What You Need To Know About Animal Staphylococci

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Dr. Robert Hilton BVSc (Hons) MANZCVS  MRCVS

RCVS (UK)  Certificate Holder in Veterinary Dermatology

P.O. Box 42 Yarrambat 3091

Telephone 0433 853 560

Website www.skinvet.org

Email rob@skinvet.org

Incidence. Rising rapidly.

Staphylococcus pseudintermedius. Coagulase positive. Coagulase-negative in heavy growth, pathogenic. Occasional S. aureus. Biochemical vs genetic ID.

Mechanisms of resistance

• Penicillinase breaking beta-lactam ring. Since 50s. Amoxicillin no better than penicillin with respect to staph.
• MEC-a coded chromosomal cassette and other genetic transfers. Penicillin-binding protein.
• Point mutations. Less important with beta-lactams but most important with lincosamides (clindamycin, lincomycin) fluoroquinolone and rifampicin.

Concept of MIC  vs  MUP . What does sensitivity mean?

Heterogeneity of resistance

First line antibiotics

• Cephalexin  25-35,mg/kg bid
• clindamycin 10mg/kg bid
• Amoxiclav? 15-20mg/kg bid
• Convenia (cefovecin) ???? Gen 3

Second-line antibiotics. Not to be used without culture

• Doxycycline 5 mg/kg bid
• Sulfa trimethoprim 480 tabs 1/20 kg
• Fluoroquinolones. Empty stomach concentration dependent.

Third line antibiotics. Never to be used unless first line and second line exhausted.

• Pradofloxacin
• Rifampicin. Liver and bone marrow 5 mg/kg bid.
• Systemic fusidic acid 25-30 mg/kg bid point mutations

Duration of treatment

Classically

• Superficial pyoderma minimum of 3 weeks or 7-10 days visible cure. Evidence?
• Deep pyoderma minimum of 3 weeks after visible cure. Maybe months.

Causes of antibiotic failure

• Inadequate duration
• Inadequate dose
• Resistance
• Failure to use topical treatment
• Compliance
• Was not an infection in the first place. Pemphigus or drug reactions.

Topical treatment. Absolute essential. No animal repeat no animal should have antibiotics dispensed for a skin infection unless it is accompanied by topical treatment.

Sometimes topical is enough. Surface pyoderma hotspots. Some cases of superficial pyoderma. Allowing client pick up after 3 to 5 days.

First line topical treatment

• Chlorhexidine. Pyohex shampoo and lotion. Think do you need a shampoo? Malaseb completely inappropriate for bacterial pyoderma due to strong surfactants.
• 2.5 % SOLUTION chlorhexidine dab on . Stability of made up?????
• BLEACH  RCH protocol

https://www.rch.org.au/uploadedFiles/Main/Content/derm/eczema-bath-information.pdf

• Silver sulphadiazine FLAMAZINE. Potential chlorhexidine synergy.

Second line topical therapy

• Topical fusidic acid (Fucidin human)
• Mupirocin topical bid point mutations
• Topical gentamicin

CHLORHEXIDINE RESISTANCE

Reduced susceptibility to chlorhexidine in staphylococci: is it increasing and does it matter?

Carolyne Horner, Damien Mawer, Mark Wilcox

Journal of Antimicrobial Chemotherapy, Volume 67, Issue 11, November 2012, Pages 2547-2559, https://doi.org/10.1093/jac/dks284

https://academic.oup.com/jac/article/67/11/2547/711827

As well as a broad range of activity, a key potential advantage of chlorhexidine, especially when used as a skin disinfectant, is its 'residual activity

In staphylococci, chlorhexidine resistance is often defined as an MIC ≥4 mg/L,

The presence of organic matter, biofilms and biocide residues at sublethal concentrations are additional factors that need to be taken into account when comparing the in vitro and in vivo susceptibility of biocides.

The concept of heterogeneous resistance to chlorhexidine, defined as the presence of subpopulations of staphylococci that can survive at in-use concentrations of the agent, is a plausible one

Staphylococci have the capacity to efflux lipophilic cations, such as quaternary ammonium compounds, intercalating dyes, diamidines and biguanidine compounds, including chlorhexidine.

Genetic linkage between the qacA/B genes and β-lactamase resistance  has been reported; an association that has been noted in both S. aureus and coagulase-negative staphylococci

Specific incidence in humans still not clear because of clonal variations, geographic differences and testing method variations. Incidence is rising.

How to culture

• Superficial pyoderma. Pustules or multiple collarettes with a dry swab, then put in the transport medium.
• Deep pyoderma. Draining sinuses or needle aspiration.

Must go to a laboratory that is prepared to test for third line antibiotics.

When to culture?

• More a question of when not to culture rather than when to culture
• History of previous antibiotic use
• Generalized superficial pyoderma
• Failure of first-line antibiotic

Corticosteroids

• Generally like a fish needs a bicycle
• Topical steroids make no sense in superficial or deep pyoderma. Helps surface hotspots.
• Most patients are immunosuppressed enough already
• Lokivetmab (Cytopoint) to deal with itch if needed, but unlikely to work in the face of active infection. Neither will anything else.

Policies that need to be developed

Decontamination of clippers and rooms. Handwashing and protocols.

Decontamination after clinical cure? … value?

• Whole body topical therapy
• Combined culture of nasal and perianal