Bacterial Skin Diseases Flashcards
Erysipelas
Infectious disease of swine caused by Erysipelothrix insidiosa (rhusipathiae)
Gram positive, pleomorphic facultative anaerobe
World wide distribution, serious economic importance
Acute, subacute, chronic clinical forms
Acute form: fever, depression, anorexia, lameness
Bluish to purplish discoloration of the skin, especially the abdomen, ears and extremities
Pinkish to red macules and papules may also been seen
Subacute form: erythematous papules, wheals enlarge and assume square, rectangular or rhomboidal shapes ‘Diamond skin disease’
Develop purplish center and either regress spontaneously or progress to the chronic phase
Chronic form: necrosis and sloughing, resulting in dry, firm areas of skin which peel away
Occasionally, the ears, tail and feet may slough as well
Histopathology: marked dermal vascular dilatation and engorgement in the acute phase and neutrophilic vasculitis (arteritis) and suppurative hidradenitis in the subactue and chronic phase
Treatment: penicillin 11,000 IU/kg/day
Humans are susceptible and is an occupational disease for people in contact with affected animals
Wound contamination results in erysipeloid
Often seen on hands and fingers
Slowly progressive, discrete, painful violaceous to erythematous cellulitis
TH2 inflammatory environment can promote skin binding by Staph and that this binding is mediated by ____ and ______. We suspect this might happen in S. pseudintermedius
fibronectin and fibrinogen
Bacterial superantigens are _______ exhibiting potent polyclonal T-lymphocyte proliferating activity.
exotoxins
What staph enterotoxin has also been shown to be a potent inducer of IL-31 production by Th2 cells in the skin of patients with AD
Staph Ent B
Describe exfoliative toxins
are virulence factors produced by pathogenic staphylococci, which can cause blister formation in the epidermis. In human S. Aureus infections they are associated with bullous impetigo and staphylococcal scalded skin syndrome
List 3 Staph exfoliative toxins
o SIET
o EXI
o ExpB - Degradation of desmoglein-1
Ceramidase from PSA is inactivated in a dose dependent way by _____ and the use of this has been shown to alleviate atopic dermatitis is an animal model.
citric acid
What enzyme in pathogenic fungi may act as a virulence factor by providing resistance against reactive oxygen species generated within phagocytic cells.
superoxide dismutase enzymes
Yeast hypersensitivity in Bassett hounds in uncommon although this breed commonly develops yeast dermatitis. Why?
Type 1 hypersensitivity and AD are uncommon in this breed.
Despite the possible role of T lymphocytes in protective immunity, there is evidence that these cells are involved in sensitisation of humans and dogs that become allergic to the yeasts. Basset hounds with Malassezia dermatitis usually show delayed rather than immediate intradermal test reactivity to Malassezia antigens although contact sensitization, as demonstrated by patch test reactivity and characterised histologically by infiltration with CD3+ lymphocytes and neutrophils, more closely correlates with disease status in this breed.
Bacterial Proteolytic Acantholytic Dermatoses in Animals
In humans, two infectious blistering skin diseases share a similar pathogenesis that involves the proteolytic action of exfoliatin toxin A, B or D (ETA, ETB, ETD) produced by Staphylococcus aureus. In bullous impetigo, a common skin infection of children, local production of exfoliatin toxin within each blister results in a gradual expansion of subcorneal pustules. In newborns, young children or adult humans with immunosuppression or renal failure, extracutaneous infection with exfoliatin-producing staphylococci results in high levels of these toxins in the circulation, and this leads to sloughing of the epidermis that exfoliates in large sheets overlying widespread erosions. There is now strong evidence that ETA, ETB and ETD are trypsin-like glutamate- specific serine proteases that bind to and then cleave the extracellular segment of desmoglein-1, the human PF antigen. In pigs and dogs, various species of staphylococci also can result in blistering associated with acantholytic-causing exfoliatin toxins
Exudative Epidermitis (“Greasy Pig Disease”) in Piglets
- Exudative epidermitis (EE) is a severe skin disease that affects principally suckling and weaned piglets. It is now known to be due to exfoliatin toxin-producing strains of several Staphylococcus species that include – mostly – S. hyicus, but also S. chromogenes and S. sciuri.
