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*Colonise mucous membranes
*Colonise mucous membranes
===''Arcanobacterium pyogenes''===
*Characteristics:
**Formerly known as ''Actinomyces pyogenes'' and ''Corynebacterium pyogenes''
**Small facultatively anaerobic rod
**Grows slowly on blood agar to produce small, white colonies surrounded by a zone of beta-haemolysis after 48 hours
**Produces hazy haemolysis after 24 hours; pin-point colonies after 48 hours
**Coryneform morphology, like Chinese characters; may be curved with slightly swollen ends
**Found in nasopharyngeal mucosa and genital tract of cattle, sheep, pigs
*Pathogenicity''
**Opportunistic infections following injury or viral/mycoplasma infection in ruminants and pigs
**Extracellular toxins including haemolysin, proteases, DNase and neurominidase
**Haemolytic toxin, pyolysin, member of the thiol-activated cytolysins (pore-forming toxins); possibly cytotoxic to phagocytic cells; dermonecrotising activity
*Clinical infections:
**Suppurative infections
**Abscesses especially in liver
**Pyometra
**Summer mastitis
**Ovine foot disease
**Umbilical infections
**Pneumonia
===''Actinomyces''===
*Usually long and filamentous branching Gram positive rods
*Usually long and filamentous branching Gram positive rods
*Anaerobic or facultativlyy anaerobic and capnophilic
*Anaerobic or facultativlyy anaerobic and capnophilic
***Two types of colonies: large and smooth colonies with V, Y and T configurations or small and rough colonies with short branching filaments
***Two types of colonies: large and smooth colonies with V, Y and T configurations or small and rough colonies with short branching filaments
===''Actinobaculum suis''===
**Found in preputial mucosa of boars
**Found in preputial mucosa of boars
**Anaerobic
**Anaerobic
**3mm diameter colonies with shiny raised centre and dull edge
**3mm diameter colonies with shiny raised centre and dull edge
''Nocardia''
===''Nocardia''===
*Aerobic short branching rods
*Aerobic short branching rods
*Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)
*Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)
''Dermatophilus congolensis''
===''Dermatophilus congolensis''===
*Aerobic
*Aerobic
*Motile zoospores
*Motile zoospores
*No growth on Sabouraud dextrose agar
*No growth on Sabouraud dextrose agar
*Found in scabs and in foci on skin of carrier animals
*Found in scabs and in foci on skin of carrier animals