Managing a Large-scale Occupational Exposure to Brucella abortus in a High-throughput Clinical Laboratory

Abstract

Background. A 51 year old male patient with 5 months of unresolved fever grew Brucella abortus in blood culture. His only potential exposure was residence in Mexico 20 years ago. Clinical suspicion was low and Gram stains from two aerobic bottles stained atypically as tiny Gram-positive cocci. This led to manipulation of the organism outside a biosafety cabinet (BSC) and subsequent exposure of 100 laboratory workers to B. Abortus. Methods. Patient blood cultures were incubated in automated monitoring instruments (BACTEC FX) and showed growth on blood and chocolate media. Identification was attempted in-house using MALDI-TOF mass spectrometry (Vitek) and biochemical testing. The Centers of Disease Control and Prevention (CDC) confirmed organism identification by PCR. Time points of high-risk events (e.g., catalase reactions), zones of operation, and involved personnel were identified through review of organism workup documentation in the laboratory information system. Serological testing of employees was performed at CDC by the BrucellaMicroagglutination Test (BMAT). Results. Cultures were manipulated 7 times outside of the BSC. Institutional members from infection control, employee health services (EHS), microbiology, laboratory safety, and public health partners at CDC and the New York city and state laboratories were assembled to assess risk with 24 hours of the exposure alert. High-risk employees (n = 33) were defined as being within 5 feet of culture manipulation outside a BSC. Low-risk employees (n = 67) were any personnel within the microbiology room (∼3,000 sq. ft.) after individual risk factors were assessed by EHS. All exposed personnel were offered counselling and risk assessments, serological monitoring by BMAT at 0, 6, 12, 18, and 24 weeks, daily temperature checks, and weekly symptom monitoring. Recommendations for prophylaxis were based on risk. A total of 17 individuals completed prophylaxis and 100/102 completed baseline serologies. These were all negative. Conclusion. Laboratory controls for high-risk organisms like B. Abortus are paramount in a sizeable, highly active clinical laboratory to prevent future large-scale exposures.