Aeromonas hydrophila disturbs water and electrolyte transport in Mugil cephalus L. intestine

Abstract

Fish diseases create a menace to aquaculture farms. They provoke disastrous economic losses and sanitary risks for the consumer. The present study aims to investigate the effect of the bacteria,
Aeromonas hydrophila on water and electrolyte (Na+, K+, Cl-, HCO3
-) flux of Mugil cephalus (L, 1758) intestine. Anterior, middle and distal gut segments of M. cephalus (L) intestine were used in an in vitro
model; Everted Gut Sac (EGS). The sacs were exposed to bacteria suspension (108 cells/ ml) at 25°C for 2 h. Our results showed a significant reduction of water absorption at the anterior and the mid
intestine (P< 0.05), and a significant increase of K+ secretion only at the anterior intestine (P < 0.01). However, HCO3-secretion increase was significant at the anterior and the mid intestine (P < 0.05).
Paradoxically, an increased absorption of Na+, and Cl- was recorded at the mid (P < 0.01) and at the distal gut segments (P < 0.05). Histological studies were assessed by light microscopy. EGS exposed
to Ringer solution (12%, pH 8.5) revealed the presence of intact intestinal tract. However, infected EGS showed intestinal damages characterized by epithelium lesions, detachment of degenerate
enterocytes with voluminous and spherical shape, disappearance of enterocyte brush border and lesions at cellular junction. It can be concluded that A. hydrophila resulted in a disturbance of
hydroelectrolytic flux and alterations of M. cephalus intestinal tract. The most serious damage was noted at the anterior segment.