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Salmonella in “Grade Cracks” Shell Eggs
Can. Inst. Food Sei. Teehnol.1. Vo!. 13, No. 4, pp. 184-187, October 1980 Pergamon Press Ltd. Printed in Canada.
Salmonella in "Grade Cracks" Shell Eggs J.Y. D'Aoust, P. Stotland Bureau of Microbial Hazards, Health Protection Branch Health and Welfare Canada, Tunney's Pasture Ottawa, Ontario K lA OL2
and c.J. Randall Livestock and Poultry Division Food Production and Inspection Branch, Agriculture Canada Ottawa, Ontario K I A OC5
Abstract
(FWDC, 1975; CDC, 1977). Although the presence of Salmonella in liquid egg preparations and shell eggs is well documented (Garibaldi et aI., 1969; Cantoni et aI., 1976; Krepel and MacPherson, 1976; Evans, 1977; Bollegraaf, 1978; Moats, 1978), few outbreaks associated with shell eggs have been reported recently (Cohen and Blake, 1977). In 1977, an outbreak in Ontario involving 44 cases of illness with 4 cases requiring hospitalization resulted from use of "Grade Cracks" shell eggs infected with S. bareilly in cake batter and icing prepared by a commercial bakery; the economic impact due to lost wages and medical and investigational costs was considerable (Evans, 1977; Lavigne, 1978). In 1979, an Ontario outbreak of S. infantis affected 61 members of a senior citizens home; eggnog prepared with cracked eggs was tentatively identified as the vehicle of infection (Bollegraaf and Lior, 1979). Unrestricted sale of cracked eggs to the public is prohibited in British Columbia, Alberta, Manitoba, Quebec and Newfoundland. "Grade Cracks" is the grade name for eggs with cracked shells whose internal contents do not leak; candling characteristics of these eggs meet standards for at least Canada Grade C. The present study was undertaken to monitor the incidence of Salmonella in "Grade Cracks" shell eggs and to evaluate the efficacy of different analytical conditions in detecting salmonellae in shell eggs.
Thirty-nine (13%) of 299 samples of "Grade Cracks" shell eggs and 13 (34%) of 40 egg wash-water samples obtained from I1 egg-grading stations in Ontario were found to contain Salmonella; S. infant is was isolated frequently from shell eggs but was not detected in wash-water samples. Standard plate counts (35° C) ranged from < 10' to 108 cells per ml of wash-water. Salmonella was also detected in I of 13 egg meat samples obtained from cracked eggs and in 2 of94 intact shell egg samples. Following pre-enrichment in nutrient broth, tetrathionate brilliant green enrichment broth in combination with bismuth sulfite or brilliant green sulfa agar media identified 98% and 91 %, respectively, of all positive samples; homologous selenite cystine combinations were substantially less productive. The wide distribution of Salmonella in the egg-grading station environment underlines the need for stringent hygienic control of in-plant operations to obtain shell eggs of high bacteriological quality.
Resume Des salmonelles ont ete isolees de 39 (13%) des 299 echantillons d'oeufs en coquille Categorie Hies et de 13 (34%) des 40 echantillons d'eau de lavage provenant de 11 postes de c1assement en Ontario; la proeminence de S. infantis dans les echantillons d'oeufs etait d'autant plus notoire que son absence dans les eaux de lavage. Les comptes d'heterotrophes aerobies (SPC) it 35°C variaient de < 104 it 10 8 organismes par ml d'eau de lavage. Des salmonelles ont aussi ete identifiees dans I des 13 echantillons d'albumen et jaune provenant d'oeufs feles et dans 2 des 94 echantillons d'oeufs en coquille nonfeles. Suivant un preenrichissement en bouillon nutritif, le taux d'isolement de salmonelles avec le bouillon d'enrichissement tetrathionate-vert brillant combine it la gelose au sulfite de bismuth ou au vert brillant-sulfamide etait de 98% et 91 % respectivement; un bouillon similaire de selenite-cystine s'avera beaucoup moins product if. La presence marquee de Salmonella dans les postes de classement d'oeufs accentue l'importance de mesures de contr6le hygienique adequates pour la mise en marche d'oeufs de qualite bacteriologique superieure.
