Listeria

What would you see under microscope

Short gram positive rods/coccobacilli

What agent causes listeriosis in ruminants

Listeria monocytogenes

What does l. monocytogenes cause

Neural listeriosis, abortions, septicemia, stiff necks, 

How is it transmitted 

Contact with contaminated feeds, soils, equipment and through teats

Role of internalins

Mediate adherence and invasion of non phagocytic cells → facilitates crossing barriers

Role of listeriolysin

After bacteria is engulfed in host cell, they are trapped in a membrane bound comprtment called a phagosome 

Listeriolysin allows bacterium to create pores, breaking into host cell cytoplasm where it can replicate 

Samples

Samples from brainstem tissue (post mortem), CSF, placenta, fetal tissues, liver, spleen

Culture

Blood agar

Small greyish colonies 

Weak beta hemolytic 

Biochemical features

Catalase positive 

Camp test positive

What other test can you use

Immunofluorescence using monoclonal Ab