Rhodococcus

Question 1

Structure ?

Answer 1

Gram+, aerobic, non-sporulating, facultative intracellular bacteria. ubiquitous in the environment.

releases plasma bearing virulence factor and its virulence associated protein (VAP)

Question 2

Pathogenesis ?

Answer 2

inhalation/ingestion/wound infection –> phagocytosed by macrophages –> VAP prevents phagolysosome fusion, allowed to live in macrophage –> survives and replicates –> necrosis –> cytokines released (inflammatory response

Question 3

Clinical Signs ?

Answer 3

non-specific.
3 lesions :
- pyogranulomatous pneumonia
- pyogranulomatous typhlocolitis
- pyogranulomatous lymphadenitis

sometimes polyarthritis, hypopyon, pyogranulomas in liver/spleen/skin and osteomyelitis

Question 4

Grossly ? (including on cut surface)

Answer 4

elevated, firm nodules throughout the lung, white to tan in colour

on cut surface, see tan to green coloured fluid (purulent exudate) causing a pyogranuloma

Question 5

Histologically ?

Answer 5

pyogranulomatous inflammation (mixture of macrophages, neutrophils and necrosis surrounded by a capsule)

Question 6

Diagnosis ?

Answer 6

PCR with VAP amplification
bacterial culture