Antimicrobial Chemotherapy 2 Flashcards
What is the clinical indication for linezolid?
Oxazolidinone antibiotic
- binds 50s ribosomal sub-unit to block initiation phase of translation
- MRSA, VRE and PRP infections
- gram positive bacteria
What is the clinical indication for daptomycin?
Lipopeptide
- binds to cell membrane to produce rapid bactericidal effect
- MRSA, VRE, penicillin-resistant strains of S. pneumoniae
- gram positive bacteria
What is the clinical indication for tigecycline?
Tetracycline
- inhibits 30s ribosomal subunit
- MRSA, VRE, penicillin-resistant strains of S. pneumoniae
- gram positive bacteria
How many deaths are caused by antimicrobial resistance around the world each year?
700,000
How many deaths are predicted to be caused by antimicrobial resistance by 2050 if no action is taken?
10 million at a cumulative cost of $100 trillion
Give examples of bacteria for which treatment is sub-optimal
Methicillin-resistant Staphylococcus aureus (MRSA)
Clostridium difficile
Vancomycin-resistant enterococci (VRE)
Penicillin-resistant enterococci
Vancomycin insensitive Staphylococcus aureus (VISA)
Multidrug resistant (MDR) Mycobacterium tuberculosis
Carbapenemase [e.g. NDM1 (New Delhi metallo-beta-lactamase 1)] enterobacteria
ESBL Escherichia coli (extended spectrum beta-lactamase)
Multidrug resistant Acinetobacter spp.
What is the structure of gram-positive bacteria?
No outer membrane
What is an extensively drug resistant (XDR) bacteria?
One which is resistant to more than 6 antibiotics
Which bacteria have become an important therapeutic challenge to treat?
Extended spectum beta-lactamase (ESBL) and carbapenamase producing Gram-negative bacteria
What is the MIC?
Minimum inhibitory concentration
- the lowest concentration of an antimicrobial which prevents visible growth of a bacterium
What is the definition of antimicrobial resistance?
A strain able to grow in the presence of a higher antimicrobial concentration than that inhibiting the majority of other strains belonging to the same species
A strain able to grow in the presence of a higher antimicrobial concentration than that it is possible to reach in vivo
What are the three clinical categories of bacteria for treatment?
Susceptible/Sensitive - high probability of treatment success
Intermediate - unpredictable treatment success
Resistance - high probability of treatment failure
What is an antibiogram?
An agar plate inoculated with bacteria, with antibiotic discs added. The zone of inhibition which is present around the antibiotic disc indicates how sensitive the bacteria is to the antibiotic - the wider the zone, the more sensitive it is
How is MIC determined?
With serially diluted anti microbial agents, which bacteria is added to
Positive and negative controls must be run
MIC is determined by the lowest concentration of the anti microbial that inhibits growth
Give three mechanisms that can cause intrinsic resistance in bacteria
Impermeability barrier
- change in permeability
Efflux
Enzymatic inactivation
