AntimicrobialResistant Organisms: An Update

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Antimicrobial-Resistant Organisms An Update

• Bruce Gamage
• Infection Control Consultant
• BC Centre for Disease Control

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Outline

• Background
• MRSA
• VRE
• VISA/VRSA
• Current guidelines and recommendations
• Prevention and control

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The Antibiotic Era

• 1928 Fleming discovers penicillin (PCN)
• 1940s PCN becomes widely used
• Present 235 million doses of antibiotics
  consumed in the US annually

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Antimicrobial-Resistant Organism (ARO)

• Definition
• An organism that is resistant to two or more
  unrelated antibiotics to which the organism is
  normally considered susceptible.
• Bennett and Brachman, 4th edition.

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Why Is Antimicrobial Resistance a Problem?

• Fewer drug choices
• Increased costs
• Increased morbidity and mortality

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Costs Associated With AROs

• Costs associated with AROs in Canadian
  Hospitals is estimated to be 42 million to 59
  million annually.

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How Resistance Develops

• Previously silent (unexpressed) genes can be
  inherited
• Genetic mutations can spontaneously produce a
  resistance trait (hypermutation)
• Genes can be transferred between organisms

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Emergence of AROs
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Factors That Promote Resistance

• Resistance genes are prevalent in nature
• Rapid multiplication of organisms favors genetic
  mutations
• Selective pressure from antimicrobial use in
  humans and animals allows resistant organisms to
  predominate
• Biofilms?

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Practices That Promote Resistance

• Overuse of antimicrobials in outpatient settings
• Overuse of broad-spectrum antimicrobials in
  hospital settings
• Poor compliance with regimens
• Use of antimicrobials in animals

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Colonization vs. Infection

• Colonization
• Organism is present in a normally nonsterile body
  site
• No clinical symptoms are present
• Infection
• Organism present in a normally sterile body site
• Clinical signs and symptoms of infection are
  present
• Fever
• Purulence
• Pneumonia
• Inflammation

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MRSA

• Gram-positive cocci in clusters
• Causes variety of infections (cellulitis,
  abscess, wound infection, osteomyelitis,
  arthritis, endocarditis, pneumonia, bacteremia)
• MRSA and MSSA appear to be equally virulent
  (capable of causing infection)

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MRSA Reservoir

• The major reservoir for MRSA is humans
• S aureus (whether sensitive to methicillin or
  not) can be normal flora
• Nares
• Wounds
• Skin

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MRSA Epidemiology

• In the US MRSA is endemic in majority of
  hospitals (35 of all S. aureus isolates)
• In Canada (CNISP)
• 1995 0.9 of S. aureus isolates and 0.3 cases
  per 1000 admissions
• 1999 6 of S. aureus isolates and 4.12 cases per
  1000 admissions

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BCCAMM Surveillance Project
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MRSA Transmission

• Patient-to-patient via transient carriage on the
  hands of HCWs
• Via devices or environmental surfaces

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MRSA Risk Factors

• Exposure in the healthcare setting
• Dialysis
• Injecting drug use
• Burn unit exposure
• Diabetes
• Chronic skin conditions
• ICU

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MRSA Treatment

• Vancomycin is indicated for the treatment of
  serious MRSA infections (bacteremia, meningitis)
• May use combination of other antibiotics if
  organism is susceptible
• Linezolid
• New class of antimicrobial

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VRE

• Gram-positive coccus
• Causes a variety of infections
• Bacteremia
• Endocarditis
• Wound infections
• Urinary tract infections
• Intra-abdominal infections

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Enterococcus Species

• Most enterococcal infections are caused by
• E faecalis 85-90
• E faecium 5-15

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Vancomycin Resistance carried on Genes

• vanA High-level resistance to vancomycin most
  common in E faecium
• vanB Variable level of resistance to vancomycin
• vanC Low-level resistance to vancomycin

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VRE Reservoir

• Enterococci are part of the normal flora of the
  GI tract and the female genital tract
• The GI tract is the most important reservoir

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VRE Epidemiology

• In US 1995 gt 10 of enterococcal strains VRE
• In Canada
• First VRE reported in 1993
• 411 cases reported in 23 hospitals between
  October 1998-September 2000
• 95 are colonization picked up on screening

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BCCAMM Surveillance Project
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VRE Transmission

• Patient-to-patient via transient carriage on
  hands of HCW
• Devices, equipment, or environmental surfaces
  contaminated with VRE from a patient

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VRE Risk Factors

• Critical illness, severe underlying disease, or
  immunosuppression
• Prolonged hospital stay
• Indwelling urinary catheters or central venous
  catheters
• Prior exposure to vancomycin, cephalosporins, or
  other antibiotics

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VRE Treatment

• Linezolid (Zyvox)
• Quinupristin/dalfopristin (Synercid)
• Indicated for life-threatening infections with
  VRE

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Decolonization?

• Controversial
• Not recommended unless there is evidence that
  colonized person is spreading the organism
• 40 of attempts fail and repeated attempts result
  in further resistance
• There is no proven regimen for VRE

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Transfer of Vancomycin Resistance From VRE to
MRSA

• vanA and vanB genes can be transferred between
  bacteria
• In vitro studies demonstrate that vancomycin
  resistance can be transferred from VRE to MRSA

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VISA and VRSA

• VISA first recognized in 1996 in Japan
• Additional cases reported from Europe, Asia, and
  the US
• Resistance has not been caused by the vanA, vanB,
  or vanC genes
• VRSA seen in US in 2002
• Resistance gene vanA was detected in the isolate
• No detected transmission to others

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Guidelines and Recommendations

• 1999 APIC/CHICA/ICNA Global Consensus
  Conference Final Recommendations
• 2001 BC Guidelines for the Control of Antibiotic
  Resistant Organisms
• Available at www.bccdc.org

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Contact PrecautionsHand Hygiene

• Hands must be washed after any direct contact
  with a patient and before contact with the next
  patient
• Use of and alcohol-based hand sanitizer may be
  substituted if hands not visibly soiled

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Contact PrecautionsGloves

• Wear gloves when having direct contact with the
  patient
• Change gloves between dirty and clean procedures
  on the same patient
• Change gloves between patients
• Wash hands after removal of gloves

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Contact Precautions Gowns/Face Masks

• Gown if clothing may contact the patient or
  environmental surfaces
• Insufficient evidence to support the use of
  masks/eye protection use if patient is coughing
  in your face or anticipate splashes of body
  fluids

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Environmental Cleaning

• Routine daily
• Standard cleaning
• Emphasis on touched
• surfaces in room (bed
• rails, door knobs)

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Environmental Cleaning (cont.)

• No need to use special disinfectants/detergents
• Disinfect patient-care equipment that are used on
  multiple patients
• Dedicate patient equipment if possible

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Conclusions

• Antimicrobial-resistant organisms are here to
  stay
• We can make a difference by
• Educating HCWs
• Using antibiotics wisely
• Identifying the organisms accurately
• Putting infection control measures into place and
  following them!