Methicillin ResistantStaphylococcus AureusPeter Daley MD FRCPC DTM+H     Memorial University
Staphylococcus                 Figure 19.1
Staphylococci• Gram-positive cocci, nonmotile, facultative  anaerobes• Cells occur in grapelike clusters because cells  di...
• Two species are commonly associated with  staphylococcal diseases in humans  – Staphylococcus aureus – the more virulent...
Pathogenicity• “Staph’ infections result when staphylococci  breach the body’s physical barriers• Entry of only a few hund...
Staphylococcus aureus in wound swab
Impetigo    •   Superficial, local    •   Pustular/crusted    •   GAS/SA    •   Children    •   Topical therapy
Folliculitis      •   Follicle infection      •   SA      •   Apocrine regions      •   Whirlpool folliculitis      •   Ma...
Erysipelas     • GAS     • Portal of entry     • Lymphatic       involvement     • Bright red, painful     • Raised border...
Cellulitis     • Systemic illness     • Vague border     • GAS/SA     • Portal of entry     • Returns     • Occasional Vib...
Skin Abscess      •   Furuncle, carbuncle      •   Deep collection      •   SA      •   Needs drainage      •   IVDU      ...
Fournier’s Gangrene post-op
Evolution of Resistance in S. aureus          Penicillin                   Methicillin                    Penicillin-resis...
Mechanism of Methicillin Resistance• Mediated by mecA gene  – Encodes abnormal low-affinity binding protein,    PBP-2a  – ...
HA-MRSA in Hospitals in                   CANADA vs. U.S. (CNISP)                                US       Canada          ...
Many are colonized, few are infected                       Clinical                       Infections             Colonized...
MRSA Surveillance Definitions•   Colonization – asymptomatic•   Infection – symptomatic•   Hospital acquired•   Healthcare...
S. aureus Colonization• About 30% of people are colonized• Average 2.8 strains /person• Colonization more frequent in   – ...
CNISP 2009
CNISP 2009
CNISP 2009
CNISP 2009
CNISP 2009
Risk Factors for HA-MRSA•   Hospitalized within the last year•   Surgery within the last year•   Dialysis within last year...
Were Hospital acquired MRSA so successful       only because they were antibiotic                   resistant?• Probably: ...
Community-Associated Methicillin-Resistant              S. aureus (CA-MRSA)• First described in Australia in 1993• In the ...
The emergence of CA-MRSA in      the United States Methicillin-Resistant S. aureus Infections among Patients in the Emerge...
Prevalence of MRSA Among                     422 ED Patients With SSTI     7/13 (54%)                            11/28 (39...
SSTIs in 11 US EDs,                                     August 2004  • 422 patients total                                 ...
185 cases from 1999-2002
CA-MRSA in athletes
A Clone of Methicillin-Resistant Staphylococcus aureus          among Professional Football Players             Kazakova S...
Results• Attack rate: 5 out of 58 – 9%• At sites of skin abrasions (turf burns)  on elbows, forearms, knees –  unprotected...
Case Player Position
Results• Skin abrasions common     • 2-3 turf burns/week from sliding on the field     • More frequent/more severe on arti...
MRSA as a community and hospital                pathogen        CA-MRSA                      HA-MRSA   Invasive/high rate ...
Panton-Valentine leucocidin (PVL) toxin• Cytotoxin present in <5% of MSSA• Rare in HA-MRSA• Carried on bacteriophage …inco...
How to treat CA-MRSA SSTIs• Culture                        • Antibiotics   – Severe skin infections        –   TMP/SMX   –...
When to suspect CA-MRSA• When CA-MRSA reaches 10-15% of strains, all  patients with SSTIs should be suspected.• Severe Sta...
Significance of S. aureus                   Nasal Carriage   Nasal carriage of S. aureus is a risk for   infection in hosp...
Significance of MRSA Colonization  Colonization with MRSA associated with a greater risk  of subsequent infection:• Nasal ...
