Lecture 2 - Staphylococcus spp.

What are the characteristics of staphylococcus?

-Gram positive cocci

-Facultative aerobes

-Salt tolerant (6.5%)

-Coagulase (+) or (-)

What are the main pathogenic species of staphylococcus?

-S. aureus

-S. pseudointermedius

-S. hyicus

What allows staphylococci to be very hardy and resistant to environmental stress?

Thick peptidoglycan layer and polysaccharide capsule

How is staphlyococci pathogenic?

-Opportunistic pathogen on skin and mucosal surfaces

-Usually secondary to allergies or other inflammation

What is the function of secreted proteins that contribute to virulence with S. aureus?

Carry out quorum sensing

What are the surface proteins that contribute to virulence in S. aureus? When are they present?

-Coagulase

-Protein A

-Fibronectin binding protein

-Always present

How does Staphylococci adhere? Where do they commonly adhere to and what does it cause?

-Mediated by protein A and fibronectin binding proteins

-Forms biofilms (can adhere to abiotic factors)

How do protein A and polyuronic acid capsules contribute to virulence?

Confer resistance to phagocytosis

How do carotenoids and catalase contribute to virulence?

Causes anti-oxidative burst (allows for intracellular survival in phagocytes)

How do hyaluronidase and hydrolases contribute to virulence?

Cause host tissue necrosis and degradation

How does coagulase contribute to virulence?

Walls off necrotic areas causing abscesses

How do DNAse’s contribute to virulence?

Degrades NETs and METs

What is staphyloxanthin? What does it do?

Carotenoid pigment that causes staph to become more resistant to oxygen dependent killing mechanisms by phagocytes

What are the stages of abscess formation?

Release of bacterial products → neutrophils infiltrate → staph leukocidin and hemolysins cause neutrophil lysis → coagulase walls off necrotic areas causing abscesses

What are the characteristics of Staphylococcus epidermidis? Where is it found? How does it cause infections?

-Coagulase negative, non pigmented and non hemolytic colonies

-Found on skin, teats, and hair

-Opportunistic infection

What are staphylococcus exfoliative toxins?

Degrade desmoglein causing splitting of the stratum granulosum

What kind of infections does S. pseudointermedius cause?

-Mixed infections of skin, wounds, and surgical sites (itching)

-UTIs often causing uroliths

What disease does staphylococcus hyicus cause in swine? How?

-Greasy pig disease

-Exfoliating toxin degrades desmosomes

What is the prevention for Staphylococcus hyicus?

-Teat dip sow’s udder

-Keep environment clean and dry

-Avoid skin injuries with gates/sharp objects

What is the treatment for staphylococcus hyicus?

-Antibiotics (amoxicillin, oxytetracycline, cefalexin, gentamycin, lincomycin, penicillin)

-Topical novobiocin spray

What bacteria is the most common cause of mastitis?

Staphylococcus (S. aureus most severe)

How does S. aureus cause damage with mastitis?

-Suppuration of mammary gland

-Infiltration of macrophages and neutrophils

-Damaged epithelium

What is the treatment for mastitis?

Intramammary infusions with beta lactams, pen-novo, amoxicillin, and ceftiofur

What can cause staph sepsis? What are the clinical signs?

-Organism in deep wounds

-Walled-off abscesses and high fever