W6- Lecture 27.1- Antibiotic Resistance A

Question 1

describe the structure of a bacteria cell

Answer 1

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

Question 2

Key Differences/Similarities between bacterial and mammalian cell

Answer 2

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)

Question 3

describe the growth requirements for bacteria

Answer 3

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)

Question 4

What are the main groups of bacteria

Answer 4

Gram stained bacteria
1Gram positive
2Gram negative
(aerobes or anaerobes)
3Acid-fast bacilli (Mycobacteria)
4Atypicals

Question 5

What are the portals of entry into the body for micro-organisms?

Answer 5

Skin
Respiratory tract
Gastro-intestinal tract
Urogenital system
Conjunctiva (eye)

Question 6

name 6 Natural immunity mechanisms

Answer 6

Physical or Chemical barriers 
Inflammation 
Phagocytosis
The complement system
Antibacterial substances eg lysozyme
Antiviral substances eg interferon

Question 7

what are the two types of active immunity

+e.g

Answer 7

Naturally acquired active immunity = Suffer from the infection
Artificially acquired active immunity = live vaccination

Question 8

what are the two types of passive immunity

+e.g

Answer 8

Natural passive immunity eg mother passing antibodies to baby during pregnancy & breastfeeding
Artificial passive immunity eg antibodies injected from a serum (tetanus immunoglobulin

Question 9

what are the two categories of antibiotics (by mechanism of action )

Answer 9

Bactericidal - kill bacteria

Bacteriostatic - suppress growth/reproduction of bacteria

Question 10

do the activity worksheet

Answer 10

thanks/ well done

Question 11

name 5 mechanisms in which antibiotics fight against bacteria

Answer 11

Inhibit bacterial cell wall synthesis
Inhibit bacterial protein synthesis
Inhibit folate synthesis
Inhibit transcription of bacterial RNA
Inhibit DNA gyrase and topoisomerase

Question 12

name two antibiotic classes that Inhibit bacterial cell wall synthesis
and how they are selectively toxic

Answer 12

Beta-lactams
Glycopeptides

Beta-lactams are structural analogues of cell wall precursors, they inhibit enzymes involved in cell wall synthesis

Question 13

name 5 antibiotic classes that Inhibit bacterial protein synthesis

and how they are selectively toxic

Answer 13

Aminoglycosides
Chloramphenicol
Sodium fusidate
Macrolides
Tetracyclines

Bacterial ribosomes have different RNA content and protein composition

Question 14

name 2 antibiotic classes that Inhibit folate synthesis

and how they are selectively toxic

Answer 14

Sulphonamides
Trimethoprim

Inhibit dihydrofolate reductase (enzyme)

Question 15

name 1 antibiotic class that Inhibit transcription of bacterial RNA

and how they are selectively toxic

Answer 15

Rifampicin

Binds to bacterial DNA – dependent RNA polymerase

Question 16

name 1 antibiotic class that Inhibit DNA gyrase and topoisomerase

and how they are selectively toxic

Answer 16

Quinolones

Modulate replication/expression of DNA

Question 17

name two examples of Beta-lactams

Answer 17

penicillins, cephalosporins

Question 18

how do Beta-lactams prevent cell wall synthesis ?

Answer 18

interfere with cross linkage of peptidoglycans

bactericidal

Question 19

name two examples of Glycopeptides

how do these prevent cell wall synthesis ?

+ what type of bacteria are they used to treat

Answer 19

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

Question 20

describe how Tetracyclines inhibit bacterial protein synthesis

bacteriostatic or cidal ?

Answer 20

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

Question 21

describe how Aminoglycosides inhibit bacterial protein synthesis

bacteriostatic or cidal ?

Answer 21

Aminoglycosides interfere with mRNA attachment to the ribosome. Bactericidal

Question 22

describe Linezolid how inhibit bacterial protein synthesis

bacteriostatic or cidal ?

Answer 22

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

Question 23

describe how Chloramphenicol inhibit bacterial protein synthesis

bacteriostatic or cidal ?

Answer 23

Chloramphenicol binds to the 50s ribosomal subunit and interferes with binding of amino acids to the growing chain. Bacteriostatic

Question 24

describe how Macrolides and lincosamides inhibit bacterial protein synthesis

bacteriostatic or cidal ?

Answer 24

Macrolides and lincosamides attach to the 50s ribosomal subunit causing termination of the growing protein chain. Bacteriostatic

Question 25

which three antibiotics effect bacterial nucleic acid synthesis

Answer 25

Quinolones
Rifampicin
Metronidazole

Question 26

name one antibiotic that is a Quinolones

Answer 26

ciprofloxacin

Question 27

describe how Quinolones effects nucleic acid synthesis in bacterial cells

Answer 27

It functions by selectively inhibiting DNA gyrase, and a type II topoisomerase, topoisomerase IV, necessary to separate bacterial DNA, thereby inhibiting cell division

Question 28

describe how Rifampicin

effects nucleic acid synthesis in bacterial cells

Answer 28

It inhibits DNA-dependent RNA polymerase activity by forming a stable complex with the enzyme, thus suppresses the initiation of RNA synthesis

Question 29

describe how Metronidazole

effects nucleic acid synthesis in bacterial cells

Answer 29

Binds to bacterial DNA which leads to strand breakage

Question 30

describe how Trimethoprim interferes with the metabolic pathway of bacterial cells

Answer 30

Inhibits dihydrofolate reductase, a key stage in the development of nucleic acids
Exerts antimicrobial activity by blocking the reduction of dihydrofolate to tetrahydrofolate, the active form of folic acid