Risk of MRSA Colonization Becoming           an Infection• 60 of 209 (29%) adults with newly identified  colonization deve...
Decolonization• Decolonization is not recommended for usual  management.• Decolonization may be tried when patients have  ...
S. aureus Decolonization                Recommendations• possibly useful in patients with recurrent skin/soft  tissue infe...
S. aureus Decolonization            Recommendations• no routine decolonization pre-op or in  nonsurgical patients; perhaps...
Environmental contamination of surfaces in an            MRSA patient roomResistant bacteria on the skin or in the gastroi...
Manorapid      Synergy      …………      …………      …………      …………      …………      …………      AntisepticaRemember!!
Methicillin resistant staphylococcus aureus
Methicillin resistant staphylococcus aureus
Methicillin resistant staphylococcus aureus
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Methicillin resistant staphylococcus aureus

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Methicillin resistant staphylococcus aureus

  1. 1. Methicillin ResistantStaphylococcus AureusPeter Daley MD FRCPC DTM+H Memorial University
  2. 2. Staphylococcus Figure 19.1
  3. 3. Staphylococci• Gram-positive cocci, nonmotile, facultative anaerobes• Cells occur in grapelike clusters because cells division occurs along different planes and the daughter cells remain attached to one another• Salt-tolerant – allows them to tolerate the salt present on human skin• Tolerant of desiccation – allows survival on environmental surfaces (fomites)
  4. 4. • Two species are commonly associated with staphylococcal diseases in humans – Staphylococcus aureus – the more virulent strain that can produce a variety of conditions depending on the site of infection – Staphylococcus epidermidis – normal microbiota of human skin that can cause opportunistic infections in immunocompromised patients or when introduced into the body
  5. 5. Pathogenicity• “Staph’ infections result when staphylococci breach the body’s physical barriers• Entry of only a few hundred bacteria can result in disease• Pathogenicity results from three features – Structures that enable it to evade phagocytosis – Production of enzymes – Production of toxins
  6. 6. Staphylococcus aureus in wound swab
  7. 7. Impetigo • Superficial, local • Pustular/crusted • GAS/SA • Children • Topical therapy
  8. 8. Folliculitis • Follicle infection • SA • Apocrine regions • Whirlpool folliculitis • May scar • Acne • Local treatment
  9. 9. Erysipelas • GAS • Portal of entry • Lymphatic involvement • Bright red, painful • Raised border • Oral or IV therapy
  10. 10. Cellulitis • Systemic illness • Vague border • GAS/SA • Portal of entry • Returns • Occasional Vibrio, Erysipelothrix • Oral/IV therapy • Edema control
  11. 11. Skin Abscess • Furuncle, carbuncle • Deep collection • SA • Needs drainage • IVDU • May be recurrent
  12. 12. Fournier’s Gangrene post-op
  13. 13. Evolution of Resistance in S. aureus Penicillin Methicillin Penicillin-resistant Methicillin-S. aureus resistant [1950s] S. aureus [1970s] S. aureus (MRSA) Vancomycin [1997] [1990s] Vancomycin Vancomycin Vancomycin-resistant resistant [ 2002 ] intermediate- enterococci (VRE) S. aureus resistant S. aureus (VISA)
  14. 14. Mechanism of Methicillin Resistance• Mediated by mecA gene – Encodes abnormal low-affinity binding protein, PBP-2a – Encodes resistance to all beta-lactams – MecA gene is located on a mobile genetic element called SCCmec staphylococcal chromasomal cassette – That cassette may contain many other resistance genes
