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Antimicrobial Resistance & MDRO Flashcards

Caoimhe (38 cards)

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1
Q

Antibiotics may be bacteriostatic/bactericidal

What does a bacteriostatic antibiotic do?

A

The antibiotic prevents the growth of bacteria

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2
Q

Antibiotics may be bacteriostatic/bactericidal

What does a bactericidal antibiotic do?

A

The antibiotic kills bacteria

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3
Q

Various antimicrobial agents act by interfering with what? (4)

A
  1. Cell wall synthesis
  2. Plasma membrane integrity
  3. Nucleic acid synthesis
  4. Ribosomal function
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4
Q

Antibiotic Classes

What do B-Lactams do to kill bacteria? and an example?

A

Inhibit bacteria cell wall synthesis
Eg; Amoxicillin

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5
Q

AMR

When does AMR occur?

A

When microbes evolve mechanisms that protect them from the effects of antimicrobials

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6
Q

AMR

AMR consequences (4)

A
  1. Limited treatment for infections -> delayed treatment
  2. Increased risk of transmission
  3. Accumulation of antimicrobial resistance
  4. Panresistance -> microbe resistant to everything
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7
Q

AMR

(3) Stages of AMR evolution

A
  1. Genetic mutation as a result of selective pressures
  2. Horizontal gene transfer (HGT)
  3. Vertical gene transfer (clonal dissemination) and subsequent transmission of resistant strains from person -> person or from other sources (animals, environmental sources)
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8
Q

AMR

Main drivers of AMR (3)

A
  1. Overuse and misuse of antimicrobials
  2. Poor hygiene/ sanitation
  3. Substandard infection control measures in healthcare/agriculture
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9
Q

(3) Stages of horizontal gene transfer

A
  1. Transformation
  2. Translation
  3. Conjugation
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10
Q

What happens during the third stage of HGT?

A

Conjugation:
Cells need direct contact, with this a channel forms for DNA to pass

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11
Q

AMR

What are plasmids?

A

Small, extra-chromosomal DNA molecules that can replicate independently.

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12
Q

AMR

What were antibiotics used for in agriculture and what did this promote?

A

Antibiotics in low concentrations were used as growth promoters for animals in agriculture. This resulted in resistance among bacteria

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13
Q

AMR

MDRO definition

A

Microorganisms resistant to three or more classes of antimicrobial drugs

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14
Q

AMR

Beta lactam antibiotics examples? (2)

A
  1. Penicillins
  2. Carbapenems
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15
Q

AMR

Clinically significant resistance -> Gram positive organisms examples? (4)

A

Staphylococcus species:
1. Staphylococcus aureus
2. Coagulase negative Staphylococci (CNS)
Enterococcus species:
3. E. faecium
4. E. faecalis

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16
Q

AMR

CNS are examples of opportunistic bacteria. Define opportunistic bacteria?

Study These Flashcards
A

Microorganisms that don’t usually cause disease, however can become pathogenic under certain conditions -> weakened immune system - immunocompromised

17
Q

Staph aureus infection associated with?

Study These Flashcards
A
  1. Skin (abscesses, cellulitis)
  2. UTI
  3. BSI (blood stream infection)
  4. Osteomyelitis
  5. Foodpoisoning
18
Q

Staph aureus infection treatment (2)

Study These Flashcards
A
  1. Cephalexin (beta lactam) for uncomlicated skin infection
  2. Vancomycin (glycopeptide antibiotic) for comlicated/invasive infections -> bacteraemia, pneumonia, etc.
19
Q

MRSA definiton

Study These Flashcards
A

Any strain of S. aureus that has developed (through natural selection) or acquired (throughHGT) mutiple drug resistace to several beta-lactam antibiotics, most notably methicillin

20
Q

Explain how MRSA works !

Study These Flashcards
A
  • Methicillin and beta-lactams bind to and inhibit penicillin binding protein (PBP)
  • PBP is an enzyme that assists with peptidoglycan assembly.
  • When PBP is inhibited the peptidoglycan matrix cannot properly be formed and the bacterial cell will burst
  • An alternative penicillin binding protein is coded for, preventing methicillin binding
  • Confers resistance to multiple beta-lactam antibiotics (penicillin based)
21
Q

Enterococcus Species

Infections caused by Enterococci species? (4)

Study These Flashcards
A
  1. UTIs
  2. Bacteraemia
  3. Endocarditis (inflammation of the endocardium)
  4. Meningitis
22
Q

Enterococcus Species

Enterococcus species infection treatment? (2)

Study These Flashcards
A
  1. Nitrofurantoin (nitrofuran class) for uncomplicated UTI
  2. Vancomycin (glycopeptide class) for invasive infections
23
Q

VRE

VRE description

Study These Flashcards
A
  1. Nosocomial pathogens that are persistant in hospital environment
  2. Resistance to several antibiotics limits treatment options
  3. VRE infection liked with extended hospital stays
24
Q

How does vancomycin work?

Study These Flashcards
A
  • Binds to the D-Ala-D-Ala terminus of peptidoglycan precursor, inhibiting transglycosylation and transpeptidation, and causing cell wall damage
25
How is resistance to vancomycin conferred?
By the acquisition of the *vanA* or *vanB* gene that **alter the D-Ala-D-Ala target of vancomysin**
26
Treatment for vancomycin resistant strains
1. Linezolid and daptomycin 2. Final resort antibiotics
27
# VRSA (Vancomycin Resistant S. Aureus) What is VRSA mediated by?
A *vanA* gene cluster which is transferred from vancomycin resistant enterococci via **transposon**
28
Clinically significant resistance-> gram negative microorganisms (2)
Primarily **Enterobacterales** 1. Extended spectrum beta-lactamase producers **(ESBL)** 2. Carbapenemase producing enterobacterales **(CPE)**
29
How do ESBLs work?
They are associated with **enzymes (beta-lactamases)** that **hydrolyse the beta-lactam ring of penicillins and cephalosporins**
30
Solution to ESBLs? (2)
1. Supplement antibiotics with a **beta-lactamase inhibitor** eg: augmentin 2. Use **carbapenems**
31
# CPEs What are CPEs resistant to?
All antibiotics **derived from penicillins**
32
What are Carbapenems?
Drugs of last resort, with broad spectrum of activity against gram negs and some gram pos.
33
Antimicrobial control measures (4)
1. Screening before entering intensive wards (for MRSA, VRE, CPE) 2. Surveillance reporting 3. Patient isolation 4. Hygiene measures
34
How is MRSA screened for
Swabs from **nose, axilla, groin** are plated on **selective and differental media** in hospital lab
35
VRE screening
Culture from **rectal swabs** plated on **selective and differential media** in hospital lab
36
CPE (and ESBL) screening
Culture from **rectal swabs**. Molecular approach available for urgent swabs.
37
How could bacteriophages be used as an AMR solution?
Regulation of ecosystem: **maintenance of population levels by predation**
38
Bacteriophage and viral infection of bacteria: how does it work?
* Bacteriophage attaches itself to bacterium and infects host cell * It hijacks the bacteriums cellular machinary to produce viral components * New bacteriophages assmeble and burst out of bacterium -> called **lysis**

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