Radioimmunoassay for detection of IgG antibodies against enterobacterial antigens.

The rough mutant of Salmonella minnesota (Re 595) contains several broad reacting antigens including a core LPS common to many aerobic gram-negative bacteria without sugars that confer serotype specificity to most gram-negative bacteria. Therefore, antibodies against this organism can be evoked by a large number of gram-negative bacteria. Using radioimmunoassay methods, sera from 59 patients with bacteremia due to enterobacteriaceae had higher concentrations of IgG antibodies against the rough mutant of Salmonella minnesota (Re 595) than control subjects. There was a significant correlation between concentrations of antibodies against Salmonella minnesota and concentrations of antibodies against a single strain of E coli. Sera from patients with bacteremia due to E coli or Klebsiella were tested against one strain of E coli and one strain of Klebsiella. The concentrations of antibodies against the homologous antigen were not higher than the concentrations of antibodies against the heterologous antigen. Sera from patients infected with S aureus or Pseudomonas aeruginosa did not have high concentrations of antibodies against S minnesota. Antibodies against common antigen(s) in Salmonella minnesota (Re 595) are useful in diagnosis of enterobacterial infections.