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Block 4 > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Define:

Infection

A

Infection = invasion and multiplication of pathogenic microbes in an area they are not normally foud

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2
Q

Define :

Antibiotic

Antibacterial

A

Antibiotic = anti bacterial medication (not including disinfectants)

Antibacterial = kills or inhibits the growth of bacteria

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3
Q

Define:

Bactericidal Antibiotic

Bacteriostatic Antibiotic

Is one treatment better than the other?

A

Bactericidal = kills bacteria, tends to target specific parts of the bacteria and have devastating effect e.g. by affecting the bacterial cell wall

Bacteriostatic = inhibits the growth of bacteria e.g. by affecting RNA and DNA

Less devastating effect but inhibits the growth.

Bacteria usually dont live very long and therefore inhibition may actually be sufficient.

Bactericidal and bacteriostatic action may depend on the dose used, there is some overlap in the two drugs.

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4
Q

What does broad spectrum mean?

What does narrow spectrum mean?

A

Broad spectrum = active against many different bacteria (may kill normal flora therefore natural bacteria in gut/ throat will be depleted, can put you at risk of other complications.)

Narrow spectrum = active against few bacteria (may not kill all pathogens).

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5
Q

What are the features of bacteria?

What makes good drug targets?

How do bacteria stain with different types of cell walls?

A
  • Small (1- 10 um in size)
  • DNA present as single chromosome –> prokaryotes (could be targeted)
  • Independent metabolism
  • Lacking organelles
  • Cell wall = distinguishing feature, very different to cell membrane of hosts. Cell wall very good target for antibiotics.
  • Remember: Peptidoglycan cell wall –> Gram +ve stain
  • Lipopolysaccharide celll wall –> Stain gram -ve
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6
Q

Classifications of bacteria:

How are they classified?

Give examples of each type of classification

A

Bacteria are classified based on 1) Gram staining 2) shape

Gram –> either positive or negative

Shape –> coccus or bacillus/ rod shaped

1) Gram positive cocci --> Staphylococcus and Streptococcus

2) Gram positive bacilli –> Bacillus anthracis, Lactobacilli species

3) Gram negative cocci –> Neisseria meningitidis, Haemophilus influenzae

4) Gram negative bacilli –> Escherichia Coli, Salmonella species

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7
Q

Antibiotic mechanisms:

Potential Targets?

A
  1. Bacterial cell wall
  2. Bacterial RNA and protein synthesis
  3. Bacterial DNA structure and function
  4. Folic Acid synthesis (important for DNA synthesis in both bacteria and humans, need to be careful in antibiotics that target folic acid synthesis as can have toxic effects.)
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8
Q

What groups of antibiotics target the bacterial cell wall?

Antibiotics that target the cell wall usually bactericidal (Kill bacteria)

A
  • Beta- lactams (penicillin, cephalosporins and carbapenems)
  • Glycopeptides
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9
Q

What groups of antibiotics target bacteria RNA and protein synthesis?

These are usually bacteriostatic (halt the growth of bacteria)

A
  • Macrolides
  • Tetracyclines
  • Aminoglycosides
  • (lincosamides)
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10
Q

What groups of antibiotic drugs target DNA structure and function?

These are bacteriicidal if high dose

A
  • Quinolones
  • Nitroimidazoles
  • Nitrofuratoin
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11
Q

What antibiotics target Folic acid synthesis?

A
  • Folic acid required for DNA synthesis, likely to have bacteriostatic effect
  • Trimethoprim
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12
Q

Beta lactams: Penicillins

What do they target?

What are the key drugs to know and their properties?

A
  • Target of penicillin : Bacterial cell wall, therefore cell lysis by blocking cell wall synthesis. (Bactericidal)
  • Examples:
    • Penicillin -> Original and still sometimes the best e.g. tonsilitus
    • Amoxicillin –> Modified penicllin that has increased uptake by bacteria, good for LRTI
    • Flucloxacillin –> Good for skin and soft tissue infections
      • ​Penicillinase resistant (penicillinase is an enzyme produced by resistant bacteria that breaks down penicillin)
    • Co -amoxiclav –> Amoxicillin plus clavulanic acid
      • ​Good for mixed infections e.g. dental abcess or chronic bronchitis infection
        • ​Betalactamase inhibitor (betalactamase = another enzyme produced by resistant bacteria that can break down betalactase antibiotics).
        • Clavulanic acid inhibits the betalactamase
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13
Q

What must you be aware of with the penicillins?

A
  • Penicillins are notorious for allergies
  • However, anaphylatic reactions are very rare
  • Always ask what happens when somone has had a reaction, 90% of the time it is not an allergy.
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14
Q

Betalactams: Cephalosporins

Name the cephalosporin on the drugs list.

How does it act?

How were they developed and what is their spectrum of activity?

Uses?

Any issues/limitations with use?

A
  • Betalactam cephalosporin : Ceftriaxone
  • (still part of the betalactams as has betalactam ring)
  • Again targets bacterial cell wall inducing cell lysis by inhibiting cell wall synthesis –> bactericidal
  • Developed through multiple generations (1st to 3rd gen), with each generation had a wider spectrum of activity:
    • Issue is targets natural flora –> limitation of use is Clostridium difficile associated diarrhoa (CDAD), life threatening serious diarrhoea that occurs with loss of gut flora and infection by C diff.
    • Also loses efficacy against gram positive bacterioa
  • Uses:
    • Ceftraixone –> Abdominal sepsis and orthopaedic infections
    • General cephalosporin uses –> bacterial meningitis (penentrate into the brain), UTI and LRTI’s
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15
Q

Betalactam : Carbapanems

Name the carbapanem on the drugs list

What is its mechanism of action?

