11

Hospital-acquired and Hospital-acquired and community-acquired MRSA in community-acquired MRSA in

hospitalshospitals..

22

Hospital-acquired methicillin Hospital-acquired methicillin resistant resistant s.aureuss.aureus

• High percentage of hospital S.aureus isolates has been found to be also resistant to methicillin

or oxacillin .• Antibiotic resistant is caused by chromosomal

acquisition of the gene for a modified penicillin-binding protein.This protein codes for a new peptidoglycan transpeptidase with a low affinity for all currently available beta-lactam antibiotics,and thus renders infections with methicillin-resistant S.aureus unresponsive to beta-lactam therapy.

33

•Community –acquired methicillin –ristant S.aureus:

• MRSA emerged in the community setting occurring among young healthy individuals with no exposure to the healthcare setting.since then this CA-MRSA has rapidly spread throughout the world.Outbreaks of CA-MRSA have been reported among children,athletes,nurseries and

obstertical wards.

44

..

•The patients in the hospital are divided into five compartments:

-number of susceptible patients.•-number of patients colonized with the CA- MRSA strain.

•-number of patients colonized with the HA- MRSA strain .

•-number of patients infected with the CA-MRSA strain

•-number of patients infected with the HA-MRSA strain.

55

Estimated methicillin-resistant Estimated methicillin-resistant S.aureusS.aureusMRSA-related hospitalization rates duringMRSA-related hospitalization rates during7 years7 years

66

Pediatric pneumonia caused by Pediatric pneumonia caused by CA-MRSACA-MRSA

• CA-MRSA, which carries genes for Panton-Valentine leukocidin (PVL), has become a major concern worldwide. CA-MRSA is mainly associated with skin and soft tissue infections in young, otherwise healthy, persons in the community and also with life-threatening sepsis and community-acquired pneumonia (preceded by influenza). PVL, in combination with staphylococcal protein A, destroys respiratory tissue and bacteria-engulfing immune cells.

)6(

77

..

•Necrotizing Fasciitis is a life-threatening infection of the superficial muscle fascia and adjacent subcutaneous tissue. staphylococcus aurous has been occasionally reported as a monomicrobial causative agent of necrotizing fasciitis and methicillin-resistant staphylococcus aureus was described as the cause of hospital-

associated necrotizing.

88

..

•Necrotizing fasciitis of the back caused by MRSA. The lower back showed erythematous lesions with skin necrosis.

99

.. •Some studies suggest that CA-MRSA will become the dominant MRSA strain in the hospital setting and other studies shown that when no colonized or infected patients enter the hospital, competitive exclusion of HA-MRSA by CA-MRSA will occur with increased severity of CA-MRSA infections resulting in longer hospitalizations and a larger in-hospital reservoir of CA-MRSA. Improving compliance with hand hygiene and decolonization of CA-MRSA carriers

are effective control strategies. .

1010

..

•.