Pathophysiology of experimental Aeromonas hydrophila infection in mice

A virulent fish strain of Aeromonas hydrophila was inoculated intramuscularly into laboratory mice (B10.G strain). Histological, biochemical and haematological changes during the first 36 h of the infection were measured. Inoculation led to septicaemia, tissue damage, endotoxic shock and death. Histological examination revealed: (1) severe muscle necrosis at the injection site; (2) oedema, haemorrhage and neutrophil infiltration of the lung; and (3) focal parenchymal necrosis in the liver. Significant increases in aspartate aminotransferase, alanine aminotransferase, intestinal bilirubin and blood urea nitrogen were noted in blood and intestinal samples; decreased plasma glucose and haematological changes were also recorded. Ketones, increased protein, glucose, bilirubin and blood were detected in the urine. Endotoxaemia was demonstrated as early as 2 h after inoculation and persisted for more than 36 h. The changes resembled those described for certain other experimental infections in laboratory animals. Our results suggest that endotoxin contributed to the pathogenesis of aeromonas infection in mice.