What are its uses?

A
  • Meropanem = carbopanem betalactam
  • MOA: targets bacterial cell wall, inducing cell lysis by inhibiting cell wall synthesis
  • Resistant to antimicrobial resistance therefore kept in reserve for serious, complicated infections
  • used in intensive care units (ITU’s) and for complex multidrug resistant UTI’s
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16
Q

What other class of drug targets the bacterial cell wall synthesis other than betalactams?

A
  • Glycopeptides e.g. vancomycin
  • Particularly useful for multidrug resistance gram positive cocci e.g. MRSA
  • note: only via IV and renal toxicity, need to monitor use
17
Q

What are macrolides?

Name the drug on the drug list

what is its MOA?

What are its uses?

A
  • Erythromycin
  • Macrolides target RNA and bacterial protein synthesis
    • therefore act as bacteriostatics
  • used for URTI/ LRTI, soft tissue infection and atypical LRTI’s caused by intracellular organisms
18
Q

Tetracyclines:

Name the two drugs on the drug list

MOA

Uses

Side effects

A
  • Tetracycline and doxycycline
  • MOA: targets RNA and bacterial protein synthesis therefore bacteriostatic
  • Uses:
    • used for unusual chest infections that are unresponsive to penicillin
    • and tropical infections caused by Ricketsia
  • Side effects:
    • GI intolerance
    • Photosensitivity (rash in light)
19
Q

Lincosamides:

Name the drug on drug list

Target?

Uses?

A
  • Lincosamides: target RNA and protein synthesis (bacteriostatic)
  • Example: Clindamycin
  • Uses: soft tissue infections and in the place of penicillin when IV access is limited (e.g. in drug users with limited IV access)
  • Excellent bioavailability and tissue penentration when taken orally (hence use in limited IV access)
20
Q

Quinolones/ Fluoroquinolones:

Name drug on drug list

MOA

Uses

Any side effects or limitations

A
  • Quinolones/ Fluoroquinolones target DNA structure and function (bacteriocidal if high dose)
  • Ciprofloxacin –> MOA: inhibits DNA coiling
  • Uses:
    • ​Gram negative infections, only if aerobic (not if anaerobic)
    • MRSA infection
    • LRTI’s (levofloxacin only)
  • Limitation : CDAD (Clostridium difficile associated diarrhoea)
21
Q

Nitroimidazoles:

Name the drug on the drug list

Target / MOA

uses

A
  • Nitroimidazoles target DNA structure and function
  • Metronidazole inhibits DNA synthesis
  • used in anaerobic infections e.g. abscesses
22
Q

What is the sepsis 6?

What do you do if they do not respond?

A

Within 1 hour of suspecting severe sepsis give sepsis 6 care bundle:

  1. Give high flow oxygen
  2. Take blood cultures
  3. Give empirical IV antibiotics (best guess)
  4. measure FBC and serum lactate (any problems with tissue perfusion and anaerobic respiration)
  5. Start IV fluid resuscitation
  6. Start accurate urine output measurement (monitoring kidneys)

Call in critical care, monitor central venous pressure, vasporessor and ionotropic drugs.

23
Q

What is the diagnostic process? (6 steps)

A

1) History = presenting complaint, history of presenting complaint, PMH, allergies drugs and treatments (ADT), FH, SH,
2) Examination: General / CVS/ RS/ ABDO/ NS. LMS/ skin etc
3) Differential diagnosis
4) Investigations e.g. samples, imaging, physiology and histopathology
5) Diagnosis
6) Treatment

24
Q

What microbiology investigations are there?

A
  • Divided into direct and indirect techniques
  • Direct:
    • microscopy, culture and sensitivity
    • Antigen detection tests
    • PCR tests (detect DNA of microorganism involved)
  • Indirect:
    • Serology tests (look for antibody responses to infection in question).
25
Q

Factors affecting antibiotic choice?

A
  • Consider both the organism and the patient in question
  • If known organism you can use known antibiotics or ideally, the organism is cultured in the lab and different antibiotic treatments tried to test for sensitivity to them.
  • If you are unsure, can try and work out most likely organism to be involved (e.g. URTI is known), suspected organism then treated with antibiotic
  • Patient factors:
    • allergy or intolerance?
    • Renal and liver function (as most antibiotics metabolsied here)
    • the severity of the infection or immuncompromised patient (need to get it right first time).
    • Risk of antibiotic associated infection (e.g. cephalosporin in elderly patient with clostridium difficile diarrhoea.)
    • route of administration (oral vs iv)
    • interactions with other medications
    • age or ethnic group (occassionly, can be genetic associations)
    • pregnant, breast feeding as some antibiotics can appear in breastmilk
    • on oral contraception (some antibiotics interfere with metabolism or oral contraceptive pill).
26
Q

What are the antibiotic guidelines?

What is their purpose?

A
  • Guidelines that aim to produce effective and efficient treatment
  • Most important for when no organism is identified
  • And reduce overprescribing and use of broad spectrum antibiotics
  • therefore reducing antibiotic resistance and other complications e.g. adverse effects and antibiotic associated infections
  • The British national formulary has guidlines that are suitable to most situations
  • most healthcare units develop their own guidelines as antibiotic resistance patterns alter in different areas
27
Q
A

Block 4 (14 decks)

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