Bacterial Pathogens 5 - Staphylococci

Front 1

Give 4 examples of staphylococcal infections.

Back 1

Any 4 of: intramammary infections (e.g. mastitis in ruminants); wound infections; pyoderma (dogs and cats); exudative epidermatitis ('greasy pig disease'); tick pyemia; dermatitis, osteomyelitis and arthritis (in poultry); cystitis (generally dogs and cats); septicaemia (many animals, inc. rabbits); infective endocarditis (horses, cows, large breeds of dogs).

Front 2

Define subclinical mastitis.

Back 2

Mastitis with no overt clinical signs, but an increased SCC (Somatic Cell Count)

Front 3

Define clinical mastitis.

Back 3

Showing clear symptoms of disease, e.g. redness, tenderness, swelling and clots in the milk.

Front 4

What is peracute mastitis?

Back 4

Mastitis which is severe and systemic. It can become gangrenous, cause fever and possibly death.

Front 5

What is the rough yearly cost of mastitis to UK dairy farmers?

Back 5

~£93 million

Front 6

How do current rates of mastitis in dairy cows compare with those of the 1960's?

Back 6

1960's: ~150 cases/100 cows/year
Now: ~30 cases/100 cows/year
Much better!

Front 7

Out of subclinical, clinical and peracute mastitis, which is the most commonly seen on UK dairy farms?

Back 7

Subclinical - noticeable only by an increase in SCC.

Front 8

What is the most common staphylococcal pathogen to cause mastitis? Where does the contamination normally come from?

Back 8

Staphylococcus aureus - from contaminated milking machinery.

Front 9

What are the stages of mastitis pathogenesis?

Back 9

1. Colonisation of teat/carriage.
2. Damage to tissues lining the teat/gland cisterns within the quarter.
3. Move up the duct system and establish infection in milk secreting cells - alveoli.
4. Damage provokes inflammation and leukocyte/neutrophil influx.
5. Abscess formation, scar tissue formation, congestion.
(6. Treatment/clearance)

Front 10

During mastitis, what is often responsible for the damage done to the tissues lining the teat and gland systems within the infected quarter?

Back 10

Toxins

Front 11

What is used by the mastitis pathogen to survive the influx of leukocytes and neutrophils?

Back 11

Concealment and anti-phagocytic factors.

Front 12

Give some examples of virulence factors produced by staphylococcus aureus.

Back 12

Cell wall and capsule, anti-inflammatory proteins, MSCRAMMs (e.g. Clumping factor A,B, SdrC,D,E, Cna, Staphylococcal protein A and Fibronectin-binding proteins) enzymes (e.g. staphylokinase, hyaluronidase and coagulase) and toxins (e.g. enterotoxins A-P, TSST-1, ETA B and haemolysine).

Front 13

Staphylococcus aureus has (many/few/no) surface adhesin appendages, and thus it (sticks well/does not stick/sticks slightly) to other cells.

Back 13

many, sticks well

Front 14

S. aureus can produce around 20 surface adhesins. These all follow a basic plan. Briefly outline this.

Back 14

Composed of a signalling sequence (S), an active domain (generally containing receptors) (A) and a repeat domain (R). They may also contain repeating B sequences.

Front 15

All staphylococcus aureus isolates make the same 1-2 fibronectin-binding proteins. What are the purposes of these?

Back 15

Mediate binding to fibronectin and fibrinogen.
Mediate cellular uptake in order to avoid the host immune response (which may explain the reduced sensitivity of S. aureus to antibiotics in vivo) and undergo antigenic variation - another way of avoiding the host response.

Front 16

In what ways can Staph. aureus avoid phagocytosis by the host cells?

Back 16

Protein A binds to the Fc regions of the antibodies and holds them in the wrong orientation for presenting to macrophages, and the capsule, whilst it does activate complement, is not able to be opsonised or phagocytosed.

Front 17

What is the purpose of the polysaccharide capsule of Staph. aureus?

Back 17

Resist phagocytosis.

Front 18

True/False: Staphylococcus aurea bacteria all exhibit the same capsule serotypes.

Back 18

False - there is variation in serotypes between strains of the bacteria.

Front 19

What are superantigens and what do they do?

Back 19

Superantigens are proteins which trigger massive, non-specific T-cell activation, with a correspondingly large release of cytokines. They do this by cross-linking T-cell receptors and MHC class II molecules on host cells.

Front 20

What is the purpose of staphylococcal haemolysin alpha?

Back 20

Formation of pores, damage to the membrane, leukocidal, cytocidal

Front 21

What is the purpose of staphylococcal haemolysin beta?

Back 21

Acts as a sphingomyelinase (damages membranes rich in this lipid).

Front 22

What is the traditional test for beta toxin in a Staph. aureus strain?

Back 22

Ability to lyse sheep erythrocytes.

Front 23

Most human isolates of Staph. aureus do not express beta-toxin, whilst the majority of bovine isolates do. What does this suggest?

Back 23

That beta-toxin is important in the pathogenesis of mastitis. (This is supported by the fact that ß-toxin-deficient mutants have reduced
virulence in a mouse model for mastitis.)

Front 24

Describe delta-toxin.

Back 24

Small peptide toxin produced by most strains of Staph. aureus, and also Staph. epidermidis and Staph. lugdunensis. Has cytolytic activity.

Front 25

What is the function of gamma-toxins and leukocidins?

