EXAM 2- Austin (copy)

Antimicrobials may be

a. natural

b. synthetic

c. both (semi-synthetic)

d. all of the above

d

What’s the difference between antimicrobials and antibacterials, antifungals, antivirals, and antiprotozoals?

“antimicrobials” is a broad term that includes any substance that kills or inhibits the growth of microorganisms, including bacteria, fungi, viruses, and protozoa.

What are the 3 ways of selectively targeting a pathogen?

• (i bet there’s a test question on this topic/ LO)

1. UNIQUE- targets completely unique to pathogen, absent in host

2. SELECTIVE- targets that are similar but not identical to the host

3. COMMON- targets that are shared, but differ in relative importance

PRACTICE:

For EACH of the following identify the type of selective targeting (unique, selective, or common):

• folic acid in pyrimidine synthesis

• bacterial ribosome

• cell wall

• cell membrane

• folic acid in pyrimidine synthesis- common

• bacterial ribosome- selective

• cell wall- unique

• cell membrane- selective

What are the major targets of antibacterials? (LO)

• cell wall synthesis

• protein synthesis

• nucleic acid homeostasis

• metabolism

• cell membrane

What’s the difference between bacterioSTATIC and bacteriCIDAL? (LO)

• bacteriostatic—> agents that INHIBIT bacterial growth WITHOUT causing cell death

• bactericidal—> agents that cause bacterial death

ANYTHING that inhibits cell walls is _____________.

a. bacteriostatic

b. bactericidal

b.

Most protein synthesis inhibitors are ___________.

a. bacteriostatic

b. bactericidal

a

When antibacterials are combined, they can either be synergistic, additive, or antagonistic. Describe what each of those mean:

• synergistic- combo does MUCH better than each individually

• additive- only slightly different than best drug (hard to see)

• antagonistic- combo does WORSE than each individually

What are the 3 kinds of bacterial cell walls?

• gram +

• gram -

• mycobacteria (atypicals)

Describe gram + cell walls:

• thick/thin?

• contains what?

• outer membrane?

• LPS?

(LO)

• thick wall with teichoic and lipoteichoic acid

• no outer membrane or LPS

Describe gram - cell walls:

• thick/thin?

• contains what?

• outer membrane?

• LPS?

(LO)

• thin walls with LPS

• contain porins in outer membrane

Describe the cell walls of mycobacteria:

• thick/thin?

• contains what?

• outer membrane?

• LPS?

(LO)

• thin wall

• outer membrane contains mycolic acids

• also known as acid-fast

Peptidoglycan is also known as __________.

murein

What are the MAIN steps in bacterial cell wall synthesis? Which steps can be targets for antibacterials? (LO)

1. murein/peptidoglycan monomer synthesis

2. polymerization (stick monomers together)

3. cross-linking

each of these steps can be targets!!!!!!!!!!

Where does EACH step of cell wall synthesis take place/occur? What enzymes facilitate EACH step (if applicable)? (LO)

1. murein/peptidoglycan monomer synthesis- CYTOPLASM

2. polymerization- outside the cell

   • facilitated by PGT/ peptidoglycan glycosyltransferase enzymes

3. cross-linking- outside the cell

   • facilitated by TP/TRANSPEPTIDASES (also called PBP/ penicillin-binding proteins)

What antibacterials act by inhibition of murein monomer synthesis?

• bacitracin

• fosfomycin

Mycobacteria cell wall synthesis differs in the fact that myolic acid is used to form a large waxy outer membrane. How is mycolic acid synthesized? (LO)

by fatty acid synthetases 1 and 2

What is the importance of gram staining?

• to highlight the physical and chemical differences between cell walls

  • determine drug therapy

  • split bacteria into 2 large groups (+ or -)

Describe the actual process of gram staining:

(just focus on 2 main staining agents) (LO)

• apply primary stain (CRYSTAL VIOLET)

• add iodide

• decolorize

• counterstain (SAFRANIN)

How do each of the following stain in a gram stain test?

(for the millionth time)

• gram +

• gram -

• atypicals

• gram + = PURPLE

• gram - = PINK

• atypicals = doesn’t stain or random staining

Antibacterials can also target DNA replication, transcription, and translation. What enzymes on bacteria are targeted during each? (LO)

• replication: DNA gyrase, and Top IV

• transcription: RNA polymerase

• translation: 30S and 50S subunits

Antibacterials that target DNA replication, transcription, and translation use what mechanism?

a. unique

b. selective

c. common

b

Describe an antibacterial with a narrow spectrum:

active against ONLY a single species/small group of bacteria (ex: antibacterial that only limited to gram +)

Describe an antibacterial with a broad spectrum:

active against many or most species of bacteria

Describe an antibacterial with an extended spectrum:

• “intermediate”

• started as narrow spectrum and then add more coverage

What’s the difference between empiric and definitive therapy?

