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MBChB Year 1 Principles Microbiology > Antibiotic Therapy > Flashcards

Antibiotic Therapy Flashcards

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Biology 101 flashcards
1
Q

What are antibiotics?

A

A drug used to treat or prevent infection caused by bacteria

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2
Q

What does bacteriostatic describe?

A

Inhibiting the growth of bacteria

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3
Q

If something is bactericidal, what does it do?

A

Kill bacteria

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4
Q

What is the spectrum?

A

The range of micro-organisms an antibiotic can act on (ie how broad/narrow)

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5
Q

What are the characteristics of an ideal antibiotic?

A

Selective toxicity (to minimise host damage), tidal, long half life, appropriate tissue distribution, no adverse side effects/drug interactions and oral & parenteral preparations

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6
Q

What are the main antibiotic targets?

A

Cell wall, ribosomes, DNA replication, DNA gyrases and metabolic pathways - really want to find something in bacteria that isn’t in humans (to help prevent toxicity to humans)

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7
Q

What are the 2 types of antibiotics that target cell walls?

A

Beta-lactams - (Penicillins and cephalosporins) and glycopeptides

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8
Q

What is the main issues with penicillin?

A

Allergy (hypersensitivity), rapid excretion via kidneys (need many doses) and resistance

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9
Q

What do cephalosporins do different from penicillins?

A

Wider spectrum and more resistant to beta-lactamases

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10
Q

What does the cell wall protect the cell from?

A

Internal osmotic pressure (bursting)

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11
Q

What are the targets of beta-lactams?

A

Penicillin Binding Proteins (PBPs)

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12
Q

What is the role of beta-lactams?

A

A suicide substrate which halts the cell wall synthesis = compromised wall

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13
Q

What are the benefits to penicillin?

A

Safe (few side effects), variety, range from narrow to broad spectrum, rapid excretion via kidneys and safe in pregnancy

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14
Q

What are the benefits to amoxicillin?

A

Safe (well tolerated by body), well absorbed (when given orally), low binding to plasma proteins, good tissue distributions

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15
Q

What are the problems with amoxicillin?

A

Effectiveness challenged by spread of beta-lactamases and resistance

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16
Q

What does clavulanic acid do?

A

Inhibits the action of beta-lactamases (microbial enzyme) - nb it has no antibiotic properties of its own

17
Q

What antibiotic is commonly used for staph and strep skin infections?

A

Flucoxacillin

18
Q

What does temocillin work against?

A

Extended spectrum beta-lactamases and ampC beta-lactamases. (usually restricted to coliforms)

19
Q

What is the problem with cephalosporins?

A

Kill off gut bacteria and so allow the overgrowth of clostridium difficile = gastroenteritis

20
Q

What are the main issues with glycopeptides?

A

Not absorbed so requires hospitalisation (excreted via kidneys and urine - problem for people with kidney disease as can’t leave body causing toxic build up) and activity limited to gram +ve cell walls

21
Q

How do antibiotics that inhibit protein synthesis work?

A

Attach to bacterial ribosomes (structurally different from mammalian ribosomes) - usually protein synthesis continues when bacteria is removed (antibiotics are bateriostatic - except aminoglycosides = bactericidal)

22
Q

What is the problem with aminoglycosides?

A

Toxic - cause kidney damage and VIII cranial nerve damage = need to monitor blood levels

23
Q

How do tetracyclines get into the cell?

A

Active transport by binding to 30S subunit

24
Q

What are the problems with tetracyclines?

A

Destruction of normal intestinal flora = secondary infection and increasing resistance

25
Q

What antibiotics target nucleic acids?

A

Metronidazole, trimethoprim and fluoroquinolones

26
Q

What types of bacteria does metronidazole work against?

A

Anaerobes (nb also parasites and protozoa)

27
Q

How is folic acid synthesis inhibited?

A

Key intermediate metabolism is blocked

28
Q

What is empiric prescribing?

A

Prescribing without 100% confirmation of the micro-organism

29
Q

How do you choose an antibiotic?

A

Site of patient infection, likely infecting organism, oral vs IV, antibiotic allergy, local prescribing policies and cost-effectiveness

30
Q

What are some common side effects of antibiotics?

A

Nausea, vomiting, diarrhoea

31
Q

Why would antibiotics be given in combination?

A

To cover a broad range of possible infecting organism, prevent development of resistance and for the synergistic effect of combination

32
Q

Can you combine bacteriostatic and bactericidal antibiotics?

A

No

MBChB Year 1 Principles Microbiology (5 decks)

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