Module 5.1 (Gram Positive Aerobic Cocci) Flashcards
What are the 3 major genera of gram positive aerobic cocci?
Staphyloccocus, streptococcus, enterococcus
What is the habitat of staphylococcus and result of a catalase test?
Exposed mucosal surfaces, positive (only one), recall a positive catalase test is a virulence factor for some pathogens as it helps resist the oxidative burst in phagocytes
What is the habitat of streptococcus and result of a catalase test?
Throat and urogenital tract, negative
What is the habitat of enterococcus and result of a catalase test?
Intestine, negative
Case Report:
- 6 y/o MN Border Collie
- chronic ear scratching
- head shaking and ear discomfort
- no other conditions
- UPT on prevention and vaccine
- Ear cytology and blood test done
- Came back GP cocci, aerobic and catalase +
What genus is this bacteria in?
Staphylococcus, the only GP aerobic cocci with a positive catalase test!
Name some important characteristics of the Staphylococcus genera.
- grape like clusters
- mostly non-pathogenic
- commensals of skin and exposed mucosae in animals and humans
- opportunist pathogens
- survive well in the environment
- typically causes purulent infections and necrosis
- catalase + is a virulence factor
Staphylococcus aureus 1-OPP-Z
- found in humans and many animal species
- can cause skin infections, UTIs, bacteremia, mastitis, arthritis, bumblefoot
- commonly see pus and abscess formation with local necrosis
- can cause toxic shock syndrome in humans
- contagious
- cause of hospital acquired infections (ESKAPE) which are resistant
- it is methicillin-resistant (MRSA) which means it is resistant to all beta-lactams
Staphylococcus pseudintermedius 1-OPP-Z?
- found in dogs, cats, humans
- commonly see pyoderma, UTIs, bacteremia and infected wounds
- major and commonest opportunist pathogen of dogs
causes local skin disease like pyoderma, otitis externa, wound infections, UTI, vaginitis, metritis, conjunctivitis, bacteremia, abscesses - also methicillin-resistant MRSP
- often multiresistant
Staphylococcus hycius 3-OPP
- found in pigs (greasy pig disease)
- exudative dermatitis
- nonpruritic pustules
- affects young pigs (1-6 weeks)
Staphylococcus virulence factors
There are many but a few include:
- fibronectin-binding proteins = adhesin, colonization of wound
- DNAase, lipase and many -ase = host tissue penetration
- hemolysins
- enterotoxins = diarrhea
- toxic shock syndrome = superantigen
- coagulase = fibrin shield from phagocytes
- Protein A = bind Fc portion of immunoglobulins to hide from host
Lab Diagnosis of Staphylococcus
- smear and gram stain
- culture and identification but culture alone is not enough, we will then need MALDI-TOF MS to differentiate between Staphylococcus species
- Molecular methods: mecA for MRSA and MRSP
Prevention and treatment of staphylococcus species
- treatment with antimicrobials and elimination of the primary cause because it is an opportunistic pathogen
- Mastitis: prevent via detection of subclinical infections, hygeine, milking equipment
- Frequent antimicrobial resistance (penicillinases, MRSA, MRSP) require susceptibility testing
List the main points regarding Streptococcus
- chains of cocci
- commensals of mucous membranes of animals and humans
- DOES NOT survive well in the environment therefor need a transport media!
- pyogenic infections
- strong host specificity
What are some major streptococcus virulence factors?
- beta-hemolysis = complete lysis of red cells
- strong capsule = avoid phagocytosis and shielding from immune response
- M-proteins = antiphagocytic surface proteins on the cell wall
- Teichoic acids = triggering inflammation, PAMPs
- pyogenic = tendency to produce pus, spread locally and cause septicemia
Streptococcus equi subspecies equi 2-PR
- affects horses
- causes strangles
- highly contagious and causes morbidity
- abscessation of lymph nodes in head and neck
- transmitted by discharges of disease and infected guttural pouch carriers
- treatment/prevention: isolation and quarantine, cleaning and disinfection, early treatment with penicillin
- there are vaccines available but they’re not perfect
