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Year 1 Locomotion > Antibiotics MOA > Flashcards

Antibiotics MOA Flashcards

1
Q

Define Infection

A

invasion & multiplication of pathogenic microbes

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2
Q

Define Antibiotic

A

= anti-bacterial medication (not including disinfectants)

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3
Q

Define anti-bacterial

A

kills or inhibits growth of bacteria

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4
Q

Define broad spectrum

A

active against many bacteria (may kill normal flora)

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5
Q

Define narrow spectrum

A

active against few bacteria (may not kill all pathogens

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6
Q

Define Bactericidal

A

kills bacteria (by affecting bacterial cell wall)

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7
Q

Define bacteriostatic

A

inhibits growth of bacteria (by affecting RNA & DNA)

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8
Q

What is MINIMUM BACTERICIDAL CONCENTRATION (MBC)

A

lowest concentration that kills 99.9% of a population

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9
Q

what is Minimum inhibitory concentration (MIC)

A

lowest concentration which inhibits visible growth of bacteria

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10
Q

what is Breakpoint

A

MIC cut-off which separates strains where there is a high likelihood of treatment succeeding from those where treatment is more likely to fail

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11
Q

Describe Bacteria

size?

DNA?

metabolism?

cell wall?

A

Bacteria : 1 – 10 μm in size

DNA as a single chromosome (prokaryotes)

Independent metabolism & no organelles

Cell wall (different from cell membranes of host organism)

Peptidoglycan cell wall = Gram stain +ve

Lipopolysaccharide cell wall = Gram stain -ve

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12
Q

How are bacteria classified?

A

Bacteria are classified based on Gram staining & shape

  • Gram = positive or negative
  • Shape = coccus or bacillus/rod
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13
Q

Name examples of Gram positive cocci

A

Staphylococcus species, Streptococcus species

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14
Q

Name examples of Gram positive bacilli

A

Bacillus anthracis, Lactobacilli species

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15
Q

Name examples of gram negative cocci

A

Neisseria meningitidis, Haemophilus influenzae

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16
Q

name examples of Gram negative bacilli

A

Escherichia coli, Salmonella species

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17
Q

What are the potential targets of antibiotics?

A
  • Bacterial cell wall
  • Bacterial RNA & protein synthesis
  • Bacterial DNA structure & function
  • Folic acid synthesis
18
Q

Which type of antibiotics target the bacterial cell wall?

A

usually bactericidal

Beta-lactams (penicillins, cephalosporins & carbapenems)

Glycopeptides

19
Q

Which type of antibiotic targets Bacterial RNA & protein synthesis?

A

usually bacteriostatic

Macrolides

Lincosamides

Tetracyclines

Aminoglycosides

20
Q

Which type of antibiotic targets Bacterial DNA structure & function

A

bactericidal if high dose

Quinolones

Nitroimidazoles

Nitrofurantoin

21
Q

Which type of antbiotic targets Folic acid synthesis (required for DNA synthesis)

A

usually bacteriostatic

Trimethoprim

Sulphonamides

22
Q

Describe Beta-Lactams (Penicilins)

What is their target?

A

Penicillins :

Target : bacterial cell wall (bactericidal) - cell lysis by blocking cell wall synthesis

Penicillin (original & sometimes still the best) eg. tonsillitis

Amoxicillin (enhanced uptake by bacteria) eg. LRTI

Flucloxacillin (penicillinase-resistant) eg. SSTI

Co-amoxiclav (beta-lactamase inhibitor) eg. mixed infections

Benzylpenicillin

Piperacillin-tazobactam (anti-pseudomonal) eg. complex LRTI

23
Q

Describe Beta-Lactams (Cephalosporins)

What is their target?

A

Target = Bacterial cell wall (bactericidal)

Ceftriaxone = 4th generation

Later generations have ↑ spectrum of activity

but also kill more natural flora (& ↓ efficacy against Gram +ves)

Used in bacterial meningitis & orthopaedic infections (ceftriaxone)

24
Q

What is the target of Beta-Lactams - Carbapenems

A

Target : bacterial cell wall (bactericidal)

Examples : meropenem, ertapenem

Uses : infections in ITUs, complex & multi-drug resistant UTIs

25
Q

What is the target of macrolides?

