Epidemiology and Control of MethicillinResistant Staphylococcus aureus in hospitals Maria Kapi,MD Re

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Epidemiology and Control of Methicillin-Resistant
Staphylococcus aureusin hospitalsMaria
Kapi,MDRegistrar of Medical MicrobiologyLaiko
General Hospital of Athens, GreeceReadings MRSA
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What are MRSA?

• If we want to understand what are MRSA, we should
  first know
• What are Staphylococci?
• What is Staphylococcus aureus?

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What are MRSA?

• 3. What are penicillin and methicillin?
• 4. What are PBPs?
• 5. What are beta-lactams and beta-lactames?

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• Staphylococci Gram positive cocci ( from
  Greek staphyle, means bunch of grapes ) that
  occur singly and in pairs, short chains and
  irregular grape-like clusters.

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• Staphylococcus aureus is the staphylococcus
  which has the ability to clot plasma or in other
  words, which is coagulase positive. More than 80
  of Staphylococcous aureus strains produce
  beta-lactamases.

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• Penicillin is the antibiotic agent that
  Alexander Fleming a Scottish physician discovered
  in 1929. In 195 only 15 of
• S.aureus was susceptible to penicillin.
• Approximately 5 of S.
• aureus today are
  sensitive
• to penicillin.

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• Methicillin was with oxacillin the new line of
  penicillins in 1959, which became a new hope to
  the treatment of St. aureus. In 1961 the St.
  aureus became resistant to methicillin. Strains
  that are
• oxacillin and methicillin
• resistant, historically termed
• Methicillin-Resistant S.aureus
• (MRSA)

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• PBPs are penicillin-binding proteins. They are
  responsible for the final stages of peptidoglycan
  synthesis of the bacterial cell wall structure.
  Inhibition of one or more of these essential
  enzymes leads to bacterial lysis.

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• Beta lactams are the antibiotics that contain
  the beta lactam ring. These are penicillins,
  cephamycins, cephalosporins, carbapenems
  monobactams. The ring structure is common to all
  beta-lactams and must be intact for antibacterial
  action. They are cell
• wall synthesis inhibitors.

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• Beta lactamases are enzymes that catalyse the
  hydrolysis of the beta-lactam ring and inactivate
  these group of antibiotics. Genes encoding these
  enzymes are widespread in the bacteria.

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What MRSA are doing?

• Methicillin Resistant Staphylococcus aureus,
  when its cell is exposed to ß-lactam antibiotics,
  a supernumerary ß-lactam-resistant PBP (PBP2a),
  takes over the the biosynthetic functions of the
  normal PBPs. This protein is responsible for the
  methicillin resistance.

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Heteroresistance of MRSA

• All the cell in the population may have the
  genetic information for resistance , which is
  encoded by the mecA gene. Only a small number of
  cells can actually express the resistant
  phenotype under in vitro testing conditions. This
  phenomenon is termed heteroresistance.

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Why are MRSA important?

• Hospital acquired infections. MRSA are common
  nosocomial pathogens around the world.
• The treatment is very difficult. Vancomycin often
  is the only drug of choice for severe infections.

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Why are MRSA important?

• MRSA with reduced susceptibility to
  glycopeptides. Since 1996 has been identified in
  Europe, Asia and United States. That increases
  the possibility some strains became fully
  resistant to glycopeptides.
• MRSA are easily transmissible between patients.

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MRSA in Europe.

• In England and Wales, from
• January to December 1999
• methicillin resistance was
• 37 of the S.aureus reports.
• Except Scandinavia and
• Netherlands most countries
• have high rates of MRSA.

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MRSA in the United States

• From January till December 1999, 52,3 MRSA are
  associated with nosocomial infections in
  intensive care unit patients.
• 
  The increase
• 
  in resistance
• 
  is 37 from
• 
  1994-98.

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Epidemiology of MRSA

• Mode of Transmission. Is transmitted by
  contact with a person who has MRSA infection or
  is colonized with the organism.Hands of the
  health care workers is the most common mode of
  transmission from patient to patient.

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Epidemiology of MRSA

• Reservoirs .Colonized and infected
  patients are the major reservoir of MRSA.
  Although has been isolated from environmental
  surfaces, these are not the most likely source of
  spread.

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Epidemiology of MRSA.

• Risk factors. The factors that have been
  identified as increasing the risk of MRSA
  infection are
• Increased length of hospital stay
• Multiple hospitalizations
• Wounds

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Epidemiology of MRSA.

• Risk factors
• Invasive procedures
• Greater than 65 years old
• Severe underlying disease.
• Administration of broad-spectrum antibiotics.

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Costs of MRSA

• Directly attributable costs
• hotel costs of extended lengths of stay
• the cost of diagnostic procedures,
• morbidity and mortality that can follow infection
• glycopeptides are more expensive than other
  antibiotics e.t.c

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Costs of MRSA

• Costs of control
• costs of involvement of the infection control
  team.
• temporary closure of wards or theatres.
• re-deployment of staff.

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Control of MRSA in Hospitals

• General Principles
• Prevention of acquisition and spread of infection
  by patients and staff
• Priorities are high risk units, such as intensive
  care units and patients who are susceptible to
  infection.

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Control of MRSA in Hospitals

• Handwashing. Health care workers should wash
  their hands before and after contact with all
  patients, even when gloves are worn. A written
  protocol detailing proper hand wash technique
  should be available for reference.

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Control of MRSA in Hospitals

• Gloves should be worn when in contact with any
  body substance. Gloves should be changed and
  hands washed immediately after contact with each
  resident.
• Appropriate use of antimicrobials. Monitoring and
  auditing of drug use.

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Control of MRSA in Hospitals

• Isolation is necessary for infected patients and
  possible carriers in a single room or preferably
  in an isolation unit with designated staff.
  Isolation reduce staphylococcal cross-infection.

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Control of MRSA in Hospitals

• Ward Closure should be considered when new
  patients become infected with MRSA. The presence
  of strains of MRSA causing invasive infection is
  another indication.
• Screening of patients for MRSA at the nose,
  throat and perineum.

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Control of MRSA in Hospitals

• Carriage of MRSA by health care workers. During
  outbreaks staff should be reminded of the
  handwashing and transient carriage of MRSA. Staff
  with infected or colonized lesions should not be
  at work especially in critical areas, as
  intensive care units, cardiothoracic words e.t.c.

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Control of MRSA in Hospitals

• Treatment of carriers. Nasal carriage is treated
  topical with mupirocin.
• Systemic treatment of infections The glycopeptide
  antibiotics are currently the agents of choice
  for treatment.
• Microbiological characterization of MRSA.

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Antimicrobial resistance is a major threat to
public health.

• Bacterial resistance to multiple antibiotics
  characterises the present decade. Finding
  organisms resistant to over 10 different
  antibiotics is not unusual. Globally we need to
  look at how antibiotics are used and
• reduce their inappropriate use.