It contains information about bacterial skin diseases of animals

1. BACTERIAL INFECTIONS OF
SKIN
Ishtiaq ahmed

2. • Portal of entry for bacteria into skin include
1. Pore (follicular openings)
2. Hematogenous spread
3. Direct entry through damages skin
Cutaneous bacterial infections vary in
1. Location (Epidermis, dermis, sub cut, adnexa or systemic)
2. Morphology (Pyogenic, granulomatous, necrotizing)
3. Distribution (focal, multifocal, regional, systemic, interdigital)
4. Severity (Mild, asymptomatic to sever with systemic signs)
Variation is due to specific organism involved, host-immune
response, predisposing/co-existing factors

3. • Involve epidermis & upper infundibulum of hair follicles
• Usually heal without scaring
• Etiology: Staphylococcus spp
• Gross lesions include erythema, alopecia, papules,
pustules, crusts and peripheral expanding rings of scale
called “ epidermal collarettes”
• Microscopically intra-epidermal pustuler dermatitis which
may rupture leading to formation of crust and scales
• Superficial luminal suppurative folliculitis
• Follicular injury leads to alopecia

6. • Impetigo is a superficial pustular dermatitis that does not
involve hair follicles
• Observed in dogs, cats, cow, does, ewes, piglets
• Caused by Coagulase + Staphylococci (S. intermedius)
• Cutaneous abrasions, viral infections, increased moisture
predispose for infection
• Protein A produced by bacteria binds to Fc part of IgG
leading to activation of complement system
• Chemo -attractants for leukocytes are produced leading to
inflammation and tissue damage

7. • Older dogs with hyperadrenocorticism induced
immunosuppression may develop bullous impetigo
• Cows, does, ewes have usually lesions on udder
• Kittens: shoulders and neck due to overzealous mouthing
of the queen.
• Streptococcus and Pasteurella are cause
• Grossly pustules, crusts in non haired skin except kitten
• Non follicular neutrophillic subcorneal pustule

8. Impetigo in dog

9. Subcorneal pustule

10. Superficial spreading pyoderma
• Common bacterial infection in dog, often pruritic
• St. intermedius
• Pathogenesis poorly understood
• May be bacterial hypersensitivity as IgE agianst
Staphylococcus has been detected
• Protein A may also contribute
• Lesions mostly on ventral thoracic and abdominal skin,
dorsal and lateral trunk as well
• Erythematous macules, papules, transient pustules
• Older lesion: epidermal collarettes, alopecia, crusts,
hyperpigmentation

11. • Superficial spongiotic pustules ….crust….basophilic
debris
• Dermal lesions inculde superficial perivascular or
interstitial accumulation of neutrophils, eosinophils,
macrophages

12. Mucocutaneous pyoderma
• Putative bacterial infection of muco-cutaneous junction in
dog
• German Shepherd
• Erythema, depigmentation, crusting, ulceration
• Histologically: Lymphoplasmacytic infiltration at
epidermal-dermal junction (lichenoid)
• No basal cell degeneration
• Spongiosis, cellular exocytosis, neutrophillic pustular
crust, folliculitis

13. Dermatophilosis
• cutaneous streptothricosis, mycotic dermatitis,
cutaneous actinomycosis, lumpy wool, strawberry foot rot,
rain scald, rain rot, Kirchi, Gasin-Gishu, Senkobo disease,
Drodo-Boka, Savi, Ambarr-Madow
• Acute, subacute, or chronic superficial exudative
dermatitis caused by the actinomycete Dermatophilus
congolensis
• Worldwide occurrence, wide host range
• Hot humid tropics and subtropics and in areas with
prolonged rain
• In hot monsoon cattle usually affected

14. • In temperate climates sheep, goat primarily affected
• Lesions tend to develop on dorsum of back and distal
extremities
• Ectoparasites, trauma, wetting of skin allow zoospores to
enter in epidermis
• Bacterium grow in outer rootsheath of hair follicle
• Produces gram positive filamentous branches
• Induce acute inflammatory response
• Intraepidermal microabcess
• Repeated bacterial growth cycles and inflammation lead
to multilaminated pustular crusts

15. • Papule, pustule, crust that can mat the hairs/wool
• Hyperplastic superficial perivascular dermatitis
• Multilaminated crusts of alternating layers of keratin and
neutrophils covering the skin

19. Exudative Epidermatis pigs
• Greasy pig disease
• Staphylococcus hyicus
• In neonatal pigs fatal, mild in old pigs
• Bacteria produces exotoxin “ exfoliatin”
• Exfoliatin binds to filaggrin in the keratohyalin granuels in
st. granulosum
• It causes focal erosion of epidermis
• Dermatitis and brown exudate develop around the eyes,
pinnae, snout, chin, medial legs, spread to ventral thorax
& abdomen
• It gives animal an over all greasy appearance

20. • Lesions rapidly coalesce to become generalized
• Malodourous exudate cover skin
• If animal survive, exudate hardens, cracks and form
fissures
• Sub acute disease in older pigs with lesions face, pinnae
and perioccular lesions (Epidermal thickness and scaling)
• Histopathology:
• Subcorneal pustular dermatitis
• Superficial suppurative folliculitis

22. Ovine fleece rot
• Superficial dermatitis
• Excessive moisture due to rain cause proliferation of
Pseudmonas spp
• Approximately 1week wetting required
• Acute inflammatory response with serum exudation and
fleece mating
• Fleece discolored because of chromogens produces by
bacteria and has rotten odour
• Epidermal pustular dermatitis and folliculitis
• Secondary Myasis

