Evaluation of bacterial contamination of laying hen eggshells by using a classic and fast method: first report in Algeria

F. Mebkhout2, N.A. Khelifi Touhami1*, N. Ouchene1, T. Dahmane3, T.M. Hamdi2,3, O. Kessi4

1Institute of Veterinary Sciences, University Saad Dahlab Blida 1, Street Soumaa, 09000, Blida, Algeria
2HASAQ Laboratory, National Superior Veterinary School, 16000, Algiers, Algeria
3Department of Agricultural Sciences, Faculty of Natural and Life Sciences and Earth and Universe Sciences, Djilali Bounaama Khemis Miliana University, Ain Defla, 44000, Algeria
4Technical Institute of Breeding, Street Chebli, Baba Ali, 16000, Algiers, Algeria

(Manuscript received 5 July 2022; accepted for publication 21 November 2022)

Abstract. Chicken eggs are considered an important source of high-quality protein for humans. Many types of germs can contaminate eggshells, some of which are pathogenic. This survey aims to study the bacterial contamination of eggshells from ISA Brown laying hens of 56 weeks old. The study concerned a total of 100 eggs randomly collected. Two methods were used for investigation and enumeration of bacteria: a classical method and a rapid method Rida®Count. The classical method concerned: total bacteria, total and fecal coliforms, fecal streptococci, Staphylococcus aureus and Salmonella spp.. The rapid method RIDA®COUNT concerned: Total bacteria count, total coliforms, Staphylococcus aureus and Salmonella spp. In both methods, all eggshells were found to be contaminated with aerobic mesophilic bacteria. The average number revealed by the rapid method was 2.95 ± 1.06 Log CFU/cm² and by the classical method it was 2.85 ± 0.99 Log CFU/cm². The rapid method revealed a higher number of eggshells infected with total coliforms (90%) and Staphylococcus aureus (43%) compared to the classical method (56% and 19%, respectively). The average number of total coliforms (2.47 ± 0.95 Log CFU/cm²) and Staphylococcus aureus (1.67 ± 0.86 Log CFU/cm²) revealed by the classical method was close to the rapid method (2.35 ± 1.01 Log CFU/cm² and 1.43 ± 0.83 Log CFU/cm², respectively). Bacterial counts were not significantly different between the two diagnostic methods. The total absence of Salmonella spp. was confirmed. However, the presence of two eggs infected by Raoultella planticola (2%), and two eggs by Escherichia coli (2%) were found. This investigation provided the first partial description in Algeria of the bacterial contamination of laying hen eggshells using two methods: classic and rapid. The good hygiene and management can avoid contamination with dangerous bacteria represented mainly by Salmonella spp.. However, it is necessary to study the bacterial contamination inside the egg and to extend the research to other bacteria