Community-Associated MRSA Infections Roger D. Smalligan, MD, MPH Assistant Professor of Internal Medicine and Pediatrics Quillen College of Medicine East Tennessee State University

Staphylococcus aureus

History of MRSA 1961 – 3 isolates of MRSA discovered among 5000 isolates in Great Britain 1980s – became common in hospitals 1990s – spread to nursing homes and communities

Methicillin Resistance - Mechanism Methicillin binds to PBP (Penicillen Binding Protein - cell wall protein) and inactivates it MRSA has PBP2a - beta-lactams cannot attach

Methicillin resistance – gene location PBP2a - encoded by mecA gene mecA - on Staphylococcal Cassette Chromosome (SCC)

HA & CA MRSA are genetically distinct Hospital-associated (HA) MRSA have SCCmecA types I-III Community-associated (CA) MRSA have SCCmecA type IV or V

Genetically distinct CA-MRSA HA-MRSA (SCCmecA Type II) (SCCmecA Type IV) HA-MRSA (SCCmecA Type II)

CA-MRSA strains USA 400 clone – initially identified in midwest – now nationwide Pharmacotherapy. 2005 Jan;25(1):74-85 USA 300 clone – identified in 99% of CA-MRSA infections in Atlanta recently Ann Intern Med 2006;144:309-317

HA-MRSA CA-MRSA SCCmecA I-III SCCmecA IV-V Chronically ill Young, athletes, prisoners Hospital / healthcare No healthcare contact Previous antibiotics No previous treatment Multi-drug resistant Usually susceptible still IV cath/surgical wounds Skin infections / boils Bacteremia without focus Necrotizing pneumonia

CA-MRSA: CDC definition Positive MRSA culture as an outpatient or within 48 hours of admission No previous history of MRSA No surgery / admission / nursing home / dialysis unit in past year No indwelling catheters or devices

MRSA Awareness in Sports MRSAAwareness.com

CA-MRSA Risk Groups Prison inmates Injection drug users Men who have sex with men HIV-infected individuals Competitive sports participants US Army soldiers Children attending daycare

CA-MRSA in the Emergency Room August 2004 study of 11 ERs Skin & soft tissue infection cultures N=422; 76% Staph, 59% MRSA (98% of these SCCmecA IV PVL positive) Only 43% received appropriate antibiotics NEJM 2006;355:666

CA-MRSA in the ER Atlanta Hospital (Grady) – over 3 months 384 skin / soft tissue infections 68% CA-MRSA 2/3 received inadequate antibiotics (initially) Ann Intern Med 2006;144:309-317 >50 <18 35-49 18-34 Age of patient

CA-MRSA in general population 10 studies (8350 people) 1.3% pooled MRSA nasal colonization rate for community studies (0.2-7.4%) 0.2% MRSA prevalence among Salgado CD, et al. Clin Infect Dis 2003;36:131-9

CA-MRSA in US Soldiers 812 were screened with nasal swabs 28% were colonized with S. aureus (MSSA) 3% developed skin infections 3% colonized with MRSA 38% developed skin / soft tissue infections (10 weeks) Ellis MW, et al. Clin Infect Dis 2004;39:971-9

Panton-Valentine leukocidin (PVL) Extracellular cytotoxin leukocyte destruction tissue necrosis Most CA-MRSA produce this toxin

CA-MRSA Clinical Spectrum 77% skin and soft tissue folliculitis cellulitis furuncle, carbuncle, abscess 6% invasive pneumonia / empyema bacteremia septic arthritis osteomyelitis pyomyositis / necrotizing fasciitis

The “spider bite” trap

CA-MRSA Outpatient Treatment I & D of small abscesses +/- antibiotics SEND A CULTURE! Oral antibiotic options: - TMP/SMX - doxycycline plus rifampin - clindamycin (think “D-test”) - linezolid

JCMC Antibiogram Vanc SXT Clinda Gent Linezo JCMC MRSA 2005 100% 94% 62% 92% 99% JCMC MRSA 2006 75% 96%

JCMC MRSA Sensitivity Report SPEC#, TYPE: NARES MICROBIOLOGY Feb 21, 2007 12:48 FINAL REPORT METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS ISOLATED This {S. aureus} is presumed to be clindamycin resistant based on detection of inducible clindamycin resistance. ISOLATE 1 STAPHYLOCOC CIPROFLOXACIN >=8 R CLINDAMYCIN <=0.25 S ERYTHROMYCIN >=8 R GENTAMICIN <=0.5 S LEVOFLOX >=8 R LINEZOLID 2 S OXACILLIN >=4 R ` PENICILLIN >=0.5 R RIFAMPIN <=0.5 S SXT <=10 S TETRACYCLINE >=16 R VANCOMYCIN <=1 S

“Bowling Bummer” 15yo young man fell and hit knee 2 weeks prior Sprain diagnosed in ER Pain/swelling persisted – dx - hairline fracture Developed fever and agitation No history of recent infections or sick contacts

PMH: unremarkable PE: ill appearing, T 101, P 138, RR 40, O2 sats 92% on 2L CV- RRR no m/r/g Lungs- clear Right leg – swollen/warm/tender but no overlying erythema or skin lesions

Labs: WBC 50.2 with 27% bands HCT 26 ESR 87 Blood, urine, nasal cultures grew MRSA

ICU Course: Remained critical for weeks on vancomycin / gent / rifampin and eventually linezolid Complications included: Respiratory failure due to necrotizing pneumonia / empyema Pyomyositis Septic arthritis (hip, knee, elbow) Osteomyelitis (pelvis, femur, tibia)

CA-MRSA Inpatient Treatment IV antibiotics: (Consider an ID consult!) vancomycin linezolid clindamycin (if susceptible) daptomycin tigecycline New drugs on the horizon

CA-MRSA Prevention Cover all wounds with clean dressings Wash hands frequently Practice good hygiene Don’t share towels, razors, combs, etc. Clean sports equipment used by others Get tested - mupirocin for carriers +/- polysporin for failures

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