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MRSA AND ANTIBIOTIC-RESISTANT STAPHYLOCOCCI IN DOGS AND HORSES

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Presentation on theme: "MRSA AND ANTIBIOTIC-RESISTANT STAPHYLOCOCCI IN DOGS AND HORSES"— Presentation transcript:

1 MRSA AND ANTIBIOTIC-RESISTANT STAPHYLOCOCCI IN DOGS AND HORSES
Department of Veterinary Clinical Sciences, Leahurst, University of Liverpool, United Kingdom MRSA AND ANTIBIOTIC-RESISTANT STAPHYLOCOCCI IN DOGS AND HORSES Thomas W. Maddox BVSc CertVDI MRCVS

2 BACKGROUND Antimicrobial-resistant bacteria (especially MRSA) are recognised as an important and increasing problem in both human and veterinary medicine

3 BACKGROUND Infections resulting from resistant organisms increasingly reported Limited range of antibiotics available for animal use (especially for horses) New antibiotics likely slower in development (especially for horses) Zoonotic potential of antibiotic resistant bacteria Future restrictions on antibiotic use possible? Antimicrobial-resistant bacteria (especially MRSA) are recognised as an important and increasing problem in both human and veterinary medicine

4 BACKGROUND Antimicrobial-resistant bacteria (especially MRSA) are recognised as an important and increasing problem in both human and veterinary medicine

5 BACKGROUND Antimicrobial-resistant bacteria (especially MRSA) are recognised as an important and increasing problem in both human and veterinary medicine

6 BACKGROUND 228 cases reported of MRSA in horses
Variety of sites of infection (similar to other animals and humans) Figure courtesy of C. Scantlebury

7 BACKGROUND 228 cases reported of MRSA in horses
Variety of sites of infection (similar to other animals and humans)

8 80% of Staphylococcus aureus strains produce a
STAPHS IN ANIMALS Staphyloccus aureus Most common Staph. of people with 28-39% nasal colonisation (also throat, axilla, perineum and groin) Unknown prevalence in animals but likely lower Other staphylococci S. (pseud)intermedius in dogs, coagulase-negatives (S. epidermidis) Coagulase-negatives more common in horses (S. scuiri) 80% of Staphylococcus aureus strains produce a b-lactamase enzyme Methicillin-resistance mediated by production of alternative penicillin binding protein (PBP2a) which is the normal target for b-lactam antibiotics

9 RESISTANCE IN STAPHS SCCmec cassette
Gene cassette (mobile genetic element) Codes for PBP2a on the mecA gene (plus several other genes). 7 types of varying size and composition (and sub-types)

10 MRSA TYPING Macro restriction pulsed-field gel electrophoresis
Chromosomal DNA extracted and then digested into many (large) fragments by restriction enzymes (Sma1) Band pattern of various sizes produced on PF gel Compare bands to identify MRSA type Gold standard for strain typing MRSA BUT... inter-laboratory comparison difficult

11 MRSA TYPING Multi-locus sequence typing
PCR amplification of housekeeping gene fragments at 7 loci on chromosome These then sequenced and submitted to database to compared with known alleles Each isolate will then have a 7 integer “profile” which can be used to identify its sequence type (eg ). Sequence types (ST) named arbitrarily Grouped into clonal complexes (CC) named after first ST identified (eg ST30-MRSA was first member of CC30)

12 MRSA TYPING spa gene typing
Amplification and sequencing of a single gene loci Target is region X of the (serum) protein A gene Region X has varying number of 24 base pair repeats Highly polymorphic between MRSA types From size of fragments produced by PCR can estimate number of repeats (not actually interested in sequence itself) Normally compared with MLST-types as easier way to identify ST

13 MRSA TYPING SCCmec typing Variable Number Tandem Repeat Typing
PCR amplification of several genes within the SCCmec to differentiate between types and allow sub-typing Simple band pattern produced on gel Variable Number Tandem Repeat Typing Regions of short repeating sequences of differing length found at various loci throughout chromosome Amplified by PCR and run on gel to produce banding pattern PCR of mecA and femA/nuc genes PCR amplify these genes for identification/molecular confirmation of methicillin-resistance and S. aureus respectively

14 MRSA IN ANIMALS Epidemiology
Small animals MRSA isolates in UK are mostly EMRSA 15 (same as predominant health care strain)1,2 EMRSA type 16 seen to a lesser extent Mostly SCCmec IV Equine isolates are more variable, rarely EMRSA 15 or 16 and have greater range of reistance3 In-contact humans may have same types (unusual for humans) Rarely other than SCCmec IV4 Same types seen in small animal vets and owners. MRSA carriage in vets approx 10% (10 x public) Situation in UK, vs USA. Europe more MRSPI seen Baptiste, K.E. et al (2005) Emerg Inf Diseases, 11(12,) Loeffler, A., et al(2005) J Antimicrobial Chemotherapy, 56(4) Cuny, C., et al (2008) Microbial Drug Resistance, 14(4) Weese, J.S. (2007) Vet Rec, 161(10)