- Affected piglets usually develop an acute or peracute dermatitis that originates on the face and extends rapidly to the characteristic generalized erythema, brown exudation and crusting overlying shallow erosions.
- Histologically, there is subcorneal cleft formation at the level of the stratum granulosum with formation of vesicles and pustules that evolve into crusts.
Exudative epidermitis-causing strains of Staphyloccus hyicus produce up to ___ different exfoliative toxins
- six; (ExhA, ExhB, ExhC and ExhD, SHETA and SHETB), of which the four Exhs and SHETB have sequence homologies to those of S. aureus ETA, ETB and ETD.
- All four Exh exfoliatin toxins recognize and digest porcine desmoglein-1, a mechanism similar to skin lesions arising in S. aureus-infected human patients with bullous impetigo and staphylococcal scalded skin syndrome
Bullous Impetigo and Exfoliative Superficial Pyodermas in Dogs
- S. pseudintermedius – is the cause of several distinctive infectious acantholytic pustular dermatoses of dogs.
- Histologically, pustules of BI are large, subcorneal or intragranular, neutrophilic and they contain variable numbers of acantholytic keratinocytes. Gram- positive staphylococci may be detected in the pustular lesions.
What are considered normal residents on the dog skin?
Micrococcus spp, coaulase-neg Staph xylosus, alpha hemolytic streptococci, Clostridium, Propionibacterium acne, Acinetobacter app and various gram negative aerobes are considered normal residents of the surface of dog skin.
Hair shafts and hair follicles appear to have their own bacterial biota which includes?
Micrococcus, gram negative aerobes, bacillus app and Staphylococcus pseudintermedius.
Staph are usually found distally, whereas gram-negative organisms are found more proximally.
What are the resident biota of cats?
Micrococcus app, coagulase negative staph (Simulans and felis), alpha hemolytic streptococci and Acinetobacter app.
** Household cats have a frequency of isolation of coagulase-negative and positive staph compared to cattery cats; suggesting the these organisms nay be transferred from humans.
What are the transient organisms and which species are found on cats and dogs?
Transient organisms may be cultured from these in but are of no significant unless they become involved in a pathologic process as secondary invaders. These organisms do not multiple on the normal skin of most animals.
Transients of the dog induce E.coli, Proteus, Coryebacterium, Bacillus, PSA and coagulate POSTIVE staph
Transients of the cat include B-hemolytic streptoccou, E.coli, Proteus, PSA, Alcaligene and Bacillus.
In Staphylococcus, the toxins ____ and _____ influence bacterial binding by upregulating adhesion molecules on keratinocytes, but appear to influence the host most by acting as super antigens that can disrupt the immunologic response.
Protein A and Enterotoxin C
Describe the process of bacterial adhesion to keratinocytes?
Bacteria possess sugar adhesion molecules that bind to theist surface receptors to keratinocytes and extracellular matrix components (fibronectin, virtronectin).
In hyperproliferative disorders of the skin, there are more binding sites available making bacterial adhesion easier.
Anaerobic bacteria isolated form dog and cat infections include what organisms?
Actinomyctes, Clostridium, Peptostreptococcus, Bacteroides, Fusobacterium, and Prevotella.
Total counts of aerobic organisms on normal skin range from?
100-1000 organisms/cm2
Dogs with atopic dermatitis shave been shown to have corneocytes with enhanced adherence to S. Pseuintermedius. and defects in epidermal barrier function. What has been shown to increased permeability of canine skin to staphylococcal antigens?
Histamine
One of the most common primary immunodeficiencies diagnosed in dogs is what disease?
