Unit 1- Streptococcus Flashcards
Genus Streptococcus
Gram positive cocci in chains, facultative anaerobe, non-motile, non-spore forming, fastidious growth requirement, catalase negative, low salt tolerance
Facultative Anaerobe
Oxygen availability not critical for survival
Fastidious Growth Requirement
Requires nutritionally rich media for growth
Culture Media for Growth
Blood agar to identify type of hemolysin toxin and Edward media for selective identification and isolation
Beta Hemolysis
Most pathogenic group
Alpha Hemolysis
Partial and incomplete hemolysis with green color, commensal upper respiratory strep
Gamma Hemolysis
Fecal streptococci
Capsule
Mucoid, useful for serotyping strains within a species
M protein
Useful for serotyping within a species by ELISA as well as for vaccine production
Lancefield Carbohydrates
Useful for Lancefield serotyping, antibodies specific to these proteins used to ID them by agglutination
Serogrouping
Use antibodies adn identify by agglutination
Clinically Important Serogroups
A, B, C, D, E, and G
Catalase test
Streptococcus will be catalase negative
Equine and Canine isolate hemolysis
Mostly beta hemolytic, the more pathogenic
Alpha Hemolytic Strains
S. pneumoniae and S. suis
Habitat
Commensals in skin, upper respiratory tract, tonsils, digestive tract, lower urogenital, udder, food, soil, and fecal contaminated water
Transmission
Direct contact, aerosol, fomites, and ingestion
Disease
Opportunistic part of normal flora, disease occurs when bacteria enter cuts, abrasions, wounds, other infection, or when immune system is weakened
Virulence Factors
Structural compounds, enzymes, and toxins
Structural Compounds
Lipotheichoic acid, slime layer capsule, M protein, protein G
M Protein
Binds the arms of IgG and precents opsonization, also prevents phagocytosis
Protein G
Competes with complement to bind IgG and prevent opsonization
Enzymes
Nuclease, streptokinases, hyaluronidase, C5a peptidases
Nuclease
Convers pus to resources and has DNAse and RNAse activity to destroy host cells
Streptokinase
Converts plasminogen to plasmin, digesting fibrin to lyse blood clots and escape
C5a Peptidase
Destroys compliment chemotactic signals
Toxins
Hemolysin, streptolysin, and pyrogenic exotoxins
Streptolysin
Hemolytic, cytotoxic, and inhibits chemotaxis
Pyrogenic Exotoxins
Cause fever, strawberry tongue, cardiac and liver necrosis, T cell division, superantigenic, and increase permeability of endothelium causing shock
Pathogenesis
Throat, ear, eye, skin, and urogenital infections and pneumonia, endocarditis, meningitis, and shock
Origins of infection
Cutaneous, throat, mammary, and urogenitcal
Necrotizing Fasciitis
Destroys the muscle under the skin
Metastasis
Spread to systemic disease is serotype and host immune status dependent
Streptococcus pyogenes
Causes throat and dermatological infection, pharyngitis, and necrotizing fasciitis
Streptococcus equi
Causes pharingitis/strangles in horses
Strangles
Infection by S. equi causes abscess in the lymph nodes, coughing, difficulty swallowing, fever, yellow discharge from nose and eyes, and pus filled guttural pouch
Streptococcus suis
Generalized infection in pigs causing pneumonia, septicemia, meningitis, arthritis, abortion, metritis, blindness, and deafness
Streptococcus porcinus
Causes strangles in pigs, rare now
Streptococcus canis
Most aggressive in pets, causes pet strangles, generalized infection, eye and ear infection
Streptococcus agalactiae
Causes vaginitis, abortion, endometritis, mastitis, and prostitis in pets
Streptococcus agalatiae
Causes chronic contagious mastitis
Viridiant Streptococcus
Alpha hemolytic group that mostly affects humans, normal flora of oral cavity, intestines, and urethra
Treatment
Antibiotics are effective but resistance is rising
Control and prevention
Improve hygiene and wellbeing, reduce stress, clean wounds, isolate infected animals, control primary disease, and vaccinate for S pneumoniae in humans
