LIPOPOLYSACCHARIDE EXPRESSION AND VIRULENCE IN MICE OF AUSTRALIAN ISOLATES OF SALMONELLA-ENTERITIDIS

The lipopolysaccharide (LPS) of 54 Australian isolates, nine isolates acquired or isolated overseas, and two reference strains of Salmonella enteritidis was studied to assess its relation to pathogenicity. LPS was extracted by proteinase K digestion of whole cells, and analysed b y polyacrylamide gel electrophoresis. All isolates possessed an LPS st ructure identical to that of a reference strain of Salm. enteritidis p hage type 4. Representative strains of the clinically prevalent phage types 4, 14 and 26, which express long chain LPS, were assessed for th eir pathogenicity in mice. Salmonella enteritidis phage type 4 produce d a lethal infection in BALB/c mice, but not in C3H/HeJ or Quackenbush (outbred) strains. Phage types 14 and 26 did not produce an obvious i nfection in any mice, suggesting Australian strains of phage type 4 ar e more virulent than phage types 14 and 26.