Selective IgA deficiency
What breeds do you see Cyclic hematopoiesis and what is the mechanism of defect?
Collie, Pomeranian, Cocker Spaniel
Blockade of bone marrow release
What breeds do you see granulocytopathy and what is the mechanism of defect?
Doberman Pinchers, Irish setter, Weimaraner
Bactericidal defect in neutrophils
What breeds do you see granulocytopathy and what is the mechanism of defect?
Irish Setters
Reduced granulocyte adherence
What breeds do you see a complement deficiency and what is the mechanism of defect?
Brittany Spaniels
Absence of C3
What breeds do you see transient hypogammaglobulinemia and what is the mechanism of defect?
Many breeds
Delayed development of functioning humoral system
What breeds do you see selective IgM deficiency and what is the mechanism of defect?
Doberman Pinchers
Low levels of IgM
What breeds do you see T cell dysfunction and what is the mechanism of defect?
Bull terrier, Weimaraner
Cell-mediated defect
What breeds do you see T and B cell dysfunction and what is the mechanism of defect?
Combined immunodeficiency
Basset Hound, Cardigan Welsh Corgie
While Polymyxin B and Bactitracin in combination may be effective for gram negative and positive infections. What are they inactivated by?
Rapidly inactivated by purulent exudates and do not penetrate well
What are the anti-inflammatory properties of macrolides?
Inhibit leukocyte chemotaxis, interleukin IL-1 and lymphocyte blastogenesis
What are the anti-inflammatory properties of trimethoprim-sulfa?
Inhibits leukocyte chemotaxis
What are the anti-inflammatory properties of flouroquinolones?
Inhibit IL-1, Leukotrienes and inhibit granulamtous inflammation
Cimetidine, an ______ antagonist, may inhibit histamine-inflences immunosuppression.
H2-receptor antagonist
What disease is characterized by non-follicular sub corneal pustules the affect sparsely haired skin?
Impetigo
This is a bacterial disease that is invariably caused by coagulase-positive staphylococci. It affects young dogs.
Histopathology reveals NON-FOLLICULAR subcorneal pustules
What breed is at greater risk of developing mucocutaneous pyoderma?
GSD
Histopathology does not revealed blurring of the DEJ and there is no hydropic degeneration; however, pigmentary incontinence may be marked.
What disease is an actinomycetes disease that produced a superficial crusted dermatitis? It is also known as “cutaneous streptotrichosis”.
Dermatophilosis
This is a gram-positive organism that has rarely been found in the environment and is through to come from carrier farm animals.
Moisture releases the infectious zoospores = initiating factor
These organisms then form flagellate zoospores = persist is crusts for years.
Germinate in CO2 and produce filaments in tissue = crusts
Dermatophilus is resistant to which systemic antibiotics?
Erythromycin, novobiocin, sulfonamides, polymyxin B and penicillin.
Dermatophilus is resistant to which systemic antibiotics?
Erythromycin, novobiocin, sulfonamides, polymyxin B and penicillin.
Furunculosis, regardless of cause, is usually associated with a tissue _____, which is assumed to suggest the presence of a foreign body.
Eosinophilia
Absence = implies immunosuppression
Nasal folliculitis and furunculosis is an uncommon, painful, localized deep infection of the bridge of the nose and the area around the nostrils. It is most common in what breeds?
GSD, bull terrier, collie, point and hunting type breeds.
Parasitic pododermatitis is particularly uncommon with which parasite being the most common cause?
Demodex
Other parasites involved may be Peloderna strogyloides, Ancylostoma spp and Uncinaria stenocephala.
What is a severe, deep, suppurative infection in which the areas of infection are poorly contained and spread laterally?
Cellulitis
What type of cellulitis is characterized by rapid progression, poor demarcation, massive tissue edema and swelling, and necrosis. The wounds often have a putrid smell and are crepitant ( Clostridium and Bacterioides = gas producers).
