A COMPARATIVE-STUDY OF NOSOCOMIAL AND COMMUNITY-ACQUIRED STRAINS OF ESCHERICHIA-COLI CAUSING BACTEREMIA IN A DANISH-UNIVERSITY-HOSPITAL

In a previous study we found a considerably higher mortality rate in p atients with nosocomial (NO) compared with community-acquired (CX) Esc herichia roll bacteraemia. To establish whether this was due to host d ifferences or to differences in the infecting bacteria, we compared 20 5 NO with 172 CA bacteraemic isolates of E, roll with respect to serot ype, virulence factors and antimicrobial susceptibility. Overall the s ix most frequent O antigens were O18ac, O6, O1, O2, O15 and O75, respe ctively. The six most frequent capsular antigens were K1, K5, K52, K2, K7 and K34, respectively. No major differences were found regarding O -antigens, capsular antigens, production of haemolysin, P-fimbriation, serum sensitivity or antimicrobial susceptibility. Surprisingly we fo und 17 strains of serotype O15:E;52:[H1] of both NO (eight) and CA (ni ne) origin with similar phenotypic characteristics to a strain causing a CA outbreak in London 1986-1987. Possibly the Danish and the Englis h strains belong to the same clone. Our findings argue against the exi stence of a distinct NO flora. NO E, coli bacteraemia strains seem to originate primarily from the patients' own flora.