Materials and Methods Samples of "Grade Cracks" shell eggs were obtained from II egg-grading stations in eastern and southern Ontario by Agriculture Canada inspectors. Each station was visited on three separate occasions between August and December 1979; on each visit, approximately 200 ml of egg wash-water and 10 cartons each containing one dozen eggs were obtained. Each carton represented a different layer flock. During the study, station A (Table I) experienced financial difficulties and was replaced with station K for the last
Introduction Current economic pressures have favored greater human consumption of poultry and poultry products (Anon., 1978) and further increased the risk of human Salmonella infections. Recent summaries of foodborne outbreaks continue to show the importance of these commodities as vehicles of human infection
Copyright
©
0315-5463/80/0400184-04$2.00/0 1980 Canadian Institute of Food Science and Technology
184
Salmonella in "Grade Cracks" Shell Eggs J.Y. D'Aoust, P. Stotland Bureau of Microbial Hazards, Health Protection Branch Health and Welfare Canada, Tunney's Pasture Ottawa, Ontario K lA OL2
and c.J. Randall Livestock and Poultry Division Food Production and Inspection Branch, Agriculture Canada Ottawa, Ontario K I A OC5
Abstract
(FWDC, 1975; CDC, 1977). Although the presence of Salmonella in liquid egg preparations and shell eggs is well documented (Garibaldi et aI., 1969; Cantoni et aI., 1976; Krepel and MacPherson, 1976; Evans, 1977; Bollegraaf, 1978; Moats, 1978), few outbreaks associated with shell eggs have been reported recently (Cohen and Blake, 1977). In 1977, an outbreak in Ontario involving 44 cases of illness with 4 cases requiring hospitalization resulted from use of "Grade Cracks" shell eggs infected with S. bareilly in cake batter and icing prepared by a commercial bakery; the economic impact due to lost wages and medical and investigational costs was considerable (Evans, 1977; Lavigne, 1978). In 1979, an Ontario outbreak of S. infantis affected 61 members of a senior citizens home; eggnog prepared with cracked eggs was tentatively identified as the vehicle of infection (Bollegraaf and Lior, 1979). Unrestricted sale of cracked eggs to the public is prohibited in British Columbia, Alberta, Manitoba, Quebec and Newfoundland. "Grade Cracks" is the grade name for eggs with cracked shells whose internal contents do not leak; candling characteristics of these eggs meet standards for at least Canada Grade C. The present study was undertaken to monitor the incidence of Salmonella in "Grade Cracks" shell eggs and to evaluate the efficacy of different analytical conditions in detecting salmonellae in shell eggs.
Thirty-nine (13%) of 299 samples of "Grade Cracks" shell eggs and 13 (34%) of 40 egg wash-water samples obtained from I1 egg-grading stations in Ontario were found to contain Salmonella; S. infant is was isolated frequently from shell eggs but was not detected in wash-water samples. Standard plate counts (35° C) ranged from < 10' to 108 cells per ml of wash-water. Salmonella was also detected in I of 13 egg meat samples obtained from cracked eggs and in 2 of94 intact shell egg samples. Following pre-enrichment in nutrient broth, tetrathionate brilliant green enrichment broth in combination with bismuth sulfite or brilliant green sulfa agar media identified 98% and 91 %, respectively, of all positive samples; homologous selenite cystine combinations were substantially less productive. The wide distribution of Salmonella in the egg-grading station environment underlines the need for stringent hygienic control of in-plant operations to obtain shell eggs of high bacteriological quality.
Resume Des salmonelles ont ete isolees de 39 (13%) des 299 echantillons d'oeufs en coquille Categorie Hies et de 13 (34%) des 40 echantillons d'eau de lavage provenant de 11 postes de c1assement en Ontario; la proeminence de S. infantis dans les echantillons d'oeufs etait d'autant plus notoire que son absence dans les eaux de lavage. Les comptes d'heterotrophes aerobies (SPC) it 35°C variaient de < 104 it 10 8 organismes par ml d'eau de lavage. Des salmonelles ont aussi ete identifiees dans I des 13 echantillons d'albumen et jaune provenant d'oeufs feles et dans 2 des 94 echantillons d'oeufs en coquille nonfeles. Suivant un preenrichissement en bouillon nutritif, le taux d'isolement de salmonelles avec le bouillon d'enrichissement tetrathionate-vert brillant combine it la gelose au sulfite de bismuth ou au vert brillant-sulfamide etait de 98% et 91 % respectivement; un bouillon similaire de selenite-cystine s'avera beaucoup moins product if. La presence marquee de Salmonella dans les postes de classement d'oeufs accentue l'importance de mesures de contr6le hygienique adequates pour la mise en marche d'oeufs de qualite bacteriologique superieure.
Materials and Methods Samples of "Grade Cracks" shell eggs were obtained from II egg-grading stations in eastern and southern Ontario by Agriculture Canada inspectors. Each station was visited on three separate occasions between August and December 1979; on each visit, approximately 200 ml of egg wash-water and 10 cartons each containing one dozen eggs were obtained. Each carton represented a different layer flock. During the study, station A (Table I) experienced financial difficulties and was replaced with station K for the last
Introduction Current economic pressures have favored greater human consumption of poultry and poultry products (Anon., 1978) and further increased the risk of human Salmonella infections. Recent summaries of foodborne outbreaks continue to show the importance of these commodities as vehicles of human infection
Copyright
©
0315-5463/80/0400184-04$2.00/0 1980 Canadian Institute of Food Science and Technology
184