An outbreak of Ochrobactrum anthropi bacteraemia in five organ transplant patients

Nosocomial bacteraemia caused by Ochrobactrum anthropi occurred over a 1-month period in five organ transplant recipients, four of whom were in the same renal and pancreatic transplant unit. Bacteraemia occurred with cyclosporin A, azathioprine and steroids, and with a rabbit anti-thymocyte globulin (RATG) during the induction phase. RATG appeared to be the only common factor among the five cases. Over the period described, 71.4% of all patients receiving RATG developed O. anthropi bacteraemia. Three patients presented with fever and chills during or shortly after RATG infusion. Analysis of residues of the infusion, and the used vials of RATG, showed the presence of O. anthropi in concentrations of between 20 and 1000 cfu ml-1 in 5.3% of samples. Unused vials were found to be heavily contaminated with either O. anthropi or Microbacterium spp. in 23.5% of samples. All positive vials were of one particular lot number suggesting a malfunction in the manufacturing process. Many parenteral drugs such as the RATG used here do not contain preservatives and, although aseptically prepared, will not withstand thermal sterilization. Bacterial contamination of these small volume medications is not always easily detectable by conventional methods. This outbreak highlights the need for accurate quality control testing to detect small inocula that may occur during or after the manufacturing process.