Streptococcus Flashcards
Streptococcus are Gram (__)
Gram (+)
What are the major characteristics of Streptococci? (5)
- Fastidious bacteria
- hemolysis on blood agar
- facultative anaerobes
- catalase (-)
- susceptible to desiccation
What suppurative conditions (pus) do Streptococcus cause? (5)
- Mastitis
- Metritis
- Polyarthritis
- Meningitis
- Pneumonia
What is the habitat for Streptococcus species?
Usually are commensals - found in the normal flora of the upper respiratory and lower urogenital tract
T/F Most Streptococcal infections are opportunistic
TRUE
What type of Streptococcal specimen are collected?
pus or exudates
T/F Streptococcal specimen require transport medium.
True: highly susceptible to desiccation
How do we culture Streptococci?
Culture on blood agar plates, incubate aerobically at 37°C for 24 to 48 hours
Does Sterptocci grow on MacConkey agar?
no
What media is used for Streptococcus agalactiae and other streptococci associated with mastitis?
Edwards media
Virulence factors of Streptoccus spp. include what five factors?
- Adhesins (lipoteichoic acid) = Protein F
- Anti-phagocytic M protein
- Capsule (antiphagocytic)
- Lytic enzymes (hyaluronidase and proteases)
- Toxins
Pathogensis of Streptococci spp is associated with what type of clinical signs?
pyogenic infections
abscess formation
septicemia
other suppurative conditions
T/F Beta-hemolytic species are generally more pathogenic than those producing alpha-hemolysis
TRUE
Can Streptococcal species survive long outside a host?
NO - they are susceptible to desiccation
Which Streptococcus spp. is non-pyogenic and associated with pigs?
S. suis
Unlike Staphylococcus, Streptococcus is susceptible to what antibiotics?
Usually highly susceptible to penicillin
Streptococcus are naturally resistant to what type of antibiotics?
aminoglycosides
T/F Acquired antimicrobial resistance is not frequent with Streptococcus.
TRUE
Beta-hemolysis produces what type of hemolysis on blood agar?
a complete zone of hemolysis
Alpha-hemolysis produces what type of hemolysis on blood agar?
partial or incomplete hemolysis
Gamma-hemolysis produces what type of hemolysis on blood agar?
no observable hemolysis
S. agalactiae, S. equi, S. zooepidimicus posses what hemolysis classification?
Beta-hemolytic streptococci - complete hemolysis
groups of species of pathogenic streptococci is based on what?
Lancefield grouping
Differentiation of streptococci is done using what molecular tests
Multiplex PCR - pathogens causing bovine mastitis
What are the most important Streptococcal diseases of veterinary importance? (6)
- Bovine mastitis
- Strangles in horses
- Pneumonia
- Septicemia
- Arthritis
- Meningitis
S. suis, S. dysgalactiae, and S. uberis all possess what hemolysis classification?
Alpha-hemolytic streptococci (incomplete - “greenish” discoloration)
What streptococci species cause chronic mastitis of the milk ducts in Cattle, Sheep and Goats?
S. agalactiae
Bovine streptococcal mastitis is caused by what three Streptococci spp?
Streptococcus agalactiae
Streptococcus dysgalactiae
Streptococcus uberis
What are the steps of pathogenesis of Bovine streptococcal mastitis?
- Surface proteins → adhesion + invasion of mammary tissues
- Presence of a capsule resulting in antiphagocytic activity
- death of PMN cells and release of lysosomal enzymes → tissue damage
- inflammation blockage of milk ducts
- loss of milk production
What diagnostic tests are used to differentiate between Streptococcus species?
type of hemolysis
CAMP test
Bile aesculin hydrolysis in Edwards medium
Lancefield grouping & biochemical testing (sugar fermentation)
PCR
Bovine streptococcal mastitis - treatment and control
Antibiotics (Susceptible to ß-lactams)
Intramammary antibiotic preparations
Oxytocin
Good milking practices and animal husbandry
What streptococci species cause acute mastitis in Cattle?
S. dysgalactiae
What disease cause by S. equi is a highly contagious upper respiratory tract infection in horses also known as a febrile disease with a purulent nasal discharge and Abscessation of the regional lymph nodes?
strangles
In what type of horses do we see strangles?
Occurs in non-immune Equidae of all ages
Outbreaks common in young horses
What is the source of contamination of strangles?
Purulent exudates from the upper respiratory tract and discharging abscesses
Pathogenesis of Strangles?
- Organisms enter the tonsils and travel to regional lymph nodes
- Multiplication in lymph nodes
- Cause inflammation
What are the virulence components of S. equis?
