Lecture 23: Antibiotics Flashcards
What are Antibiotics?
Soluble compounds that are produced and released by microorganisms and that inhibit the growth or kill other microorganisms
What can bacteria be classified by?
- Aerobic vs Anaerobic
- Shapes (rod, sphere, or spirals)
- Cell wall components (gram negative or gram positive)
What are the four shapes of bacteria?
- Bacillus (rod)
- Coccus (sphere)
- Spiral
- Other
What name is the rod shape?
Bacillus
What name is the sphere shape?
Coccus
What are the two types of cell walls that bacteria can have?
- Gram-positive
* Gram-negative
What distinguishes gram-positive and gram-negative bacteria?
Gram-positive bacteria takes up the ultraviolet dye and gram-negative does not
Why does Gram-positive bacteria stain purple?
Because it has a thick peptidoglycan layer
What is the cell membrane of gram-negative bacteria like?
They have a relatively this cell wall with few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides
Which cell wall do most bacteria have?
Gram-negative cell walls
What does the Peptidoglycan structure consist of?
Strands made of alternating N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc) residues crossed linked by peptides
What does Glycotransferase (GT) do?
Polymerizes individual strands into the peptidoglycan chain
What does Transpeptidase do (TP)?
Cross links the two different strands
What is TP targeted by?
Many antibiotics
What is TP also called?
The penicillin binding protein
When does normal flora cause trouble?
If immune systems are weakened or if they gain access to normally sterile part of the body
What is the difference between pathogens and normal flora?
Pathogens do not require that the host be immunocompromised or injured
What types of diseases caused by pathogenic bacteria?
- food borne illnesses
- Sexully Transmitted Diseases
- Skin Infections
- Highly Infectious Diseases
What does Spectrum of Activity mean with antibiotics?
They can be narrow or broad spectrum depending on the number of different bacterial species against which they exhibit useful activity
What is bacterial sensitivity with antibiotics?
The ability of bacterial strain to replicate following antibiotic exposure
What do Bactericidal antibiotics lead to?
Permanent loss of replicative activity
What do bacteriostatic antibiotic activity lead to?
Temporary loss of growth and replication that returns following the removal of antibiotics
What is ability to penetrate?
Delivery of antibiotic to site of infections is the most difficult challenge of antibiotic delivery
What are the four classes of antibiotics?
- Cell wall inhibitors
- Folic acid
- DNA synthesis inhibitors
- Protein synthesis inhibitors
What kind of antibiotic in Penicillin?
A cell wall inhibitor
What kind of antibiotic is Cephalosporins?
A cell wall inhibitor
What is penicillin derived from?
Penicillium notatum
What are Cephalosporins derived from?
Acremonium
What are Beta Lactams?
4 member ring antibiotics
What are the two Beta Lactam antibiotics?
Penicillin and Cephalosporins
How do the Beta Lactams work?
They inhibit cell wall synthesis by inhibiting DD-transpeptidase which is responsible for cross-linking components of the cell wall (bactericidal)
What is another name for DD transpeptidase?
Penicillin binding protein
What did Beta Lactams only used to be effective against?
They used to only be effective against gram positive bacteria but successive generation of cephalosporins have increased activity against gram negative bacteria
What are Beta-lactamases?
Bacterial enzymes made by most staphylococci and many gram negative organisms that hydrolyze the beta-lactam ring of certain penicillins and cephalosporins (basically resistance)
What are Beta-Lactamase Inhibitors?
Potent inhibitors of beta-lactamases used in combinations to protect hydrolyzable penicillins from inactivation
What is an example of a Beta-lactamase inhibitor?
Clavulanic acid
What kind of antibiotic is Vancomycin?
A cell wall inhibitor
Which bacteria make beta-lactamases?
Gram-negative bacteria
What are the cell wall inhibitor anibiotics?
- Penicillin
- Cephalosporins
- Vancomycin
What do we give with Cell wall inhibitors usually?
Beta-lactamase inhibitors
What is Vancomycin produced by?
Actinobacteria species, Amycolatopsis orientalis commonly found in soil
How does Vancomycin work?
It also inhibits peptidoglycan cross linking
What do bacteria use to synthesize nucleic acids their DNA?
They use folic acids
What is Para-aminobenzoic acid (PABA)?
A nutrient obtained from the environment that is the precursor for folate in bacteria
What are the two Folic Acid Inhibitors?
Sulfonamide and Trimethoprim
How do Sulfonamides work?
They resemble PABA and interfere with PABA metabolic pathways
What kind of antibiotics are Sulfonamides and Trimethoprim?
Folic acid inhibitors
Where do bacteria make protein from mRNA?
In the 70s ribosomal complex comprised of a 50s and 30s subunit
What is the Ribosomal complex in humans like?
Prokaryotes have an 80s ribosomal complex (60S and 40S)
What occurs in transpeptidation?
tRNA (t6) transfers an amino acid to the growing amino acid chain
Why are Eukaryotes unaffected by protein synthesis?
Because they have an 80s ribosomal complex and the antibiotics target the 70s
What are the four types of Protein Synthesis Inhibitors?
- Chloramphenicol
- Macrolides
- Tetracyclines
- Aminoglycosides
How do Chloramphenicol and Macrolides work?
They bind to the 50S subunit and block transpeptidation
How do the Tetracyclines work?
The bind to the 30S subunit and prevent binding of the incoming tRNA
How do Aminoglycosides work?
They bind to the 30S ribosomal subunit and block the initiation of the complex, cause misreading of the code on the mRNA template, inhibit translocation
What are the four ways bacteria can become resistant to antibiotics?
- Drug inactivation or modification
- Alteration of binding site
- Alteration of metabolic pathways
- Reduced drug accumulation
What are Stevens-Johnson syndrome and toxic epidermal necrolysis?
Rare conditions in which the skin becomes detached from the underlying tissue and sloughs off the body
