skin microbiology 1+2 Flashcards
explain why different locations on the body will have different microbiology
- secretions vary by site
- immune cell distribution varies in layers
- local humidity varies
- mucosa vs keratinocyte
- local environments have an impact on microbiology
explain how skin is a barrier and defended environment against microorganisms
- barrier = keratinised cells
- turnover of cells sheds potential resident organisms (unless top layer is punctured)
- environment is dry and has specific ph
- lipids and antimicrobial peptides and immunoglobulins secreted
- immune cells within the skin (neutrophils, macrophages, intraepithelial lymphocytes and NK cells
what type of cell is indicative of bacterial infection
neutrophils
what type of cell is indicative of deeper skin infection
macrophages as they live in lower layers of skin
what are resident pathogens
commensals
can replicate on the skin and can persist
what is an opportunistic pathogens
organism that would normally be commensal but in position or condition it can cause disease
what is a nomad pathogen
organism that can colonise and reproduce on the skin for short times
what is a transient pathogen
cannot replicate so stay for a short period of time but can grow out of control if imbalance
what are pathogens
organisms that become established and can proliferate on the skin surface and deeper that are deterious to normal physiology of the skin
what does dysbiosis mean
changes from balanced (normal) to unbalanced microflora
what factors increase risk for infection
- moisture/humidity
- damage
- normal tissue maintenance
- washing (overwashing esp)
- behaviour
- health
- physical breaches to the barrier
- veterinary interventions
describe staphylococcal bacteria and its pathogenicity
- gram positive, facultative anaerobes. coccoid and often seen in clusters but sometimes in small groups and pairs
- commensals but often occur as opportunistic pathogen
- confim via Mass spec, PCR or serology
- infection can cause pyogenic lesions (neutrophil related) leading to pus and can form abscesses OR granulomatous inflammation (macrophage related) or combo (pyogranulomatous)
- minor trauma damage may predispose to disease and they can possess a number of virulence factors (coagulase, lipases, protein A inhibits opsonisation, toxins)
name clincially important staphylococcus species
- S hyicus (a species whose procine subspecies are opportunistic pathogens associated with epidermal infection in pig (greasy pig disease))
- S. pseudointermedius (commensal and can infect the skin of domestic dogs and cats)
- S. Aureus (derm infections of a number of animals and one of the possible causes of mastitis in cattle)
desribe pseudomonas and its pathogenicity
- gram neg rods, aeroibic, motile
- common in the environment and are both pathogenic and non-pathogenic strains
- colonies tend to be slimy due to a biofilm (polysaccharide mucous secreted by them)
- non spore forming but hardy. biofilms help make them refractive to treatment
describe proteus mirabilis and its pathogenicity
- gram negative rods, facultative anaerobes
- motile, swarm can be observed on plates and have characteristic fishy smell
- can cause ear infections but also associated with UTIs (likely due to fecal contamination as is an enteric commensal)
