Rapid detection and identification of microorganisms from blood cultures

In an era characterized by increasing emphasis on minimizing laboratory costs, reliable and cost-effective methods for rapidly identifying bacteria and fungi directly from blood cultures have a great deal of appeal to clinical microbiologists. A variety of methods have been evaluated and found to be useful under certain conditions, although none of the methods has been standardized and questions remain as to whether their use improves patient care or reduces hospital costs. Even if these methods do not improve patient care or reduce hospital costs, their use and expense could be justified if they improve laboratory work flow or decrease laboratory costs or both. Several issues remain unresolved, one of which is whether the use of rapid identification methods with a continuous-monitoring blood culture system might allow for a clinically important decrease in the time required to identify blood culture isolates. Another issue is whether subsequent isolation by culture is necessary for microorganisms with predictable antimicrobial susceptibility patterns. These and other issues need to be studied further before the exact clinical usefulness of rapid methods will be known. At this time, no commercial product has been cleared or approved by the Food and Drug Administration (FDA) for the direct detection or identification of both of pathogenic microorganisms from blood culture bottles (Sharon Hansen, PhD, personal communication, 1993). Consequently, laboratory directors should exercise caution in the use of commercial or other products for direct blood culture testing, because manufacturers assume no liability for products that are used for purposes other than that for which they have been approved. In addition, such use of commercial products may be in violation of the rules set forth in the Clinical Laboratory Improvement Act of 1988. Furthermore, as discussed previously, the clinical performance characteristics of many products typically have not been determined, and, therefore, test reference ranges, sensitivity, specificity, and positive and negative predictive values have not been established. Other issues, such as the effect of different blood culture media and additives, also have not been studied adequately, nor are specific controls defined. Therefore, laboratory staff who would like to use commercial products to test blood cultures directly must themselves establish the performance characteristics of the product (keeping in mind the issue of liability) or, preferably, persuade manufacturers to sponsor large-scale controlled clinical trials both to establish performance characteristics and to obtain FDA clearance or approval for such usage of the product.(ABSTRACT TRUNCATED AT 400 WORDS)