Skin microbiology Flashcards
Which microbe is seen in higher numbers in Bassets?
- Mallassezia (yeast)
- It is also high in WHW, Cockers, Daschunds
Define a resident organism
-Can replicate on the skin and can persist
Define a nomadic organism
-Can colonise and reproduce on skin for a short time
Define a transient organism
-Can NOT replicate so stay for short time
List some resident microbes found on dogs
-Skin Micrococcus spp Clostridium Acinetobacter -Hair Micrococcus spp Staphylococcus pseudintermedius -Hair follicle Staphylococcus pseudointermedius Micrococcus spp
List dome transient microbes found on the skin of dogs
- S.aureus
- E.coli
- Staphylococcus pseudinetmedius
List some examples of bacteria found on dogs and state is gram positive or negative
- Clostridium= Gram +
- Staphyloococcus= Gram +
- Micrococcus spp= Gram +
What would you not expect to find on skin?
-Gram negative bacteria or rods
Describe staphylococcus
- Gram positive
- Facultative anaerobes
- Catalase +/ Oxidase -
- S.pseudointermedius CANNOT ferment maltose but s.aureus can
Describe penicillin resistance and methicillin
- Penicillin (B-lactam) uses PBP (penicillin binding protein) to work.
- In penicillin resistant bacteria they make B-lactamas which destroys the antibiotics
- People switched to using methicillin which aren’t affected by B lactamases.
- Bcateria then expressed MecA or PBP2 channels which the methicillin cannot bind to therefore it s also resistant to methicillin.
With which bacteria is it common to have concurrent infections with malassezia?
S. pseudintermedius
Which bacteria causes greasy pig disease?
-Staphylococcus hyicus
What effect do superantigens have?
The over activate T lymphocyte and thus bypass the normal process (don’t need the peptide to be presented)
-cause massive cytokine release
What are the primary causes that can lead to proliferation of commensal microbes?
- Hypersensitivity
- Systemic disease
- Damage leading to compromise of defences
Define a secondary infection
-When defences are compromised by an existing condition allowing further organisms that wouldn’t normally cause a problem cause infection.
List a common infection found in the following species dog, cattle, pig, sheep, horse
- Dog= Staphylococcus intermedius
- Cattle= Dermatophysis (ringworm)
- Pig= greasy pig disease Staphylococcus hyicus
- Horse= Mud fever, dermatophilus
Discuss the pathogenicity of staphylococcus
- Pyogenic (pus forming)
- Virulence factors: coagulase, lipases, protein A (inhibits opsonisation)
Describe dermatophysis
- AKA ringworm
- Grows ONLY in kertinised non living tissue of skin and nails
- Causes inflammation and irritation
- Most common in cattle= Trichopyton verrucosum
- Commonly affects young stock
Name a dimorphic yeast species that produces a capsule
Cryptococcus
What medium is normally used in fungal cultures of dermatophytes?
Dermatophyte test medium
What is wood’s lamp?
Some dermatophytes produce metabolites which fluoresce green when immulinated by the lamp.
What is a trichogram?
A microscopic exam of a plucked hair
How do you take a skin scrape?
Use a scalpel blade coated with mineral oil and scrape along skin
What is a common fungal stain?
Lactophenol cotton blue
