Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) in ...

smfm.org

Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) in ...

Methicillin-Resistant

Staphylococcus

aureus (MRSA) in

Obstetrics

Vanessa Laibl Rogers, M.D.

UT Southwestern Medical Center

July 7, 2010


At the conclusion of this presentation,

the physician will be able to:

• Understand the history and course of

MRSA in the community

• Identify risk factors and signs of MRSA in

pregnant women

• Properly select antibiotic therapy for

pregnant women infected with MRSA


Staphylococcus aureus

• Bacteria commonly

carried on the skin or in

the nose of healthy people

• One of the most common

causes of skin infections

in the US

– Boils and pustules

– Surgical wound infections,

blood stream infections,

pneumonia and urinary

tract infections


Rate / 10,000 Discharges

180

160

140

120

100

80

60

40

20

0

S. aureus Infections Increase

over Time

S. aureus Infections by Type and Year

(Conservative Estimate)

1999 2000 2001 2002 2003 2004 2005

NIS Total

Septicemia

Pneumonia

Skin

Other

All infections increased over time period, Poisson regression p < .01

CDC, 2008

2005 Count

639,000

110,000

96,000

275,000

157,000


3 Major Skin Infection Classes

Surgical Site

Infection 26%

2004 Skin Infection Distribution

2%

•Carbuncle and

Furuncle

•Impetigo

•Diseases of hair

and follicles

•Other local skin

& subcutaneous

infections

Chronic Ulcer 8%

CDC, 2008

Cellulitis and Abscess 64%


Percent of All Skin Infections

100.0

75.0

50.0

25.0

0.0

Cellulitis and Abscess

Increasingly Important

S. aureus Skin Infections by Type and Year

1999 2000 2001 2002 2003 2004 2005

Cellulitis and

abscess

Chronic ulcer

Surgical site

infection

CDC, 2008

Cochran-Armitage test for trend p < .01 for all infection types


Cellulitis and abscess in Younger Age

Groups

Proportion of S. aureus Cellulitis and Abscess by Age Group

Percentage

50

45

40

35

30

25

20

15

10

5

0

1999 2000 2001 2002 2003 2004 2005

Age Group

0-14

15-44

45-64

65+

CDC, 2008

Cochran-Armitage test for trend p < .01


Methicillin Resistant

Staphylococcus aureus (MRSA)

Resistant to methicillin and often other

antibiotics

– Officially, do not use methicillin to test

anymore

– Now use oxacillin

• 25 – 30 % of the population is colonized

with Staphylococcus aureus

• 1% of the population are colonized with

MRSA


Genetics of Methicillin Resistance

• mec A gene encodes the novel penicillinbinding

protein 2a which cannot be bound by

β-lactam antibiotics

• mec A is found on a mobile genetic element

known as Staphylococcal Cassette

Chromosome mec (SCCmec)

• There are currently 5 main types of SCCmec,

although others have been recently identified

• Types I, IV, and V encode resistance to only β-

lactam antibiotics

• Types II and III confer multi-drug resistance

• PCR testing available


History of MRSA

• First strain was isolated in 1961 in England

and was a SCCmec type I

• Initial strains were limited to hospital settings

and became known as “hospital-acquired

MRSA

• In the early 90’s, reports surfaced of people

infected with MRSA who had not been

hospitalized and did not have known risk

factors

• This is became known as “communityacquired

MRSA


Hospital-acquired or Healthcareassociated

MRSA

• Healthcare-associated MRSA infections

– Limited antibiotic susceptibility

• vancomycin, linezolid, and daptomycin

– 1996 reports of MRSA strains with decreased

susceptibility to vancomycin (MIC 8-16 ug/ml)

and some strains fully resistant (MIC ≥ 32

ug/ml)

• Pulsed-field type USA100, USA200 and

less often, USA500 strains


Community-associated MRSA

CDC Surveillance Definition

• Isolated in the outpatient setting or within 48

hours of hospital admission

• Patients do not have historical risk factors:

– Hospitalization within the past year

– Indwelling catheters

– Dialysis, surgery, ventilatory support

– Residence in long-term care facilities

• Pulsed-field type USA300, USA400, USA1000

and USA1100


CA-MRSA and Athletics

• October 2000, 10 members of a college football

team in Pennsylvania diagnosed with MRSA

– Skin and soft tissue infections

– Had frequent skin abrasions and shared towels

• February 2003, cluster of cases among a

fencing team in Colorado

– Skin and soft tissue infections of the legs, thighs,

abdomen, buttocks, and axilla

– Team mates frequently shared equipment including

sensor wires

MMWR Weekly August 22, 2003

52(33);793-795


CA-MRSA and Prison

• October 2000, inmates of state prison in

Mississippi diagnosed with MRSA

– Skin and soft tissue infections of the legs and

arms

– Inmates would help each other with wound

care and share personal items

– Carrier rate was found to be 4.9% and was

higher among those incarcerated longer

MMWR Weekly October 26, 2001

50(42);919-922


CA-MRSA and Day Care

• 1998, several children attending day care

in the Dallas area diagnosed with MRSA

– Pneumonia and cellulitis requiring

hospitalization

– Prevalence of MRSA at two unrelated facilities

found to be 3% and 24%

– Health care contact was not associated with

MRSA

Adcock et.al, Jo. of Infectious

Diseases 1998 178:577-580


Transmission of MRSA

• CDC’s 5 C’s

– Crowding

– Frequent skin-to-skin Contact

– Contaminated items and surfaces

– Compromised skin (cuts or abrasions)

– Lack of Cleanliness


Risk Factors for CA-MRSA

• Day cares, prisons, nursing homes

• Antibiotic use

• Poor hygiene

• Close living conditions

• Underlying dermatologic problems

• Household contacts of those known to

have CA-MRSA

• Drug abuse, especially “skin poppers”


“Skin Popper” with MRSA


Panton-Valentine Leukocidin

• CA-MRSA commonly has

genes that encode for this

exotoxin

• Exotoxin is associated with skin

necrosis and abscess formation

• A 2007 study at Children’s

Medical Center of Dallas found

that most CA-MRSA isolates

among their patients were PVL

positive


Healing MRSA Lesion


Presentation of CA-MRSA

• Most commonly as skin and soft tissue infections

– Furuncles - abscessed hair follicles

– Carbuncles - coalesced masses of furuncles

• See clusters of cases in households

• Lesions are frequently attributed to “spider bites”


Spider Bites and CA-MRSA

• Several military facilities in 2006 reported

unusual skin lesions suspected to be spider

bites

• Cultures of the affected soldiers returned CA-

MRSA

• CA-MRSA attributed to close living conditions

• Report concluded that rashes of spider bites

should prompt an investigation for CA-MRSA

Pagac et. al, Military Medicine,

September 2006


Spiders and CA-MRSA

• Journal of Medical Entomology

– Spiders captured from homes

– Cultured for MRSA

– Few bacteria found on spiders

– No MRSA isolated

– Conclusion: common house spiders are

unlikely to be a source of MRSA

Baxtrom et. al, September 2006


CA-MRSA and Pregnancy

• Same risk factors apply to the pregnant

population

• Rectovaginal colonization varies by

geographic area, ranging from 0.5-10%

• Presents a challenge in terms of treatment

because of antibiotic selection


CA-MRSA and Pregnancy

• 57 pregnant women between January 2000 and

July 2004

• 1 in 8 patients infected with HIV

• 1 in 5 patients with history of drug abuse

• Presented most commonly in the second

trimester, often complaining of “spider bites”

• 96% presented with skin/soft tissue infections

• 63% required hospital admission

Laibl et. al, Obstetrics and

Gynecology 2005 106(3):461-465


CA-MRSA and Pregnancy

• Most common site of infection was the

extremities (44%)

• 23% presented with a breast abscess

• 58% had multiple sites of infection

• 4 of the 57 patients required 3 or more

hospital admissions

• 1 patient was admitted to the ICU for

septicemia


CA-MRSA Cultures by Year

25

20

Number of

cases

15

10

5

0

'00 '01 '02 '03 '04

Year


CA-MRSA and Pregnancy

• 7 of 57 patients initially treated with

antibiotics to which MRSA was sensitive

• In all cases, MRSA sensitive to rifampin,

trimethoprim-sulfamethoxazole, and

vancomycin

• 98% sensitive to gentamicin

• Clinical improvement in 24-48 hours,

regardless of antibiotic administered

Laibl et. al, Obstetrics and

Gynecology 2005 106(3):461-465


CA-MRSA Drug Susceptibilities

Resistant to all β-lactam antibiotics including

penicillins, cephalosporins and carbapenems

• Typically susceptible to more antibiotics than

hospital-acquired/associated MRSA

– Gentamicin

– Levofloxacin

– Rifampin

– Trimethoprim-sulfamethoxazole

– Vancomycin


Clindamycin and CA-MRSA

• There are reports of inducible resistance

to clindamycin

• Related to the erm gene

• Strains with inducible resistance will test

clindamycin sensitive but eyrthromycin

resistant in vitro

• Before using, consider a D-zone test


D-zone Test

Daum NEJM July 26, 2007

357:380-390


Does the Antibiotic Choice

Matter?

