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Dermatology 2 > Bacterial skin disease > Flashcards

Bacterial skin disease Flashcards

1
Q

What is the role of normal cutaneous microbial flora?

A

Can aid exclusion of pathogens, but can also contribute to disease

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2
Q

Define the following terms:

a: resident
b: nomad
c: transient
d: pathogen

A

a: Can replicate on skin and persist
b: organisms that can colonise and reproduce on skin for short times
c: cannot replicate so only stay for short time
d: organisms that become established and can proliferate on the skin surface and deeper, that are deleterious to normal physiology of teh skin

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3
Q

What is required in order for microorganisms to cause skin disease?

A

Skin’s barrier function must be compromised i.e. primary disease leading to secondary infection by resident and transient organisms

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4
Q

What are the innate skin defences?

A
  • Squames: shed from top layer, leading to shedding of microorganisms
  • Sebaceous glands
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5
Q

What are the specific defences in the skin?

A

Langhan’s cells in the dermis

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6
Q

What is the usual result of chemical, physical or microbiological insult on the skin?

A

Usually leads to increased turnover of skin and increased activity of the sebacious glands, leading to scaliness and dry or wet seborrhaeic skin
- Increased sebum leads to smell

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7
Q

Give examples of primary disease that may allow bacterial skin disease to occur

A
  • Any disease that affects the defences
  • Atopic dermatitis
  • Endocrinopathy
  • Nutritional deficiencies
  • trauma/overcrowding
  • Environmental damage
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8
Q

What are the 3 types of pyoderma called?

A
  • Surface
  • Superficial
  • Deep
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9
Q

What are the 2 forms of surface pyoderma?

A
  • Acute moist dermaittis (“wet eczema”)

- Skin fold pyoderma (“intertrigo”)

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10
Q

What is surface pyoderma?

A

Secondary bacterial colonisation of skin surface

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11
Q

Describe the presentation of acute moist dermatitis

A

0 Aka hot spot, pyotraumatic dermatis

  • Very acute onset (overnight)
  • Intensely pruritic and painful
  • Alopecia, exudative, erythematous
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12
Q

Outline the underlying causes of acute moist dermatitis

A

Primary pruritic conditions e.g. otitis externa, anal gland impaction, fleas/other ectoparasites, function of hair coat, breed predisposition (golden retriever)

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13
Q

Explain why dogs with thick undercoats may be predisposed to acute moist dermatitis

A
  • Thick undercoat on hot days means skin gets very hot

- Develop pruritus which leads to formation of acute dermatitis lesion very quickly

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14
Q

Where does intertrigo commonly occur?

A
  • Facial folds in brachys
  • Vulval fold (spayed with deep-set vulva)
  • Lip fold (some spaniel breeds, can be considerable cause of halitosis)
  • Tail fold (deep set tails, esp, brachys)
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15
Q

How is surface pyoderma diagnosed?

A
  • Dermatological signs main method

- may do bacterial culture and susceptibility testing, skin biopsies (histo +/- culture)

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16
Q

What is superficial pyoderma?

A

Infection involving skin and hair follicle epithelium

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17
Q

What are the 4 types of superficial pyoderma?

A
  • Impetigo
  • Superficial bacterial folliculitis
  • Pyotraumatic folliculitis
  • Mucocutoaneous pyoderma
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18
Q

Describe the occurrence of impetigo

A
  • Common, often recurrent (secondary) e.g. allergy/endocrinopathy, parasites
  • Often diffuse, ventral abdomen especially
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19
Q

Describe the appearance of impetigo

A
  • Pustules: hair in centre i.e. folliculitis
  • Papules
  • Epidermal collarettes
  • Alopecia
  • Variable pruritus: more if inflam/allergic, less if endocrinopathic
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20
Q

What is canine deep pyoderma?

A

Infection involving the dermis and subcutaneous tissue

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21
Q

What are the 3 types of canine deep pyoderma?

A
  • Cellulitis (diffuse condition)
  • Furunculosis (hard lesions and discharge to surface)
  • Acral lick furunculosis
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22
Q

Compare furunculosis and cellulitis

A
  • Furuculosis: “boil”, follicle infection spreads into dermis
  • Cellulitis: infection of follicles and surrounding dermis
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23
Q

What breed is predisposed to deep pyoderma and why?