  15. 15. HA-MRSA in Hospitals in CANADA vs. U.S. (CNISP) US Canada 50% Resistant 40 30 20 10 0 83 87 92 94 96 98 00 19 19 19 19 19 19 20 Year (Conly J. CMAJ 2002;167:885-891)
  16. 16. Many are colonized, few are infected Clinical Infections Colonized (Asymptomatic) Patients
  17. 17. MRSA Surveillance Definitions• Colonization – asymptomatic• Infection – symptomatic• Hospital acquired• Healthcare associated – clinics, long term care• Community acquired
  18. 18. S. aureus Colonization• About 30% of people are colonized• Average 2.8 strains /person• Colonization more frequent in – Newborns – Hemodialysis patients – People with dermatitis, eczema – Diabetics• Half Life: 40 months
  19. 19. CNISP 2009
  20. 20. CNISP 2009
  21. 21. CNISP 2009
  22. 22. CNISP 2009
  23. 23. CNISP 2009
  24. 24. Risk Factors for HA-MRSA• Hospitalized within the last year• Surgery within the last year• Dialysis within last year• Resided in long-term care facility• ABX >3 times w/in past year• DM
  25. 25. Were Hospital acquired MRSA so successful only because they were antibiotic resistant?• Probably: – Virulent but not hyper-virulent – They are frequent colonizers but cause a respectable number of infections. – Patients with HA-MRSA often have more co- morbidities and hence have higher mortality rates. – We have to use less effective antibiotics – Sometimes our initial guesses are wrong so patients go untreated for several days
  26. 26. Community-Associated Methicillin-Resistant S. aureus (CA-MRSA)• First described in Australia in 1993• In the late 1990s more reports of MRSA occurring in the community in patients without established risk factors (Usually skin infections) – Younger patients – Aboriginals especially in Sask and Manitoba – Outbreaks: • Injection drug users • Players of contact sports • Prison inmates • Group homes
  27. 27. The emergence of CA-MRSA in the United States Methicillin-Resistant S. aureus Infections among Patients in the Emergency Department Moran et al Volume 355:666-674, 2006
  28. 28. Prevalence of MRSA Among 422 ED Patients With SSTI 7/13 (54%) 11/28 (39%) 4/20 (20%) 59% 32/58 (55%) 43/58 (74%) 24/47 (51%) 17/25 (68%) 26/42 (62%) 23/32 (72%) 18/30 (60%) 46/69 (67%) MSSA 17%Moran GJ et al.
  29. 29. SSTIs in 11 US EDs, August 2004 • 422 patients total Site of Infection: • 62% male • Head/Neck 13% • Median age 40 (range 18-79) • Torso 17% • Racial mix: • Upper Ext 28% White 28% • Lower Ext 28% Black 46% Hispanic 22% • Perineum 15% Other 3%Moran GJ et al. Society of Academic Emergency Medicine, 2005.
  30. 30. 185 cases from 1999-2002
  31. 31. CA-MRSA in athletes
  32. 32. A Clone of Methicillin-Resistant Staphylococcus aureus among Professional Football Players Kazakova SV, Hageman J, Matava M, et al. N Engl J Med 2005; 352 (5): 468-75• September 2003 • Large skin MRSA abscesses among St. Louis Rams football team • Subsequent cases in opposing team members prompted• November 2003 • CDC invited to investigate transmission (August 1- November 30)
  33. 33. Results• Attack rate: 5 out of 58 – 9%• At sites of skin abrasions (turf burns) on elbows, forearms, knees – unprotected skin• Large abscesses (5-7 cm) – I&D; most infections lasted 10 days after treatment; no hospitalization; total 17 days off field
  34. 34. Case Player Position
  35. 35. Results• Skin abrasions common • 2-3 turf burns/week from sliding on the field • More frequent/more severe on artificial turf• Trainers who provided wound care • No regular access to hand hygiene• Towels frequently shared • 3 players/towel• No showers before using communal whirlpool• Equipment not routinely cleaned/ manufacturer guidelines for cleaning whirlpools/saunas/steam rooms not found.
