Bacteriology 1: skin pathogens

What type of bacteria does this image show?

single cocci

What type of bacteria does this image show?

cocci chains

What type of bacteria does this image show?

4’s and 8’s cocci

What type of bacteria does this imag eshow?

pairs of cocci (diplococci)

What type of bacteria does this image show?

cocci clusters

What type of bacteria does this image show?

single rods

What type of bacteria does this image show?

rod chains

What type of bacteria does this image show?

curved rods

What type of bacteria does this image show?

club-shaped rods

What type of bacteria does this image show?

filamentous rods

What type of bacteria does this image show?

rod pairs

What type of bacteria does this image show?

helical rods

What kind of DNA do bacteria have?

nucleoid

What is this part of bacteria?

mesosome

What does a gram positive cell wall contain?

• simple phospholipid bilayer

• peptidoglycan with teichoic acids 

What does this image show?

gram positive cell wall

What does this image show?

peptidoglycan

What does this image show?

gram negative cell wall

What does the gram negative cell wall contain?

• 2 layers of polysaccharides

• peptidoglycan holds together & gives shape

• lipopolysaccharides

What does this image show?

lipopolysaccharide structure

Do gram positive or gram negative bacteria change colour in the heated fixed smear/crystal violet/iodine/alcohol/dilute fuschin test?

gram negative 

In the test for bacteria, what colours to gram negative bacteria change to with alcohol?

white

In the test for bacteria, what colours to gram negative bacteria change to with dilute fuchsin?

pink

What internal structures does this image show?

glycocalyx

What is the glycocalyx?

• capsules

• slime layers

Name 4 gram positive cocci

• staphylococcus

• streptococcus

• enterococcus

• micrococcus

What do staphylococcus cause?

localised lesions (often peripheral - skin infections, mastitis)

What does streptococcus cause?

generalised lesions (deeper - strangles, mastitis, endocarditis)

What does enterococcus cause?

rarely pathogenic (found in the intestine, can cause wound infections)

Which type of gram positive cocci are very small?

micrococcus

Are micrococcus pathogenic or non-pathogenic?

non-pathogenic

What are the cellular arrangements of staphylococci?

irregular planes of division & sticky

What are the cellular arrangements of micrococci?

more regular planes of division & sticky

What are the cellular arrangements of streptococci and enterococci?

1 plane of division & some sticky

What are the habitats of staphylococcus/micrococcus?

• worldwide

• environment

• animal/human skin

• animal/human mucous membranes

Which mucous membranes are staphylococci found in?

upper respiratory & digestive tracts

Which mucous membranes are micrococcus found in?

mammary gland

Which staphylococcal species are of importance?

• staph. aureus

• staph. pseudintermedius (intermedius)

Which species is staph. pseudintermedius (intermedius) found in?

JUST DOGS

What do staph. aureus and staph. pseudintermedius (intermedius) cause?

• mastitis

• skin infections

• soft tissue infections

• surgical site infections

What are the rare opportunistic staphylococcal species?

• staph. epidermidis

• staph. saprophyticus

What does this image show?

human strain of staph. aureus

What does this image show?

dog strain of staph. aureus

What colour is staph. aureus?

golden yellow

What does this image show?

haemolytic staph. aureus

What does Staph aureus alpha-haemolysin cause?

• disrupts leucocytes

• necrosis/constriction of smooth muscle in blood vessel walls

What laboratory tests for Staph aureus alpha-haemolysin can you do?

complete red blood cell lysis (narrow, clear zone)

How does Staph aureus alpha-haemolysin affect rabbits?

• necrotic (ears)

• lethal

What are characteristics of Staph aureus beta-haemolysin?

• phospholipase C

• potent

• unique to animal strains

• role in pathogenesis unknown

• partial RBC lysis

What are general types of disease associated with staphylococci?

• pyogenic (suppurative) skin infections

• systemic infections

What is seen with pyogenic (suppurative) skin infections associated with staphylococci?

• dermatitis

• pyoderma

• abscesses

What is seen with systemic infections associated with staphylococci?

septicaemia & deposition/localised damage

What does this image show?

greasy pig disease (staph. hyicus)

What does staph. hyicus cause in pigs?

ear necrosis

How can you treat staphylococcal infections?

wound drainage and cleaning (remove body of infection)

Why is it challenging to treat staphylococcal infections?

resistance genes common/widespread (e.g. MRSA)

What does this image show?

alpha-haemolysin & greening of strep. pneumoniae

What are the habitats of lactococci?

milk/products

What is the habitat of enterococci?

gut

What are the habitats of streptococci?

• skin/mucosal membranes

• upper respiratory tract

• upper GI tract

• lower urogenital tract

What are the main disease patterns of streptococci?

• upper respiratory tract infections & lymphadenitis

• neonatal septicaemic infections

• secondary pneumonia

• urogenital tract infections

• mastitis

What does strep zooepidemicus cause in pigs?

suppurative arthritis in piglets

How does strep zooepidemicus cause suppurative arthritis in piglets?

sow flora → umbilical cord → septicaemia → chronic lameness or death

What does strep porcinus cause in pigs?

strangles-like disease in piglets 

What are the characteristics of strep porcinus?

• highly contagious

• seen mainly in young animals

• commensal organism

What streptococci cause mastitis in cattle?

• strep uberis

• strep dysgalactiae

• strep agalactiae

• strep zooepidemicus

Features of strep uberis

• commensal

• most common

• acute

• mild

• economically significant

Features of strep dysgalactiae

• commensal 

• less common

• acute

• severe

• often in summer with A.pyogenes

Features of strep agalactiae

• obligate pathogen

• less common

• chronic

• economically significant

• zoonotic

Features of strep zooepidemicus

• least common

• from horses

What do these images show?

streptococcus equi (strangles)

How can you control streptococcal infections?

• antibiotics

• disinfectants

• vaccines

Is resistance more of a problem in streptococcal or staphylococcal infections?

staphylococcal

Why are antibiotics used in the control of streptococcal infections?

help prevent local infection becoming systemic

Where should you use disinfectants for control of streptococcal infections?

• milking machinery

• stables

• troughs

Why are vaccines such an important part of controlling streptococcal infections?

for prevention of wound infections in the first place