David L. Sewell

Timing of Specimen Collection for Blood Cultures from Febrile Patients with Bacteremia

ABSTRACT Bloodstream infections are an important cause of morbidity and mortality. Physician orders for blood cultures often specify that blood specimens be collected at or around the time of a temperature elevation, presumably as a means of enhancing the likelihood of detecting significant bacteremia. In a multicenter study, which utilized retrospective patient chart reviews as a means of collecting data, we evaluated the timing of blood culture collection in relation to temperature elevations in 1,436 patients with bacteremia and fungemia. The likelihood of documenting bloodstream infections was not significantly enhanced by collecting blood specimens for culture at the time that patients experienced temperature spikes. A subset analysis based on patient age, gender, white blood cell count and specific cause of bacteremia generally also failed to reveal any associations.

Sensitivity of surveillance cultures for the detection of methicillin-resistant Staphylococcus aureus in a nursing-home-care unit

This study compared the sensitivity of nasal culture alone versus multiple-site cultures and single versus duplicate sampling for the detection of methicillin-resistant Staphylococcus aureus (MRSA)-colonized individuals in a nursing-home population. Repeat culture of 68 specimens collected from 35 colonized subjects yielded identical results for 57 specimens, (84%), and 89% of the colonized residents (31 of 35) were identified by the first culture of multiple sites. A single nares culture detected 27 (77%) of 35 (first screen) and 29 (83%) of 35 (second screen) residents colonized with MRSA at any site. The most cost-effective screening would consist of a nasal culture only or combined with a gastrostomy tube site, if applicable. To identify all colonized individuals, however, it would be necessary to culture more than one specimen from multiple sites on each resident.

Laboratory safety practices associated with potential agents of biocrime or bioterrorism.

The anthrax incident of 2001 in the United States clearly documented the threat posed by the intentional release of an infectious agent in a susceptible population. It also demonstrated that clinicians and clinical microbiology laboratories are key to the early detection of disease, identification of the putative agent, and notification of appropriate authorities. To be effective in this role, laboratories must be prepared for a possible biocrime or bioterrorism event. Preparation requires that laboratories have an awareness of the potential agents that may be used, laboratory techniques for the early identification of these agents, procedures for the management of the event, and knowledge of the safety precautions necessary to safely handle these infectious agents (7). Once prepared, laboratory personnel must constantly be alert for the possible isolation of these agents during the routine manipulations of cultures at the bench (10). With the exception of smallpox virus and viral hemorrhagic fever (VHF) agents, most of the biothreat agents are occasionally isolated from patients who have been naturally infected. To ensure a safe work environment, the laboratory must implement and strictly adhere to the routine safety practices that minimize risk to laboratory personnel (8, 9).

Laboratory-acquired infections: Are microbiologists at risk?

Abstract Exposure of laboratory workers to infectious agents in the clinical microbiology laboratory continues to be an occupational risk. This risk is mitigated by the application of safety guidelines issued by regulatory agencies and professional organizations. The Clinical and Laboratory Standards Institute (fomerly NCCLS) published a guidance document (M29-A3) in 2005 on the risk of transmission of infectious agents in the laboratory, preventative measures to reduce risk, and management of exposure to infectious agents. The key to a safe workplace is employees who are knowledgeable of the routes of transmission of infectious agents in the laboratory setting and apply safety principles and work practices to reduce the risk.

Laboratory-acquired Infections

Summary LAIs still occur but the risk can be minimized by use of standard precautions, good microbiological technique, and adherence to a comprehensive safety program. The health care organization and laboratory director must provide a safe work environment, but it is the responsibility of each employee to be aware of potential hazards and the recommended practices to minimize the risk associated with working with infectious agents.