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5-AB Resistance mrsas -1


Methicillin resistant Staphylococcus aureus (MRSA) in humans and animals Update march 2008 Overview of SA & MRSA in human Staphylococcus aureus (SA) is part of normal ... – PowerPoint PPT presentation

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Title: 5-AB Resistance mrsas -1

Methicillin resistant Staphylococcus aureus
(MRSA) in humans and animals
Update march 2008
Overview of SA MRSA in human
  • Staphylococcus aureus (SA) is part of normal
    human bacterial flora, and is found primarily in
    the nares
  • SA can causes serious invasive infections
    including endocarditis, osteomyelitis,
    bacteriema, pneumonia and toxic shock syndrome.

SA MRSA treatments
  • Before penicillin mortality rate from invasive SA
    was 90
  • Penicillin has a dramatic effect
  • However resistance developed
  • Introduction of Methicillin in 1950 to the
    treatment of SA resistant to penicillin

  • Antibiotic methicillin introduced into clinical
    practice in 1959
  • Semi synthetic penicillin
  • First resistance reported in 1961 in UK
  • Pour en savoir plus sur la meticilline

Methicillin-resistant Staphylococcus aureus
  • The organism is often sub-categorized as
    Community-Associated MRSA (CA-MRSA) or
    Hospital-Associated MRSA (HA-MRSA) depending upon
    the circumstances of acquiring disease, based on
    current data that these are distinct strains of
    the bacterial species

MRSA as a leading cause of nosocomial infections
MRSA in human nosocomial infections
  • Major cause of morbidity and mortality in human
    Intensive Care Units (ICU)
  • Up to 50 staphylococcal infections in human ICUs
    are now due to MRSA
  • Transmission via transiently colonised hands of
    health care workers
  • Hospital acquired strains commonly resistant to
    multiple classes of antibiotics

S. aureus nosocomial infections in humans
  • Superficial infections
  • Wound infections
  • Catheter infections
  • Endocarditis
  • Bacteraemia with sepsis
  • Mortality of around 50

MRSA transmission
  • Hand-to hand transmission
  • From infected patients
  • From environment
  • Floor
  • (27 of surface in room of MRSA positive
  • Door handles
  • Computer
  • etc

MRSA has become a major nosocomial pathogen in
human hospital
  • Cause concern by
  • because of the extent of antimicrobial resistance
    (to many antibiotics)
  • Potential for transmission among patients and
    hospital personnel

MRSA treatment
  • MRSA are sensitive to vancomycin, teicoplatin,
    nitrofurantoin, rifampicin, linezolid and

MRSA mechanisms of resistance
MRSA in humanmechanisms of resistance
  1. Methicillin resistance in SA is encoded by the
    mecA gene, which is located on a mobile genetic
    element called the Staphylococcal Cassette
    Chromosome mec (SCCmec)
  2. This gene encode a penicillin binding protein
    (PBP2) that has a low affinity for beta lactams
    and confers resistance to all beta lactam
    antibiotic including cephalosporins

MRSA epidemiology
MRSA epidemiology
  • In human, fist reported in UK in 1961 and now a
    world-wide problem
  • In animal, first reported in 1972 (milk of
    mastitic cow)

MRSA in human prevalence
  1. in US SA32 and MRSA0.84
  2. In Japan MRSA67 .

MRSA epidemiology
  • up until recently, MRSA was primarily associated
    to hospital acquired infections but has now been
    involved as a community-acquires bug

Overview of SA MRSA in humanepidemiological
facts (US 2005)
  • The standardized incidence rate of invasive MRSA
    was 31.8 per 100 000 persons year
  • The standardized mortality rate was 6.3 per 100
    000 and extrapolation to a national level
    predicted about 19000 deaths annually associated
    to MRSA i.e more deaths than attributed to AIDS
    in that year!
  • A meta-analysis studies found that the risk of
    mortality due to invasive MRSA infections was
    approximately twofold that seen with invasive
    methicillin sensitive SA

MRSA in animals
SA in animals
  • A ubiquitous commensal with a host range that
    span to all vertebrates
  • In domestic animals, SA is primarily an
    opportunistic pathogen associated with sporadic
  • but it is a major etiological agent of bovine
  • An Update on Staphylococcus aureus Mastitis

MRSA in animals
  • In animal, first reported in 1972 (milk of
    mastitic cow)

