MRSA

MRSA is a major nosocomial pathogen
Causes severe morbidity and mortality worldwide
Endemic in many European and American hospitals
40% of nosocomial Staph. aureus infections are methicillin resistant
Many in-patients are colonised ot infected
25% hospital personnel may be carriers
Found on inguinal, perinea, or axillary skin and anterior nares
Spread by hand, usually of health care workers

Microbiology

Staph aureus is a gram-positive coccus
Forms clusters on culture medium
Methicillin resistance is mediated by the mecA gene
Encodes a single additional penicillin binding protein PBP2a
Expression of mecA can be either constitutive or inducible

Risk factors for MRSA colonisation

Advanced age
Male gender
Previous hospitalisation
Length of hospitalisation
Stay in ICU
Chronic medical illness
Prior and prolonged antibiotic therapy
Presence and size of a wound
Exposure to colonised or infected patient
Presence of invasive indwelling device

Clinical presentations

Pneumonia
Surgical site infections
Line sepsis
Intra-abdominal infections
Osteomyelitis
Toxic shock syndrome

Infection control

Screening of patients and staff
Hand washing
Use of gowns and gloves
Topical antimicrobials
Isolation of patients
Environmental cleaning

Management

Vancomycin is the antibiotic of choice
Teicoplanin may be used if the isolate is resistant to vancomycin
Linezolid is new class of antimicrobial agent
Active against MRSA and VRE
Quinupristin / dalfopristin are newer alternative

Bibliography

Haddadin A S, Fappiano S A, Lipsett P A. Methicillin resistant Staphylococcus aureus (MRSA) in the intensive care unit. Postgrad Med J 2002; 78: 385-392.

Hardy K J, Hawkey P M, Gao F et al. Methicillin resistant Staphylococcus aureus in the critically ill. Br J Anaesth 2004; 92: 121-130.

Loeb M, Main C, Walker-Dilks C et al. Antimicrobial drugs for treating methicillin-resistant Staphylococcus aureus colonization. Cochrane Database Syst Rev 2003: CD003340.

Simor A E. Containing methicillin resistant Staph aureus: Surveillance, control and treatment methods. Postgrad Med 2001; 110: 43-48.