Staphylococcus aureus: common cause of infection in the community

Methicillin Resistant Staphylococcus aureus (MRSA) in the Community: Epidemiology and Management

Staphylococcus aureus

• Staphylococcus aureus: common cause of infection in the community

• Methicillin-resistant Staphylococcus aureus (MRSA):

• Increasingly important cause of healthcare-associated infections since 1970s
• In 1990s, emerged as cause of infection in the community

MRSA Strain Characteristics Were Initially Distinct

National Database of MRSA Pulsed-Field Types (Highlighted PFTs: historically community-associated)

Community-Associated MRSA: CDC Population-Based Surveillance Definition

• MRSA culture in outpatient setting or 1st 48 hours of hospitalization AND patient lacks risk factors for healthcare-associated MRSA:

• Hospitalization
• Surgery
• Long-term care
• Dialysis
• Indwelling devices
• History of MRSA

Outbreaks of MRSA in the Community

• Often first detected as clusters of abscesses or “spider bites”

• Various settings

• Sports participants
• Inmates in correctional facilities
• Military recruits
• Daycare attendees
• Native Americans / Alaskan Natives
• Men who have sex with men
• Tattoo recipients
• Hurricane evacuees in shelters

Factors that Facilitate Transmission

Factors that Facilitate Transmission

Factors that Facilitate Transmission

Factors that Facilitate Transmission

Factors that Facilitate Transmission

Factors that Facilitate Transmission

2004/2005 ABCs MRSA Surveillance Areas

CA-MRSA Infections are Mainly Skin Infections

Most Invasive MRSA Infections Are Healthcare-Associated

Incidence of Invasive CA-MRSA Infections and Deaths by Age Active Bacterial Core surveillance (ABCS), 2005

S. aureus-Associated Skin and Soft Tissue Infections in Ambulatory Care

• 11.6 million ambulatory care visits per year in 2001-03 for skin infections typical of S. aureus

• Increase in hospital outpatient and ED visits (2001-03 versus 1992-94)

MRSA Was the Most Commonly Identified Cause of Purulent SSTIs Among Adult ED Patients (EMERGEncy ID Net), August 2004

S. aureus Nasal Colonization National Health and Nutrition Examination Survey 2001-02

Emerging Multi-Drug Resistance in USA300?

• Clusters of USA300 isolates with multiple resistance to erythromycin, clindamycin, tetracycline, ciprofloxacin, and mupirocin1

• Resistance to ≤ one class of antibiotics other than beta-lactams is still the most common resistance pattern in MRSA USA300

• TMP/SMX resistance rare in MRSA USA300

Distribution of PFGE types among MRSA isolates from nosocomial bloodstream infections Grady Memorial Hospital, 2004

Strategies for Clinical Management of MRSA in the Community

Clinical Considerations - Evaluation

• MRSA belongs in the differential diagnosis of skin and soft tissue infections (SSTI’s) compatible with S. aureus infection:

Clinical Considerations - Evaluation

• MRSA should also be considered in differential diagnosis of severe disease compatible with S. aureus infection:

• Osteomyelitis
• Empyema
• Necrotizing pneumonia
• Septic arthritis
• Endocarditis
• Sepsis syndrome
• Necrotizing fasciitis
• Purpura fulminans

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

• Obtain material for culture

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

• Obtain material for culture

• No data to suggest molecular typing or toxin-testing should guide management

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

• Obtain material for culture

• No data to suggest molecular typing or toxin-testing should guide management

• Empiric antimicrobial therapy may be needed

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

• Obtain material for culture

• No data to suggest molecular typing or toxin-testing should guide management

• Empiric antimicrobial therapy may be needed

• Alternative agents have +’s and –’s: More data needed to identify optimal strategies

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

• Obtain material for culture

• No data to suggest molecular typing or toxin-testing should guide management

• Empiric antimicrobial therapy may be needed

• Alternative agents have +’s and –’s: More data needed to identify optimal strategies

• Use local data for treatment

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

• Obtain material for culture

• No data to suggest molecular typing or toxin-testing should guide management

• Empiric antimicrobial therapy may be needed

• Alternative agents have +’s and –’s: More data needed to identify optimal strategies

• Use local data for treatment

• Patient education is critical!

