Staphs, streps and actinomyces (+VE skin organisms) Flashcards
Staphylococcus location
Localised lesions - will get in and stay on skin, won’t go round the body
Often peripheral- skin infections, mastitis
Streptococcus location
Generalised lesions - will spread, are nastier deep rooted diseases that travel round
Tend to be deeper - strangles, mastitis, endocarditis
Enterococcus location
In intestine, rarely pathogenic, can cause would infections, are kind of just there
Micrococcus location
Non pathogenic and least important, very very small
Actinomyces location
IS A +VE COCCI NOT A FUNGUS
Localised lesions, oropharyngeal commensal - lumpy jaw
Truperella location
Generalised lesions - skin necrosis, mastitis
Dermatohphilus location
Motile spores, a highly evolved form of bacterium
Very strange- mud fever, rain scald
Cellular arangements
Staphylococci = clump together, irregular plans of division + sticky
Micrococci = in pairs or groups of pairs, more regular planes of division + sticky
Streptococci and enterococci = 1 plane of division + some sticky, snakes/ pairs/ chains
What are planes of division in relation to bacteria
Chains form when bacteria divide on one plane, clusters form when bacteria divides in two planes, sarcoma form when bacteria divide in 3 planes
https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kaiser)/Unit_1%3A_Introduction_to_Microbiology_and_Prokaryotic_Cell_Anatomy/2%3A_The_Prokaryotic_Cell_-_Bacteria/2.1%3A_Sizes_Shapes_and_Arrangements_of_Bacteria
- Good for arrangement explanations
Staphylococcal/ micrococcal habitats
- In the environment - have a peptidoglycan outside so can protect from defictaion
- On animal and human skin
- Good at surviving everywhere
- Can end up further -on mucus membranes - animal licks themselves and swallows
- Staphylococcus - upper respiratory and digestive tracts
- Micrococcus - mammary gland
Staphylococcal species of importance
Important pathogens
= Staphylococcus aureus = wound infections
= Staphylococcus pseudintermedius (aka intermedius) IS ONLY IN DOGS
= Staphylococcus hyicus
What do staphylococcal species cause?
Mastitis, skin infections, soft tissues infections, surgical site infections - They get in through where there are breaks in the skin or where there is inflammation
Staphylococcus pseudintermedius mechanism
Uses coagulase to make fibrin clot and stay in the area
Rare opportunistic staphylococcal species
Staphylococcal epidermis
Staphylococcal saprophyticus
Staphylococcus aureus
Can be seen as yellow in human strains and every other animal than dog
in dog will be seen as white dots on a blood agar plate
Haemolytic staph aureus
- Breaks down RBC and leukocytes
- it produces things that break down RBC’s and leukocytes as a way to evade the immune response
Different types of Staph aureus haemolysin
a (alpha) and b (beta) - the symbols
Staph aureus a-haemolysin
- Complete lysis of RBC
- is a plasma membrane porin - inserts self into plasma membrane of RBC
- Cytocidal - highly potent
- Disrupts leukocytes
- Will attack smooth muscle in blood vessel walls - lead to constriction/ necrosis
- Attacks many cell types - causes necrosis/ dermonecrosis (as attacks skin cells)
Laboratory test for Staph aureus a-haemolysin
Complete red blood cell lysis on a blood agar plate
- creates a narrow, clear zone
Staph aureus b-haemolysin
- Partial lysis of RBC
- Has phospholipase C which breaks down phospholipids so breaks down membranes
- Potent
- Is unique to only animal strains - will indicate that strain is from an animal
- Its role in pathogenesis is unknown
- Won’t look as well defined lysis on blood agar plate
Types of diseases associated with Staph
Pyogenic (suppurative) skin infections = puss producing
- Due to rush of leukocytes in and being killed
= Dermatitis, Pyoderma, Abscesses
Systemic infections
= Septicaemia - deposition/ local damage - due to bacteria building up
Staph. hyicus = greasy pig disease
- under the skin
- causes crisping up
- outer layer of skin comes up and layer of raw skin underneath is visible
Treatment of Staph infections
Physical treatment good as pus is protective - wound drainage and disinfection
Treat with antibiotics however there are many resistant genes so resistance to these is very common.
e.g. MRSA - Methicillin resistant staphylococcus aureus - a strain of antibiotic resistant bacteria
Differentiation between cocci = Staphs and Streps
Staphs =