Back 25

Membrane damage in susceptible cells, such as polymorphonuclear leukocyte cells. They are two-component protein toxins.

Front 26

Which toxins are commonly produced by human Staph. aureus strains?

Back 26

Alpha and delta

Front 27

Which toxins are commonly produced by animal Staph. aureus strains?

Back 27

Alpha, beta and delta

Front 28

Name 4 degradative types of enzymes which may be produced by Staph. aureus.

Back 28

Proteases, lipases, DNAases, FAME (Fatty Acid Modifying Enzyme)

Front 29

Which enzymes does the Staph. aureus bacterium use to provide nutrients for itself?

Back 29

The proteases, lipases and DNAases.

Front 30

It is thought that FAME may be important in abscesses. What is it thought that it may do?

Back 30

Modify bacterial lipids and prolong bacterial survival.

Front 31

Give an important diagnostic test for Staph. aureus.

Back 31

Testing for thermostable DNAase.

Front 32

Host susceptibility to Staph. aureus mastitis varies between individuals, with a seemingly genetic component. Give three things which may vary between hosts and alter their susceptibility to Staph. aureus mastitis.

Back 32

Any three of: variations in lactoferrin (sequesters iron) and lysozyme concentrations; variations in efficiency of MHCs (major histocompatibility complexes); depth of udder; milking speed; milk production traits.

Front 33

Hygiene is fundamental if the spread of mastitis is to be controlled. What three things can be done in the milking parlour to curb the spread?

Back 33

1. Udder and teats washed prior to milking.
2. Udder and teats disinfected after milking.
3. Milking equipment sterilised and regularly serviced.

Front 34

Suggest a reason for the reduced efficacy of antibiotics in vivo vs. in vitro.

Back 34

Fibronectin-binding proteins allow the bacteria to easily invade cells, thus reducing the efficacy of the antibiotics as the bacteria are able to evade them.

Front 35

With antibiotic resistance on the increase, what else may be able to be used to combat bacterial infections? Aside from lack of resistance, what other benefits may these carry?

Back 35

Interleukins (a group of cytokines which promote the development and differentiation of B, T and haematopoietic cells). These are also natural substances normally found in the body, simply at an increased concentration therapeutically, reducing the need for withdrawal periods, etc.

Front 36

Recently, a transgeni cow was developed which was able to produce the enzyme lysostaphin in the epithelial cells lining the milk-producing alveoli. Why is this an advantage?

Back 36

Lysostaphin is an enzyme capable of cleaving the cross-linking pentaglycin bridges in the cell wall of Staph. aureus. Thus, is functions as an antimicrobial, preventing the cow from contracting Staph. aureus mastitis.

Front 37

Staph aureus can be found in many different species. Does this therefore mean that Staph. aureus exhibits very limited host specificity?

Back 37

No - individual strains of Staph. aureus do exhibit high levels of host specificity.

Front 38

Name 4 conditions caused in poultry by the bacteria Staph. aureus.

Back 38

Septic arthritis, chondronecrosis (with) osteomyelitis and ulcerative pododermatitis (aka. bumblefoot').

Front 39

Which bacteria is known to cause canine pyoderma?

Back 39

Staphylococcus pseudintermedius

Front 40

Describe canine pyoderma, mentioning cause, symptoms and treatment.

Back 40

Very common skin disease, often secondary to atopic dermatitis - usually commensal. Symptoms include pruritus (itching), alopecia, swelling, erythema (redness). Treated with systemnic antibiotics and topical shampoo. There is currently no vaccine.

Front 41

Staph. pseudintermedius used to be known as Staph. intermedius, until it was discovered that there were two more pathogens, phenotypically identical to it, which caused the disease in other species. What were these bacteria named and in which species do they cause disease?

Back 41

Staph. intermedius - causes pyoderma in pigeons
Staph. delphini - causes pyoderma in horses

Front 42

What does MRSA stand for?

Back 42

Methicillin resistant Staphylococcus aureus.

Front 43

What is the colloquial name for exudative epidermitis in pigs?

Back 43

'Greasy pig syndrome'

Front 44

What is exudative epidermitis in pigs caused by?

Back 44

Staphylococcus hyicus bacteria

Front 45

What are the commonly recognised symptoms of 'greasy pig syndrome'?

Back 45

Oozing of fluid from inflamed skin.

Front 46

Staphylococcus hyicus is normally commensal but causes disease after skin damage/abrasions. What does it do?

Back 46

Produces exfoliative toxins resutling in skin lesion symptoms, and also damage to the liver and kidneys.

Front 47

Many piglets are infected during/shortly after birth, and only often 50% of those infected will survive. Why are so many infected during birth?

Back 47

In the days preceeding the birth, the bacteria multiplies rapidly in the vagina of the sow.

Front 48

How is exudative epidermitis treated?

Back 48

First of all, the strain of the pathogen must be identified. The antibiotic sensitivity is then determined, and the piglets are either injected daily for 5 days, or every second day with a long acting antibiotic.

Front 49

Give 2 examples of antibiotics which can sometimes be used to treat exudative epidermitis.

Back 49

Amoxycillin, OTC, ceftiofur, cephalexin, gentamycin, lincomycin or penicillin. In severe cases and autogenous vaccination can be prepare by sampling the organism - this has proved effective on some farms.

Front 50

(Very) briefly describe MRSA.

Back 50

Methicillin Resistant Staphylococcus aureus - a huge problem worldwide, strains seen to cause infection in both animals and humans.