MRSA Flashcards
Mechanism: mecA gene –> altered PBP with decreased affinity for beta-lactams
MRSA
MRSA is also clinically resistant to which 3 things?
Cephalosporins, carbapenems, and Beta-lactamase inhibitor combinations
Usually the antibiotic of choice for MRSA
Vancomycin
Often first detected as clusters of abscesses or “spider bites”
MRSA
The most common identifiable cause of skin and soft-tissue infections among patients presenting to emergency departments in 11 U.S. cities
MRSA
Community acquired MRSA is genetically distinct from
Hospital Acquired MRSA
Carriage less common in nares, so nasal screening may fail to detect
Community acquired MRSA
Can be used to treat CA-MRSA skin and soft tissue infections
Incision and drainage
To break the chain of MRSA transmission within families, we want to give every member
Chlorhexidine Gluconate (CHG)
Multiplication of organisms in the body of the host
–Usually involves invasion of tissue
Infection
Infection is usually accompanied by a measurable host response such as
Inflammation, antibody production, and Cell-mediated immunity
Multiplication of an organism at a body site or sites without evidence of infection
–May or may not be a precursor of infection
Colonization
If an infection develops, it is usually from bacteria that
Colonize patients
Bacteria that colonize patients can be transmitted from one patient to another by the hands of
Healthcare workers
What are the three most common anatomic sites for MRSA?
Nares, Rectum, and Axilla
“Pseudomonicacid” –derived from culture supernatants of Pseudomonas fluorescens
-A topical antibiotic
Mupirocin
Bacteriostatic, but activity dependent on pH and inoculum size
–may be bactericidal at low pH (skin pH <5.5)
Mupirocin
Binds to isoleucyltRNA synthetase( ile S) disrupts protein synthesis
Mupirocin
Mupirocin has been shown to decrease carriage of S. aureus in
Nasal cavities (and on hands)
Intrinsic resistance (gram negatives) from inability to bind to tRNA synthetase, not from altered drug transport or increased drug destruction
Mupirocin resistance
A low-level mupirocin resistance is due to a
Point mutation in ileS
A high-level mupirocin resistance is due to the acquisition of a
Plasmid containing a novel ileS gene
Transmissible between SA and coag neg Staph, but not to enterococci
High-level Mupirocin resistance
been classified as being of “dubious” clinical significance
Low-level resistance
“MRSA strains with Mup-R were often more susceptible to other antimicrobial agents, such as
TCN and TMP-SMX
What is the fastest form of MRSA screening?
Xpert MRSA/GeneXpert
The gold standard for MRSA detection
Broth enrichment
Anaerobic spore-forming bacillus
-Causes pseudomembranous colitis, toxic mega colon, sepsis, and death
Clostridium difficile
Fecal-oral transmission through contaminated environment and hands of healthcare personnel
Clostridium difficile
Antimicrobial exposure is a major risk factor for
Clostridium difficile
What is the only antimicrobial that KPC producing K. pneumoniae (CRKP) is susceptible (S) to?
Tigecycline