A

GSD: immunodeficiency in some lines of GSD breed, impaired barrier function of skin

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24
Q

Describe the appearance of deep pyoderma

A
  • Papules
  • Pustules
  • Alopecia
  • Nodules (furuncles, palpable lumps in dermis)
  • Sinuses
  • Draining tracts
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25
Q

Describe the clinical signs of cat bite abscesses

A
  • Acute onset
  • Pyrexia
  • Painful
  • Inappetance, depression
  • Fluctuant swelling (often head/back end)
  • Scab +/- puncture wounds
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26
Q

What aerobes are commonly involved in cat bite abscesses?

A
  • Pasteurella spp
  • Actinomyces spp
  • Nocardia spp
  • Staphylococcus spp
  • Rhodococcus sp
  • Enterobacteriaceae
  • Streptococcus
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27
Q

What anaerobes are commonly involved in cat bite abscesses?

A
  • Porphyromonas spp
  • Fusobacterium
  • Peptostreptococcus spp
  • Clostridium spp
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28
Q

When is culture and sensitivity required for abscesses?

A

Only if recurrent

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29
Q

Compare rabbit and cat abscesses

A
  • Cat bite abscess pus thin, drains easily
  • Very thick in rabbits, does not drain and lancing and flushing alone often ineffective, usually require complete surgical excision
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30
Q

Other than bacteria, what else may cat bite abscesses be a source of?

A

Viral infections e.g. FIV

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31
Q

For a rabbit abscess where surgical excision is not possible, what other treatments are available?

A
  • e.g. a jaw abscess
  • Aggressive debridement
  • removal of affected teeth and bone
  • Marsupilisation
  • Systemic antibiotics required
  • Euthanasia (very difficult to treat)
  • Adjunctive treatments e.g. honey, sugar solutions, AIPMMA-beads, calcium hydroxide
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32
Q

What is meant by marsupiliation?

A

Remaining abscess capsule suture to skin to allow topical therapy on remaining abscess tissue

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33
Q

Where are abscesses most common in large animals and what is a key differential?

A
  • Umbilical, esp. in young stock

- Umbilical hernias are a key differential

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34
Q

How can umbilical hernias be differentiated from umbilical abscesses?

A
  • Hernias are soft and should reduce on palpation

- Abscesses are more likely to be firm

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35
Q

What is a common complication that may occur with umbilical abscesses in large animals?

A

May erode through abomasal wall, but are easily stitched up and tend to do well

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36
Q

List non-bacterial differentials for “bacterial” type presentations

A
  • Anal furunculosis
  • Juvenile cellulitis (aka puppy strangles)
  • Are autoimmune conditions
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37
Q

What is anal furunculosis?

A

Sinuses that track through skin around anus, occasionally may affect inside back of legs. Are not fistulas

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38
Q

Where does anal furunculosis occur?

A

Near anal sacs, but do not connect with them, rectum or colon

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39
Q

What are the clinical signs of anal furunculosis?

A
  • Open areas of ulceration
  • Become very tail shy
  • Lick and bite at affected region
  • Pain
  • Difficulty straining on defaecation
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40
Q

What breed is predisposed to anal furunculosis?

A

GSD

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41
Q

What is the cause of anal furunculosis?

A

Unknown, not bacterial (may be secondary infection), tail carriage suggested as a cause

42
Q

What causes juvenile cellulitis?

A

Not bacterial, may be immunological

43
Q

Describe the appearance and clinical signs of juvenile cellulitis

A
  • Typically face
  • Alopecic inflamed lesions with oedema
  • Papules, pustules and crusts
  • Often affects perioral, periocular, chin, muzzle and ears
  • Significant sub-mandibular lymphadenopathy
  • Lethargy, fever and anorexia in some, joint pain in others
44
Q

Describe the nature of aspirates taken from lymph nodes in a dog with juvenile cellulitis

A

Suppurative lymphadenitis with many neutrophils without bacteria

45
Q

What is the diagnostic importance of primary dermatological lesions?

A

Usually most obvious in early stages of the disease and are those upon which a definitive diagnosis should be based

46
Q

What is the diagnostic importance of secondary dermatological lesions?

A
  • Mostly non-specific and caused by pathological changes resulting from primary disease and related lesions
  • Not as valuable for diagnosis
47
Q

How is canine superficial pyoderma diagnosed?

