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MBBS IV - Junior Clerkship WCS > JC88 (Microbiology) - Antibiotics resistnace > Flashcards

JC88 (Microbiology) - Antibiotics resistnace Flashcards

1
Q

Methods of identifying microbes

A

Traditional: Subculture and biochemical test (long turnover time)

New: Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) (short turnover time)

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2
Q

3 examples of penicillins

A

 Penicillin G^ (strep)
 Cloxacillin (staph)
 Piperacillin (pseudomonas)

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3
Q

5 examples of cephalosporins (1 by each generation)

A

 1GC: cephalexin

 2GC: cefuroxime (+ gram neg)

 3GC: ceftriaxone (++ Gram neg), ceftazidime (non- fermenters), cefoxitin

 4GC: cefepime (+ Gram pos)

 Anti-MRSA cephalosporins: ceftaroline

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4
Q

4 examples of Penicillin+ Beta-lactamase inhibitor

A

 Augmentin (amoxicillin + clavulanate)

 Timentin (ticarcillin + clavulanate)

 Tazocin (piperacillin + tazobactam)

 Unasym (ampicillin + sulbactam)

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5
Q

2 examples of carbapenems

A

 Imipenem

 Meropenem (broadest Gram pos/neg spectrum)

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6
Q

9 classes of non-beta lactams

A 
Fluoroquinolones 
Aminoglycosides 
Macrolides
Tetracyclines 
Glycylcyclines 
Glycopeptides
Oxazolindinone 
Linocosamide 
Rifampicin 
Metronidazole
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7
Q

Examples of fluoroquinolones, aminoglycosides

A

Fluoroquinolones
 Levofloxacin
 Ciprofloxacin
 Moxifloxacin (better Gram pos)

Aminoglycosides
 Gentamicin
 Amikacin (part of combination/synergy)

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8
Q

Examples of macrolides and tetracyclines and glycopeptides

A

Macrolides
 Erythromycin
 Clarithromycin
 Azithropmycin

Tetracyclines
 Doxycycline
 Minocycline

Glycopeptides
 Vancomycin
 Teicoplanin (Gram pos)

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9
Q

Compare intrinsic and acquired resistance

A

Intrinsic:
- a trait of the bacterial genus/ species, all members
in the genus/ species are resistant

Acquired:

  • Mutational or Horizontal gene transfer through conjugation (plasmid transfer)
  • Conjugation mechanisms: Integron and Transposons
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10
Q

Describe horizontal gene transfer by integron and transposons mechanism

A

Integron: consists of integrase gene: can integrate,
express, and exchange specific DNA elements

Transposon: “jumping genes” with ability to change their genomic/ plasmid positions before horizontal transfer

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11
Q

Name a method to quantify antimicrobial resistance

A

Antibiogram: table summarizing the % of individual bacterial pathogens susceptible to different antimicrobial agents in local area

e.g. 51% of S. aureus = MRSA

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12
Q

List 3 different calculation methods for antibiogram

Sample size cut-off for antibiogram calculation?

A

“All isolates” – calculations include all isolates of a given species equally, even those of patients with multiple isolates

“First isolate” per patient – calculations include the
results of only the first isolate of a given species recovered from each patient during the investigated time interval

First isolate per episode (most useful, worse case scenario) - calculations include only the most resistant interpretation observed for each separate antimicrobial agent, tested among all isolates of a given species from an individual patient.

Cut-off: should not calculate if no. <30

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13
Q

Name a laboratory test for testing inducible antibiotic resistance

A

D test

Culture organism and place antibiotic tablets in two quadrants

Observe for zone of bacteria killing by antibiotic tablets

If killing zone flattens on one side, antibiotic resistance is developed

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14
Q

List the leading anti-microbial resistant bacterial pathogens and their resistance pattern (5)

A

MRSA (methicillin-resistant Staphylococcus aureus) - Total beta-lactams failure

VRE (vancomycin-resistant enterococcus) - Vancomycin failure

ESBL (extended-spectrum beta-lactamases) - Cephalosporin failure

CRE (carbapenem-resistant Enterobacteriaceae)- Total beta- lactam failure

CRAB (carbapenem-resistant Acinetobacter baumanii)

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15
Q

Antibiotics of choice for top 5 leading anti-microbial resistant bacteria pathogens

A

MRSA - Vancomycin, (linezolid, daptomycin)

VRE - Linezolid, daptomycin

ESBL - Carbapenem

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16
Q

Treatment option for severe, life-threatening infections with no available standard therapy?

