Pathogenicity of Salmonella Enteritidis Phage Type 1 (Malaysian isolate) in Specific Pathogen-Free Chickens.

Salmonella enteritidis (SE) is one of the major concerns to poultry industry thoughout years. SE causes food poisoning due to consumption of poultry or poultry products contaminated by the bacteria. Many SE phage types have been prevailed around the world especially phage types 4, 8, 13a and 23 and few others with less isolation rates. The SE phage type 1 has increased in incidence to become one of the major phage types isolated from Europe, Asia and few other countries. It was the objective of this study to isolate and characterize the phage type of SE isolated from commercial poultry farm in Malaysia and to determine its pathogenicity in one-day-old and 21-day-old specificpathogen-free (SPF) chickens, upon oral inoculation. White Leghorn SPF one-day-old and 21-day-old chicks were divided into three groups namely the SE, Control and Mortality groups. The chicks in the SE and Mortality groups were inoculated orally with SE phage type (PT) 1 at a concentration of 1x10 8 cfu/mL. The clicks in SE and Control groups were sacrificed at 6 and 12 hrs post inoculation (pi) and at 1, 2, 3, 5, 7, 10, 14 and 21 days pi. The chicks were observed for the clinical signs, body weight gain and gross lesions. Tissue samples were collected for bacteriological isolation, histopathological and ultrastructural analysis. The study in one-day-old chicks showed weight loss in the SE group starting from day 2 pi and until the end of the trial reaching its peak at day 21 pi when the SE group weight was 39% less compared to the Control group. Diarrhea, pasty vents, inappetance and stunted chicks were recorded starting at 12 hrs pi and until the end of the trial throughout the trial. No mortality was recorded in the Mortality group. However two chicks from the SE group died at days 3 and 5 pi. Grossly the chicks exhibited mild air sacculitis, peritonitis and mild congestion of the liver and kidney starting at day 2 pi until the end of the trial. No abnormal gross changes or clinical sign were recorded in the Control group throughout the trial. The bacteria were isolated in the SE group as early as 6 hrs pi from all organs which include the liver, spleen and cloacal swabs (66%), caecum and caecal tonsils (100%) and small intestine content and blood (33%). At day 14 pi, SE was isolated only from the liver, spleen and caecal tonsils (33%). Histopathological observed were enteritis in the duodenum, jejunum, ileum and caecum and necrosis of the enterocytes at the apical part of the intestinal villi with the presence of necrotic debris and bacterial clusters in the lumen starting at 12 hr pi until the end of the trial. Hepatitis with coagulative necrotic foci was recorded starting at 3 days pi until the end of the trial. The splenic tissue showed an increased heterophilic infiltration and mild congestion with few focal necrotic areas at 2 days pi until the end of the trial. While in the bursa of Fabricius congestion, heterophilic infiltration and necrosis of the lymphoid follicles were recorded starting day 5 pi until the end of the trial. The villi height showed a significant (p