• empiric- “we’re guessing”

  • tx based on educated guess like symptoms, usually broad spectrum

• definitive- “we know”

  • we know exactly what’s causing the infection and how to treat it

What is MIC or EC₉₀?

lowest concentration of an agent that inhibits visible growth of the organism after 18-24hrs

(basically what’s the least amount of abx I can give to inhibit the bacteria)

For measuring the MIC of an abx what 2 tests can be used?

• broth-dilution

• disk-diffusion

Describe broth-dilution:

1. fill a bunch of test tubes with equal amounts of microorganism

2. in each test tube, add a different conc of abx

3. after 18-24 look at the test tubes

4. the LOWEST concentration of an abx that results in the inhibition of visible growth of the organism is your MIC

For disk-diffusion, the larger the zone of inhibition, the _______ the MIC of the abx for the organism tested.

a. higher

b. lower

b

Minimum bactericidal concentration (MBC) is the lowest concentration of an abx that…

kills 99.9% of the bacteria

Antibiotics are generally considered bactericidal if MBC ≤ ___ MIC

MBC ≤ 4x MIC

Optimally effective abx doses achieves IC___ to IC___ at the site of infection.

IC₈₀ to IC₉₀

Once the pathogen is known, what 2 components heavily influence what abx we select?

(not that important)

• susceptibility testing

• pharmacokinetics

Can’t think of how to write a card on this—> just know EACH

Can’t think of how to write a card on this—> just know EACH

When antibiotics continue to suppress bacterial growth after concentrations fall below the MIC it is called…

post-antibiotic effect

Antimicrobial stewardship is…

ensuring proper use of antimicrobials

What are some mechanisms of antimicrobial resistance?

• reduced entry of

• increased export of

• release of

• alteration of antimicrobial…

• alteration of proteins…

• development of…

• reduced entry of abx into pathogen

• increased export of abx by efflux pumps

• release of enzymes that destroy abx

• alteration of antimicrobial targets

• alteration of proteins required to take prodrugs—>drugs

• development of alternative pathways to those inhibited by abx

How are low level mechanisms of resistance, like porins and efflux pumps, countered?

increased dose or cell permeability

How are higher level mechanisms of resistance, like target site mod and enzyme inactivation, countered?

• target site—> drug modification, novel MOAs

• enzyme inactivation—> countered inhibitors

A clinical breakpoint is…

concentration above which treatment is unlikely

What are the pros and cons of combination therapy?

pros: may decrease/slow resistance, treat mixed infections or life-threatening infections

cons: toxicity, cost, increase abx exposure to pathogen, risk of superinfections

What’s a superinfection?

a new infection that is caused by overgrowth of highly resistant or opportunistic organisms

Describe each of the following about prokaryotes:

• nucleus?

• smaller or larger ribosomes?

• cell wall composition?

• how do they reproduce?

• motility?

• no true nucleus—> nucleoid

• smaller ribosomes

• peptidoglycan cell wall

• reproduce by binary fission

• some motility—> flagella

Whether a bacteria is aerobic or anaerobic is based on whether they have what enzymes?

catalase and superoxide dismutase

For each of the following bacteria, list their oxygen requirements:

• obligate aerobes

• facultative anaerobes

• obligate anaerobes

  (“austin said test question dealing with these!!!!!!)

• obligate aerobes- require O2 to live/generate ATP

• facultative anaerobes- can live with/without O2

• obligate anaerobes- unable to grow in presence of O2

Remember that LPS is an endotoxin found in the outer membrane of gram - bacteria. In some causes it can be the direct cause of…

symptoms of disease such as fever and shock

What is the structure of LPS? Which component is responsible for toxic effect?

• Lipid A- responsible for toxic effect

• Core polysaccharide

• outer polysaccharide

Match the virulence factor to its definition:

	gelatinous layer covering the entire bacteria
	slime layer polysaccharide coating of some bacteria
	resistant structures formed in response to adverse conditions
	long, whip-like structures
	shorter filaments that mediate attachment

Word Bank: Pili, Glycocalyx, Spores, Flagella, Capsule

Capsule	gelatinous layer covering the entire bacteria
Glycocalyx	slime layer polysaccharide coating of some bacteria
Spores	resistant structures formed in response to adverse conditions
Flagella	long, whip-like structures
Pili	shorter filaments that mediate attachment

What is the function of a capsule?

• limits phagocytosis

• aid in adhesion

• antigen components in some vaccines (ex: PPV-23)

What is the function of a flagella?

• facilitate chemotaxis (movement of a bacteria in response to certain chemicals)

Motile bacteria are common causes of _____.

UTIs

What is the function of a glycocalyx?

• covers surfaces like a film

  • component of biofilms

• adhesion

Spores are important for what species of bacteria?

gram + rods Bacillus and Clostridium

Bacteria colonize and thrive in human tissue with the help of enzymes. What are these enzymes, and what do they do?

• collagenase & hyaluronidase- break down connective tissue

• coagulase- formation of fibrin clot—> immune cells can’t get to bacteria

• IgA protease- adherence to mucous membranes

• leukocidins- destroy WBCs

Bacteria need iron to survive. How do they get it? By producing what?

