with normal microbiota?

shape

size

texture

What are the colony characteristics?

diplococci

Identify the bacteria's shape.

tetrads

Identify the bacteria's shape.

streptococci (chains)

Identify the bacteria's shape.

staphylococci (clusters)

Identify the bacteria's shape.

Bacillus (rod-shaped) single

Identify the bacteria's shape.

Bacillus (rod-shaped) chains

Identify the bacteria's shape.

Bacillus (rod-shaped) palisades

*palisades line up side by side

Identify the bacteria's shape.

Spirilla (spiral)

Identify the bacteria's shape.

Spirochetes (corkscrew)

Identify the bacteria's shape.

gram-positive (Positive=purple)

Identify the gram-stain.

gram-negative (negative=red)

Identify the gram-stain.

Biochemical tests (ex. mannitol fermentation)

PCR

What are some of the other identification methods besides gram-staining?

Single, double-stranded circular DNA in the nucleoid region

What is the structure of the bacterial chromosome?

Extrachromosomal DNA circles; confer advantages (antibiotic resistance)

What are plasmids?

plasmids

What cytoplasmic structures are involved in antibiotic resistance?

70s ribosome (30s and 50s subunits) which is different than the 80s eukaryotic

What ribosome is in bacteria?

70s ribosome (30s and 50s subunits) which is different than the 80s eukaryotic

What bacterial structure is good for drug targeting?

• Thick, multi-layered peptidoglycan

• Teichoic acid: linked to peptidoglycan, essential for viability

• Lipoteichoic acid: anchored in cell membrane, important for virulence

• May contain specific proteins (M protein in Streptococci, Protein A in S. aureus)

What are the characteristics of the Gram-positive cell wall?

• More complex structure with two layers

• Thin peptidoglycan layer

• Outer membrane with LPS (lipopolysaccharide)

• Periplasmic space: contains transport systems and enzymes

• Type III Secretion System: acts as molecular syringe to inject proteins into host cells

What are the characteristics of the Gram-negative cell wall?

linked to peptidoglycan in the cell wall and is essential for viability

What is teichoic acid?

Lipoteichoic acid

What part of the cell wall in gram-positive bacteria is anchored in the cell membrane and essential virulence?

gram positive

What type of cell has a thick, multilayered peptidoglycan cell wall?

Gram positive bacteria

What type of bacteria may contain specific proteins such as M and A proteins?

gram-negative

What type of bacteria has a thin peptidoglycan layer?

gram-negative

What type of bacteria has an outer membrane with LPS?

transport systems and enzymes

What is the periplasmic space used for?

acts as molecular syringe to inject proteins into host cells

What is a Type III secretion system?

gram-negative

What type of bacteria has a Type III secretion system?

1. Lipid A: Responsible for endotoxin activity

2. Core Polysaccharide: Necessary for structure and viability

3. O Antigen: Distinguishes serotypes

What are the three parts of the LPS?

Responsible for endotoxin activity

What is Lipid A for LPS (endotoxin) function?

Necessary for structure and viability

What is the core polysaccharide for LPS (endotoxin) function?

Distinguishes serotypes

What is the function of O antigen for LPS (endotoxin)?

- Powerful immune stimulator

- Causes fever, shock, DIC (disseminated intravascular coagulation)

- Binds to pattern recognition receptors (PRRs)

What is the clinical significance of LPS (endotoxin)?

- Waxy lipid coat of mycolic acid

- Antiphagocytic - important virulence factor

What type of cell wall does mycobacteria have?

- No peptidoglycan

- incorporate steroids from host into membranes

What type of cell wall do mycoplasmas have?

- Outer coating of polysaccharides and/or proteins

- Antiphagocytic - poorly antigenic

- Physical/chemical barrier

- Helps adherence to surfaces

What is the Capsule/Slime Layer/Glycocalyx for bacteria and what is the function?

- Composed of flagellin protein subunits (flagellin is a PAMP)

- Main function: motility

What is the flagella for bacteria and what is its function?

- Hair-like, composed of pilin subunits

- Smaller than flagella, usually several hundred per cell

- Promote adhesion - important virulence factor

- F pili (sex pili): for genetic transfer (conjugation)

What is the function of fimbriae and pili for bacteria and what is the function?