Anerobic cellulitis
Bacteroiodes, Peptostreptococcus, Fusobacterium, Porphyromonas, Clostridum and Prevotella.
All of these microbes are susceptible to metronidazole, chloramphicol and Clavamox.
Other than Bacteroides, susceptibility to penicillin and clindamycin can be excreted.
Bacterial pseudomycetoma (botryomycosis) is a chronic, suppurative, granulomatous disease caused by ________ bacteria.
non-branching
They room grains of compact colonies in tissues that er surrounded by pyogranulomatous inflammation.
Usually Coagulase positive Staph
_______ causes TB in voles, wood mice and crews, and in cats mostly likely following altercation with these animals. Low risk to man.
M. microti
The M. Avium complex (MAC) includes what species?
M. Avium avium
M. Avium hominissus
M. Avium paratuberculosis
The M. Avium complex (MAC) is associated with what two forms for the disease?
Localized infection os fate skin and subcutis in immunocompetent cats and dogs
Disseminated disease in immunodeficient hosts, particularly Abyssinnian and Somali cats.
The M. Avium complex (MAC) is diagnosed how?
Acid-fast stains are needed to positively highlight the organisms. Differentiation of this organism from other mycobacterial species requires culture or PCR
The M. Avium complex (MAC) - what is the recommended treatment?
For maximum efficacy and to precent development of resistance, the intercurrent use initially of three antimiucrobials for a period of two moths followed by a continuation hoagie with two for a further 6 months ir recommended.
Rimfampin + fluoroquinolone + clarithromycin
**There is a lack of efficacy of older fluoroquinolone and ciprofloxacin and enrofloxacin should don’t be used for MAC infections. Marobfloxacin is still effective.
What is a granulomatous, nodular, cutaneous infection of cats with acid-fast bacilli that are difficult or impossible to culture? What are the two forms?
Feline Leprosy
M. lepraemurium - syndrome in young adult cats caused by infection y the rat leprosy bacillus.
Mycobacterium visible (US) - old cats
Unnamed novel mycobacterium (Australia and New Zealand) which I think is Mycobacterium simiae (strain Tarwin)
Diagnosis of mycobacterium lepraemurium infections - which histologic stains should be used?
Fites Faraco and ZN
Tissue samples of suspected mycobacterial infections should be submitted to rule out which slow-growing mycobacterial organisms?
M. avium subs. avium, hominissus and paratuberculosis
Animals should be destroyed if contacted with M. Bovis or M. tuberculosis
Identification usually required PCR application and nucleotide sequencing.
What is the recommended of mycobacterium lepraemurium infections?
Clofazimine has the best reported success rate for M. Lepraemurium infections. Combined with clarithromycin and or rifampine has been recommended as optimal therapy for feline leprosy for Australian form.
Canine Leproid Granulomas (slow growing) are common in what breed of dog?
Boxers and their crosses - ears most affected.
Usually self resolve (or surgical excision) - if they are still there is a few months then treat with clarithromycin and rifampin.
What is the rapidly-growing mycobacteria that cause cutaneous granulomas in cats and dogs?
Mycobacterium Foruitum Group (fortuitous, perigrinum)
Mycobacterium Chelonae/abscesses group
Mycobacterium Smegmatic Group (smegmatis, goodii and wolinskyi)
Mycobacterium Phlei
Mycobacterium thermoresistble
These organisms typically follow a penetrating route (soil) and occur in fatty areas. Stain with ZN or Fite Faraco modification
Infections by rapidly-growing mycobacterium usually affect what area of the cat?
Most common in the cat in the caudal abdominal or inguinal region or the lumbar region.
What is the empirical treatment for rapidly growing mycobacterium?
