An Epidemiological Analysis of Salmonella Enteritidis Contamination in a Rat-Infested Chicken Layer Farm, an Egg Processing Facility, and Liquid Egg Samples by Pulsed-Field Gel Electrophoresis

Abstract

ABSTRACT. In order to determine the epidemiological link between the Salmonella Enteritidis contamination in a rat-infested chicken layer farm, an attached egg processing facility and liquid egg samples, several S. Enteritidis isolates were analyzed by pulsed-field gel electrophoresis (PFGE) and bacteriophage typing. A total of 33 S. Enteritidis strains were isolated from a total of 4,081 samples. Similar pulsed-field patterns were generated by S. Enteritidis isolates from liquid eggs, rats and effluent water. Additionally, only two phage types were detected among the S. Enteritidis isolates, PT 1b and PT 6. These results suggest that S. Enteritidis isolates from rats, egg processing facility, and liquid eggs are genetically related. Furthermore, S. Enteritidis infection in rats in layer farms poses a serious public health concern and should be included in future epidemiological studies. KEY WORDS: layer farm, rat, Salmonella Enteritidis.J. Vet. Med. Sci. 69(6): 649-652, 2007 Human illness caused by infection with Salmonella enterica subsp. enterica serovar Enteritidis increased worldwide beginning as early as 1970s and by 1990, became the primary cause of salmonellosis in the world [2]. A major factor in this increase has been attributed to consumption of undercooked eggs and egg products such as liquid egg, contaminated with S. Enteritidis [4]. Rodents, dirty environment, recent poultry farming practices, chicks, pullets, and feeds have all been considered as major sources for contamination with S. Enteritidis in chicken layer farms [5,7,[17][18][19]. In Japan, liquid egg is commonly used in making egg custard products. Murakami et al. [13] were able to isolate S. Enteritidis from unpasteurized liquid egg and epidemiologically linked it to isolates from human salmonellosis outbreaks. But little is known of the origin and mechanism of S. Enteritidis contamination in liquid egg.DNA-based typing by pulsed-field gel electrophoresis (PFGE) has been widely used as a molecular fingerprinting technique for the epidemiological analysis of bacterial infections. In this study, several S. Enteritidis isolates obtained from a rat-infested chicken layer farm, its attached egg processing facility and liquid egg samples from a liquid egg factory for 2 years were characterized by PFGE. The purpose of this study was to determine if there are epidemiological links between S. Enteritidis isolates obtained from layer houses, egg processing facility and liquid egg samples and more importantly to determine the mechanism of S. Enteritidis contamination in the field.A commercial chicken layer farm and an attached eggprocessing facility (GP center) were sampled regularly for S. Enteritidis contamination monitoring for 2 years. Samples for Salmonella isolation were 81 batches (6,480 eggs) of dirty and broken eggs, 130 batches (3,900 eggs) of nest run eggs, 720 environmental samples from the layer houses and 820 environmental samples from GP center, 1,436 samples of GP effluent water, 180 batches of rat fecal samples, and 87 rats. The...

Phage types and pulsed-field gel electrophoresis patterns of Salmonella enterica serovar Enteritidis isolated from humans and chickens

“…Salmonella contamination in chicken is a major concern in Asian countries (Lapuz et al, 2007;Vindigni et al, 2007). S. Enteritidis is the principal contaminating serotype in chickens and chicken products (Sarna et al, 2002).…”

Frequency of Detection ofEscherichia coli,Salmonellaspp., andCampylobacterspp. in the Faeces of Wild Rats (Rattusspp.) in Trinidad and Tobago

“…and have been implicated in contaminating foods with the pathogen and transmitting the pathogen in livestock farms [15, 16]. Rodent-borne salmonellosis has also been reported in humans [17, 18].…”

Molecular Characterization ofSalmonellaEnteritidis: Comparison of an Optimized Multi-Locus Variable-Number of Tandem Repeat Analysis (MLVA) and Pulsed-Field Gel Electrophoresis

“…Epidemiological studies have been performed to study the relatedness of isolates from human infections to contaminated eggs. Typing is a powerful tool to investigate outbreaks and to study the sources and transmission routes in the human and veterinary context (Lapuz et al, 2007;Much et al, 2009). However, availability of large number of genotypic and phenotypic methods (Foley et al, 2007;Kang et al, 2009) complicates selection of the most appropriate technique for characterizing SE.…”