Chemotherapy of infectious disease (antimetabolites)

Question 1

Germ theory

Answer 1

Germ theory of diseases states that microorganisms, known as pathogens, or germs
can lead to disease
Diseases caused by pathogens are called infectious diseases

Question 2

Types of pathogeen

Answer 2

Question 3

ESKAPE pathogens

Answer 3

Question 3

Bacteria: general structure

Answer 3

Bag: capsule, cell wall, plasma membrane
•Contents: cytoplasm, ribosomes, plasmid DNA, nucleoid (cDNA)
•NB: no nucleus

Question 4

Bacteria: Gram staining

Answer 4

Gram staining classifies bacteria by cell wall type
•Cells are stained with crystal violet
–Gram +ve cells retain the primary stain
–Gram –ve cells primary stain washes out, counterstained (pink)

Question 5

Gram +ve

Answer 5

thick peptidoglycan layer

cytoplasmic membrane

Question 6

Gram –ve

Answer 6

•lipopolysaccharide outer
envelope
•thin peptidoglycan layer
•cytoplasmic membrane

Question 7

Commensal bacteria

Answer 7

–Live on the outer surfaces of our bodies e.g. skin, mucus membranes, gut
–May be beneficial
–May cause serious illness in host or infect another person
–Examples:
•streptococcus – tonsillitis
•Pneumococcus – pneumonia
•Haemophilus influenzaetype B – meningitis

Question 8

Virulence– ability to cause disease

Virulence factors- molecules produced by bacteria that add to their effectiveness

Answer 8

–Colonization of a niche in the host – includes attachment to cells
–Immunoevasion – evasion of the host’s immune response
–Immunosuppression – inhibition of the host’s immune response
–Entry into and exit out of cells – if the pathogen is intracellular
–Obtain nutrition from the host

Question 9

Antibacterials: targeting the cell wall

Answer 9

•Cell wall is essential to bacteria survival

1. stop synthesis of cell wall
2. disrupt cell wall integrity

Question 10

Peptidoglycan cell wall synthesis

Answer 10

•Gram +ve bacteria
•Polysaccharide chains 
–(NAG-NAM) repeating units
•Peptide Chains
–connect to 3-OH of NAM
–L-Ala-D-Glu-L-Lys-D-Ala-D-Ala
•Pentaglycine crosslinks 
–formed by Transpeptidase enzyme (PBP) 
–D-Alanine leaving group

Question 11

Transpeptidase essential for bacterial cell viability

Answer 11

–catalyses crosslinking NAG-NAM chains
–membrane bound protein
–cleaves terminal D-Ala residue

Question 12

Summary: b-lactams

Answer 12

•Target cell wall biosynthesis
•Target transpeptidase enzyme
•Affinity labels
•Three main classes:
–penicillins
–cephalosporins
–carbapenems
•Resistance via b-lactamase
–clavulanic acid

Question 13

Vancomycin

Answer 13

•Branched tricyclic glycosylated
non-ribosomal peptide
•Usually given IV 
•Used for serious, life-threatening infections by 
resistant Gram +ve bacteria

Question 14

Question 15

Answer 15

Question 16

Answer 16

Question 17

Answer 17

Question 18