A

Limited population Antibacterial drug (LPAD) - Fast track FDA approval pathway

  • Approve products with smaller clinical trials, fast track clinical use
17
Q

Define Multi-drug resistant organism (MDRO)

A

Micro-organisms that are resistant to one or more classes of antimicrobial agents

18
Q

MRSA

  • Resistance mechanisms
  • Resistant to what Abx
A

MSSA (virulent) + SCCmec (mecA)*** = MRSA (virulent + resistant)

Resistant to all beta-lactam antibiotics, except anti-MRSA beta-lactams e.g. ceftaroline

19
Q

ESBL

  • Included bacteria
  • Resistant to which Abx
  • Infection temporal pattern
A 
ESBL (extended spectrum beta lactamase) = a group of enzymes produced by some Enterobacteriaceae:
 Escherichia coli
 Klebsiella pneumoniae
 Proteus
 Enterobacter
 Shigella
 Salmonella

multidrug resistance:
 Cotrimoxazole (septrin)
 Fluoroquinolones (levofloxacin, ciprofloxacin)
 Aminglycosides (gentamicin)
 3rd generation cephalosporin: ceftazidine, Rocephin® (ceftriaxone)

Temporal pattern: winter surges

20
Q

Acinetobacter baumannii

  • Resistant to which Abx
  • 2 resistant subtypes
A

Intrinsic resistance to a wide range of drugs - very limited treatment options
Acquired resistance occurs readily during treatment (carbapenem previously worked)

  1. CRAB – carbapenem-resistant Acinetobacter baumannii
  2. MRAB – multidrug-resistant Acintobacter baumannii (not standardized)
21
Q

Define MDR, XDR and PDR

A

 MDR (multidrug-resistant) = nonsusceptible to ≥1 agents in ≥ 3 classes

 XDR (extensively-resistant) = nonsusceptible to ≥1 agents in all but ≥2 classes

 PDR (pandrug-resistant) = nonsusceptible to all agents listed

22
Q

Main strategies for containment of antimicrobial resistance

A
  • High-grade antibiotics e.g. carbapenem, tazocin…etc
  • Limited population antibacterial drug (LPAD)
  • Antibiotic algorithm to strategize risk of resistance
23
Q

Harms of escalating Abx treatment for low risk infections

A
  • Increase budget/ cost
  • Increase ecological selection pressure in hospital setting, worsen resistance
  • Increase yeast, C. difficile and superbug proliferation
24
Q

Harms of de-escalating Abx treatment for high-risk infection

A

Delay treatment decreases survival rate

Lower ecological selection pressure and allow proliferation of superbugs

25
Q

Hospital antibiograms is used for what purpose

A

Monitoring susceptibility patterns

26
Q

Incidence rate of bacteria infection has what purpose

A

Estimate infection burden

27
Q

What metric is used to estimate the exposure burden of a bacteria infection

A

Infection point prevalence rate

Admission infection prevalence rate

28
Q

Name 2 antibiotic that can treat mild skin and soft tissue infection by MRSA

A

Co-trimoxazole Oral
Ceftaroline IV

MRSA is resistant to all beta-lactams except Ceftaroline

29
Q

Name antibiotics that target MRSA cell membrane, cell wall synthesis and protein synthesis

A

Cell membrane: Daptomycin

Cell wall : Vancomycin

Protein: Linezolid

MBBS IV - Junior Clerkship WCS (131 decks)

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