Methicillin resistance Flashcards
Methicillin resistance
Only really applies to staphylococcus
-we don’t use methicillin anymore. Now just refers to resistance to all beta-lactam drugs
Beta-lactams
act on cell wall and break it down
*beta-lactamases will prevent this from happening
Is methicillin resistance acquired?
Yes, not an intrinsic resistance
Penicillin resistance staphylococcus
-When exposed to beta-lactams
-Bacteria produces enzyme (beta-lactamase) to break down the beta-lactam
**counteract this with beta-lactamase inhibitors
What makes methicillin resistant staph?
They have altered binding sites which make them unrecognizable by our Beta-lactams
*Often also means the bacteria does not need to even make beta lactamases
**therefore beta lactamase inhibitors will do nothing
Components of methicillin resistance
Have mec family of genes which code for a different PBP
Results in decreased binding affinity of beta lactam drugs
=resistance to penicillins, cephalosporins, carbapenems
**often multidrug resistant; especially concerned about coagulase positives
Detecting methicillin resistance
Phenotypic resistance:
If resistance/no growth to these drugs then = resistance
S. aureus: use cefoxitin or oxacillin
S. pseudointermedius: only use Oxacillin
Methicillin resistance original ID
-first in hospitals; associated with high mortality and health care costs
-negative outcomes not common in dogs but likely because they are superficial infections
Staphylococcus characteristics
-ubiquitous, 30% in people nasal cavity; 90% of dogs
MRSP in Western Canada
-originally very wimpy, little resistance
-but has developed.
Common MRSP infections
-opportunistic and can be community acquired
-pyoderma, otitis, UTIs, wound infections, surgical site infections, nosocomial infections
Zoonotic transmission
-Can easily have S. aureus going from people to dogs
and S. pseudomonas going from dogs to people
If pet is positive for MRSP?
-MRSP not commonly a major zoonoses
**SA 600x greater chance
-MRSA likely came from people; no need to decolonize. Remember good hygiene (keep animals away from wounds, avoid saliva and nasal secretions, wash hands)
What may be causing increasing reports of methicillin resistance?
-increased awareness (One health- lead to more awareness of zoonoses by physicians)
-impacts of resistance (resistance among coagulase + staph raising the profile of whole genus)
-taxonomic changes (S. pseudintermedius became solely recognized)
-improved lab methods (introduction of MALDI-TOF)
MRSA in vet species
Dogs and cats: often human strains
Horses: equine specific strains
Wildlife: identified everywhere
Livestock: Pigs and cattle have ST398 strain. Spills over into people but not an efficient spread between people
