Effect of Common Isolated Bacteria on Health Status and Meat Quality of Oreochromis niloticus

Abstract

n different seasons of the year in Oreochromis niloticus and Clarias lazera and effects of most common bacteria on health status and meat quality of Oreochromis niloticus. Samples were collected randomly from Jabal Aulia Dam, Shajara Research Centre Pond and El -Mourada market. A total of 600 fish samples consisting of 120 gills, 120 intestines, 120 livers, 120 kidneys, and 18 water samples were examined and cultured aerobically. 74% of the isolated bacteria were identified as Gram-negative bacteria and 26% were Gram- positive. All together comprising 19 genera from different fish samples and water. The study revealed that the load of bacterial species differed seasonally and in different locality. The most common bacteria were Aeromonas hydrophila and Vibrio furnissii had different effects on O. niloticus in blood parameters, meat chemical composition, symptoms and mortality rate. In case of blood parameters, O. niloticus infected by V. furnissii had a high erythrocytic count after 10 days, but after 40 days the control group had highest erythrocytic count compared to the other two infected groups (P>0.05). Also O. niolticus inoculated with A. hydrophila and V. furnissii showed hairy appearance of the red blood cells membrane while control group showed normal appearance of the red blood cells and there is a cluster of neutrophils after 10 days of iv inoculation. The results obtained showed that a decrease of packed cell volume and an increase in mean cell volume of erythrocytes at the end of the experiment were due to infection of both bacteria and there are vacuoles in the cytoplasm and nucleus of the red blood cells developed hypochromic anaemia. After 10 days of experiment O. niloticus infected with V. furnissii had lower value of white blood cells, but after 40 days a higher value of white blood cells was observed compared to the other two groups. Low lymphocytes count were found after 10 days of infection of O. niloticus with V. furnissii, but after 40 days there was a remarkable increase of lymphocytes which became quite similar to O. niloticus infected with A. hydrophila while the control group had a lesser number of lymphocyte count compared to the other groups. Monocytes count in fish infected with V. furnissii had the highest count after 10 days, and a clear decrease occurred after 40 days, but fish inoculated by A. hydrophila showed the opposite. Also the control group had a lowest monocyte count compared to the other two groups. There was a significant difference in neutrophils count between the control and the two inoculated groups. Concerning the proximate chemical analysis, the control group had lower dry matter, higher moisture content, higher protein percent and higher potassium level compared to the inoculated groups while there was a significant difference between control group and inoculated O. niloticus in ether extract, non free energy, ash, phosphorus, calcium and sodium. v The fish infected with V. furnissii showed symptoms of vibriosis as haemorrhage at the base of the fin and distention of the abdomen and had mortality rate of 30% while fish infected with A. hydrophila showed no symptoms nor mortality rate.