MRSA in animals
Davies P Methicillin resistant Staphylococcus
aureus people, pigs and pets In Am Assoc Swine
Vet 2008 P15-20
MRSA in animals
MRSA transmission between animals to man
  • Until recently, it was accepted that epidemiology
    of transmission and antimicrobial resistance of
    MRSA were essentially confined to the human
    arena, and that animals reservoir were of
    negligible importance
  • Animal can act as reservoir of MRSA ( cat, dogs,
    horse, chicken, rabbit, pig, guinea pigs, turtle,
    parrot, etc.)
  • Currently we have evidences of MRSA
    animal-to-human transmission (e.g from horse to

MRSA in animals
  • SA is a highly versatile organism that
    demonstrates a considerable degree of adaptation
    among host species explaining that interspecies
    transmission is a common event

MRSA in animals
  • 11 dogs from USA/UK with clinical MRSA infection
    reported in 1999
  • Increasing isolation rate by UK veterinary
    clinical microbiology laboratories
  • Recent reports of an outbreak in a Canadian
    equine hospital
  • Horse and humans had same MRSA
  • 9.6 environmental sites cultured positive
  • 4.7 of horses are colonised

MRSA transmission between animals to man
  • recently, 2 outbreaks of infections in separate
    vet teaching hospitals in US and Canada
  • In US, the hospital staff were the primary source
    of infection
  • In Canada, environmental contamination (stalls
    housing MRSA-positive horses)

MRSA in horse (Ontario Vet College 2002)
  • Asymptomatic nasal carriage of MRSA in 26
    hospitalized horses and 16 vet personnel

To read the full article
MRSA at Ontario
  • Canadian epidemic MRSA 5 (CMRSA-5)
  • Indistinguishable from an uncommon human isolate,
    and it is suspected that this strain originated
    in people but has adapted for survival in horses
  • Now being propagated in the equine population
  • High prevalence of colonization on some horse
  • Horse can transmit MRSA to vet personnel

Isolation of MRSA from environment in a vet
teaching hospital (Weese 2002)
  • Stalls MRSA positive horses62
  • Stalls MRSA negative horses6.9
  • Medical equipment 5.6
  • Floors 0
  • Personal equipment (clinician)4.8
  • twitches10.5
  • Horse handling equipment, soap dispenser,

  • Colonisation is transient and elimination within
    few weeks if no re-infection from other horses
  • Treatment
  • Avoid to use vancomycin and related antibiotics
    in horse (ethical reasons)
  • Other treatments to be validated (e.g.
    antimicrobial nebulization)

MRSA An Irish survey 2005 (1)Objectives
  • To report the isolation of MRSA from animals and
    their corresponding personnel attendants
  • To investigate relationship between the isolates
    from animals and the vet staff
  • To investigate relationship between the isolates
    from animals and general human population to
    elucidate whether human-to-animal or
    animal-to-human transmission might have occurred

MRSA An Irish survey 2005 (2)sampling
  • Recovery of MRSA in animals with respiratory,
    urinary tract or wound infection and animal
    subjected to surgery following treatment in 1 vet
    hospital and 16 private vet clinics
  • MRSA was recovered from 25 animals ( 14 dogs, 8
    horses, 1 cat, 1 rabbit 1 seal) and also 10
    attendant vet personnel (healthy carriers)

MRSA An Irish survey 2005 (2)Epidemiological
  • Epidemiological typing by antibiogram-resistogram
    (AR) typing, biotyping and by chromosomal DNA
    restriction fragment length polymorphism analysis
    using SmaI digestion followed by pulsed field gel
    electrophoresis (the gold standard for DNA
    fingerprint of MRSA)

MRSA An Irish survey 2005 (3)Results
  • Clinical susceptibility testing suggested that
    the 35 isolates from animals fell into 2 groups
  • Group1 (non-equine isolates) ressistant to 1
    or more of the following AB (macrolides,
    lincosamines, tetra and/or fluoroquinolones
  • Group2 (equine isolates) resistant to
    macrolides, aminoglycosides, tetra, TMP/sulfa and
    variably rsistant to fluoroquinolones,
    lincosamines and rifampicin

MRSA An Irish survey 2005 (4)Epidemiological
typing confirmed the 2 major clusters
  • Most non-equine isolates were indistinguishable
    from each other and from the isolates from
    personnel caring for these animals
  • MRSA isolated from horses and from their
    attendant personnel were indistinguishable and
    were unlikely the pattern obtained from other
    animal isolates

MRSA An Irish survey 2005 (5) Comparison of
isolates from vet sources with patterns from MRSA
recovered in human hospital
  • It was shown that the most frequently occuring
    pattern of MRSA from non-equine animals was
    indistinguishable from the predominant pattern
    obtained from the most prevalent MRSA strain in
    the human population

