A novel cryohemagglutinin associated with adherence of enteroaggregative Escherichia coli.

Strain O42 (serotype O44:H18) of enteroaggregative Escherichia coli (EAggEC) has been shown to be pathogenic in volunteer experiments. This strain exhibited plasmid (pO42)-encoded D-mannose-resistant hemagglutinating activity (MRHA) that was detected only at low temperatures (e.g., 0 degrees C) and only with human erythrocytes. The production of this cryogenic MRHA (cryo-MRHA) was observed when the bacteria were grown in liquid media and was strictly regulated by bacterial growth temperatures. Transposon-insertion mutagenesis revealed that this MRHA is associated with (i) bacterial clump formation in liquid cultures, (ii) bacterial adherence to HEp-2 cells as well as (Formalin-fixed) human colonic mucosa, and (iii) production of a 16-kDa outer membrane protein. The PCR designed on the basis of the determined cryo-MRHA-associated DNA sequence sharply distinguished strain O42 from eight other EAggEC strains whose MRHAs were detected at both cold and room temperatures to the same (or similar) extent. Strain O42 possessed a surface layer that may enhance the pO42-mediated adherence. The data suggest that a plasmid-encoded cryo-MRHA is a candidate for a major adhesin of EAggEC strain O42.