Community- Associated MRSA Maha Assi, MD, MPH

MRSA Hits the Media October 16, 2007 October 16, 2007 Lead story on MRSA Lead story on MRSA “superbug killing many in US” “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 An Epidemic A great deal of media attention A great deal of media attention Public concern Public concern

MRSA and the Media

How Common is CA-MRSA colonization ? General population analysis of data from the NHNES General population analysis of data from the NHNES Colonized with Staph aureus 31.6% Colonized with Staph aureus 31.6% 84 million 84 million Colonized with MRSA 0.84% Colonized with MRSA 0.84% 2 million 2 million Annals of Internal Medicine 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. In 2005 in US 94,360 cases of invasive MRSA infection with 18,650 deaths. Of those, 14% were community-acquired infections. Of those, 14% were community-acquired infections.

Traditional MRSA Risk Factors Newborns, elderly, hospital workers, HD, IVDU, Diabetics, patients with chronic dermatitis Newborns, elderly, hospital workers, HD, IVDU, Diabetics, patients with chronic dermatitis Hospitalized patients, antibiotic receipt, chronic illness of any kind Hospitalized patients, antibiotic receipt, chronic illness of any kind

Community-Associated MRSA without Identifiable Risk Factors Herold reported 25 fold increase in MRSA colonization in children at a Chicago Hospital Herold reported 25 fold increase in MRSA colonization in children at a Chicago Hospital Adcock day care centers with from 3-24% colonization- 40% in children with no contact with health care system Adcock 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 1999 Deaths of 4 children in MN/ND 1999 Herold et al JAMA 1998:279:593-8 Adcock et al JID 1998:178: MMWR 1999;48:707-10

Community outbreaks Native and aboriginal communities Native and aboriginal communities Sports teams Sports teams Child care centers Child care centers Military personnel Military personnel Men who have sex with men Men who have sex with men Prison inmates and guards 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. 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. 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. 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). 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 Penicillin=B-lactamases Resistance to Methicillin=Penicillin binding protein 2a (PBP 2a) Resistance to Methicillin=Penicillin binding protein 2a (PBP 2a) Alterations in PBP 2a carried on SCCmec Alterations in PBP 2a carried on SCCmec Nosocomial MRSA=SCCmec II and III Nosocomial MRSA=SCCmec II and III CA-MRSA=SCCmec IV CA-MRSA=SCCmec IV The USA300 strain The USA300 strain

Necrotizing pneumonia caused by CA-MRSA

Outcomes in Patients Treated for CA-MRSA 33% nonresponse at day 30 33% nonresponse at day 30 Failure related to lack of I & D (p=.005) Failure related to lack of I & D (p=.005) Failure not associated with wrong antibiotic choice Failure not associated with wrong antibiotic choice Trend for close contacts to develop a similar infection by day 30 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. 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. 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. The optimal regimen and duration of therapy for eradicating MRSA colonization is uncertain.

Topical regimen washes Chlorhexidine washes Mupirocin or Bactroban ointment applied to nares with a cotton-tipped applicator two to three times daily Mupirocin or Bactroban ointment applied to nares with a cotton-tipped applicator two to three times daily

Prevention of CA-MRSA Handwashing Handwashing Isolation Isolation Decolonization Decolonization Vaccination?? Vaccination??

Vaccine for Staph aureus Capsular polysaccharides serotypes 5 and 8 Capsular polysaccharides serotypes 5 and 8 Conjugated with protein from Pseudomonas exotoxin Conjugated with protein from Pseudomonas exotoxin Randomized trial in hemodialysis patients Randomized trial in hemodialysis patients Partial immunity, decreased Staph aureus bacteremias at 40 weeks Partial immunity, decreased Staph aureus bacteremias at 40 weeks By 54 weeks no difference By 54 weeks no difference ?booster doses ?booster doses Passive immunization Passive immunization