15 MRSA IN ANIMALS Epidemiology
Difference of colonisation versus clinical infection Also transient carriage vs persistent colonisation

16 Colonisation of hospitalised/unwell horses ranges
MRSA IN HORSES Epidemiology Varying prevalence of nasal colonisation reported of 0-12% for horses in the community1-3 Colonisation of hospitalised/unwell horses ranges from %4,5 (3.5% at PLEH) Resistance patterns variable (usually gentamicin, sometimes tetracyclines and/or TMS, occasionally fluoroquinolones) Usually spa or MLST typed as belonging to CC8 (eg ST8 or ST254) In-contact humans may have same types (unusual for humans) 44 farms some which had upto 45% MRSA prevalence Burton et al (2008) Can. Vet. J. 49(8) Vengust et al (2006) Let Appl Microbiology 43(6) Weese (2005) JAVMA 226(4) Van den Eede et al (2009) Vet. Microbiology 133(1-2) Weese et al (2006) JVIM 20(1)

17 Colonisation of hospitalised/unwell dogs reported at
MRSA IN DOGS Epidemiology MRSA colonisation has not been identified in healthy dogs in the community1-2 Colonisation of hospitalised/unwell dogs reported at 9-23%3,4 (3% at SATH) Resistance patterns more consistent (usually fluoroquinolones, occasionally tetracyclines and/or TMS, rarely gentamicin) SCCmec type IV (occasionally type II or V5) Usually spa or MLST typed as ST22 or ST36 In-contact humans may have similar types (common to humans) 23% from outbreak cluster Part of small study (35 dogs) Baptiste 2005 UK situation Lisa Williams abstract Rescue Kennels Murphy et al (2005) J Vet Int Med. 19 Bagcigal et al (2007) Vet Microbiol 121 (3-4) Loeffler (2005) J Antimicr Chemotherapy 56 (4) Baptiste (2005) Emerg Inf Disease Witte et al 2007 Emerg Inf Disease 13 (2)

18 MRSA IN ANIMALS ST398-MRSA
New “untypeable” (spa t011) strain of MRSA first identified in 2005 Cause of disease in humans and appears readily transferred from animals (pig farmers in Netherlands) Recently reported causing disease in horses1-3 and dogs4 Some human cases reported in UK (Scotland) None reported in dogs, just reported in 2 horses from UK5 Van den Eede et al (2009) Vet. Microbiology 133(1-2) Cuny et al (2008) Microbial Drug Resistance14(4) Hermans et al (2008) Vlaams Dierg Tijdschrift 77(6) Witte et al 2007 Emerg Inf Disease 13 (2) Loeffler et al (2009) Hosp Inf Soc 72 (3)

19 Frequently produce PVL toxin
CA-MRSA Community associated MRSA MRSA but without known risk factors (immunosuppressed/ hospitalisation/antibiotics etc) Not nosocomial like HA-MRSA. Carry smaller SCCmec types IV and V (hence survival?) Different antibiotic susceptibility (resistance to fewer antibiotics- often just b-lactams) Small animal prevalence unknown but has been reported1, not definitively identified in horses2 Frequently produce PVL toxin More virulent Human associated term not so useful in veterinary medicine Rankin et al (2005) Vet Microbiol 108 Maeda et al (2007) Vet Rec 161

20 MRSA AS A ZOONOSIS Zoonotic Potential
Transmission between people and animals has been reported Usually from humans to animals (unsurprising given respective prevalence) 1-3 Some cases of animals transmitting to people4,5 Transmission freq for in-contacts relatively common but rare as actual infection Cows also transmitted to dairy workers Co-colonisation of animals and in-contacts may be relatively common but actual cross-infection seems to require normal risk factors Rutland et al (2009) Emerg Inf Disease 15 (8) van Duijkeren (2005) J Clin Microbiol 43 (12) van Duijkeren (2004) Emerg |Inf Disease 10 (12) Sing (2008) New Eng J Med 358 (11) Weese et al (2006) Vet Microbiol 114

21 MRSA AS A ZOONOSIS Zoonotic Potential
Transmission between people and animals has been reported Usually from humans to animals (unsurprising given respective prevalence) 1-3 Some cases of animals transmitting to people4,5 Survey of 274 veterinary personnel at equine conference in 20066 22 people identified with nasal carriage of MRSA (8.0%) 9 isolates typical human strains Remainder were non-human strains more commonly seen in horses (EMRSA-10, ST8, ST254) Transmission freq for in-contacts relatively common but rare as actual infection Cows also transmitted to dairy workers 6. Scantlebury (2007) BEVA Conf Proceedings