23. Deep bacterial pyodermas
• Bacterial infections of hair follicles, dermis and sub cutis
• Staphylococcus, streptococcus, corynebacterium,
pseudotuberculosis, pseudomonas, Proteus, E.coli,
pasturella
• Staphylococcus intermedius is primary pathogen of
canine skin
• Immunosupperssion and demodicosis are predisposing
factors

24. Staphylococcal folliculitis & furunculosis
• Folliculitis may be superficial or deep
• Superficial involve infundibulum, it can spread deeper
• Severe folliculitis can result in frunculosis
• Most common in dog. Horse, sheep, goat may also
develop disease
• In dog lesions on dorsal nose, pressure points, interdigital
areas
• Deep pyoderma in German Shepherd with genetic
predispostion
• In horses lesions develop under the saddle, tail, pastern

25. • Pastern or fetlock (equine pastern folliculitis)
• In goats, face, pinnae, udder, ventral abdomen, medial
thigh, perineum
• Grossly: initially papules, crusted papules, pustules,
collarettes, alopecia
• Deep lesions have hemorrhagic bullae, nodules, draining
tracts
• Microscopically: luminal folliculitis, pyogranulomatous
furunculosis , draining sinuses and occasionally
panniculitis
•

26. Subcutaneous abscess
• Localized collection of purulent exudate in dermis and sub cutis
• Common in cats because of contamination of puncture wounds
• Also common in large animals
• Foreign bodies, shearing and clipping wounds, injections
• Granulation tissue or fibrous tissue surrounds the exudate
• Abscess drain and heal with scarring
• Commonly isolated bacteria Pasteurella multocida (dog, cat
bite wounds), Corynebacterium pseudotuberculosis (horse,
sheep, goat), Arcanobacterium pyogenes (sheep, goat, cattle,
pig)
• Other bacteria include b-hemolytic streptococci, staphylococci,
fusobacterium, bacteroids, clostridium

27. Bacterial Granulomatous dermatitis
• Usually due to traumatic implantation of bacteria
• Mostly saprophytes of low virulence
• Initiate strong cell mediated immune response
• Grossly lesion can be slow progressing, nodular or diffuse
• Mixed cellular population , chiefly macrophages
• Granulomas, giant cells, caseous necrosis

28. Mycobacterial granulomas
• Mycobacteria produce granulomatous to
pyogranulomatous dermatitis in skin especially in cats
• Intracellular bacteria
• Survive and multiply by preventing formation of
phagolysosome
• Tissue destruction with persistence of antigen and CMI
response
• Obligate (M. bovis, M. tuberculosis, M. lepraemurium) or
saprophytic bacteria(M. fortuitum, M. smegmatis etc),
opportunistic (M. avium-intracellular complex)

29. • Infection via wound contamination or traumatic
implantation
• Infection with M. bovis & M. tuberculosis is referred as
tuberculosis
• Infection with other is called mycobacteriosis (atypical,
avian etc)
Mycobacterial infection is more common with rapidly
multiplying opportunistic organism
More common in cat
Lesions are recurrent nodules with draining sinuses in the
inguinal areas

30. • Organisms mostly found in extracellular space line by
neutrophils
• In cattle skin lesions caused by opportunistic
mycobacteria historically called skin tuberculosis occur as
single or multiple nodules (1-8 cm ) in dermis and sub
cutis especially in lower legs.
• Lesions may spread via lymphatic to other regions
• Udder skin is sometimes involved
• Causative agent is mostly saprophytic atypical
mycobacteria e.g. M. kansasii
• Firm (pyogranulomas with fibrosis & mineralization) or
fluctuating nodules (thick wall abcess) connected by thin
cords of tissue

31. • False positive reaction for tuberculosis

32. Atypical mycobateriosis, pyogranuloma
cat

34. • Feline leprosy caused by M. lepraemurium is common in cats
in cold areas of the world
• Biting of cats or rodents, insect vectors, soil contamination of
wounds
• Lesion develop on head, neck and limbs
• Does not grow in culture with routine techniques
• PCR used for identification
• M. visibile also identified in skin lesions
• Two histological pattern of lesion
• One with diffuse granulomatous without necrosis and large
number of acid fast bacilli
• Other central necrosis surrounded by lymphocytes
•

35. • Cutaneous infection with M. bovis & M. tuberculosis are
rare

36. • Mycobacteria in macrophages ZN staining

37. Botryomycosis
• Granulomatous dermatitis caused by non-filamentous
bacteria typically staphylococcus spp, streptococcus,
pseudomonas aeruginosa, proteus, actinobacillus
lignierisii
• These bacteria form small yellow “ sulfur” containing
granules with centrally located bacterial colonies
surrounded by radiating club shaped eosinophilic bodies
called splendore hoeppli material.
• The material is considered antigen antibody material
• Lesions are progressive nodular lesions in cutaneous or
subcutaneous areas
• Differential: Actinomycotic mycetomas, Eumycotic
mycetomas (fungi)

38. • Filamentous bacteria also cause granulomatous
dermatitis
• Nocardia, Actinomyces
• Differentiated from botryomycosis by gram stain and
culture
• Granulomas contain mycelial filaments upto 1 cm
• Progressive nodular lesions can involve underlying bones
• E.g. lumpy jaw

40. • Source: Jubb kennedy and palmer’s Pathology of
domestic animals