Methicillin resistant S.aureus (MRSA) Dr Ritabrata Kundu Professor of Pediatrics Institute of Child Health, Calcutta.
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Methicillin resistant S.aureus (MRSA) Dr Ritabrata Kundu Professor of Pediatrics Institute of Child Health, Calcutta DEFINITIONS • Staphylococcus aureus gram positive coccus. • Resistant to penicillin by enzyme lactamase or penicillinase. • Penicilllinase resistant penicillin like methicillin (MSSA). • Methicillin resistant S. aureus (MRSA) by altering the penicillin binding protein (PBP2a). Characteristics of the -Lactam Ring 6-Aminopenicillanic acid Antibiotic inactivation due to enzymatic cleavage of beta lactam ring by beta lactamase Modified penicillin binding protein (PBP) site makes methecillin inactive Types of MRSA • Nosocomial MRSA – increasing prevalance • Community acquired MRSA (CA MRSA) • VISA – Since 1996 • VRSA – June 2002 Pathogenesis • S. aureus colonizes nares, axillae, vagina etc. • Mucin appears to be the critical host surface. • Spread by Direct contact with infected people. Indirect contact by touching contaminated object. Not through the air. • Presence of foreign material or devices. Clinical presentation of CA MRSA • Skin infections – Bacteriocin High salt tolerance Panton-Valentine Leukocidin (PVL) • Necrotising pneumonia • Other presentation Toxic shock syndrome like illness Osteomyelitis Mediastinitis Furunculosis Cellulitis Clinical Presentation of Nosocomial MRSA • Pneumonia – Ventilator associated pneumonia (VAP). • Bacteremia – 16% of all nosocomial bacteremias. • Metastatic involvement of bones, jts, kidneys and lungs. • Endocarditis. • Surgical site infections (SSI). Risk factors for MRSA carriage Previous colonization (nasal/cutaneous) Age > 60 yrs Exposure MRSA infected/colonized patient Host factors • H/o ICU stay/surgery in last 5 yrs • Prolonged hospital stay>21 days • Open skin lesion • Increased antibiotic exposure Chronic medical illness l Diabetes mellitus Type I l Patients on hemodialysis Impaired immune function • AIDS • Quantitative/Qualitative leukocyte dysfunction Why increased incidence of MRSA colonization? 1. Cephalosporine/Quinolines/ lactams are readily excreted in sweat. 2. CA MRSA carry small SCC mec type IV gene which grows and spreads faster. 3. Bacteriocins reduces other commonsel flora. 4. CA MRSA higher tolerance to salt helps to survive as skin flora. Susceptibility of MRSA Nosocomial MRSA Multiresistant Current antibiotic in use : Vancomycin Daflopristin-quinupristin Linezolid Tigecycline (Tygacil) Daptomycin CA MRSA Suceplibility to variety of non beta lactam antibiotic : Erythromycin Clindamycin Tetracycline Aminoglycosides Cotrimoxazole Quinolones Non beta lactam antibiotics Clindamycin – Bacteriostatic, should not be used treat serious infection. Inducibe resistance. Rifampicin – Should not be used alone. Gentamycin – Added for synergy. Ciprofloxacilin – Not consistently associated with high cure rate. Teicoplanin – A derivative of vancomycin. Empirical antibiotic therapy for suspected staph. infection •Prevalance of MRSA in the community. •Presence/absence of health care associated risk factors. •Severity and type of clinical presentation. Suggested initial empiric therapy with suspected Staph. infection in pts with healthcare associated risk factor First line agents Severe infection Vancomycin Second line agents Linezolid, Quinupristin/ dalfopristin, Daptomycin For empiric treatment add penicillinase resistant penicillin Non severe infection Penicillinase resistant pencillin First generation cephalosporine Vancomycin Linezolid Cotrimoxazole Clindamycin Tetracycline Suggested initial empiric therapy with suspected Staph. infection in pts. with out healthcare associated risk factor First line agents Severe infection Vancomycin Second line agents Linezolid, Quinupristin/ dalfopristin, Daptomycin Penicillnase resistant penicillin PLUS one of the following : Cotrimoxazole, Clindamycin, Tetracycline Non severe infection Penicillinase resistant penicillin First generation cephalosporine Cotrimoxazole Clindamycin Tetracycline Infection Control Methods for Methicillin Resistant Staphylococcus Institute of Child Health, Calcutta Golden Jubilee Celebration 22-26 January 2006 Thanks and warm welcome to all of you Prevent antimicrobial resistance at healthcare settings 1. Prevent infection. 2. Diagnose and treat infections effectively. 3. Use antimicrobial wisely. 4. Prevent transmission – decolonisation with mupirocin.