Title: Epidemiology and Control of Methicillin-Resistant Staphylococcus aureus in hospitals Maria Kapi,MD Registrar of Medical Microbiology Laiko General Hospital of Athens, Greece Readings: MRSA
1Epidemiology and Control of Methicillin-Resistant
Staphylococcus aureusin hospitalsMaria
Kapi,MDRegistrar of Medical MicrobiologyLaiko
General Hospital of Athens, GreeceReadings MRSA
2What are MRSA?
- If we want to understand what are MRSA, we should
first know - What are Staphylococci?
- What is Staphylococcus aureus?
3What are MRSA?
- 3. What are penicillin and methicillin?
- 4. What are PBPs?
- 5. What are beta-lactams and beta-lactames?
4- Staphylococci Gram positive cocci ( from
Greek staphyle, means bunch of grapes ) that
occur singly and in pairs, short chains and
irregular grape-like clusters.
5- 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.
6- 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.
7- 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)
8- 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.
9- 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.
10- 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.
11What 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.
12Heteroresistance 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.
13Why 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.
14Why 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.
15MRSA 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.
16MRSA 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.
17Epidemiology 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.
18Epidemiology 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.
19Epidemiology 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
20Epidemiology of MRSA.
- Risk factors
- Invasive procedures
- Greater than 65 years old
- Severe underlying disease.
- Administration of broad-spectrum antibiotics.
21Costs 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
22Costs of MRSA
- Costs of control
- costs of involvement of the infection control
team. - temporary closure of wards or theatres.
- re-deployment of staff.
23Control 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.
24Control 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.
25Control 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.
26Control 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.
27Control 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.
28Control 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.
29Control 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.
30Antimicrobial 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.