mrsa (methicillin resistant staph. aureus) geog 380
TRANSCRIPT
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MRSA (Methicillin Resistant Staph.
aureus)Geog 380
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GENERAL COMMENTS about resistance
Inevitable “dance” of co-evolution Post WW II—steadily growing Widespread overuse Use in cattlefeed
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“The way to the wound is through the nose”--Creech II et al, 2006
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Chronology of MRSA
First reported UK 1961 First reported USA 1968 Community associated MRSA
(CA-MRSA) first reported 1980– Initially US– Pts lack risk factors for MRSA
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CA-MRSA Georaphically Dispersed (community
acquired) Australia--Aboriginals/native
peoples Native Americans in US--rural Subpopulations in US
– IDUs– Prisoners– Sports players– kids
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Bilateral Necrotizing Fasciitis--Pseudomonas
Source: Akamine et al, Internal Medicine 2008;47:553-6
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Paradigms of CA-MRSA
It spread from hospital– Patients– Visitors– Staff
Current findings– It has been in reservoirs in community– The strain has been different than
hospital MRSA– Some nosocomial MRSA is CA-MRSA!!!!
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Sobering Quotes
“Community-associated…MRSA now appears to be among the most common etiologies of skin and soft tissue infections.”
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“MRSA may be replacing methicillin-susceptible S.
aureus (MSSA) as the typical community
staphylococcal strain.”
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“it is difficult to justify using drugs like
cephalexin…if it is known that the majority of
patients will be infected with resistant isolates.”See Moran and Talan, Annals of
Emergency Medicine, 2004;11:321-22.
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Prevalence of CA-MRSA
No national data collected Community data difficult to get Hospital data easier Varies 76% of MRSA in AK to
12% MN for soft tissue infections Huang et al, Journal of Clinical
Microbiology 2006;44:2423-27
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Hospital MRSA
Formerly:–Few large university hosps– ICUs
Now:–97% teaching hosps report MRSA
Risk factors:– Long hospital stay, surgery,
catheter sites (prop to # of sites), long or recurrent exp to abx’s
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Evidence of CA-MRSA Increase
10/100,000 admissions, kids, 1988-90 259/100,000 1993-5 See Herold et al, JAMA 1998;279:593-8 1993: 2,000 MRSA 2005: 368,000 APIC: 46/1000 hosp adm had life threatening
MRSA CDC: 94,000 life threatening hosp MRSA infs
and 19,000 deaths!!!! STAY HEALTHY
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Frazee Study (Frazee et al, Annals of Emergency Med, 2005;45:31-20
Done in ER in Alameda County, CA 18% homeless, 28% IDU, 63% w abscess,
26% admitted to hosp
Nearly 50% patients w/ skin and soft tissue infections MRSA
74% of staph was MRSA “When skin and soft tissue infections require
antibiotic therapy, we recommend choosing an agent that is active against MRSA”
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Findings of Huang et al
45% of pts w/MRSA had community associated MRSA
Not susceptible to usual abx’s for soft tissue infections but susceptible to:– TMP/SMX (Bactrim or Septra)– Gentamicin– Rifampin– Vancomicin– Clindamicin
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Necrotizing Fasciitis
“flesh eating bacteria” Fairly rate Spectacular Life-threatening Surgical emergency Polymicrobial
– Toxin producing– Necrosis of fascia
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Historical Background
Hippocrates 5th Cent BCE 19th C:
– “gangrenous ulcer”, “malignant ulcer”, “putrid ulcer”, phagedema gangrenosa
1800’s– Feared in the military…
Confused by multiple terms@ present
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Epidemiology
Estimated 500-150 cases/yr in US Not specific by age or sex Increased risk in:
– IVDU– Alcoholics– Immunosuppressed– Peripheral vascular disease– diabetics
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Typical Presentation
Any break in the skin Increased risk w/trauma
– Penetrating– Blunt– Surgical wound– IVDU– SC drug use– Perirectal abscesses– Bites– Da da da da
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Clinical Presentation
Within 7 days of “injury” Red, swollen, tender, hot, painful
area Pain out of proportion to
physical findings Pain extends beyond boundaries
of erythematous area Rapid, rapid expansion
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CFR
Typically 75%– Sepsis– ARDS
Higher at Harborview
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WARNING: SOME SLIDES AFTER THIS GET VERY GRAPHIC. NO KIDDING
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Hsiao F and Hsieh C. N Engl J Med 2008;358:940
A 65-year-old woman with a 15-year history of diabetes presented with fever (temperature, 38.5{degrees}C), chills, malaise, and a rash on the medial surface of the right thigh, vulva, and
lower abdominal wall (Panel A)
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Necrotizing Fasciitis of Left Lower Leg
Source: Kihiczak et al, JEADV
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Nec Fasc of the Perineum
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Infections and Layers
Source: Chest 1996
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NDM-1New Delhi Metallo-beta-
lactamase-1
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HUH????
“What’d the dude say?” “Sounded like he was barfing” “I’m texting my girlfriend. How
do you spell that?” “Will it be on the test?” “You mean this isn’t Philosophy
101”?
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NDM-1
Not a specific bacterium A genetically coded mechanism in
gram negatives (klebsiella, etc), E. coli
Cleaves ring in carbapenems (carbapenamase)
Relatively new broad spectrum antibiotics including imipenem, meropenem
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Why should we care?
Renders a major class of antibiotics useless
These antibiotics are frequently the only effective ones against enterobaceteriacae
Also many other pathogens Few if any treatments then work
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Lancet ID, April 7, 2011
“such pathogens typically are resistant to multiple other antibiotic classes, leaving very few treatment options available”
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So let me explain
Enzyme is made by the bacterium based on instructions from its genome
This attacks the chemical structure of the “new” class of antibiotics
Cuts a ring Neutralizes the antibiotic
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Journal of Chinese Medical Association, Nov. 2010
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NDM-1 in Water Supply, New Delhi Source: Lancet ID, 4-2011