A
  • Based mainly on dermatological signs
  • May do bacterial culture and susceptibility testing
  • Skin biopsy (histology +/- culture) if recurrent to look for underlying skin disease rather than diagnosis of pyoderma
48
Q

How is canine deep pyoderma diagnosed?

A
  • Dermatological signs
  • Cytology (aspirate/impression smear)
  • Bacterial culture and susceptibility testing (systemic antimicrobials required for long periods)
  • May also do skin biopsies (histology +/- culture)
49
Q

How is anal furunculosis diagnosed?

A
  • Physical examination

- Rule out other causes

50
Q

What is the function of an abscess?

A
  • Defensive reaction to tissue to prevent the spread of infectious material (granulation tissue)
  • Barrier may prevent immune cells from attacking bacteria in the pus
51
Q

Compare abscesses and emphyaemas

A

Emphyaema is an accumulation of pus in pre-existing rather than newly formed anatomical cavity

52
Q

What is an important differential for a lesion that looks like deep pyoderma on a paw?

A

Need to rule out abscess secondary to a foreign body

53
Q

Describe the typical treatment and management approach to an abscess

A
  • Sedate/GA, analgesia
  • +/- systemic antibacterials
  • Clip and prep, local anaesthetic
  • Lance abscess, drain and lavage
  • Leave open
  • If large, insert drain/marsupialise
  • may need to continue systemic antibacterials depending on degree of abscess, systemic signs and practice policy
54
Q

What factors need to be addressed in the treatment of canine surface pyoderma?

A
  • The primary disease
  • The bacterial infection
  • THe inflammation
55
Q

Describe the treatment of the primary disease in canine surface pyoderma

A
  • Identify cause
  • Skinfolds: surgical resection possible if required, or regular cleaning with anti-bacterial wipes
  • Consider fleas/ears/other allergens
56
Q

Describe the treatment of the bacterial infection in canine surface pyoderma

A
  • Use anti-staphylococcal antibacterials
  • IN order of choice:
  • 1: clindamycin, lincosamides/macrolides
  • 2: amoxycillin clavulanate
  • 3: TMPS (cheap, but resistance an issue, hard to get)
  • 4: Cefalexin (20-25mg/kg BID) or quinolones (C+S only if no alternative), last resort only if long standing deeper pyoderma non-responsive to linco/macrolides
  • If non-responsive to amoxy-cav/cefalexin, suggests beta-lactam resistance
57
Q

Describe the treatment cascade for the bacterial infection in superficial pyoderma in a cat

A
  • 1: Amoxyclav
  • 2: Clindamycin
  • 3: Cefalexin
58
Q

What treatment is most commonly used to treat the inflammation in surface pyoderma?

A
  • Usually corticosteroid, often topical antibacterial + corticosteroid e.g. Isaderm (fusidic acid + betamethasone)
  • Fuciderm gel and surolan ear drops also licensed
  • Easy, as is a surface disease
  • Glucocorticoid injection may be required to allow handling as is very painful condition
59
Q

What is the antibiotic protocol used in the treatment of superficial pyoderma?

A
  • Systemic anti-staphylococcal antimicrobial

- Minimum 3 weeks + 1 week beyond cure

60
Q

Other than antibacterials, what else is required in the treatment of canine superficial pyoderma?

A

Manage underlying cause e.g. flea management

61
Q

Outline the use of antibacterial shampoos/rinses in the treatment of canine superficial pyoderm

A
  • Long term maintenance
  • Physically reduces microbial population
  • Reduces levels of microbial by-products
  • Removes debris/discharge
  • Allows active agent to reach site of action
  • Soothing
  • Surface grease/debris may adversely affect activity of therapies
  • Keeps owner aware of therapy and involved with condition
  • E.g. malaseb shampoo, pacutol shampoo, seleen
62
Q

Describe the use of topical antibacterials (not shampoos) in the treatment of canine superficial pyoderma

A
  • Many available, most unlicensed
  • Chlorhexidine, ethyl lactate, benzoyl peroxide, piroctone olamine, selenium sulphide
  • Most effective treatments tend to contain chlorhexidine
63
Q

Describe the systemic antibacterial protocol used in the treatment of canine deep pyoderma

A
  • Long course of systemic antibiotics
  • Based on culture and sensitivity
  • NOT clindamycin (only bacteriostatic)
  • Minimum 6 weeks + 2 weeks beyond cure
  • Must be anti-staphylococcal
64
Q

Describe the treatment of canine deep pyoderma

A
  • Treat primary cause
  • Topical antibacterial shampoo/rinse
  • Long courses of systemic antibacterials
  • Discuss with owner re. risk of recurrence, management difficult
65
Q

What is the long term management required for canine deep pyoderma?

