Antibiotics

What are the 2 types of bacterium?

1. bactericidal: kills bacteria

2. bacteriostatic : slows growth

Name the 3 main bacterial cell components that antibiotics target

1. cell wall or membrane

2. ribosomes & associated proteins

3. DNA/RNA

What is the difference between gram positive and gram negative bacteria?

gram positive - thick peptidoglycan layer

gram negative - thin peptidoglycan later + outer membrane containing lipopolysaccharides 

How do beta-lactam antibiotics work? Name an example

inactivate enzymes that synthesise cell wall e.g. penecillin

Name the 2 types of cell wall synthesis inhibitors

beta-lactam antibiotics & glycopeptides

How do glycopeptides work?

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ribosomes - 30S 50S

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What is transcription?

1. DNA → mRNA

2. mRNA travels out nucleus to ribosomes in cytoplasm 

What is translation?

1. transfer RNA (tRNA) carries correct amino acids to ribosome

2. ribosome links amino acids together to create a codon

3. protein is released from ribosome to Golgi body for moderation

What is the tunnel called where a protein leaves ribsosome to travel to Golgi apparatus?

nascent peptide exit tunnel

How do protein synthesis inhibitors work?

inhibit transcription or translation, preventing proteins from being made

How does clarithromycin work?

bind to nascent peptide exit tunnel and partially occlude it, preventing protein synthesis

What type of bacteria is clarithromycin? Bacteriostatic or bacteicidal?

macrolides - bacteriostatic

What is clarithromycin used to treat?

multiple infections e.g. chest, skin

How does tetracycline work?

binds to 30S subunit and prevents tRNA binding to ribosome in translation

What type of bacteria is tetracycline? Bacteriostatic or bacteicidal?

tetracyclines - bacteriostatic

What is tetracycline used to treat?

• acne

• cholera

How does cycloserine work?

binds to 50S subunit and prevents tRNA binding to ribosome in translation

What type of bacteria is cycloserine? Bacteriostatic or bacteicidal?

oxazolidinones - bacteriostatic

What is cycloserine used to treat?

tuberculosis

How does streptomycin work?

binds to unique portion of 30S which inhibits mRNA, causing miscoding errors 

What type of bacteria is streptomycin? Bacteriostatic or bacteicidal?

aminoglycosides - bactericidal

What is streptomycin used to treat?

endocarditis 

How does streptogramin A work?

blocks peptidyl transferase, an enzyme responsible for forming peptide bonds between amino acids, preventing protein synthesis.

How does streptogramin B work?

binds to different site on ribosome and prevents elongation and release of streptogramin A. Also helps binding of streptogramin A.

What are

What are streptogramins used to treat?

• VRSA (vancomysin-resistant staphylococcus aureus)

• VRE (vancomycin-resistant enterococcus)

Which enzyme do RNA synthesis inhibitors inhibit?

RNA polymerase

How do RNA synthesis inhibitors work?

• bind to RNA polymerase 

• prevents transcription of DNA → mRNA

• prevent ribosome receiving instructions needed for translation

• prevent protein synthesis

Ansamycins????

Name 2 examples of ansamycins 

1. rifamycin

2. geldanamycin

How do DNA synthesis inhibitors work?

• inhibit DNA synthesis enzymes (gyrase, topoisomerase IV) which help unwind and separate DNA strands, thus preventing DNA replication

• inhibit synthesis of nucleotides 

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What are mycolic acid synthesis inhibitors?

inhibit production of mycolic acid in cell walls of mycobacterium tuberculosis, weakening bacterial cell wall making it vulnerable to destruction

What is the role of mycolic acid?

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slide  34!!

What is folic acid?

synthetic version of vitamin folate (B9) essential in diet for RBC formation andhealthy cell growth and formation

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Why is diarrhoea a side effect of antibiotics?

antibiotics can affect beneficial bacteria in gut, hindering digestion, nutrient absorption and immune system regulation, leading to diarrhoea

What are some side effects of antibiotics?

• lethargy 

• seiures

• confusion

• hallucinations

• prolonged QT

• diarrhoea 

• allergic reaction 

• effects on metabolism 

Why is streptomycin not used in pregnancy?

may cause foetal auditory nerve damage

Why is tetracycline not used in pregnancy?

• stain developing bone and teeth in foetus

• IM administration can cause maternal liver failure

When is trimethoprim safe to use in pregnancy?

after 1st trimester

Why is trimethroprim not used before 1st trimester of pregnancy?

as it may affect levels of folic acid which is important for early stages of baby development

Why is vanomycin not used in pregnancy?

may cause ototoxicity (hearing/balance problems) and nephrotoxicity in foetus

Why are there many risks involved in medication use during breastfeeding?

may be excreted via breast milk