Staphs, streps and actinomyces (+VE skin organisms)

Question 1

Staphylococcus location

Answer 1

Localised lesions - will get in and stay on skin, won’t go round the body
Often peripheral- skin infections, mastitis

Question 2

Streptococcus location

Answer 2

Generalised lesions - will spread, are nastier deep rooted diseases that travel round
Tend to be deeper - strangles, mastitis, endocarditis

Question 3

Enterococcus location

Answer 3

In intestine, rarely pathogenic, can cause would infections, are kind of just there

Question 4

Micrococcus location

Answer 4

Non pathogenic and least important, very very small

Question 5

Actinomyces location

Answer 5

IS A +VE COCCI NOT A FUNGUS
Localised lesions, oropharyngeal commensal - lumpy jaw

Question 6

Truperella location

Answer 6

Generalised lesions - skin necrosis, mastitis

Question 7

Dermatohphilus location

Answer 7

Motile spores, a highly evolved form of bacterium
Very strange- mud fever, rain scald

Question 8

Cellular arangements

Answer 8

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

Question 9

What are planes of division in relation to bacteria

Answer 9

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

Question 10

Staphylococcal/ micrococcal habitats

Answer 10

• 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

Question 11

Staphylococcal species of importance

Answer 11

Important pathogens
= Staphylococcus aureus = wound infections
= Staphylococcus pseudintermedius (aka intermedius) IS ONLY IN DOGS
= Staphylococcus hyicus

Question 12

What do staphylococcal species cause?

Answer 12

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

Question 13

Staphylococcus pseudintermedius mechanism

Answer 13

Uses coagulase to make fibrin clot and stay in the area

Question 14

Rare opportunistic staphylococcal species

Answer 14

Staphylococcal epidermis
Staphylococcal saprophyticus

Question 15

Staphylococcus aureus

Answer 15

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

Question 16

Haemolytic staph aureus

Answer 16

• Breaks down RBC and leukocytes
• it produces things that break down RBC’s and leukocytes as a way to evade the immune response

Question 17

Different types of Staph aureus haemolysin

Answer 17

a (alpha) and b (beta) - the symbols

Question 18

Staph aureus a-haemolysin

Answer 18

• 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)

Question 19

Laboratory test for Staph aureus a-haemolysin

Answer 19

Complete red blood cell lysis on a blood agar plate
- creates a narrow, clear zone

Question 20

Staph aureus b-haemolysin

Answer 20

• 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

Question 21

Types of diseases associated with Staph

Answer 21

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

Question 22

Staph. hyicus = greasy pig disease

Answer 22

• under the skin
• causes crisping up
• outer layer of skin comes up and layer of raw skin underneath is visible

Question 23

Treatment of Staph infections

Answer 23

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

Question 24

Differentiation between cocci = Staphs and Streps

Answer 24

Staphs =