Staphylococcus and Streptococcus

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Staphylococcus and Streptococcus
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Nightmare bacteria
Super bugs
Flesh eating bacteria
Streptococcal necrotizing fasciitis
MRSA
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Common characteristics
Staphylococcus
Streptococcus

• Gram positive cocci
• Facultative anaerobes
• Non-sporing, non-motile
• Important pathogens
• Pyogenic suppurative infections
• Commensals of mucous membranes and skin

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Differentiating characteristics
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Staphylococci - EM
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Staphylococci of veterinary importance
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Laboratory diagnosis

• Specimens
• May include exudates, pus, mastatic milk, skin
  scraping, etc
• Direct microscopy
• To examine gram stained smears (pus/exudates)
• Isolation
• Routine medium is blood agar (24 hours).
• MacConkey agar in parallel, to detect any gram
  negative bacteria.

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S.aureus cultural characteristics
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Staphylococcal haemolysins
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Differentiating pathogenic from non pathogenic
Staphylococci
S.aureus S.intermedius S.hyicus Non pathogenic strains (S.epidermidis)
Coagulase variable -
DNAase -
Haemolysis - -
Oxidase - - - -
Catalase

• Coagulase correlates with pathogenecity.
• Micrococci are O-F positive, Streptococci
  enterococci are negative?

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Coagulase and DNA tests
DNAse agar. Not definitive
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S. aureus Infections
Toxic Shock Syndrome
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Terminology
Impetigo A contagious skin infection that is
characterized by the eruption of superficial
pustules and the formation of thick yellow
crusts, commonly on the face. Septicaemia blood
poisoning caused by pathogenic microorganisms and
their toxic products in the bloodstream
Osteomyelitis infection of bone and bone marrow
in which the resulting inflammation can lead to a
reduction of blood supply to the bone
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Strategies of extracellular pathogens
Counteract complement Counteract
phagocytes Acquire nutrients
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Staphylococcus virulence factors

• Anti-opsonic anti-phagocytic
• Staphylococcal complement
• inhibitor (SCIN)
• Protein A
• Capsule
• Staphylokinase
• Fibrinogen-binding proteins
• Haemolysins Leukocidins

Iron-uptake systems Staphyloferrin B
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Staphylococcal resistance to phagocytosis
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S.aureus disease in animals
Mastitis
Bumble foot
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Staphylococcal scalded skin syndrome (SSSS)
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Staphylococcal skin diseases
Pyogenic infections following penetration of
skin, boils etc many species.
Exfoliative skin diseases.
Humans
Dogs
Pigs
S.aureus
S.intermedius
S.hyicus
Scalded skin syndrome
Pyoderma
Greasy pig disease
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Exfoliative conditions skin diseases

• Prevalent Staph on skin of particular host
• Humans S.aureus
• Pigs S.hyicus
• Dogs S.intermedius
• Virulence factors Exfoliative toxin (ET).
• S.aureus at least 4 ET
• Protease cleaves desmoglein 1 in desmosomes
• Separation of the upper epidermis
• S.hyicus
• At least 5 ET
• S.intermedius
• An ET-like toxin has been described

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Tampon disease

• Staphylococcal toxic shock syndrome (TSS) high
  fever, hypotension, renal failure

• Increase in staphylococcal TSS in menstruating
  women in early 1980s in USA
• Particular S.aureus strains producing toxic shock
  syndrome toxin-1 (TSST-1) is a SUPERANTIGEN
• Associated with super absorbent tampons
• ? Absorb Mg low Mg act as cue for S.aureus
  to produce TTST-1.

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Superantigens (SA)
Superantigens (SAgs) are a class of antigens
which cause non-specific activation of T-cells
resulting in polyclonal T cell activation and
massive cytokine release. SAgs can be produced by
pathogenic microbes as a defense mechanism
against the immune system.
S.aureus and Streptococcus pyogenes produce many
SA
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Pattern-recognition receptors
Toll-like receptors (TLRs)
Peptidoglycan, Lipoproteins
Toll-like receptors (TLRs) are a class of
proteins that play a key role in the innate
immune system. They recognize structurally
conserved molecules derived from microbes. Once
these microbes have breached physical barriers
such as the skin or intestinal tract mucosa, they
are recognized by TLRs which activates immune
cell responses.
LPS, lipid A
Flagellin
Bacterial DNA
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Host defence against Staphylococcus aureus
infection require recognition of bacterial
lipoproteins
Juliane Bubeck Wardenburg, Wade A. Williams, and
Dominique MissiakasHost defenses against
Staphylococcus aureus infection require
recognition of bacterial lipoproteinsPNAS 2006
103 13831-13836
S.aureus mutant can not make lipoproteins
Infection of mice
Survivors S.aureus
90 S.aureus mut
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MRSA in pets
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Streptococci
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Haemolysis
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Streptococi cultural characteristics
S.zooepidemicus
S.equi
S.uberis
MacConkey No growth
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Typing of Streptococci

• Superficially grouped based on their growth on
  blood agar plates into
• Alpha haemolytic produce green discoloration
  around the colonies, but RBCs are intact.
• Beta haemolytic lyse RBCs and produce clear zone
  around the colonies.
• Gamma haemolytic non-haemolytic. Most are not
  pathogenic.