MRSA An Irish survey 2005 (5)
  • Pattern of isolates from horses were unlike any
    pattern previously reported in man isolates

MRSA An Irish survey 2005 (6)
  • 2 strains of MRSA is occurring in vet practice
    and one of the strain (non-equine) may have
    arisen from human hospital
  • The souce of the second strain (equine) remains
    to be determined

MRSA in food producing animals
MRSA in animals the 3 key questions
  1. What is the relative importance of animal
    reservoirs and animal-to-human transmission of
    MRSA (particularly in relationship to the
    increase in community acquired disease)
  2. What is the role of antibiotic use in food
    animals and companion animals in the epidemiology
    of MRSA in animal reservoir
  3. What is the risk of farm-to-table foodborne
    transmission of MRSA via meat?

MRSA in swine
  • Several species of staphylococci, including SA, S
    hyicus and S epiermidis can be routinely isolated
    from domestic pigs and can be considered part of
    the normal flora of swine
  • No specific disease associated to SA in pigs

  • A French studies has documented antimicrobial
    resistance of commensals in pigs and pig farmers,

In that study, 5 MRSA isolates were found in
pigs, including one strain (ST 398 on multilocus
sequence typing) that has since been associated
with pigs in other countries. A small number of
pig associated strains were found in farmers
across a wide geographic range in France, leading
the authors to conclude that pig farming could be
a risk factor of staphylococcal infection of
farmers. To read the full article
MRSA in swine
  • A national Dutch survey of 540 pigs slaughtered
    in nine slaughterhouses, found 39 of the pigs
    (and 44 out of 54 groups of pigs) to be positive
    for MRSA in their nares.
  • 39 All the isolates belonged to a single clonal
    group, MLST 398,
  • Dutch studies estimate the prevalence of the
    ST398 clone in people with occupational exposure
    to pigs to be 760 times higher than that of the
    general population.
  • investigations in other European countries
    (Belgium, Germany, Denmark) indicate that the
    occurrence of MRSA in swine is not a problem
    limited to the Netherlands

MRSA foodborne route of transmission
  • S aureus can frequently be isolated from pig
    carcasses, though generally resistant isolates
    have not been predominant
  • However concerns about foodborne risk have been
    reinforced by the first report of a life
    threatening infection with the pig ST 398
    MRSA-strain in a 63-year-old Dutch woman who was
    not exposed to pigs, suggesting indirect
    (possibly foodborne) routes of transmission.

MRSA in pigs
  • The role of antibiotic use remains uncertain
  • isolates have been almost uniformly resistant to
  • a study of 65 pig associated MRSA in Holland
    found all isolates were sensitive to vancomycin,
    teicoplanin, nitrofurantoin, rifampicin,
    linezolid, and quinupristin-dalfopristin, with
    variable sensitivity to erythromycin (40),
    clindamycin (48), cotrimoxazole (48),
    aminoglycosides (92), and quinolones (94)

MRSA colonization is an occupational risk for
veterinary professionals
MRSA was isolated from nares of 27/417 (6.5)
attendees at an international veterinary
conference 23/345 (7.0) veterinarians, 4/34
(12.0) technicians, and 0/38 others.
To read the full article
MRSA in vets
In Clin Microbiol Infect. 200814 (1)29-34.
To read the full article
MRSA in vets (Wulf et al 2008)
  • A convenience sample of 272 participants at an
    international conference on pig health in Denmark
    was screened for MRSA carriage using combined
    nose / throat swabs and were asked to complete a
    questionnaire concerning animal contacts,
    exposure to known MRSA risk-factors, and the
    protective measures taken when entering pig
  • In total, 34 (12.5) participants from nine
    countries carried MRSA.
  • Thirty-one of these isolates were non-typeable
    by pulsed-field gel electrophoresis
  • All of the non-typeable isolates belonged to spa
    types (t011, t034, t108, t571, t567 and t899)
    that correspond to multilocus sequence type 398.
  • Protective measures, e.g., masks, gowns and
    gloves, did not protect against MRSA acquisition.
  • Transmission of MRSA from pigs to staff tending
    to these animals appears to be an international
    problem, creating a new reservoir for
    community-acquired MRSA (CA-MRSA) in humans in
    Europe, and possibly worldwide.
  • .

To read the full article
MRSA in animalWhat to do?
  • If MRSA become endemic, the problem is extremely
    difficult to control
  • Aggressive infection control measures can be
    successful if applied when MRSA is first
    recognized in an institution
  • Guidelines for the control of MRSA in animals
    need to be formulated as a matter of urgency to
    minimise futur problems
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