Chromobacterium violaceum Infection in a Horse.

This research reports an identified case of Chromobacterium violaceum infection – an opportunistic pathogenic bacterium – in a horse, leading to pneumonia and septicaemia. The study traces the process of diagnosing the disease from clinical features to necropsy examination, and ultimately bacteriological and genetic identification.

Clinical Observations and Necropsy Examination

In this case, the horse displayed signs of recurrent pneumonia, fever, breathing difficulty, and bloody nasal discharge. Necropsy results revealed:

• Non-collapsed lungs but having dark red foci and white areas alongside several firm nodules.
• Within the liver and kidney, multiple white pinpoint lesions scattered randomly, extending from the capsule into the parenchyma.
• Numerous petechiae (small, round spots due to bleeding into the skin) in the brain and spinal cord.

Microscopic Examination

Microscopic studies showed:

• Severe infiltration of degenerate neutrophils into the alveoli and parenchyma of the lung, extensive areas of necrosis and haemorrhage, and rod-shaped bacteria in the centre of the lesions.
• Increased intra-alveolar exudation of fibrin and degeneration of blood vessels associated with thrombosis and ischaemic necrosis adjacent to intense haemorrhage areas.
• Presence of similar lesions in the liver and kidneys as well.

Bacterial Culture and Genetic Analysis

For the definite identification of the pathogen:

• Pure bacterial culture was obtained from lung and liver samples.
• The bacterial gene 16S rRNA was amplified and sequenced, followed by a sequence similarity analysis, confirming Chromobacterium violaceum as the causative organism.

In conclusion, this research provides critical insights into the abnormal pathology in a horse caused by Chromobacterium violaceum infection, ultimately aiding in the accurate diagnosis and better understanding of the disease process and progression.