Lecture 20: Antimicrobial Resistance Flashcards
Intrinsic resistance
Due to structural and functional traits present in all members of a given bacterial species or group
Examples of intrinsic resistance
- Reduced permeability of outer membrane
- Reduced affinity of the target
Two ways bacteria acquire resistance
- Mutation
- Horizontal gene transfer
Three types of horizontal gene transfer
- Transformation
- Transduction
- Conjugation
Transformation
Uptake of free DNA
Transduction
Transfer mediated by phage delivery
Conjugation
Transfer cell-to-cell contact
Salmonella is resistant to
- Cephalosporins
- Fluoroquinolones
Campylobacter is resistant to
- Macrolides
- Fluoroquinolones
Three emerging resistant bacteria in animals
- MRSA
- MRSP
- ESBL producers
What is MRSA?
- Methicillin resistant Staph. aureus
- Acquired resistance gene mecA which encodes a penicillin binding protein PBP2A with low affinity to most b-lactams
What is MRSP?
- Methicillin resistant Staph psuedointermedius
- Acquired mecA
Approx. 70% of cases of MRSP are
Skin and wound post-surgical infections acquired in the clinic
Are MRSP infections in humans common/
Nope, and are generally only due to transmission from household pets
What is ESBL?
- Extended spectrum beta lactamase
- Enzyme hydrolizing/inactivating most B-lactams that are produced by gram negative bacteria
True ESBL’s are susceptible to
B-lactamase inhibitors
Three main classes of ESBL’s
- CTX-M
- SHV
- TEM
Each class of ESBL is classified into variants based on
Sequence identity
The frequency of each variant of ESBL depends on
Host and geographical factors
Most common type of ESBL in animals is
CTX-M-1
The widespread false ESBL is
CMY-2
ESBL plasmid transmission is common in what group of humans?
farm workers
Whenever possible, you should use what to treat MRSP?
Topical treatments
Three drugs used to manage unusual infections of MRSP and ESBL
- Chloramphenicol
- Rifampicin
- Nitrofurantoin
