Micro Chpt. 20

Broad spectrum

broad range (gram + / gram -) ex. ampicillin

An antimicrobial drug that inhibits peptidoglycan synthesis is most likely to be effective against __________

gram-positive bacteria

What does ethambutol inhibit?

incorporation of mycolic acid into the cell wall

what usually clears TB cases in 9 months?

isoniazid + rifamein

what usually clears TB in 6 months?

isoniazid +pyrazinamide

Sensitive/resistant of Natural penicillin

sensitive to B-lactamases

Drawbacks of broad spectrum antibiotics?

1. can lead to problems of imbalance b/t good and bad bacteria which can lead to secondary infections such as yeast infections/ diarrhea. 2. antibiotic resistance

What are the Anti-mycobacterial Antibiotics?

1. isoniazid 2. ethambutol 3. pyrazinamide

Sensitive/resistant of Synthetic Penicillin

some resisitant to B-lactamases (oxycillin, methicillin)

what are antibiotics?

substances that are produced by certain microbes that in small amounts inhibit growth of other microbes

Phage Theory

viruses that kill bacteria ; kill bacteria n viruses on deli meats

How to u know if drug is bacteriostatic or bactericidal through Broth Dilution test?

You can treat bacteria with different concentrations of chemical in question and after the desired time point you can inoculate a fixed volume inoculum in fresh media. You can now determine the growth rate of the bacteria by measuring OD

Source of Natural Penicillin

extracted from Penicillin fungal cultures

Alexander Flemming

first discovered antibiotics (figured fungus was stopping growth of staphylococcus)

Potassium claculanatae

it is a competitive inhibitor and competes with amoxicillin to the active site of the B-lactamase enzyme

What does isoniazid inhibit?

mycolic acid synthesis

E- test(MINIMAL inhibitory concentration , MIC)

Epsilometer

Sequenser iron

bacteria need ions so by prevent ions you prevent growth of bacteria

Block quorum sensing

block communication b/t bacteria of chemical receptors

Mehchanism 1:

break the ring; B-lactamases/ penicillinases break the b-lacatam rings aka destroy the structure of the antibiotic which results in a inactive antibiotic

Modes of actions of antimicrobial drugs

can target different structures such as cell wall synthesis, plasma membrane, protein synthesis (thru ribosomes), metabolic pathways (by key enymes essentrial for growth/metabolism), or DNA/RNA synthesis

what is the source of antibiotics?

fungi & filamentous bacteria

MBC aka minimum bactericidal concentration is associated with....

no antibiotic

Antimicrobial peptides

target cell membrane

MIC aka minimum inhibitory concentration is associated with....

the growth of the antibiotic

How do microbes develop resistance to penicillins?

through Mechanism 1 or Mechanism 2

What is Bacitracin?

topic to prevent minor skin infections against gram POSITIVE

What is Vancomycin?

Last line of antibiotics against this was Methicillin. Staphylco. & Streptococ. -MRSA infections

Mechanism 2:

MRSA resistance; antibiotic resistant & antibiotic sensitive Antibiotic resistant: bacterium produces a modified penicillin binding protein (it can crosslink the peptidoglycan but penicillin cnt bind to it)

True or False: All Penicillins & Cephalosporins contain the beta-lactam ring

True

Disk-diffusion method (Kirby test)

different antibioitcs. Limitations of this test? 1. solubility can affect the results 2. cant distinguish b/t bacteriostatic & bactericiidal

Transpeptidese (penicillin binding protein)

function is to crosslink peptidoglycan chains.

what does pyrazinamide inhibit?

plasma membrane and interferes with ATP synthesis production

what does neomycin target?

protein synthesis

Narrow spectrum

narrow range (gram + mostly) ex. penicillin

Spectrum of Natural penicillin

narrow spectrum

Howard Florey & Ernst Chain

scaled up penicillin production, purified it, demonstarted it on animal models

Antisense agents

small interfering RNA's & stop protein synthesis

What is Polymyxin B?

-ingredient in first aid skin ointments. -narrow spectrum and effective against gram NEG. -inserts itself into outer membrane of gram bacteria & made up of fatty acids -once drug binds to membrane it creates cytoplasmic channels/posres in cell membrane -membrane integrity is disrupted

What are the polypeptide antibiotics?

1. Bacitracin 2. Vancomycin

Why are penicillin and Daptomycin ineffective against gram-negative organisms?

1. They cannot penetrate the outer membrane of gram-negative organisms. 2. enzymes will break the antibiotic 3. efflux pumps (which pushes out the antibiotic) 4. bacteria might produce certain modified enzymes to which the antibiotics cant bind

future of chemotherapeutic agents?

1. antimicrobial peptides 2.antisense agents 3.sequenser iron 4. Phage therapy 5. Block quorum sensing

What antibiotcs are in neosporin?

1. bacitracin 2. Polymycin B 3. neomycin

What can u do for antimcrobial resistance?

1. complete whole antibiotic course 2. have correct antibiotic dosage 3. dont use other ppls antibiotics 4. dont save ur antibioitcs 5. try to protect yourself from diseases and sickness through proper procedures and hand washing 5. cook food properly, do not consume raw milk

how does resistance to antimicrobial drugs spread?

1. fertilizer (animal feces containing drug resistant bacteria) 2.consuming meat that has antibiotic resistant bacteria 3. spread anti resistant germs to facilities

what are the advanatges of Cephalosporins over penicillins?

1. more resistant to many b-lactamases 2. 4th & 5th gen have a more broader spectrum than penicillin and are active against both 3. gram + & gram - & have increased b-lactamase resistance

What gives resistance to antimicrobial drugs?

1. natural selection 2. overprescription (misuse, not completing dose, no correct dosage) 3.animal fed antibiotics (we eat these animals and this will result in emergence of superbugs)

what are the bacterial cell membrane inhibitors?

1. paptomycin 2. polymyxin B

Bacterial cell wall inhibitors?

1. penicillin 2. Cephalosporins 3. Bacitracin 4.Vancomycin

Augmentin pill

2 drugs inside (amoxicillin and Postassium clavulanate)

Of the three drugs often found in over-the-counter antiseptic creams—polymyxin B, bacitracin, and neomycin—which one damages the bacterial cell wall?

Bacitracin

Mechanism for Penicillin

Penicillin binds to penicillin binding protein which makes the penicillin binding protein not functional anymore & cannot cross the peptidoglycan . Which means there will be no cell wall and the cell will burst my osmotic lysis.

spectrum of Synthetic penicillin

broad spectrum

What does polymyxin B target?

cell membrane

What is paptomycin?

cell membrane inhibitor, narrow spectrum, mostly against gram NEG/serius infections -for MRSA & vancomycin resistant enterococal infections found in INTESTINES & ANIMALS -causes CA 2 dependent efflux of K ions -heads to loss of membrane potential -inhibits DNA/RNA/protein synthesis

What does Bacitracin target?

cell wall synthesis in narrow spectrum bacteria

Source of Semisynthetic Penicillin

chemically added to side chains