A

Target : RNA & bacterial protein synthesis (bacteriostatic)

Examples : erythromycin, clarithromycin, azithromycin

Uses : URTI, LRTI, SSTI (in place of penicillins)

Atypical LRTIs (intracellular organisms)

26
Q

What is the target of Lincosamides?

A

Target : RNA & bacterial protein synthesis (bacteriostatic)

Example : clindamycin

Uses : SSTI (in place of penicillins or when IV access is limited)

Note : excellent bioavailability & tissue penetration when taken orally

27
Q

What is the target for Tetracyclines?

A

Target : RNA & bacterial protein synthesis (bacteriostatic)

Example : doxycycline, Tetracycline

Uses : “atypical” bacteria that lack usual cell wall eg. Chlamydia, Mycoplasma

Rickettsia infections eg. typhus

28
Q

What is the target of Aminoglycosides?

A

Target : RNA & bacterial protein synthesis (bactericidal if high dose)

Example : gentamicin

Uses : severe Gram –ve infections

synergistic treatment for endocarditis

Note : renal toxicity & need for therapeutic drug monitoring limits use

29
Q

What is the target for Quinolones?

Examples?

Uses?

A

Target : bacterial DNA structure & function (bactericidal if high dose)

Examples : ciprofloxacin, levofloxacin

Uses : Gram –ve infections (excluding anerobes)

MRSA infections

LRTIs (levofloxacin only)

Note : also associated with CDAD

30
Q

What is the target for Nitroimidazoles?

Example?

Uses?

A

Target : bacterial DNA structure & function (bactericidal if high dose)

Example : metronidazole

Uses : anaerobic infections (abscesses)

31
Q

What is the target for Ntrofurantoin?

Uses?

A

Target : bacterial DNA synthesis (bactericidal if high dose)

Uses : uncomplicated UTIs

Note : poor bioavailability, but is concentrated in urine

32
Q

What is the target for anti-folates?

Example?

Uses?

A

Target : folic acid synthesis & so DNA synthesis (bacteriostatic)

Examples : trimethoprim, sulphonamides

Uses : uncomplicated UTIs (but not in pregnant women)

33
Q

What do you need to consider when choosing an antibiotic?

A
  • Sepsis & supportive treatments
  • Use the diagnostic process
  • Microbiology tests
  • Consider antibiotic guidelines
34
Q

What is the Sepsis 6 care bundle?

A
  1. Give high-flow oxygen
  2. Take blood cultures
  3. Give empirical IV antibiotics
  4. Measure FBC & serum lactate
  5. Start IV fluid resuscitation
  6. Start accurate urine output measurements
35
Q

Briefly outline the diagnostic process?

A

History = PC, HPC, PMH, ADT, FH, SH, ROS

↓

Examination = General, CVS, RS, ABDO, NS, LMS etc.

↓

Differential Diagnosis

↓

Investigations = (bedside), body fluids, imaging, physiology, histopathology

↓

Diagnosis

↓

Treatment

36
Q

What microiology samples would you request?

A

Samples : Swabs = pus, skin, nose, throat, urethra, vagina etc.

Body fluids = pus, urine, faeces, blood, CSF etc.

Body tissues = biopsies (rarely)

37
Q

What microbiology investigations would you request?

A

Can be divided into direct & indirect techniques …

Direct :

  • Microscopy, culture & sensitivity (usually refers to bacteria or fungi)
  • Antigen detection tests (eg. malaria, Legionella, C. difficile toxin)
  • PCR tests (eg. Mycobacteria, 16S Ribosomal DNA)

Indirect :

• Serology tests (eg. rare or neglected tropical infections)

38
Q

Name some factors affecting antiobiotic choice relating to the organism

A
  • Known organism +/- sensitivities & resistance profile
  • Or the most likely organisms and their sensitivities/resistance
39
Q

Name some factors affecting antiobiotic choice relating to the patient

A
  • Allergy/Intolerance
  • Renal & liver function
  • Severity of infection/Is patient immunocompromised?
  • Risk of antibiotic-associated infection
  • Route of administration
  • Interactions with other medication
  • age/ethnic group
  • Pregnant, breast feeding or taking oral contraception
40
Q

Why do we need antibiotic guidelines?

A
  • To produce effective and efficient treatment
  • To reduce over-pescribing and use of broad spectrum antibiotics which can lead to antibiotic resistance and other complicatons

Year 1 Locomotion (18 decks)

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