Micro Chapter 14

Describe narrow spectrum

Targets a specific subset of pathogens

Explain broad spectrum

Targets a wide variety of pathogens

Why do we use broad spectrum antibiotics

Bc we don’t always know what pathogen it is or how to treat it

What do B-lactams, glycopeptides, and bacitracin do

Inhibit cell wall synthesis

What do antibiotics that inhibit cell wall synthesis target

PSPs (penicillin-binding proteins) and peptidoglycan

What do polymyxins and lipopeptides do

Disrupt cell membrane

What do antibiotics that disrupt cell membrane target

Lipopolysaccharides, inner and outer cell membrane

What do 30s subunit and 50s subunit do

Inhibit protein synthesis

What do antibiotics that inhibit protein synthesis target

Ribosomes

What do folic acid synthesis and mycolic acid synthesis do

Antimetabolites

What do antimetabolies target

Metabolic pathways

What do fluoroquinolones and rifamycin do

Inhibit nucleic acid synthesis

What do antibiotics that inhibit nucleic acid synthesis target

DNA and RNA synthesis

What are B lactams mode of action

Bind to transpeptidase active site

How do B lactams kill cells

Block crosslinking of peptide chains when new peptidoglycan is synthesized

What do B lactams have

A B lactam ring

How to cells resist B lactams

Prokaryotes produce enzymes that hydrolyze and inactivate B lactam ring

Explain bacteriostatic

Prevents growth of bacteria by inhibiting DNA replication

Explain bactericidal

Kills bacteria by inhibiting cell wall fomation

Bacteriostatic vs Bactericidal which has action that is reversible and which doesn’t

static- reversible

cidal- not reversible

Bacteriostatic vs Bactericidal which works with host immune system and which doesn’t

static- works with host immune system

cidal- doesn’t work with host immune system

Polymyxins and lipopeptides both are _____ which have ____ like properties

lipophilic, detergent

Explain polymyxins

Interact with lipopolysaccharides in outer cell membrane of gram negatives which disrupts outer and cytoplasmic membrane and causes cell death

What is an issue with polymyxins

Can damage human cells (kidney and nervous sytem)

Explain lipopeptides

Inserts into cytoplasmic membrane of gram positives which disrupts the cell membrane and causes death

Explain chloramphenicol, macrolides and lincosamides 

Bind to 50s ribosomal subunit, prevent peptide bond formation whcih stop protein synthesis

Explain aminoglycosides

Bind to 30S ribosomal subunit, impair proofreading which produces faulty proteins

Explain tetracyclins

Bind to 30S ribosomal subunit, blocks binding of tRNAs which inhibits protein synthesis

Explain rifamycin

Is narrow spectrum, G+ and few G-; inhibits RNA polymerase activity which blocks transcription and leads to cell death

Explain fluroquinolone

Is broad spectrum, G+ and G-;  inhibits DNA gyrase activity which blocks DNA replication and leads to cell death

Explain antimetabolies

Competitive inhibition of metabolic enzymes, blocks bacterial synthesis of folic acid

What is antibiotic resistance

Ability of the microbe to reduce/ counteract the effect of the chemical agent

What are the two general/ main ways antibiotics can become resistant

Acquires antibiotic resistance gene or develops antibiotic resistance spontaneously 

What are the four different ways bacteria acquire/ develop antibiotic resistance

1. Random Mutation

2. From another bacterium that possessed the F+ plasmid

3. Random piece of DNA that was released (cell lysis) by another bacteria in the environment 

4. Random piece of bacterial NA that was packaged inside a newly synthesized bacteriophage

What do human cell memebranes use

Cholesterol

What do fungi use in their cell membrane and cell wall

Cell membrane- ergosterol

Cell wall- chitin

What are antiprotozoals a causative agent of

Malaria

What are the three different results reported when measuring effectiveness of antibiotics/ doing antimicrobial susceptibility testing

Susceptible, intermediate, or resistant

Explain broth dilution

Minimum inhibitor concentration, compare to charts

Explain gradient disc diffusion

MIC (minimum inhibitory concentration), compare to charts

Explain kirby bauer disc diffusion

zone of inhibition, compare to charts

What are the steps for Kirby Bauer Assay

1. Apply bacterial culture to entire plate

2. Place agent impregnanted discs onto prepared plate. Incubate overnight

3. Measure zone of inhibition

4. Compare to published reference standards by bacterium to determine if microbe is susceptible or resistant