A Pseudo Outbreak of Pantoea dispersa in Total Joint Replacement Procedures

BACKGROUND/OBJECTIVES: Kaiser Sunnyside Medical Center is a 196 bed acute care hospital located in a suburb of Portland, Oregon. Infection Control staff includes two full time practitioners (ICPs). In March of 2005 Infectious Disease notified Infection Control of an unusual bacterium cultured from intra-operative tissue specimens of two patients who underwent total joint procedures in March. The organism, Pantoea dispersa, is a gram negative bacillus usually found in the environment and in agriculture. METHODS: Infection Control reviewed charts of both patients and consulted with both surgeons, microbiology and the Orthopedic Charge Nurse. Both patients had complex cases with surgical site infections, caused by coagulase negative Staphalococcus (CNS), complicating the original joint replacement procedure. The procedures when Pantoea was cultured were the second step in a two step process to treat the infection caused by CNS. The first step was to remove the original joint prosthesis and place antibiotic impregnated spacers. The second step was to remove the spacers and insert a new prosthesis. During this second step tissue was taken for stat gram stain and culture. Gram stains for both patients were negative. Cultures grew Pantoea dispersa. Operating Room visits by Infection Control included extensive interviews with Orthopedic Charge Nurse with detailed explanation of procedure for antibiotic impregnated spacers, the only commonality between the two patients. Investigation did not reveal possible source of organism during procedures when spacers were placed. Investigation of procedures when tissue cultures were taken identified three common staff. The OR environment was evaluated including the HVAC system. Cultures of the environment, staff, prep, and scrub solutions did not yield Pantoea. Infection Control staff observed a similar case that included stat gram stain. Tissue samples were taken and handed to the ICP who transported them to the lab. RESULTS: In the lab both ICPs observed the process for stat gram stain. During this procedure sterile saline is added to the tissue and ground up. It was noted that tape on the rack of test tubes containing sterile saline was dated September 2001. Sterile saline used for stat gram stains was prepared by the Regional Lab. The gram stain was negative and the tissue was sent for culture. Two test tubes of sterile saline were also sent for culture. Cultures from tissue and both test tubes grew Pantoea dispersa. CONCLUSIONS: Pantoea dispersa cultured from the intra-operative tissue of 3 total joint patients was a laboratory contaminant and did not cause infections in the patients. This pseudo-outbreak was caused by contaminated sterilized saline used to process stat gram stains that was close to four years old. Saline sterilized at the regional lab and sent to the KSMC lab is now labeled with outdates and discarded after two weeks.