Doxycyline, fluoroquinolone and/or clarithromycin
M. Smegmatis is usually susceptable to everything except clarithromycin.
M. Fortiutum is resistant to a lot of drugs - high MIC
M. Chelonae - stains may be resistant to all common drugs expect clarithromycin, linezolid and moxifloxacin.
What is the different in empirical treatment for rapidly growing mycobacterium in Australia vs. US?
In the US, where M. fortiutum and M Chelonae predominate, clarithromycin is appropriate.
In Australia, both M. Smegmatis and M. Fortuitum infection occur with similar frequency, doxycycline or fluoroquinolone is the appropriate first choice.
Clavamox doesn’t work regardless of what the lab says on report….
What is a gram-positive, non-acid-fast, catalase positive, filamentous aerobic rod that is opportunistic commensal inhabitant of oral cavity and bowel?
Actinomyces organisms
What is the normal progression of Actinomycosis infection?
Hunting and field dogs are usually affected.
It can take 2 months to 2 years for signs to develop after injury; although organisms in exudate can be found in 2 weeks.
How do you diagnose Actinomycosis infection?
Diagnosis is made by aerobic culture (takes 2-4 weeks)
Biopsy using Gram, Brown-Brenn or GMS
Sulfur granules are found in about 50% of cases
Looks VERY similar to Nocardia
Surgical debunking with penicillin (empirical treatment)
Relapses are common and takes months to resolve
Actinobacillosis is a rare disease caused by what organism?
Actinobacillus lignieresii
It resembles actinomycosis clinically - but this is a gram negative aerobic coccobacillus that does not survive for long outside the animal. Commensal found in oral cavity of animals
Tissue grains are usually present - need staining to demonstrate that it is gram negative.
Treat with streptomycin or sulfonamides - course is long and prognosis is poor.
What is a gram-positive, partially acid-fast, branching filamentous aerobe that causes suppurative infection of the skin or the lungs in immunocompromised patients?
Nocardiosis
N. Nova is the main species that affects cats.
How do you diagnose Nocardiosis?
Diagnosis with direct smear, fine needle aspirate and aerobic culture.
How do you distinguish Nocardiosis from Actinomycosis?
Nocardia can be distinguished from Actinomyces excuse they are partially acid fast (with Fite-Faraco Modified) and usually branch at right angles = Chinese characters
Prognosis is guarded - varying susceptibilities to antibiotics
Meliodosis is an infectious nodular skin disorder of dogs and cats in SE Asia, Australia and South Pacific caused by what organism?
Burkholderia pseudomallei
This organisms is a saprophyte, and infection occurs by inhalation, arthropod bite or wound contamination.
Diagnose with culture, PCR of IHC
Treat with tetracyclines, sulfonamides, chloramphenicol and clavamox.
What organism is responsible for streptococcal toxic shock syndrome in dogs?
Group C streptococci - especially S. Canis (although this has been associated with Staph)
Rapid development of sepsis, shock and necrotizing fasciitis
Treat empirically with clindamycin or clavamox. DONT use enrofloxacin.
What organisms can cause secondary scrotal dermatitis?
Brucellosis
This is due to painful epididymitis and orchitis
Humans can get this
Hard to treat - usually use a combination of tetracyclines, floroquinolones, and aminoglycosides and sulfonamides.
Plague is an acute febrile infectious sieges that has a high mortality rare and is caused by what gram negative organism?
Yersinia pestis
This is a bipolar coccobacillus of the Enterobacteriaceae family. It is a anaerobic nonmotile, non-spore forming organisms that cannot penetrate unbroken skin BUT can invade mucous membranes.
This disease primarily affects rodents, especially prairie dogs, squirrels and rats.
How is Yersinia pestis transmitted?
Transmitted by fleas or ingestion of infected animals.
What species of rodent flea is the common carrier of the plague?
Diamanus montanus
How do you diagnose plague?
Diagnosis is made by culture of the exudate, immunofluroescense of impression smears, or serologic confirmation based on a fourfold increase in antibody titers form acute to convalescent. Pasturella is usually cultured from lesion too.
