It was verified that pathogenic microorganisms in a hen house environment could be transferred to the surface of table eggs causing a risk to consumer health, which is confirmed by a number of recorded cases of bacterial food-borne illnesses. On eggshells, the pathogenic bacteria and other microorganisms occur together; therefore, a model study was performed on the survival of and competing interactions between native eggshell microflora and selected pathogens. Two groups of eggs were prepared: with sterile and unsterile eggshell surface. The two groups of eggs were contaminated with E. coli O2 inoculants: H1: K4 PCM 413 and PCM 843 S. enteritidis bacteria, and with a mixed culture of both bacteria. The samples were cold stored during a four week period. A microbiological assay was performed using a classical pour-plate method with an eggshell homogenate seeded on a suitable chromogenic substrate. As a result of the experiments performed, it was found that the longer the eggs storage time was, the lower the count of transferred bacteria was, and, often, those bacteria totally disappeared. This is probably caused by disadvantageous conditions for the bacteria to grow on the surface of eggshells, i.e. low water activity and low availability of nutrients. In addition, the survival of the E. coli strain on a sterile surface was much higher than on unsterile eggshells, what was associated with lack of competition for habitat. In each case analysed, the studied S. enteridis strain better tolerated the competitiveness of native microflora on the unsterile rather than sterile surface of eggshells. During storage, the E. coli bacteria significantly faster died out on the surface of eggshells than the S. enteritidis bacteria. Additionally, this process was intensified by the coexistence of native microflora on the eggshells.
eggshell, S. enteritidis, E. coli, competition