1. GRAM +ve Bacteria: COCCI
BACTERIA STAPHILOCOCCI STREPTOCOCCI
VIRULENT OPORTUNISTIC TONSIL GENITAL
TRACT
BOVINE MAMMARY
GLAND
INTESTINE
S.aureus (biotypes: A-D) S.
(pseud)intermedius (E-F)
(and S.hyicus*)
S.epidermis
S.capits
S.xylosus
S.pyogenes
(A)
S.equi (C)
S.suis
S.canis (G)
S.zooepidemicu
s
Group B strep.c
S.agalactae Faecal
strep.c
PATHOGENESIS S.a & S.i = pyogenic
Cell leakage = necrosis
Cause disease when access
sterile site/able to grow due to
reduced immunity
(immunocompromised)
Display multple antbiotc
resistance
Classifed on haemolysis on blood agar: α, β, γ
- Pyogenic (pus forming): *A, B, C, D and G
- Viridans (greening) – oral – non-pathogenic (S.salvarius)
- Enterococci (faecal)
- Lactc (found in milk etc) – milk scour (S.lacts)
*Lancefeld grouping (20): based on carbohydrate cell wall
TOXINS Haemolysins: α-toxin (S.a; S.i) = zone of β-haemolysis
β-toxin: wider zone of RBC change (sphingomyelin -> ceramide)
Leucocidins: Panton-Valentne Leukocidin (S.a)
TSST-1: superantgen (TCR-MHC II), cytokine over-producton
(TNFα)
Enterotoxins: Protein & heat liable; superantgens
Proteases, hyaluronidase, lipases: Digestve enz: tssue
destructon
Exfoliatve toxins: blistering (humans/infants) (S.a)
Digestve enzymes toxic to mammalian cells: digest proteins & lipids = aa
nutriton
Streptolysin O: haemolysin; inactvated by O2 (A,B,C,F and G)
Streptolysin S: haemolysin; O2 stable
Hyaluronidase: hydrolysis hyaluronic acid of CT (A,B,C and S.suis)
Streptokinase: lyses fbrin clots breaking down fbrin barrier = spread (A, C and
G)
CELL-SURFACE
ASSOCIATED
PATHOGENICITY
DETERMINANTS
Fibronectn-binding proteins: adhere and colonise (S.a)
Fibrinogen-BP: adhere fbrin in wounds, coat in host-protein
Protein A: Bind Fc of IgG. Fab free to bind Ag, but IgG can’t
actvate complement = C3b depositon = Ant-opsonin (S.a)
Capsule: inhib phag-opsin (inhib complement actvaton)
Intracellular survival: multply in leukocytes=persist following
treatment and apparent recovery! (resume infecton and
disease :o)
Hyaluronic acid capsule (non-antgenic and antphagocytc)
M-protein: fbrillar structures; antphagocytc
(A and C)
SPREAD Normally commensals of SKIN and MUCOUS MEMBRANES of
UPPER REST TRACT and INTESTINAL TRACT
Found in normal fora of animals (UPPER RESP TRACT and GUT)
Those that are phagocytosed are killed inside the phagocytc cell
CHARACTERISTIC
S/
STERILISATION
Grow in bunches
Facultatve anaerobes
Metabolically actve
Intracellular
Grow in chains
Do not immediately separate into individual daughter cells
Usually aerotolerant (Peptostreptococcus = strict anaerobes)
Survival outside body is poor: live on host w/abundant nutrients
Extracellular *except S.suis
TRANSMISSION Proteases, hyaluronidase, lipases: spread and nutriton Direct contact/aerosol

2. GRAM +ve Bacteria: COCCI
DIAGNOSIS Catalase(DNase)+ve
Coagulase +ve (bound
coagulase)
S.hyicus: Catalase(DNase)+ve
But Coagulase –ve
Catalase (DNase) +ve
Coagulase–ve
Adheres to plastc
Catalase –ve = Do not split H2O2 (no O2 release)
While can be most aggressive pathogens; β-haemolytc strep.c of Lancefeld
groups A,C and G remain sensitve to Penicillin G and other penicillins.
Resistance unknown/