A colloquium was convened by the American Academy of Microbiology and the American College of Microbiology to discuss the role of the clinical microbiology laboratory in the detection, identification, and confirmation of biological agents that could be used in a bioterrorism event. The colloquium was held in San Antonio, Texas, October 27-29, 2000. The principal findings of the colloquium are summarized below. Professional microbiologists, in conjunction with clinicians, will play a central role in the detection of agents associated with bioterrorism. In collaboration with state and federal agencies, they will help to determine when a bioterrorism event has occurred. In the case of a possible bioterrorism event, the key responsibilities of the hospital-based clinical microbiology laboratory are to be familiar with the likely agents of bioterrorism and to be prepared to use the Level A laboratory algorithms designed for the detection of these agents. Using these algorithms, clinical microbiology laboratories rule out bioterrorism-related microorganisms and identify suspicious isolates. However, at the present time, there is an acute shortage of trained clinical microbiologists who will be required for clinical microbiology laboratories to carry out these responsibilities. In particular, relaxation of the educational standards for laboratory workers by the Clinical Laboratory Improvements Amendments of 1988 (CLIA ’88) legislation has potentially increased the likelihood of bioterrorism pathogens being overlooked. Several other factors may hamper recognition of a possible bioterrorism threat. Terrorists are likely to select the most vulnerable locations: perhaps small cities or rural areas where microbiology expertise may be difficult to find. Widely used, commercially available identification systems utilized by clinical microbiology laboratories in routine daily operations do a poor job of identifying uncommon and slow-growing microorganisms that are expected to be associated with bioterrorism events, such as and . Moreover, the cause of a bioterrorism event may be an agent not on the list of likely pathogens. A bioterrorism attack with an emerging agent, such as West Nile virus or Hantavirus, might be difficult to deliver, but would be most difficult to detect. An event is most likely to be signaled by many people getting sick around the same time and with similar symptoms. Event recognition is thus a team effort; effective channels of communication must be in place between clinicians, particularly infectious disease physicians and emergency room personnel, and the microbiology laboratory. Since recognition depends on clusters of infections, the small number of cases seen by a laboratory or infectious disease physician at a single institution might not arouse suspicion. Recognition may require sharing knowledge of cases occurring at several institutions within a region. However, at the present time, the infrastructure for interinstitutional communication of possible bioterrorism cases needs augmenting. Most clinical microbiology laboratories have access to the Laboratory Response Network (LRN), a system created to provide an organized response for the detection and diagnosis of biological agents. The LRN is the essential organizational unit for detection of and response to a possible covert bioterrorism threat. At the advanced level, where specimens suspected of containing a possible bioterrorism agent would be subjected to detailed analysis, effective components of the LRN have been put in place. But additional training and communication need to be established in clinical microbiology laboratories that will act as sentinels to detect a possible bioterrorism threat. When a bioterrorism event occurs or is even suspected, several consequences will impact the laboratory's ability to function effectively. A flood of specimens may overwhelm the laboratory's capacity and exhaust available testing reagents. Fearful workers may be reluctant to handle specimens that could contain dangerous pathogens; some technologists may not come to work. Many specimens or isolates may need to be shipped to a higher-level laboratory for further testing, which requires special packaging. In addition, the laboratory may be subject to numerous inquiries about test results from patients, families, and the news media. For a laboratory to manage these disruptions it must have a bioterrorism response plan and laboratory workers must be trained in and familiar with the plan. Several new rapid technologies are available in the clinical micro-biology arena. Exploitation of these technologies to devise improved assays for identifying possible agents of bioterrorism would enhance the ability of both sentinel and advanced micro-biology laboratories to detect a possible bioterrorism threat. The success of the public health response to the bioterrorism threat depends on a national effort that must involve all levels of the health care system, from local to federal. Benchmarks must include public education, medical laboratory and practitioner training, standardization of emergency preparedness plans, and defined lines of communication both within the health care system and extending to law enforcement agencies.