  36. 36. MRSA as a community and hospital pathogen CA-MRSA HA-MRSA Invasive/high rate of High rate of colonisation infection High %age of soft tissue Less likely to cause soft infections tissue infection Susceptible to non-beta- Multi-resistant lactams (to date)Causes necrotising infection Bacteremias, pneumonia and wound infections
  37. 37. Panton-Valentine leucocidin (PVL) toxin• Cytotoxin present in <5% of MSSA• Rare in HA-MRSA• Carried on bacteriophage …incorporated into chromosome• Capable of destroying WBC /severe tissue damage and associated with necrotic skin lesions /severe necrotizing pneumonia Lina et al, CID: 29:1128, 1999
  38. 38. How to treat CA-MRSA SSTIs• Culture • Antibiotics – Severe skin infections – TMP/SMX – All treatment failures of – Doxycycline presumed S.aureus skin – Levo, Moxi might be OK infections – Clindamycin (if D-tested)• Drainage is essential – No Macrolide or Amoxicillin /clavulanic acid
  39. 39. When to suspect CA-MRSA• When CA-MRSA reaches 10-15% of strains, all patients with SSTIs should be suspected.• Severe Staph aureus infections, ie, necrotizing fasciitis, necrotizing pneumonia, or neonatal sepsis.• When CA-MRSA risk factors are present.• When there has been a poor response to initial beta-lactam therapy.
  40. 40. Significance of S. aureus Nasal Carriage Nasal carriage of S. aureus is a risk for infection in hospital (usually same strain):– nosocomial bacteremia (RR 30; 95% CI 2.0-4.7) (von Eiff, NEJM 2001; Wertheim, Lancet 2004)– BSI, exit site infection in dialysis patients (Luzar, NEJM 1990; Kluytmans, ICHE 1996)– SSI (2-9 X increased risk) (Kluytmans, JID 1995; Perl, NEJM 2002; Kalmeijer, CID 2002)– ICU-acquired infection (2-5 X increased risk) (Honda, ICHE 2010)
  41. 41. Significance of MRSA Colonization Colonization with MRSA associated with a greater risk of subsequent infection:• Nasal carriers of MRSA 3.9 times more likely to develop nosocomial staphylococcal bacteremia than were MSSA carriers (Pujol, Am J Med 1996)• MRSA colonization at ICU admission associated with higher risk of ICU-acquired S. aureus (MRSA) infection; RR 4.1 (Honda, Infect Control Hosp Epidemiol 2010)
  42. 42. Risk of MRSA Colonization Becoming an Infection• 60 of 209 (29%) adults with newly identified colonization developed a subsequent MRSA infection during 18 months of follow-up (Huang, CID 2003)• 8 of 38 (21%) with newly identified colonization developed MRSA infection in 1 year of follow-up (Davis, CID 2004)
  43. 43. Decolonization• Decolonization is not recommended for usual management.• Decolonization may be tried when patients have multiple infections over several months.• The recommended regimen is mupirocin ointment bid for 10 days.• Mupirocin susceptibility should be tested.• “A combined strategy of intranasal mupirocin topical antiseptics and systemic antibiotics, eg. rifampin or clindamycin may be considered.”
  44. 44. S. aureus Decolonization Recommendations• possibly useful in patients with recurrent skin/soft tissue infection (need more data for CA-MRSA)• mupirocin susceptibility testing should be done prior to use for decolonization• MRSA as an infection control measure needs to be studied; consider in outbreaks or select patients
  45. 45. S. aureus Decolonization Recommendations• no routine decolonization pre-op or in nonsurgical patients; perhaps consider in surgical patients known to be S. aureus carriers• consider in dialysis patients, but risk of mupirocin resistance in the long-term
  46. 46. Environmental contamination of surfaces in an MRSA patient roomResistant bacteria on the skin or in the gastrointestinal tract of patientscan often be found on common items. Bed Linen Patient Gown Overbed Table BP Cuff Side Rails Bath Door Handle IV Pump Button Room Door Handle 0 10 20 30 40 50 60 Percent of Surfaces Contaminated
  47. 47. Manorapid Synergy ………… ………… ………… ………… ………… ………… AntisepticaRemember!!

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