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Laboratory diagnosis

• Specimens
• May include exudates, pus, mastatic milk, skin
  scraping, etc
• Direct microscopy
• Smears (pus/exudates) are fixed and gram stained.
• Isolation
• Routine medium is blood agar (18-24 hours).
• MacConkey agar as a selective media (to
  distinguish from Staph).
• Identification
• Colonial appearance, G-stained smears, Catalase,
  Lansfield grouping, etc.

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CAMP test

• Based on the haemolytic synergism between S.
  aureus toxins and group B Streptococci.
• A culture of Staph aureus is streaked across the
  centre of a blood agar plate.
• A streak of the suspect of group B Streptococci
  is streaked at right angle (90 degree).
• After 24 hour incubation, a positive CAMP test is
  indicated by an arrow-head of complete haemolysis.

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Typing of Streptococci
Lansfield serologic typing place streptococci
in 22 (Lansfield) groups (A-V), based on
differences in carbohydrate antigen in cell wall.
Use antisera against different antigens to type.
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Streptococci of veterinary importance
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Pathogenicity factors of pyogenic (?-haemolytic)
streptococci)

• Adherence to epithelium etc
• Fibronectin binding proteins
• Facilitate internalisation and subsequent
  localisation in the sub-epithelial space

• Anti-chemotaxis
• C5a peptidase
• IL-8 protease (ScpC)

Systemic toxicity Streptococcal superantigens

• Anti-opsonic
• anti-phagocytic factors
• Capsule
• M-protein M-like proteins
• Haemolysins
• (Streptolysins O S)

• Degradative enzymes
• DNAases
• Proteases
• Hyaluronidase
• Streptokinase
• Cysteine protease

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M-protein - structure function
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M-protein - structure function
Cell wall
Hypervariable region
Fibrinogen binding
Cell membrane
Host cross-reactive epitopes
Factor H binding (destroy C3 convertase and
preventing opsonization)
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Bovine mastitis
incidence (2004) S. agalactiae 2
S. dysgalactiae 7 S.
uberis 28
Staphylococcus aureus 25 E.
coli 25
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Streptococcal mastitis
Species Group Characteristics
S.agalactiae B CONTAGOUS MASTITIS Udder commensal. Invades teat duct. Leads to duct blockage. Usually Mild, chronic mastitis.
S.dysgalactiae C ENVIRONMENTAL MASTITIS Mouth, vagina udder commensal invades wounds, etc. Acute, permanent damage.
S.uberis 50 E rest NT ENVIRONMENTAL MASTITIS Skin, tonsils, vagina GI commensal. Contamination of bedding etc - teat duct colonisation. Mild, often asymptomatic, changes to milk maybe only sign.
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Equine Group C streptococci
S. equisimilis Nasopharyngeal commensal Opportunis
tic sepsis e.g. wound
S. zooepidemicus Nasopharyngeal
commensal Opportunistic e.g. 2 respiratory
infections wound metritis etc. Infects various
host species cattle, sheep, dogs, etc.
S. equi carrier animals? Pharyngitis Lymphadenit
is Fever, swollen lymph nodes, discharge -
STRANGLES Septicaemia (fatal) - BASTARD
STRANGLES Highly contagious Quarantine
antibiotic treatment
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Horse with strangles swollen lymph nodes at neck
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Head of horse with strangles split to show
gutteral pouch empyaema
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Virulence factors of S.equi
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Strangles vaccine
Intervet Equilis StrepE. Live genetically
modified S.equi vaccine, S.equi aro
mutant Administer inside upper lip.
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S.canis toxic-shock syndrome
Canine toxic-shock syndrome. An emerging
disease? Symptoms of toxic shock syndrome vary
depending on the underlying cause. Typically
characterized by high fever, accompanied by low
blood pressure, malaise and confusion, which can
rapidly progress to coma, and multi-organ failure.
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Strep suis china
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Enterococci In Veterinary Medicine

• Commensals in gut of humans and animals
• Referred as group D Streptococci
• Resistant to Bile Salts
• Grow on MacConkey agar
• Grow on 6.5 NaCl
• Opportunist pathogens in all species
• Bacteraemias in immunosuppressed animals and
  people
• Often very resistant to antibiotics