A
  • Intermittent pulses of antibacterial treatment e.g. 2 days on, 5 days off, or 1 week on, 2 weeks off
  • Immunostimulants e.g. staphage lysate (SPL), sterile staphylococcal vaccine, discussion with dermatologist re. management of recurrent deep pyoderma
66
Q

Explain the use of staphylococcal vaccines in the treatment of canine deep pyoderma

A
  • Vaccine contains components of S. aureus, bacteriophage and some culture medium ingredients in solution
  • Induces cell mediated immunity
67
Q

Describe the treatment of anal furunculosis

A
  • Often recurs
  • Cyclosporin most used as is immune mediated condition, responds well
  • Radical surgery where all tissue removed
  • Cryosurgery (apply freezing nitrogen)
  • Radical and cryo less common and result in very painful patient
68
Q

Outline the treatment used for juvenile cellulitis

A
  • Corticosteroids (immunosuppress, often respond well)

- Usually cover with antimicrobials

69
Q

What does MRSA stand for?

A

Methicillin resistant Staphylococcus aureus

70
Q

What is the significance of MRSA regarding the treatment of canine pyoderma?

A

MRSA is resitant to all beta-lactams; cefalexin is often used in the treatment of canine pyoderma, but this will not be effective against MRSA

71
Q

List the possible sources of MRSA in dogs

A
  • Human
  • Other dogs/animals
  • Hospital (nosocomial infection)
  • Pigs
72
Q

How should suspected MRSA pyoderma cases be handled in a practice/hospital situation?

A
  • Known/suspected cases taken immediately into consulting room to avoid contamination of waiting area
  • Reduce movement of contaminated animals around pracice
  • Cover discharging wounds
  • Limit staff contact
  • Isolate form healthy patients
  • Barrier precautions e.g. wearing gloves
  • Bathe in chlorhexidine to reduce cutaneous carriage
73
Q

What advice should be given to the owners of patients infected with MRSA (or other bacterial skin infections)?

A
  • Handwashing and disinfection important
  • Discourage hospital visits
  • If live with/are immunocompromised must seek medical advice
  • Limit contact with other pets
  • Set up isolated areas in home
  • Wash bedding and disinfect home
74
Q

Describe the appearance of dermatophilosis skin infection

A
  • Exudative dermatitis with scab formation
  • Paint brush leasions
  • Scale
  • Site determined by predisposition i.e. dorsum (rain run off, rain scald), feet/lower limd (underfoot conditions), clipping/shearing, ectoparasites
75
Q

What is the most common species of dermatophilus? What are the most frequent hosts?

A
  • Dermatophilus congolensis

- Wide host range, but most common are cattle, sheep, goats and horses (rare in pigs, dogs and cats)

76
Q

Give alternative names for dermatophilosis

A
  • Horse: Mud fever, scratches, dew poisoning
  • Cattle, goats, horses: cutaneous streptothrochosis
  • Sheep: lumpy wool (if wooled areas affected)
77
Q

Describe the Dermatophilus organism

A
  • Actinomycete
  • Gram +ve filamentous bacterium
  • Non-acid fast
78
Q

What is required for initial infection with Dermatophilus to occur?

A

At least superficial skin damage, and activation of motile zoospore stage to form a mycelium

79
Q

Where is dermatophilus found in the skin?

A

Confined to the epidermis

80
Q

What are the 2 characteristic forms of dermatophilus?

A
  • Filamentous hyphae

- Motile zoospores

81
Q

Describe the pathogenesis of dermatophilus

A
  • Zoospore attracted to by respiratory efflux of low levels of CA2 from the skin to susceptible areas on skin surface
  • Zoospore can remain dormant in skin debris and scabs for many months in dry conditions
  • Activate and germinate to produce hyphae which penetrate into living epidermis and subsequently spread in all directions from initial focus
  • Penetration causes acute inflammatory reaction
82
Q

Describe acute infection with dermatophilus

A
  • Filamentous infavion of epidermid ceases in 2-3 weeks

- Lesions heal spontaneously

83
Q

Describe how chronic infection with dermatophilus may develop

A

Affected hair follicles and scabs are sites from which intermittent invasions of non-infected hair follicles and epidermis occur

84
Q

What agent causes caseous lymphadenitis and what species are affected?