22 STUDIES AT LIVERPOOL Nationwide cross-sectional study on the microbiology and epidemiology of antimicrobial-resistant E. coli and staphylococci in dogs and horses Longitudinal study on the microbiology and epidemiology of antimicrobial-resistant E. coli in horses in the community All studies on-going currently Some preliminary results will be summarised

23 CROSS-SECTIONAL STUDY
Study Design Animals seen by vets from 65 equine and 87 small animal randomly selected veterinary practices across the UK Nasal swab obtained from each animal, with owner completed questionnaire on veterinary history and treatment, housing and management Majority of animals (88%) seen for routine reasons

24 CROSS-SECTIONAL STUDY
Microbiological Methods Nasal swabs enriched in 6% NaCl nutrient broth. Streaked onto mannitol salt agar (MSA) and oxacillin-resistance screening agar (ORSA) Antimicrobial Potency Ciprofloxacin (CIP) 1mg Fusidic acid (FS) 10mg Gentamicin (GM) Methicillin (MET) 5mg Mupirocin (MUP) Rifampicin (RIF) 2mg Tetracycline (TET) 30mg Co-trimoxazole(TMS) 2.5mg Teicoplanin (TEC) Vanocmycin (VAN) Typical isolates selected and characterised by Gram stain, catalase, coagulase and stapylase testing Staphylococci subjected to antibiotic susceptibility testing in accordance with BSAC guidelines 1. mecA PCR for methicillin-resistance confirmation and femA and nuc PCR. (MRSA isolates: SCCmec typing and spa gene typing) British Society for Antimicrobial Chemotherapy (2007), Methods for Antimicrobial Susceptibility Testing

25 STAPHYLOCOCCI IN HORSES
Nasal samples from 677 horses returned 617 horses (91.1%; %) had at least one Staphylococcus spp 215 horses (31.8%; %) had at least one methicillin-resistant Staphylococcus (mostly coagulase-negative) Low prevalence of MRSA (0.6%; %)

26 STAPHYLOCOCCI IN DOGS Nasal samples from 672 dogs returned
394 dogs (58.6%; %) had at least one Staphylococcus spp 42 dogs (5.3%; %) had at least one methicillin-resistant Staphylococcus (more coagulase-negative) Low MRSA prevalence of 6 dogs (0.9%; %) Data courtesy of A. Wedley

27 STAPHYLOCOCCI IN HORSES
Varying levels of resistance to all antibiotics except teicoplanin and vancomycin High levels of resistance to fusidic acid, as well as to mupirocin, tetracycline and co-trimoxazole 78.4% ( %) of MR-staphylococci were multidrug resistant Do not recommend Teic or vanc. Fusidic and mup useful as topical therapy (AL paper case series 10 cases MRSP)

28 MRSA IN HORSES 4 confirmed MRSA isolates (mecA, fem and nuc positive)
Variable resistance pattern seen in the four isolates (isolate 060 slightly unusual pattern for horse MRSA) All multidrug-resistant (to three or more antimicrobial classes) Isolate Cip F. Acid GM Meth Mup Rif Tet TMS Teic Vanc 060 R S 206 846 953

29 Presumptive Sequence Type Presumptive Clonal Complex
MRSA IN HORSES All 4 equine isolates confirmed MRSA SCCmec type IV by PCR spa typing carried out for all isolates (one failed) spa types represent common equine strains (no ST398 identified) Isolate spa type Presumptive Sequence Type Presumptive Clonal Complex 060 unidentified N/A 206 t064 ST8 CC8 846 953 t451 ?ST8 ?CC8

30 CONCLUSIONS Animals can carry antibiotic-resistant staphylococci
Carriage of MRSA appears rare, especially in animals in the general community The epidemiology of MRSA carriage is distinct in different species -Dogs carry common (local) human epidemic strains -Horses carry strains uncommon in humans Animal-related MRSA strains can be found in humans in close contact with animals Transmission may occur both ways between animals and humans Companion animals may act as a reservoir for infection of humans in close contact Issue for decolonisation (of humans or animals) in both vet and medical patients

31 AKNOWLEDGEMENTS PhD colleague
Amy Wedley MSc Student Andrew O’Donnell Ph.D Supervisors Dr. Nicola Williams Prof. Pete Clegg Dr. Gina Pinchbeck Dr. Susan Dawson Dr. Tim Nuttall Colleagues in the lab… Ruth Ryvar Gill Hutchinson Antimicrobial resistance in companion animals project DEFRA Bransby Home of Rest for Horses PhD funding


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