Community- Associated MRSA Maha Assi, MD, MPH
Community-Associated MRSA
Maha Assi, MD, MPH
MRSA Hits the Media
October 16, 2007 Lead story on
MRSA “superbug killing
many in US”
MRSA Kills High School Student
17 year old Ashton Bonds died of disseminated MRSA infection
Prompts closing of school for cleaning
MRSA kills Football Player
20 year old college football player who developed a skin infection. He was seen and treated with antibiotics. MRSA was not suspected. He died within days of disseminated CA-MRSA
CA-MRSA
An Epidemic A great deal of
media attention Public concern
MRSA and the Media
How Common is CA-MRSA colonization ?
General population analysis of data from the NHNES Colonized with Staph aureus 31.6%
84 million Colonized with MRSA 0.84%
2 million
Annals of Internal Medicine. 2006 March 7;144(5):318-25
How common is disease due to CA-MRSA?
In 2005 in US 94,360 cases of invasive MRSA infection with 18,650 deaths.
Of those, 14% were community-acquired infections.
Traditional MRSA Risk Factors
Newborns, elderly, hospital workers, HD, IVDU, Diabetics, patients with chronic dermatitis
Hospitalized patients, antibiotic receipt, chronic illness of any kind
Community-Associated MRSA without
Identifiable Risk Factors Herold 1988- reported 25 fold
increase in MRSA colonization in children at a Chicago Hospital
Adcock 1998-2 day care centers with from 3-24% colonization- 40% in children with no contact with health care system
Deaths of 4 children in MN/ND 1999Herold et al JAMA 1998:279:593-8Adcock et al JID 1998:178:577-80MMWR 1999;48:707-10
Community outbreaks
Native and aboriginal communities Sports teams Child care centers Military personnel Men who have sex with men Prison inmates and guards
Risk factors
Skin trauma (e.g. lacerations, abrasions, tattoos, injection drug use), cosmetic body shaving, incarceration, sharing equipment that is not cleaned or laundered between users, and close contact with others who have MRSA colonization or infection.
Animals can also carry MRSA and function as a source of transmission.
What about me?
Importantly, many patients with CA-MRSA have no risk factors.
Is that all?
CA-MRSA may cause disease without previous nasal colonization, and/or favor other sites of colonization over the nares (such as the skin, throat, or gastrointestinal tract).
The Molecular Biology of MRSA
Resistance to Penicillin=B-lactamases
Resistance to Methicillin=Penicillin binding protein 2a (PBP 2a) Alterations in PBP 2a carried on
SCCmec Nosocomial MRSA=SCCmec II and III CA-MRSA=SCCmec IV
The USA300 strain
Necrotizing pneumonia caused by CA-MRSA
Outcomes in Patients Treated for CA-MRSA
33% nonresponse at day 30 Failure related to lack of I & D
(p=.005) Failure not associated with wrong
antibiotic choice Trend for close contacts to develop a
similar infection by day 30
Clin Infec Dis. 2007;44:483-92
Eradication of MRSA Colonization
The role of decolonization in the control of methicillin-resistant Staphylococcus aureus (MRSA) spread is uncertain.
Decolonization does not appear to be consistently effective for eliminating MRSA carriage.
The optimal regimen and duration of therapy for eradicating MRSA colonization is uncertain.
Topical regimen
Chlorhexidine washes Mupirocin or Bactroban ointment
applied to nares with a cotton-tipped applicator two to three times daily
Prevention of CA-MRSA
Handwashing Isolation Decolonization Vaccination??
Vaccine for Staph aureus
Capsular polysaccharides serotypes 5 and 8
Conjugated with protein from Pseudomonas exotoxin
Randomized trial in hemodialysis patients Partial immunity, decreased Staph aureus
bacteremias at 40 weeks By 54 weeks no difference ?booster doses
Passive immunization