Recurrent Escherichia coli bacteraemia--clinical characteristics and bacterial properties.

The aim of the present study was to determine if recurrent bacteraemia due to Escherichia coli might be caused by the same strain in spite of apparently adequate antimicrobial therapy. Eleven patients who, altogether, experienced 24 episodes of E. coli bacteraemia were studied. All had underlying diseases; five biliary-intestinal disease, four were severely immunocompromised and two had urinary tract disorders. During the first bacteraemic episode, nine patients were treated with various combinations of drugs which included gentamicin and two with co-trimoxazole alone. Antibiotic treatment was continued for at least 12 days in each case and all patients were clinically cured. All isolates of E. coli were characterized by biochemical fingerprinting, O and K serotyping, the presence of cell-surface hydrophobicity and production of aerobactin. In two patients, the recurrent infections were due to strains different from those causing the previous episodes. In nine patients who, altogether, had 19 episodes of bacteraemia, the strain of E. coli isolated during the first and all later episodes were identical, according to all tests performed. We suggest that in such circumstances, the infecting strain may remain in the patients' environment and after recolonising the faecal flora may give rise to further infections. It may be, however, that if necessary steps are not taken, the original bacterial focus remains within the same patient so leading to emergence of the infecting strain which may then cause further episodes of bacteraemia.