Carumonam enhances reactivity of Escherichia coli with mono- and polyclonal antisera to rough Escherichia coli J5.

Escherichia coli O111 reacts only slightly with antiserum to its rough mutant E. coli J5 in an enzyme-linked immunosorbent assay. When E. coli O111 was grown in the presence of sub-MICs of the monocyclic beta-lactam antibiotic carumonam, however, the enzyme-linked immunosorbent assay titer increased from 1,280 to 81,920. When the bacteria were grown in the presence of carumonam, the titer that was obtained with antiserum against E. coli O111 was not affected. This reaction was abolished after this antiserum was absorbed with E. coli J5 in the case of the carumonam-treated strain, whereas this absorption did not affect the reaction with E. coli O111. Thus, the O-antigenic side chain of E. coli O111 seems to be affected if this strain is cultured in the presence of carumonam. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a relative loss of the O polysaccharide in E. coli O111 when this strain was grown in the presence of carumonam. Also, a much stronger reaction of the antibiotic-affected lipopolysaccharide with a monoclonal antibody against E. coli J5 lipopolysaccharide was shown in immunoblots. The results of this study indicate that there is a synergism between certain antibiotics and monoclonal antibodies, something that could have clinical implications.