UPDATE ON MRSAUPDATE ON MRSA

Benjamin Ehst, MD, PhD

Assistant Professor,

Department of Dermatology,

Oregon Health & Science University

61st Annual Meeting,

Pacific Dermatologic Association,August 14th, 2009

Disclosures:

I have no relevantfinancial or commercialinterests

OverviewOverview

� Definitions of HA-MRSA and CA-MRSA

� Basics

� Pathogenesis

� Incidence

� Presentation

� Treatment

� Prevention

DefinitionsDefinitions

� HA-MRSA

_ Infection isolated >48hrs after admission or

_At least 1 risk factor

� Invasive device present at

admission

� h/o MRSA infection or

colonization

� h/o surgery, hospitalization,

dialysis or residence in

long-term care facility in

prior year

� CA-MRSA

_ Infection isolated <48hrs after admission with

no risk factors

� HA-MRSA transmission to community

� CA-MRSA transmission to inpatients

% MRSA infections, SF 2004-2005

Hospital-onset Community-onset

USA300 43 79

Clonal 5 complex 37 12

However, definitions areHowever, definitions are

becoming less important forbecoming less important for

clinical practiceclinical practice

Liu et al., Clin Infect Dis, 2008

BasicsBasics

� HA-MRSA

_Emerged in 1960!s inU.S.

_Older patients,

hospitalized

_Multi-drug resistant

_Staphylococcal cassette

chromosome (SCC) type

I-III

_Strains USA 100, 200

� CA-MRSA

_Emerged in 1990!s

_Young, healthy; athletes,

IDU, prisons, MSM

_ß-lactam resistant

_SCC type IV, V

_Panton-Valentine

Leukocidin (PVL)

dermotoxin

_Strain USA 300, 400

Pathogenesis of USA300Pathogenesis of USA300

� Why predominant strain of CA-MRSA in U.S.?

_PVL

� No longer clear if this contributes to pathogenicity (other

superantigen toxins are as likely)

_SCCmec type IV

� No fitness disadvantage (unlike the larger cassettes in HA-MRSA

strains)

_Arginine catabolic mobile element (ACME) type 1

� Perhaps acquired from S. epidermidis

� Linked to SCCmec (mobilized together)

� Enhances hematogenous spread

� Confers fitness advantage or pathgenicity

Diep et al., J Infect Dis, 2008

Incidence (why do we care?)Incidence (why do we care?)

U.S. estimate invasive MRSA (2006)

� 104,228 cases (34.83 cases/100,000

people)

� 18,964 deaths (6.33/100,000)

http://www.cdc.gov/ncidod/dbmd/abcs/survreports/mrsa06.pdf

McCaig et al., Emerg Infect Dis, 2006

11,600,000 annual outpatient visits for SSTIs, 2001-2003

Only 4% resulted in admission

Incidence (varies byIncidence (varies by

geography)geography)Incidence of MRSA per 100,000 (2005)

Total CA-MRSA

U.S. 31.8 4.6

Baltimore, MD 116.7 29.7

Denver metro, CO 21.2 2.8

Portland metro, OR 19.8 4.7

Klevens et al., JAMA, 2007Liu et al., Clin Infect Dis, 2008

Invasive and non-invasive (>80% were CA-MRSA)

PresentationPresentation

� SSTIs (85%-95% of CA-MRSA)

_ folliculitis, furunculosis,abscess), “spider bite”

� Invasive

_Endocarditis

_Osteomyelitis, myositis

_Necrotizing pneumonia

_Necrotizing fasciitis

_Sepsis, purpura fulminans

Outpatient management of SSTIs (CDC recommendations,Outpatient management of SSTIs (CDC recommendations,

2007)2007)Signs/symptoms of skin infection:• redness, swelling, warmth, pain/tenderness, “spiderbite”

Possible cellulitis w/o abscess:

• Abx coverage for Streptococcusspp. and/or other suspectpathogens• close f/u• add MRSA coverage if not

responding

Purlence? (any of following

present):• fluctuance• yellow or white center• “head”• draining pus

• able to aspirate pus

YES

YES

NO

1. Drain lesion2. Send cx for susceptibility3. Advise on wound care and

hygeine4. Close f/u

If systemic symptoms, severe local

symptoms, immunosuppression, failure of

I&D:

Add Abx coverage for MRSA

TreatmentTreatment

I&D is primary approach

_Many observational studies

_Randomized, double-blind study in San Francisco

� 166 outpatients with skin abscesses

� All received I&D, then randomized to cephalexin x 7 days or

placebo

� 70% cultures were S. aureus (88% were MRSA)

� No difference in clinical cure rate (90% vs 84%)

Rajendran et al., Antimicrob Agent Chemo, 2007

% Resistant

Clinda TCN TMP-SMX Ery

HA 60 5 2 95

CA 18 8 0 93

CA 12 9 1 53

CA 22 19 1 93

CA 15 39 17 88

CA 13 11 3 89

Portland

Minneapolis

BaltimoreSan Francisco

Atlanta

http://oregon.gov/dhs/ph/cdsummary; 2007, 56(23)Fridkin et al., NEJM, 2005

Liu et al., Clin Infect Dis, 2008

Multi Drug-Resistant CA-Multi Drug-Resistant CA-

MRSAMRSA

� “MDR USA300”_ Contains plasmid pUSA03, confers resistance to mupiricin,

clindamycin, erythromycin (potential to acquire others)

� Retrospective analysis of MRSA infections 2004-2006_ SF HIV clinic, 30/183 MRSA cases (16%) were MDR

_ Boston Community-health clinic, 60/130 (46%) were MDR% Resistant

Clind

a

TCN TMP-

SMX

Ery Mu

p

Rif Vanc Cipro

MDR USA300 100 63 0 10

0

100 0 0 77

Diep et al., Ann Int Med, 2008

Colonization ratesColonization rates

� S. aureus

_~ 30% general population of U.S.

� MRSA

_~ 1% general population

_But many studies cite higher rates in certain groups:

� ~8% in ICUs

� Disease groups; DM, HIV, dialysis patients

?? AD, psoriasis, CTCL

Pets, farm animalsCoates et al., J Antimicrob Chemo,

2009

OHSU studyOHSU study

� 222 inflammatory disease patients, 130 (57%) on biologic

therapy

� 78 (35%) colonized with S. aureus,

� 4 (5%) MRSA

Colonization rates were similar between biologic users and

non-users (33% and 38% respectively), between RA and

psoriasis patients, and to general U.S. population (30%).

DecolonizationDecolonization

Why?

_Prevent infection� 23% of longterm MRSA carriers develop MRSA

infections in the year after determining carrier status

� MRSA nasal carriers 3.9 times per likely than MSSA

carriers to develop bacteremia

_Prevent transmission

Simor and Daneman, Infect Dis Clin N Am,2009

DecolonizationDecolonization

� Success?

_Meta-analysis of 23 studies (1977-2008), 2114 subjects

_BID mupirocin intranasal for 4-7 days

� ~90% clearance at 1 week

� ~60% longer-term clearance (2 weeks to 1 year)

� Recurrence

_ Incomplete clearance

_Extranasal sites, co-morbidities, resistance

_Recolonization

Ammerlaan et al., Clin Infect Dis,2009

DecolonizationDecolonization

For extra-nasal sites, possibly co-morbidities

� 146 Canadian hospitalized patients, colonized w MRSA

� Open label randomized trial of mupiricin TID, 2%

chlorhexidine wash daily, doxy 100 BID and rifampin 300

BID for 7 days versus no treatment

� 74% (64/87) of treated patients no MRSA at 3 months – 32% of

untreated

� 54% at 8 months

Simor et al., Clin Infect Dis, 2007

DecolonizationDecolonization

But does it prevent,

_ Infection?

� Cochrane Review of 9 RCTs (3396 subjects) showed:

� Mupirocin BID for 4-7 days significantly reduces all S. aureus infections

in nasal carriers, 4.8% v 8.8% (but not specifically surgical site

infections)

� 1 RCT for SSTIs

� 134 military recruits colonized w MRSA

� 5 days of mupirocin had no effect on subsequent SSTIs

_Recurrence?� RCT of 34 healthy adults w recurrent MSSA skin infections

� Mupirocin for 5 days significantly decreased colonization and

recurrent SSTIs van Rijen et al., Cochrane Database Syst Rev, 2008

Ellis et al., Antimicrob Agents Chemo, 2007Raz et al., Arch Int Med, 1996