Incidence and characterisation of Salmonella Enteritidis in poultry products and human diarrhoea cases in Lusaka District, Zambia

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Hang'ombe, Bernard Mudenda
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This study was conducted to find out the incidence of Salmonella enteritidis in table eggs and chicken carcasses entering the consumer market in the city of Lusaka. Diarrhoea stool samples from humans admitted to the University Teaching Hospital (UTH) were also included in the study to investigate Salmonella enteritidis in the population. Table eggs were collected from eight randomly selected layer farms in and around the city. Specimens from the chicken carcasses were sampled from a big processing plant operating in Lusaka city. Two thousand four hundred (2400) commercially purchased table eggs and three hundred eighty two (382) chicken carcasses were cultured on suitable media for isolation of Salmonella enteritidis. The shell membranes and yolks from table eggs were pooled in units of ten and cultured. Nine (3.75 per cent) of the two hundred and forty samples of table eggs were found contaminated with Salmonella enteritidis, while eighteen (4.7 per cent) of the carcasses sampled were found positive for Salmonella enteritidis. Other Salmonella serovars isolated from the chicken carcasses were Salmonella infantis. Salmonella gallinarum and Salmonella mbadaka while Salmonella gallinarum was the only other serovar from the table eggs. A total of eighty six (86) diarrhoea stool samples from humans obtained from UTH, Lusaka were also cultured and eight of these were found positive for Salmonella typhimurium. Phage typing of the Salmonella enteritidis isolates showed that all the isolates from the table eggs and seven from chicken carcasses belonged to the enteropathogenic invasive PT4, while three from the carcasses were PT7 and eight were untypable. Efforts were made to characterise the Salmonella enteritidis isolates by carrying out pathogenicity test, biochemical test and antibiogram test. The characterisation involving animal models of mice, embryonated eggs and seven days old chicks displayed that Salmonella enteritidis isolates from the table eggs were more virulent than the isolates from the chicken meat. Biochemical test did not reveal anything significant. Salmonella enteritidis isolates from table eggs and chicken carcasses tested for antibiotic sensitivity had several features in common. They were sensitive to amoxycillin, ampicillin, co-trimoxazole, furazolidone, gentamycin and tetracycline while Salmonella typhimurium isolates from diarrhoea cases were resistant to amoxycillin and ampicillin. Several Salmonella mbadaka isolates showed resistance to tetracycline. Salmonella enteritidis has been isolated from the table eggs and poultry meat carcasses for the first time in Zambia. The results of the study further demonstrated that poultry products from Zambia have a higher incidence of Salmonella enteritidis contamination compared to reports in other parts of the world. It warrants a planned epidemiological study of Salmonella enteritidis in the country to formulate appropriate control measures.
Poultry -- diseases -- Lusaka district, Zambia