W6- Lecture 27.1- Antibiotic Resistance A Flashcards
describe the structure of a bacteria cell
Cell Wall
Contains peptidoglycan (differentiates bacteria cells from mammalian cells)
Plasma membrane
Permeability barrier for molecules
Cytoplasm
Gel like substance enclosed within cell wall
Ribosomes
Site of biological protein synthesis
Plasmid
DNA molecule within a cell which is physically separated from a chromosomal DNA
Pili
Protein tubes extending out from outer membrane
Flagellum
Whip like structure outside cell wall responsible for movement
Key Differences/Similarities between bacterial and mammalian cell
Bacterial Cell Cell Wall Cell membrane No nuclear membrane (DNA) Ribosome (30s) (50s)
Mammalian Cell No Cell Wall Cell membrane Nuclear membrane (DNA) Ribosome (40s) (60s)
describe the growth requirements for bacteria
Optimum temperature
Optimum pH
Atmospheric conditions
Nutrients
(Anaerobic - is any organism that does not require oxygen for growth
Aerobic -which grows in the presence of air or requires oxygen
Facultative - can use oxygen but also has anaerobic methods of energy production)
What are the main groups of bacteria
Gram stained bacteria 1Gram positive 2Gram negative (aerobes or anaerobes) 3Acid-fast bacilli (Mycobacteria) 4Atypicals
What are the portals of entry into the body for micro-organisms?
Skin Respiratory tract Gastro-intestinal tract Urogenital system Conjunctiva (eye)
name 6 Natural immunity mechanisms
Physical or Chemical barriers Inflammation Phagocytosis The complement system Antibacterial substances eg lysozyme Antiviral substances eg interferon
what are the two types of active immunity
+e.g
Naturally acquired active immunity = Suffer from the infection
Artificially acquired active immunity = live vaccination
what are the two types of passive immunity
+e.g
Natural passive immunity eg mother passing antibodies to baby during pregnancy & breastfeeding
Artificial passive immunity eg antibodies injected from a serum (tetanus immunoglobulin
what are the two categories of antibiotics (by mechanism of action )
Bactericidal - kill bacteria
Bacteriostatic - suppress growth/reproduction of bacteria
do the activity worksheet
thanks/ well done
name 5 mechanisms in which antibiotics fight against bacteria
Inhibit bacterial cell wall synthesis Inhibit bacterial protein synthesis Inhibit folate synthesis Inhibit transcription of bacterial RNA Inhibit DNA gyrase and topoisomerase
name two antibiotic classes that Inhibit bacterial cell wall synthesis
and how they are selectively toxic
Beta-lactams
Glycopeptides
Beta-lactams are structural analogues of cell wall precursors, they inhibit enzymes involved in cell wall synthesis
name 5 antibiotic classes that Inhibit bacterial protein synthesis
and how they are selectively toxic
Aminoglycosides Chloramphenicol Sodium fusidate Macrolides Tetracyclines
Bacterial ribosomes have different RNA content and protein composition
name 2 antibiotic classes that Inhibit folate synthesis
and how they are selectively toxic
Sulphonamides
Trimethoprim
Inhibit dihydrofolate reductase (enzyme)
name 1 antibiotic class that Inhibit transcription of bacterial RNA
and how they are selectively toxic
Rifampicin
Binds to bacterial DNA – dependent RNA polymerase
name 1 antibiotic class that Inhibit DNA gyrase and topoisomerase
and how they are selectively toxic
Quinolones
Modulate replication/expression of DNA
name two examples of Beta-lactams
penicillins, cephalosporins
how do Beta-lactams prevent cell wall synthesis ?
interfere with cross linkage of peptidoglycans
bactericidal
name two examples of Glycopeptides
how do these prevent cell wall synthesis ?
+ what type of bacteria are they used to treat
Vancomycin, teicoplanin
Interfere with peptidoglycan formation by preventing joining of N-acetylglucosamine and N-acetylmuramic acid dimers
Molecules too large to penetrate Gm –ve outer membrane
Spectrum of activity largely Gram +ve organisms – used largely against staphylococci (including MRSA) and streptococci
describe how Tetracyclines inhibit bacterial protein synthesis
bacteriostatic or cidal ?
Tetracyclines bind to the 30s ribosomal subunit and block attachment of transfer RNA (tRNA) and addition of amino acids to the protein chain. Inhibits the binding of aminoacyl-tRNA to the mRNA-ribosome complex . Bacteriostatic
describe how Aminoglycosides inhibit bacterial protein synthesis
bacteriostatic or cidal ?
Aminoglycosides interfere with mRNA attachment to the ribosome. Bactericidal
describe Linezolid how inhibit bacterial protein synthesis
bacteriostatic or cidal ?
Linezolid binds the 23s ribosomal RNA of the 50s subunit and prevents formation of a functional 70s initiation complex which is necessary for protein synthesis. Bacteriostatic
describe how Chloramphenicol inhibit bacterial protein synthesis
bacteriostatic or cidal ?
Chloramphenicol binds to the 50s ribosomal subunit and interferes with binding of amino acids to the growing chain. Bacteriostatic
describe how Macrolides and lincosamides inhibit bacterial protein synthesis
bacteriostatic or cidal ?
Macrolides and lincosamides attach to the 50s ribosomal subunit causing termination of the growing protein chain. Bacteriostatic