HEMOLYSIS—> produce hemolysins= destroy RBC= IRON

Match the hemolytic pattern with its type?

	partial hemolysis
	complete hemolysis
	minimal/no hemolysis

word bank: α, β, γ

α	partial hemolysis
β	complete hemolysis
γ	minimal/no hemolysis

What are exotoxins? are they toxic?

• substances that are produced and secreted by bacteria (not a structural component like endotoxins)

• may be extremely toxic

What is the structure of exotoxins? What does each DETERMINE?

• A subunit- active subunit

  • determines EFFECT of toxicity

• B subunit- binding subunit

  • determines LOCATION of toxicity

What are the 3 shapes of bacteria?

• cocci- spheres

• bacilli- rods

• spirals

What are the IMPORTANT roles of “the normal flora” in human health?

1. protective host defense mechanisms

   • indirect—> colonization resistance (ur bacteria resist other bacteria)

   • direct—> secretion of antibacterials

2. nutritional functions (help digest food)

3. may cause disease

How are bacteria classified? Which form is most precise?

• phenotypic

• analytic

• genotypic—> most precise

Which of the following are most common infectious agents?

a. gram + cocci, gram - rods

b. gram - cocci, gram + rods

a

Answer the following about STAPHYLOCOCCI:

• Gram + or -

• catalase + or -

• strains present in normal flora/pathogenic (or both)

  • disclaimer—> sing says something slightly different

• KEY structural components

• gram +

• catalase +

• S. epidermidis- normal flora

• S. aureus- normal or pathogenic

• S. saprophyticus- pathogenic

• Structural components

  • capsule

  • teichoic acid

  • protein A

What are the enzymes and toxins that S. aureus secretes?

• enzymes

  • catalase

  • coagulase

  • hyaluronidase

  • B-lactamase

• toxins

  • a/b-toxin (hemolysins)

  • leukocidin

  • superantigen

  • enterotoxins

  • exfoliative toxin

The toxins secreted by S. aureus can cause what toxic mediated diseases?

• toxic shock syndrome

• food poisoning

• scaled skin syndrome (SSS)

S. aureus can cause different disease based on the location of infection. List the diseases S. aureus causes based on the following locations:

• cutaneous

• subcutaneous

• deep tissue

• cutaneous- impetigo, folliculitis, carbuncles

• subcutaneous- cellulitis

• deep tissue- bacteremia, pneumonia, endocarditis, osteomyelitis, arthritis

S. saprophyticus can cause ______.

UTIs

What are 3 resistance mechanisms identified in staphylococci that determine the treatment strategy?

• MSSA

• MRSA

• VRSA

Answer the following about STREPTOCOCCI:

• Gram + or -

• catalase + or -

• KEY structural components

• Gram +

• catalase -

• key structural components

  • capsule

  • lipoteichoic acid

  • pili (S. pneumoniae)

  • M protein

Function of M protein?

• adhesion to keratinocytes

• inhibition of complement activation

S. pyogenes (group A streptococci) has what enzymes and toxins?

• enzymes: streptokinase, hyaluronidase, DNases, proteases

• toxins: streptolysins O and S, pyrogenic exotoxins

S. pneumoniae (group A streptococci) has what enzymes and toxins? What does it bind to activate complement?

• enzymes: IgA protease, hydrogen peroxide (H2O2)

• toxins: pneumolysin

• binds C-reactive protein

Answer the following about Enterococcus:

• found in normal flora in…

• aerobic/anaerobic?

• name the 2 pathogenic strains?

  • What type of resistance is associated with these strains?

  • disclaimer: slightly different than sing****

• found in noraml flora in GI tract

• facultative anaerobe

• 2 pathogenic enterococcus

  • E. faecalis and E. faecium

    • associated with VRE (vancomycin-resistant enterococcus)

Answer the following about Pseudomonas:

• Gram +/ -

• aerobic/anaerobic?

• key structural components?

• gram - rods

• aerobic

• key structural components

  • flagella

  • pili

  • capsule

  • LPS

What enzymes and toxins do Pseudomonas aeruginosa have?

• enzymes: elastase, exoenzymes (S,T,U,Y)

• toxins: exotoxin A, pyocyanin

What are exoenzymes?

secreted into host cells by needle-like appendage

Pseudomonas species use Quorum Sensing. What is it and how do Pseudomonas species use it?

• Quorum sensing—> a cell-to-cell signaling mechanism bacteria use to coordinate gene expression based on population density

• pseudomonas—> once the bacteria population reaches a certain amount—> the bacteria make a BIOFILM = increases resistance

What are some common diseases caused by Pseudomonas disease?

• pulmonary infections

  • common cause of hospital-acquired pneumonia

• bacteremia

• UTI

  • especially nosocomial

• dermal

What are the key mechanisms of resistance for Pseudomonas?

• efflux pumps

• decreased porin permeability

• drug degrading enzymes

• target alteration

• biofilms

• multidrug resistance