Drugs of choice are gentamicin with or without rifampin, chloramphenicol, tetracycline and fluoroquinolones.
Trichomycosis axillaries is caused by what organism?
Corynebacterium
What are partially cell wall-deficient bacteria that resemble Mycoplasma?
L-form Infections
What is the difference between L-forms and Mycoplasma infections?
Retention of some cell wall, variability in size and morphologic characteristics and ability to revert to the parental type with in vitro passage differentiate L forms from Mycoplasma.
L-forms can not be cultured by routine techniques .
Usually present as a polyarthropic presentation.
Tetracycline results in rapid resolution.
To bind to host surface components such as fibrinogen, fibronectin and cytokeratins, which are derived from epidermal keratinocytes, S. aureus utilises microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), such as?
fibronectin-binding protein A (Fnbp A) and Fnbp B
fibrinogen-binding proteins/clumping factors (ClfA and ClfB) iron-regulated surface determinant A and cell wall teichoic acid
What are considered anaphylotoxins?
C3a, C2b and C4a ( also C5a)
They can increase blood vessel permeability, allowing influx of humoral factors to the site of infection. They can also degranulate mast cells and act as potent chemoattractants for neutrophils.
C5a is another ________, whereas C5b initiates a process that leads to the formation of _________.
anaphylotoxin
The membrane attack complex (MAC)
Another major serum protein with anti-bacterial effects is _______, an iron binding protein that can deprive bacteria of an important cofactor for growth and reproduction
transferrin
Pathogenic Staphylococcus aureus contains transferrin binding pro- teins on its surface that enable it to capture the molecule and extract the iron stores for its own use
_____ mediated adhesion of staphylococci to the surface of mammalian cells can promote subsequent internalisation.
Fibronectin-Binding Protein
What are the PRRs keratinocytes use to recognize Staph?
Toll-like receptors (TLRs) and a cytoplasmic receptor known as nucleotide-binding oligomerization domain containing 2 (NOD2)
What are the most common organisms isolated from ‘Udder Rot’?
The most common organisms isolated include: Fusobacterium, Trueperella, Treponemes, occasionally Staphylococci. Methicillin-resistant Staphylococcus aureus (MRSA)
What is the major MRSA strain associated with swine? Though it has been recovered from calves, chickens, dogs, horses, pigs, rats, and humans. Its spread around the globe as a community-acquired strain suggests that it has relatively non-specific host requirements.
ST398
What organism is a gram-positive facultative anaerobe that causes caseous lymphadenitis in small ruminants and cattle? It can also be a cause of ulcerative lymphangitis in these same species, and can infect horses too.
Corynebacterium pseudotuberculosis
What organisms is a gram-positive anerobe and an oral commensal which explains the common manifestation as “lumpy jaw” due oral trauma? Firm swelling over the mandible occurs and then commonly ulcerates and drains. This discharge may contain “sulfur” granules which are 1-3mm diameter yellow to white granules the consistency of sand.
Actinomyces bovis
What organism is a gram negative coccobacillus or rod and oral and rumenal commensal. The classic, though actually uncommon manifestation is “wooden tongue” due to pyogranulomatous glossitis. The more common presentation is firm ulcerated nodules to abscesses in the mouth, jaw, neck region. Discharge may contain “sulfur granules’’ as for Actinomyces.
Actinobacillus lignieresii
What organisms is gram positive acid-fast rods that are widespread in the environment though infection is rare? M kansasii, M. ulcerans have been isolated. Clinical presentation can be subcutaneous nodules or abscesses, or ulcerative lymphangitis consisting of a swollen limb and with corded lymphatics (palpable and enlarged), firm to fluctuant nodules becoming abscesses with draining tracts
Atypical mycobacteria (nontuberculous mycobacteria)
Methicillin resistance among staphylococci is mediated by the mec-A gene that results in what?
production of a novel penicillin-binding protein
