Iron restriction and the growth ofSalmonella enteritidis

Abstract

SUMMARY: Strains ofSalmonella enteritidiswere examined for their ability to remove ferricions from the iron chelating agents ovotransferrin, Desferal and EDDA. Growth ofS. enteritidisphage type (PT) 4 (SE4) in trypticase soy broth containing ovotransferrin resulted in the expression of iron regulated outer membrane proteins (OMPs) of 74. 78 and 81 kDa. and unexpectedly the repression of expression of OMP C. The 38 MDa ‘mouse virulence’ plasmid was not required for the expression of the iron-regulated OMPs (IROMPs). SE4 was able to obtain iron bound to the iron chelator Desferal and EDDA without expressing a high-affinity iron uptake system. Strains ofS. enteritidisbelonging to PTs 7. 8, 13a, 23. 24 and 30 were also able to remove ferric ions from Desferal and EDDA without expressing a high-affinity iron uptake system. We conclude that strains of SE4 possess a high-affinity iron sequestering mechanism that can readily remove iron from ovotransferrin. It is likely that iron limitation, and not iron restriction, is responsible for the bacteriostatic properties of fresh egg whites.