They are used for genetic transfer (conjugation)

What are F pili?

some gram-positive

What type of bacteria can form spores?

- Form under harsh conditions

- Can survive boiling and desiccation

- Become vegetative when conditions improve

What is the purpose of spore formation?

- eukaryotic organisms

- Cell wall made of chitin and glucan

- Cell membrane contains ergosterol (vs cholesterol in mammals) - drug target

- Main purpose: degrade organic material

What are the characteristics of fungi?

degrade organic material

What is the main purpose of fungi?

chitin and glucan

What are the cell walls of fungi made out of?

ergosterol (different than cholesterol in mammals)

What is in the cell membrane of fungi that is the target for drugs?

saprobes

What fungi decompose organic matter?

symbionts

What type of fungi hae mutualy benefical relationships?

commensals

What type of fungi benefit without harming the host?

parasites

What type of fungi cause disease?

Microorganism capable of causing disease

What is a pathogen?

False (minority)

T/F. Majority of microorganisms are pathogenic.

- Cause disease in immunocompromised individuals

- Normal (commensal) organism in wrong location (endogenous infection)

What is a opportunisitic pathogen?

- Quantitative measure of pathogenicity

- Related to toxigenic potential and invasiveness

What is virulence?

LD50: Number of organisms to kill 50% of hosts

ID50: Number needed to infect 50% of hosts

How is virulence measured by?

Number of organisms to kill 50% of hosts

What is LD50?

Number needed to infect 50% of hosts

What is ID50

spread host-to-host (e.g., tuberculosis via airborne droplets)

What does communicable mean?

not spread between hosts (e.g., staph food poisoning)

What is a noncommunicable disease?

non-communicable

Staph food poisoning is a non-communicable or communicable disease?

communicable

Tuberculosis via airborne droplets is a non-communicable or communicable disease?

highly

Contagious means ___________ communicable.

1. Incubation period

2. Prodromal period

3. Acute specific illness

4. Recovery

What are the steps to infectious disease?

Time between acquiring organism and start of symptoms (hours to weeks)

What is the incubation period for an infectious disease?

Nonspecific symptoms (fever, malaise)

What is the prodromal period?

Characteristic signs and symptoms

What is the acute specific illness period?

Illness subsides

Waht is the recovery period?

Subclinical infection: Without overt symptoms; may become chronic carriers

Latent state: Reactivation possible (e.g., HSV in trigeminal ganglion)

What are the special cases of the steps to infectious disease?

exogenous

What is the transmission route acquired from external source?

endogenous

What is the transmission route from normal organisms acting as opportunists?

1. Inhalation

2. Ingestion

3. Inoculation

What are the transmission methods?

airbone route

What is the inhalation method of transmission?

Fecal contamination of food/water

What is the ingestion method of transmission?

Sexual contact, needles, skin contact, transfusions, insect bites

What is the inoculation method of transmission?

- skin

- respiratory tract

- gastrointestinal

- genital tract

What are the portals of entry?

organisms must adhere to cause disease

What is the first step in an infection?

True

T/F. Mutants lacking adherence mechanisms often nonpathogenic

- Pili/Fimbriae

- Extracellular polysaccharides

- Afimbrial adhesins

What are some structures that facillitate attachment?

Degrades hyaluronic acid in connective tissue

What does hyaluronidase do?

Breaks down collagen

What does collagenase do?

Forms fibrin clot (S. aureus)

What does coagulase do?

Cleaves secretory IgA (major virulence factor at mucosal surfaces)

What does IgA protease do?

N. gonorrhoeae, H. influenzae, S. pneumoniae, periodontal pathogens

What is igA protease produced by?

leukocidins

What is an example of a toxin targeting immune cells?

Kill white blood cells

What are leukocidins?

- Acute response with neutrophil infiltration

- Predominates in acute periodontal abscess

What is Pyogenic (Pus-Forming) Inflammation?

- Chronic with macrophage/giant cell formation

- Associated with: Mycobacterium tuberculosis, fungi

What is Granulomatous Inflammation?

Pyogenic (Pus-Forming) Inflammation

What type of inflammation predominates with acute periodontal abscesses?

Granulomatous Inflammation

What type of inflammation is associated with mycobacterium tuberculosis and fungi?

True

T/F. Exotoxins are produced by both Gram-positive and Gram-negative bacteria