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.