38 – Methicillin Resistance

Question 1

When we say methicillin resistance, we are really referring to…

Answer 1

• Staph
  o Concerned mainly with coagulase positives
• **beta-lactam resistance (MULTI-DRUG RESISTANT)
• NOT INTRINSIC RESISTANCE, it is ACQUIRED

Question 2

If just penicillin resistant vs. methicillin resistant

Answer 2

• Penicillin resistant: can use beta-lactamase inhibitors
• Methicillin resistant: can’t do anything!

Question 3

mec family of genes

Answer 3

• Codes altered PBP (PBP2a)
  o Decreased binding affinity beta-lactam drugs (Can’t recognize)
  o Resistance to pencillins, cephalosporins and carbapenems
  o Beta-lactamase inhibitors wont restores susceptibility (since no beta-lactamase to bind to)

Question 4

*What is the indicator for methicillin resistance?

Answer 4

• OXACILLIN

Question 5

Detecting methicillin resistance of S. pseudintermedius can only be done by

Answer 5

• ONLY Oxacillin (indicator drug)

Question 6

Dogs with MRSP vs. humans with MRSP

Answer 6

• Not as likely to die or have higher health care costs
• Recognized MRSA and MRSP in mid-late 2000s

Question 7

Staphylococci are UBIQUITIOUS

Answer 7

• In 90% of healthy dogs (S. pseudointermedius)
• *why we care about it=so common

Question 8

MRSP in Western Canada: S. pseudintermedius

Answer 8

• Historically was rare in Western Canada
• First report in 2009, male pug dog, UTI
• Then a case of necrotizing fasciitis

Question 9

What are the types of S. pseudintermedius infections in animals?

Answer 9

• **Pyoderma (skin)
• **Otitis (ears)
• UTI
• Wound infections
• Surgical site infections
• Nosocomial infections
• *OPPORTUNITISTIC PATHOGENS

Question 10

Zoonotic/interspecies transmission

Answer 10

• S. pseud: dogs to people
• S. aureus: people to dogs
• *don’t panic
  o if dog is MRSA: likely got it from the people
  o MRSP: NOT typically considered zoonotic
• *do NOT want to try decolonize the dog
• *do GOOD HYGIENE

Question 11

Can occasionally see zoonotic transmission

Answer 11

• Mostly skin and soft tissues infections (likely from dog licking)
  o No evidence of point source
• **incidence of S. aureus is 600x greater than S. pseudintermedius

Question 12

How come it seems like we have increased reports?

Answer 12

• Increase awareness: One Health
• Impacts of resistance
• Taxonomic changes
• Improved lab methods

Question 13

MRSA: humans

Answer 13

• Increase in community associated vs. health care associated

Question 14

MRSA: dogs and cats

Answer 14

• Frequently human associated strains

Question 15

MRSA: horses

Answer 15

• Equine specific strains
• Not common in this region yet

Question 16

MRSA: wildlife

Answer 16

• Many species
• Everywhere!

Question 17

MRSA: livestock associated

Answer 17

• Particular strain: ST398
  o Pigs and cattle

Question 18

MRSA ST398

Answer 18

• Highly prevalent among pigs: ~40%
• Spill over can happen to people:
  o Those in contact with pigs: 760x more likely
  o Inefficient human-human spread
• Reported in veal calves, dairy cattle, poultry, horses, dogs, people

Question 19

MRSA: general population vs. vets

Answer 19

• General: 1.5%
• Small animal: 4.4%
• Pig vets: 45%
• Equine: 10%
• Large animal: 15.6%
• *OCCUPATIONAL RISK

Question 20

Treatment options

Answer 20

• *susceptibility profile of Staph are changing
• Lab guidance is VERY IMPORTANT for aiding therapeutic selection

Question 21

Methicillin resistance in livestock: examples

Answer 21

• Mastitis in cattle
• Bumble foot in chickens
• S. hyicus greasy pig disease or MRSA skin infection in pigs