Effect of enzyme catalase on the inhibitory activity of the isolates in study indicated that the antimicrobial activity of L.lactis 2, L.paracasei1 and 2 against S. enteritidis might have been due to hydrogen peroxide as their activities were completely eliminated after addition of the mentioned enzyme (Table 4). However, the remaining isolates remained unaffected by this enzyme, which excluded inhibition by hydrogen peroxide.