JC88 (Microbiology) - Antibiotics resistnace Flashcards
Methods of identifying microbes
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)
3 examples of penicillins
Penicillin G^ (strep)
Cloxacillin (staph)
Piperacillin (pseudomonas)
5 examples of cephalosporins (1 by each generation)
1GC: cephalexin
2GC: cefuroxime (+ gram neg)
3GC: ceftriaxone (++ Gram neg), ceftazidime (non- fermenters), cefoxitin
4GC: cefepime (+ Gram pos)
Anti-MRSA cephalosporins: ceftaroline
4 examples of Penicillin+ Beta-lactamase inhibitor
Augmentin (amoxicillin + clavulanate)
Timentin (ticarcillin + clavulanate)
Tazocin (piperacillin + tazobactam)
Unasym (ampicillin + sulbactam)
2 examples of carbapenems
Imipenem
Meropenem (broadest Gram pos/neg spectrum)
9 classes of non-beta lactams
Fluoroquinolones Aminoglycosides Macrolides Tetracyclines Glycylcyclines Glycopeptides Oxazolindinone Linocosamide Rifampicin Metronidazole
Examples of fluoroquinolones, aminoglycosides
Fluoroquinolones
Levofloxacin
Ciprofloxacin
Moxifloxacin (better Gram pos)
Aminoglycosides
Gentamicin
Amikacin (part of combination/synergy)
Examples of macrolides and tetracyclines and glycopeptides
Macrolides
Erythromycin
Clarithromycin
Azithropmycin
Tetracyclines
Doxycycline
Minocycline
Glycopeptides
Vancomycin
Teicoplanin (Gram pos)
Compare intrinsic and acquired resistance
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
Describe horizontal gene transfer by integron and transposons mechanism
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
Name a method to quantify antimicrobial resistance
Antibiogram: table summarizing the % of individual bacterial pathogens susceptible to different antimicrobial agents in local area
e.g. 51% of S. aureus = MRSA
List 3 different calculation methods for antibiogram
Sample size cut-off for antibiogram calculation?
“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
Name a laboratory test for testing inducible antibiotic resistance
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
List the leading anti-microbial resistant bacterial pathogens and their resistance pattern (5)
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)
Antibiotics of choice for top 5 leading anti-microbial resistant bacteria pathogens
MRSA - Vancomycin, (linezolid, daptomycin)
VRE - Linezolid, daptomycin
ESBL - Carbapenem
Treatment option for severe, life-threatening infections with no available standard therapy?
Limited population Antibacterial drug (LPAD) - Fast track FDA approval pathway
- Approve products with smaller clinical trials, fast track clinical use
Define Multi-drug resistant organism (MDRO)
Micro-organisms that are resistant to one or more classes of antimicrobial agents
MRSA
- Resistance mechanisms
- Resistant to what Abx
MSSA (virulent) + SCCmec (mecA)*** = MRSA (virulent + resistant)
Resistant to all beta-lactam antibiotics, except anti-MRSA beta-lactams e.g. ceftaroline
ESBL
- Included bacteria
- Resistant to which Abx
- Infection temporal pattern
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
Acinetobacter baumannii
- Resistant to which Abx
- 2 resistant subtypes
Intrinsic resistance to a wide range of drugs - very limited treatment options
Acquired resistance occurs readily during treatment (carbapenem previously worked)
- CRAB – carbapenem-resistant Acinetobacter baumannii
- MRAB – multidrug-resistant Acintobacter baumannii (not standardized)
Define MDR, XDR and PDR
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
Main strategies for containment of antimicrobial resistance
- High-grade antibiotics e.g. carbapenem, tazocin…etc
- Limited population antibacterial drug (LPAD)
- Antibiotic algorithm to strategize risk of resistance
Harms of escalating Abx treatment for low risk infections
- Increase budget/ cost
- Increase ecological selection pressure in hospital setting, worsen resistance
- Increase yeast, C. difficile and superbug proliferation
Harms of de-escalating Abx treatment for high-risk infection
Delay treatment decreases survival rate
Lower ecological selection pressure and allow proliferation of superbugs
Hospital antibiograms is used for what purpose
Monitoring susceptibility patterns
Incidence rate of bacteria infection has what purpose
Estimate infection burden
What metric is used to estimate the exposure burden of a bacteria infection
Infection point prevalence rate
Admission infection prevalence rate
Name 2 antibiotic that can treat mild skin and soft tissue infection by MRSA
Co-trimoxazole Oral
Ceftaroline IV
MRSA is resistant to all beta-lactams except Ceftaroline
Name antibiotics that target MRSA cell membrane, cell wall synthesis and protein synthesis
Cell membrane: Daptomycin
Cell wall : Vancomycin
Protein: Linezolid
