PSEUDOBACTEREMIA WITH AMOXICILLIN-CLAVULANIC ACID-RESISTANT ESCHERICHIA-COLI TRACED TO CROSS-CONTAMINATION DURING BLOOD CULTURE PROCESSING

Escherichia coli has seldom been reported to cause pseudobacteremia. T he investigation of an outbreak of amoxycillin-clavulanic acid-resista nt E. coli pseudobacteremia is described. Seventeen cases occurred ove r a five-day period. The source of the E. coli was traced to the blood culture specimen of a patient (index patient) with genuine bacteremia as a result of urinary tract infection. The other 16 case-patients ha d pseudobacteremia which was found to be the result of cross-contamina tion during subculture of blood specimens. The E. coli strain was carr ied over from the culture bottle of the index patient, through the con taminated gloved hands of a technician to the culture bottles of the o ther 16 cases. Although the pseudobacteremia occurred over a five-day period, they all resulted from cross-contamination during blood cultur e processing within one day. An early outbreak investigation was promp ted by the unusual finding of amoxycillin-clavulanic acid resistance i n the case E. coli isolates in a short period. The relatedness of the E. coli strains from the 17 cases was confirmed by arbitrary-primed po lymerase chain reaction. Clinicians should be alerted to the possibili ty of a blood E. coli isolate being a contaminant despite its predomin ant role as a true pathogen.