Hyaluronic acid capsule and M protein
Streptokinase facilitates spreading
Streptolysin S causes lysis of erythrocytes and damages keratinocytes
Produces a superantigen
Clinical signs of Strangles
- Fever, depression, anorexia
- Oculonasal discharge which becomes purulent
- Lymph nodes on the head and neck become swollen and painful
- Submandibular lymph nodes eventually rupture discharging purulent material
- Guttural pouch empyema
- Death may result from complications: pneumonia, neurological involvement, asphyxia
- Bastard strangles - metastasis of abscesses to other organs may develop in 1% of cases
Differential diagnosis for strangles:
Streptococcus zooepidemicus
Streptococcus equisimilis
Diagnosis of Strangles:
History and clinical signs
Culture of nasal swabs
Must distinguish from other streptococci: Sugar fermentation tests, PCR
Treatment of strangles:
Supportive care
Antimicrobial therapy: Penicillin (when external node is not affected)
Good husbandry (Isolate sick and new horses for 2 weeks, Clean and sanitize equipment, Reduce overcrowding)
Vaccines
What is the importance of the CAMP factor produced by Group B streptococci species?
(Christie, Atkins and Munch-Petersen) - heat-stable protein produced by group B streptococci that enhances the damages done to mammary tissue as well as the action of Staph Beta-toxin
T/F Most cases of Strangles do not recover
FALSE - ~75% of cases recover with immunity, while death is typically associated with complications like pneumonia and asphyxia (enlarged lymph nodes)
What test must be performed to distinguish S. equi from other lancefield group C streptococci?
Sugar fermentation in peptone water containing serum
What antibiotic would you prescribe to Horses suffering from Strangles?
Penicillin NOTE: either prophylactically or soon after clinical signs DO NOT GIVE if external lymph nodes are affected
T/F There are vaccines available in North America for S. equi
TRUE (live attenuated intranasal vaccine)
Transmission of S. suis:
- Asymptomatic carriers with S. suis in tonsils spread via respiratory and oral routes
- Sows are carriers infecting litters
Predisposing factors of S. suis:
- Poor ventilation
- Overcrowding
- Stress factor in intensively reared pigs
Which Streptococci species causes meningitis, arthritis, septicemia, and broncho-pneumonia in all aged pigs?
S. suis
Pathogenesis of S. suis:
- Bacteria in the tonsils ->
- Septicemia ->
- Enter the joints, meninges, lungs, heart ->
- Meningoencephalitis, pneumonia, endocarditis
What are the five major virulence factors for S. suis?
- Capsular polysaccharide
- Extracellular factor (EF) and muramidase-released protein (MP)
- Suilysin - cause hemolysis on BAP
- Adhesins
- Hyaluronidase
T/F With appropriate treatment, mortality from S. suis is usually low, but can grow if left untreated
TRUE
What type of prophylactic antibiotics would you provide to herds of pigs to prevent S. suis?
- penicillin or ampicillin - Long acting penicillin to Sows 1 week prior to birth - Piglets during the first 2 weeks of life
Why is S. suis especially important to account for in veterinary medicine?
it is zoonotic - occupational disease = pig farmers, butchers, abattoir workers and veterinarians
Clinical signs of S. suis in pigs:
• Fever • Inappetence • Depression • Meningitis - tremors, incoordination, opisthotonos, convulsions and fatality • Peaks during weaning at about 6 weeks
S. suis in other animal species:
• Wild boars may act as reservoirs • Cause Human infections • Can cause mortalities in wild mammals
Lab diagnosis of S. suis:
• Culture, isolation α-hemolytic mucoid colonies, Gram-positive cocci • Lancefield grouping D
Streptococci are gram (_____) cocci in what morphology?
gram + in chains
T/FStreptococci are commensals of the mucosae of the upper respiratory tract and lower urogenital tract
TRUE
What two things need to be done when collecting swabs from animals suspected of have a Streptococcus spp. infection?
• Use transport swabs • Process as soon as possible
Differentiation between species of Streptococci are done how?
- Type of hemolysis produced on blood agar * CAMP test
- Bile aesculin hydrolysis in Edwards medium
- Lancefield grouping & biochemical testing (including sugar fermentation)
- Molecular: PCR
What causes strangles in horses?
S. equi subsp. equi
What streptococci is a zoonotic disease of pigs?
S. suis
T/F Streptococci are catalase-negative
TRUE
T/F: Streptococci are non-fastidious
FALSE
T/F: Streptococci are usually highly resistant to beta-lactams
False: this is true for Staphylococcus
T/F: Streptococci are commensals of the mucosa of the upper respiratory tract and lower urogenital tract
TRUE
Which of the following is CAMP-test positive? A. Streptococcus uberis B. Streptococcus agalactiae C. Streptococcus dysgalactiae D. Streptococcus suisE. Streptococcus pyogenes
B. Streptococcus agalactiae
Which of the following is used for the determination of the Lancefield grouping A. M protein B. F-protein C. Group-specific cell-wall carbohydrates/polysaccharides D. Capsule E. Peptidoglycan
C. Group-specific cell-wall carbohydrates/polysaccharides
Vaccinations for S. suis are commercially available at _________weeks of age
3-4 weeks
