Methicillin-resistant Staph Flashcards
From JCA's MRS notes
What is the main mechanism of methicillin-resistance in Staph sp?
A. Beta-lactamase enzyme that resists degradation by all beta-lactam antibiotics
B. Alteration of peptidoglycan binding site reducing affinity of all beta-lactam antibiotics
C. Production of PBP2a, a non-native PBP that resists all beta-lactam antibiotics
D. Presence of Panton-Valentine Leukocidin (PVL) toxin that degrades all beta-lactam antibiotics
C. Production of PBP2a, a non-native PBP that resists all beta-lactam antibiotics
Genes that encode methicillin-resistance in Staphylococcus sp are shared by horizontal transmission of mobile genetic elements by what mechanism? A. Bacteriophage B. Staphylococcal chromosome cassette C. Plasmid D. Transposons
B. Staphylococcal chromosome cassette
Which subtype of methicillin-resistant Staphylococcus sp is most important in the equine community? A. MRSA USA 100 B. MRSA USA 300 C. MRSA USA 400 D. MRSA USA 500
D. MRSA USA 500
In human cases, which of the following is a more common finding in community associated methicillin resistant staphylococcus (CA-MRSA) than Hospital associated methicillin resistant strains (HA-MRSA)
A. Presence of Panton-Valentine Leukocidin (PVL) toxin
B. Vancomycin resistance
C. Inducible Clindamycin resistance
D. Trimethoprim-sulfa antibiotic resistance
A. Presence of Panton-Valentine Leukocidin (PVL) toxin
Name 3 methicillin-resistant Staphylococcal species
S pseudintermedius, S schleferi, S hyicus
How does penicillin and other beta-lactam ring antibiotics work on bacteria?
They inactivate penicillin binding protein (PBP) which are essential for building the bacterial cell wall –> osmotic lysis of bacteria
Name the gene that results in methicillin resistance
MecA gene
What does the methicillin resistance gene code for?
The mecA gene codes for production of PBP2a, a non-native PBP
T/F
Presence of PBP2a confers complete resistance to all beta-lactam antibiotics
True
Where is the mecA gene located?
Staphylococcal chromosome cassette mec (SCCmec)
What is Staphylococcal chromosome cassette mec (SCCmec)?
A mobile gene cassette that can be transferred horizontally between Staphylococcus
What is the method used to classify MRSA?
Pulse field gel electrophoresis (PFGE)
What is the most common HA (hospital assoc)-MRSA?
USA100 and USA200
What is the most common CA (community assoc)-MRSA?
USA300
What is the D-zone test?
Double disk diffusion D-zone test is for inducible clindamycin resistance
What strain of MRSA most often has inducible clindamycin resistance?
HA-MRSA
Which subtype of MRSA has more tissue damage?
CA-MRSA
What is Panton-Valentine Leukocidin exotoxin?
PVL is a cytotoxin that forms pores that penetrate cell membranes causing osmotic lysis of leukocytes and tissue necrosis
Classic “spider-bite” appearance
Rapid forming cutaneous abscess, cellulitis, or furunculosis
T/F
HA-MRSA causes more tissue damage but is resistant to fewer non-beta lactam antibiotics than CA-MRSA
False
CA-MRSA causes more tissue damage but is resistant to fewer non-beta lactam antibiotics than HA-MRSA
What SCCmec type is the equine MRSA?
Equine MRSA USA500 is SCCmec type IV (CA-MRSA)
USA500 strain is most commonly highly resistant to what antibiotic?
Potentiated sulfa antibiotic
high frequency of use of TMS in equine practice
What is the gold standard test for identification of MRSA?
PCR detection of mecA
Latex agglutination test can be performed to detect what for MRSA?
PBP2a
T/F
Community acquired strains tend to have less antimicrobial resistance
True
Typically community acquired strains are resistant to only beta-lactams and erythromycin