• Lee et. al 2004 studied children with skin

and soft tissue abscesses from MRSA

• Incision and drainage performed for

abscesses

• Patients given ineffective antibiotics did

just as well as those administered

antibiotics to which the MRSA was

sensitive


Does the Antibiotic Choice

Matter?

• Ruhe et. al 2007 studied 531 cases of CA-

MRSA in adult patients

• Majority of patients had incision and drainage

• 95% successful treatment when effective

antibiotics were administered

• 87% successful treatment when ineffective

antibiotics were administered

• Use of an ineffective antibiotic was an

independent predictor of treatment failure

(OR=2.8)


Management of CA-MRSA Lesions

• Incision and drainage of abscess

• Culture

• No evidence to suggest molecular typing

or toxin-testing will help guide

management

• Antibiotics – empiric initially

– Clindamycininducible resistance

– Rifampin – not usually used as a single agent

– Linezolid – expensive, restricted, resistance

– Tetracycline – not in young age or pregnancy


Management of CA-MRSA Lesions

• Antibiotics can be changed depending on

culture sensitivities

• TMP-SMX has been used

• Hospitalization should be based on site

and severity of infection

– Vancomycin 1 st line for severe infections


Treatment in Pregnancy

• Patients treated with ineffective antibiotics

whose lesions resolve, do not have to be

given a course of antibiotics after the fact

• Recurrences should be treated initially

with antibiotics to which the previous strain

was sensitive

• Vancomycin 1g should be administered in

addition to the cephalosporin routinely

given at the time of surgical prophylaxis


Labor and Delivery

• Contact isolation

• Epidural is acceptable

• Infant does not need to be isolated from

mother

• Preference is to keep the infant out of the

nursery

• Breast feeding is not contraindicated


Postpartum Mastitis and CA-

MRSA

• 48 cases of S. aureus-associated postpartum

mastitis

• 44% CA-MRSA

• 95% of cases of CA-MRSA SCCmec type IV

• 46/48 patients also had an abscess; 39 had

drainage

• Over 40% required hospitalization

• Patients with MRSA were more likely to be

febrile and multiparous

Reddy et. al, Emerging Infectious

Diseases, February 2007


Postpartum Mastitis and CA-

MRSA

• 127 women admitted to our hospital

(9.3/10,000 deliveries)

• 29 had I&D of an abscess

• Culture results available for 54/92 of

mastitis only patients

– 44% MSSA; only 1 patient had MRSA

• Culture results available for 27/35 abscess

patients

– 59% MRSA, 19% MSSA

Stafford et al, Obstetrics and

Gynecology, September 2008


Severe and Invasive MRSA

Infections

• Necrotizing pneumonia

• Osteomyelitis

• Necrotizing fasciitis

• Septic arthritis

• Empyema

• Sepsis syndrome


Active Bacterial Core Surveillance

(ABCs)/Emerging Infections Program

Network

• Population based active surveillance

system of the CDC

– 10 EIP sites undertake surveillance for invasive

MRSA yearly. For 2008:

• 19 million people in these sites

• Active and laboratory based

– Invasive MRSA case defined as isolation of

MRSA from a normally sterile body site

CDC, 2008


Active Bacterial Core Surveillance

(ABCs)/Emerging Infections Program

Network

• 5408 cases of invasive MRSA

– Health care associated

• 59% community onset

• 24% hospital onset

– 17% community-associated (no established

health care risk factors)

• National estimate of invasive disease was

29.5/100,000


Preventing the Spread

• Hand washing

• Cover draining wounds

• Avoid sharing contaminated items

• Keep wounds clean

• Shared athletic equipment should be

cleaned with a product effective against

MRSA

• Awareness of its presence cannot be

overstated


Decolonization

• Efficacy is unclear

• Should only be considered in cases of

multiple recurrences or ongoing

transmission within a contact group

• Involves nasal mupirocin and antiseptic

body washes (chlorhexidine)

• To avoid resistance, courses should be

short and limited

• Multisite carriage is a risk factor for failure

of decolonization


Conclusion

• CA-MRSA is a significant problem in our

community

• A complaint of “spider bites” warrants

investigation for MRSA

• Patients presenting with skin and soft

tissue infections should have cultures sent

• Antibiotic choice may not affect outcome,

but antibiotics to which MRSA is sensitive

should be used if culture results are known

More magazines by this user
Similar magazines