Multi-drug Resistant Organisms: MRSA, VRE, and Clostridium difficile (Online Course)

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Authors: Carolyn M. Law, PhD, MT(AMT); Catherine Dragoni, MT(ASCP)SM

Over the last two decades, bacterial resistance to antibiotics has become widely recognized as a serious problem, making many diseases increasingly difficult if not impossible to treat. Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci, and drug-resistant Clostridium difficile are recent examples of organisms that have been reported in hospital settings; some resistant organisms have also become problematic for otherwise healthy individuals that are not, and were not recently hospitalized. This course discusses the pathogenicity of these organisms, how they are detected in the microbiology laboratory, and future perspectives.

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Continuing Education Credits

  • P.A.C.E.® Contact Hours: 2 hour(s)
  • Florida Board of Clinical Laboratory Science CE - General (Microbiology/Mycology/Parasitology): 2 hour(s)


  • Identify the virulence factors that are expressed by drug resistant strains of Staphylococcus aureus, Clostridium difficile, and Enterococcus faecium and faecalis.
  • List the risk factors and clinical syndromes that are associated with these drug resistant organisms.
  • Describe the recommended laboratory procedures involved in screening for and detecting drug-resistant organisms.
  • Name the drugs that are currently available for treatment of these infections and describe the proper treatment protocols.

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(based on 921 customer ratings)

Course Outline

  • Introduction
      • Methicillin Resistant Staphylococcus aureus
      • Vancomycin Resistant Enterococci
      • Clostridium difficile
      • MRSA is only a problem for patients who are hospitalized.
  • Staphylococcus aureus
      • Staphylococcus aureus
      • S. aureus Virulence Factors
      • The pathogenicity of S. aureus, as well as the frequency with which this organism produces infections, can be attributed to:
      • Clinical significance of S. aureus
      • Beta-lactam antibiotics and S. aureus
      • Which of these describes the mode of action of the beta-lactam class of antibiotics?
      • Beta-lactam antibiotics interfere with cell wall synthesis by:
  • MRSA
      • Beta-lactams and Methicillin Resistant Staphylococcus aureus
      • Healthcare (Hospital)-Associated MRSA (HA-MRSA) versus Community-Associated MRSA (CA-MRSA)
      • Risk Factors
      • The increased resistance of MRSA strains to beta-lactam antibiotics is due to production of which of the following penicillin binding proteins (PBPs)?
      • Which are true statements regarding HA-MRSA and CA-MRSA?
  • Laboratory Diagnosis of MRSA
      • Laboratory Identification of S. aureus
      • Screening Cultures for MRSA
      • Assume you perform microbiology for an institution submitting surveillance cultures for MRSA. Which isolate should receive further workup to rule out ...
    • Susceptibility Testing of Isolates
      • Susceptibility Testing
      • Selection of Drugs for Testing
      • Interpretation of Oxacillin Broth Dilution Tests.
      • Interpretation of Oxacillin and Cefoxitin Disk Diffusion Tests
      • Detection of Oxacillin Resistance
      • Which of the following scenarios represents appropriate detection of MRSA by the Kirby Bauer method?
      • A laboratory performs MIC tests, in addition to Kirby Bauer, and a PBP 2a assay on blood culture isolates. Which of the following isolates should be r...
  • MRSA Treatment/Vancomycin Resistance in S. aureus
      • MRSA Treatment/Vancomycin Resistance
      • VISA and VRSA
    • Testing for Vancomycin Susceptibility
      • Testing for Vancomycin Susceptibility
      • A laboratory's primary susceptibility testing method is disk diffusion. The cefoxitin disc has a zone size of 19 mm and the vancomycin disc has a zone...
  • Future Perspectives
      • Future Perspectives
      • Future Perspectives, continued
      • Future Perspectives, continued
      • Moving forward, important strategies for dealing with MRSA strains will include the following:
  • Enterococcus
      • Enterococci
      • Risk Factors and Resistance
      • Enterococci can possess both intrinsic and acquired resistance. Which of the following represents the intrinsic resistance of a typical enterococcal s...
  • Vancomycin Resistant Enterococci
      • Vancomycin-Resistant Enterococci (VRE) Phenotypes
      • Which statements concerning vancomycin resistance in Enterococci are true?
  • Laboratory Diagnosis of VRE
      • Identification of Enterococcus Species From Clinical Cultures
      • Screening Cultures for Vancomycin-Resistant Enterococci (VRE)
      • Susceptibility Testing of Enterococci
      • Detecting Vancomycin Resistance
      • High Level Aminoglycoside Resistance (HLAR) Screening
      • Which of the following statements reflect accurate identifications of Enterococcus species?
      • With regards to identifying resistance in enterococci, which general statements are true?
  • Treatment of Resistant Enterococci
      • Newer antibiotics for Treatment of Resistant Enterococci
  • Clostridium Species
      • Clostridium Species
  • Clostridium difficile
      • Clostridium difficile
      • C. difficile Toxin A and Toxin B
      • Pathogenisis of C. Difficile-Associated Diarrhea
      • Risk factors for C. difficile Infection
      • C. difficile-associated Diarrhea (CDAD)
      • C. difficile disease is more likely to occur when:
      • Strain BI/NAP1/027
  • Laboratory Diagnosis of CDAD
      • Laboratory Detection of C. difficile
      • Stool Culture
      • Cell Cytotoxicity Neutralization Assay (CCNA)
      • Enzyme Immunoassay Methods
      • Various methods have been employed for detection of C. difficile disease: cultivation of the organism, cell cytotoxin neutralization assays, and enzym...
      • Glutamate Dehydrogenase (GDH) Antigen Assays
      • Molecular Methods
      • Which of the following approaches for diagnostic testing have been indicated by recent literature?
  • Treatment of C. difficile infection
      • Treatment of C. difficile Infection (CDI) and C. difficile Associated Disease (CDAD)
      • Disinfection & Control of C. difficile Infection
  • Future perspectives
      • Future perspectives - CDI/CDAD
  • References
      • References

Additional Information

Level of instruction: Intermediate
Intended audience: Medical laboratory scientists, medical technologists, and technicians, This course is also appropriate for clinical laboratory science students and pathology residents.
Author information: Carolyn M. Law, PhD, MT(AMT) is the CEO of Celtic Labs Diagnostic Microbiology Services in Trinidad. She holds a PhD in Microbiology from National University of Ireland, Maynooth.
Catherine Dragoni, MT(ASCP)SM received her BS degree in medical technology from the State University of New York, Upstate Medical Center, Syracuse. She began her career as a bench microbiologist at Maine Medical Center, Portland, Maine. Currently she is the Assistant Chief Technologist of Microbiology and Molecular Pathology at NorDx Laboratories, Scarborough, Maine.
Course description: Multiple drug resistant organisms (MDROs) are a serious problem facing healthcare and the general public. This course details the clinical significance, risk factors, and laboratory detection of these multi-drug resistant organisms: methicillin resistant Staphylococcus aureus, vancomycin resistant Enterococcus species, and Clostridium difficile. Future perspectives are also discussed.    

Multi-drug Resistant Organisms: MRSA, VRE, and Clostridium difficile Keywords

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