A
  • Corynebacterium pseudotuberculosis

- Sheep and goats

85
Q

Describe the signs of caseous lymphadeitis

A
  • Lesions take weeks to develop

- Swollen LN draining head and lungs

86
Q

In what cells does Corynebacterium pseudotuberculosis survive?

A

Macrophages

87
Q

What are the main bacterial skin infections in pigs?

A
  • Exudative dermatitis caused by Staphylococcus hyicus

- Erysipelas caused by Erysipelothrix rhusiopathiae

88
Q

Describe mycobacteria as a cause of skin TB in cattle

A
  • Many species identified incl. bovis, microti, avium
  • Common in cats
  • Occurs due to environmental and wound contamination e.g from hunted small animals
  • No evidence of zoonotic transmission (but may be reverse zoonosis)
89
Q

Outline a logical diagnostic approach to a chronic, non-healing wound

A
  • In any chronic, non-healing wound need to consider MRSA
  • Swab for C+S
  • Sensitivity may be specific to hospital
  • Cover wound and barrier nurse or isolate patient
  • Maintain basic hygiene
  • Stop antibiotics as soon as granulation tissue present
  • when sending sample to lab, notify concerns over MRSA/MRSP in order to optimise chance or organisms being detected
90
Q

Outline the diagnostic approach to dermatophilosis

A
  • Clinical signs and lesions
  • Examination of fresh crusts and or impression smears of underside of fresh lesions
  • Giemsa or DiffQuik staining
  • Histology
  • Culture and identification
  • In chronic/recurrent infections use skin biopsies for histology +/- culture
91
Q

Outline the diagnostic approach to caseous lymphadenitis

A
  • Clinical exam
  • Serological testing
  • Bacterial culture and susceptibility testing (chronic/recurrent)
  • Skin biopsies for histo +/- culture (chronic/recurrent)
92
Q

Describe the clinical signs of greasy pig disease

A
  • Dark, localised areas of grease and scale
  • Excess sebum (smell)
  • May become generalised due to stress (more common in piglets, weaners or gilt litters)
  • If severe, skin turns black due to necrosis and pigs die
  • Systemic illness due to toxin release causing liver/kidney damage
93
Q

What are the potential primary causes of greasy pig disease?

A
  • Damage (teeth, floors)
  • Abrasions from concrete surfaces, metal floors, troughs, side panels
  • Faulty procedures for iron injections, teeth/nail removal
  • Fighting and skin trauma at weaning
  • Mange giving rise to skin disease
  • Damage to face by metal feeding troughs
  • Abnormal behaviour (tail biting, ear biting, navel sucking, flank biting)
94
Q

How is greasy pig disease diagnosed?

A
  • Dermatological signs

- Bacterial culture and susceptibility testing

95
Q

What are the clinical signs of erysipelas?

A
  • Sudden death
  • Very high temperature
  • Sick pigs
  • Skin lesions
  • Lameness
  • Reproductive failure
96
Q

What are the clinical signs of feline skin TB?

A
  • Granulomatous disease
  • Mainly in skin (lumps)
  • May be in lymph nodes, occasionally lungs or GI
97
Q

How is feline skin TB diagnosed?

A
  • Dermatological signs
  • Skin biopsies (histology +/- culture)
  • Bacterial culture and susceptibility; with high index of suspicion use ZN stain
98
Q

Outline the management procedures for MRSA/MRSP skin infections

A
  • Hygiene crucial
  • Maximise topical therapy where possible, esp. chlorhexidine (2-4%) washes
  • Be aware affected animals/in-contacts can be carriers after resolution of clinica disease
  • Address underlying cause of infection to reduce risk of recurrence
99
Q

Outline the management for dermatophilosis

A
  • No treatment needed, often heal rapidly and spontaneously
  • Manage skin problem e.g. flies, rain etc.
  • Susceptible to a wide range of antimicrobials
  • Short course usually enough
  • Soak and remove crusts
  • Topical antibacterials e.g. chlorhex, benzoylperoxide
100
Q

List the antimicrobials that are effective against dermatophilosis

A
  • Erythromycin
  • Penicillin G
  • Ampicillin
  • Amoxicillin
  • Tetracyclines

Dermatology 2 (23 decks)

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