Management of Skin Infections in the Era of CA-MRSA

• I&D should be routine for purulent skin lesions

• Obtain material for culture

• No data to suggest molecular typing or toxin-testing should guide management

• Empiric antimicrobial therapy may be needed

• Alternative agents have +’s and –’s: More data needed to identify optimal strategies

• Use local data for treatment

• Patient education is critical!

• Maintain adequate follow-up

Clinical Considerations - Management

• Alternative agents (More data needed to establish effectiveness!):

• Clindamycin – Potential for inducible resistance, Relatively higher risk of C. difficile associated disease?
• TMP/SMX – Group A strep isolates commonly resistant
• Tetracyclines – Not recommended for <8yo
• Rifampin – Not as a single agent
• Linezolid – Expensive, Potential for resistance with inappropriate use

Clinical Considerations - Management

• Not optimal for MRSA (High prevalence of resistance or potential for rapid development of resistance):

• Macrolides
• Fluoroquinolones

D-zone test for Inducible Clindamycin Resistance

Management of Severe / Invasive Infections

• Vancomycin remains a 1st-line therapy for severe infections possibly caused by MRSA

• Other IV agents may be appropriate Consult an infectious disease specialist.

• Final therapy decisions should be based on results of culture and susceptibility testing

• Severe community-acquired pneumonia: Vancomycin or linezolid if MRSA is a consideration*

Screening and Decolonization

• In general, colonization cultures of infected or exposed persons in community settings are not recommended. (May have a role in public health investigations).

• Decolonization regimens:

• May have a role in preventing recurrent infections (more data needed to establish efficacy and optimal regimens for use in community settings).
• After treating active infections and reinforcing hygiene and appropriate wound care, consider consultation with an infectious disease specialist regarding use of decolonization when there are recurrent infections in an individual patient or members of a household.

Preventing Transmission

• Persons with skin infections should keep wounds covered, wash hands frequently (always after touching infected skin or changing dressings), dispose of used bandages in trash, avoid sharing personal items.

• Uninfected persons can minimize risk of infection by keeping cuts and scrapes clean and covered, avoiding contact with other persons’ infected skin, washing hands frequently, avoiding sharing personal items.

Preventing Transmission

• Exclusion of patients from school, work, sports activities, etc should be reserved for those that are unable to keep the infected skin covered with a clean, dry bandage and maintain good personal hygiene.

• In general, it is not necessary to close schools to “disinfect” them when MRSA infections occur.

• In ambulatory care settings, use standard precautions for all patients (hand hygiene before and after contact, barriers such as gloves, gowns as appropriate for contact with wound drainage and other body fluids).

Role of Pets

• Greatest risk of Staph aureus / MRSA exposure in most humans is other humans

• When household pet animals carry MRSA, likely acquired from a human

• Transmission of MRSA from an infected or colonized pet to a human is possible, but likely accounts for a very small proportion of human infections

• Reasonable to consider pet as a source if transmission continues in a household despite optimizing other control strategies

• Little evidence that antimicrobial-based eradication therapy is effective in pets; however, colonization tends to be short-term*

Conclusions

• New strains of MRSA have emerged in the community, with implications for management of skin infections and other staphylococcal infections.

• Incision and drainage remains a primary therapy for purulent skin infections.

• Oral treatment options are available for patients with skin infections that require ancillary antibiotic therapy.

• Patient education on proper wound care is a critical component of case management for patients with skin infections.

• Strategies focusing on increased awareness, early detection and appropriate management, enhanced hygiene, and maintenance of a clean environment have been successful in controlling clusters / outbreaks of infection.

DHQP Posters and Patient Tear Sheet

CA-MRSA Working Group Meeting Participants, July 2004

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