Is there any regulation or accreditation requirement for the temperature at which a blood product should be cultured, when the blood product is considered as a possible cause of an adverse reaction due to suspected bacterial contamination?

A Clinical Laboratory Operations Manager of a Blood Bank, Apheresis and Donor Room in Georgia wonders if any requirement exists for the temperature at which a blood product should be cultured, when the blood product is considered the possible cause of an adverse reaction due to suspected bacterial contamination. His initial investigation reveals that most hospital facilities perform a gram stain of the suspected product, and culture a sample of the product at 35C. However, he is aware that some facilities perform culturing over a wider temperature range. In his review of AABB and FDA literature, he was unable to find specifics as to the temperature at which suspect products should be cultured. He asks if any colleagues are aware of standard requirements for the temperature at which a blood product should be cultured, if the product is involved in an adverse reaction that suggests bacterial contamination is the cause.

The following comments have been received.

ADDENDA Nov. 26, 2006

1. A colleague affiliated with the National Institutes of Health (NIH) reports that organisms are subdivided into psychrophiles (optimum growth at 15-20C), mesophiles (optimum growth at 25-40C), and thermophiles (optimum growth at 50C or higher). Most organisms are capable of growth at a much wider range than their optimum temperature. Historically, USP recommended incubating bacterial cultures at 25C and 35C with the thought that the two temperatures would optimally support the growth of both psychrophiles and mesophiles. In reality, incubation at 35C supports the growth of all clinically significant organisms although some fungi grow less well at 35C vs. 25C. In the experience of the respondent, all organisms that have been associated with transfusion reactions grow at 35C, even organisms such as Yersinia enterocolitica which grows perfectly well in refrigerators. Thus, there is no reason to incubate cultures at lower temperatures. Indeed, in the opinion of the respondent, because most organisms grow optimally at 35-37C, incubation of specimens at the lower temperatures would delay detection of positive cultures, which is what the respondent found in the work they did with Cell Processing samples.
   
   
2. Dr. Richard Kaufman, Medical Director, Adult Transfusion Service at the Brigham and Women's Hospital (attribution used with permission) reports that to his knowledge, there is no formal standard for the temperature at which a suspected unit should be cultured. While it is true that individual bacterial strains may optimally grow at different temperatures, he thinks a reasonable approach would simply be to culture at whatever the standard temperature is that is used at a given hospital's microbiology laboratory. In practice, hospital microbiology labs culture at 35 - 37 C. Dr. Kaufman adds that he called Biomérieux, the manufacturer of the BacT/ALERT® system to discover what temperature they recommend for culturing, since "no recommendation is made in the device package insert". Dr. Kaufman reports that "According to their technical support, the BacT/ALERT® system can be set to culture at 35-37 C. The device can easily maintain a temp that is <0.5 C above or below the set temp. Most hospital microbiology laboratories use 35 or 36 C as their set temperature."

ADDENDA Nov. 27, 2006

3. A colleague in Ohio reports that in their hospital's clinical microbiology laboratory, they investigate blood products that are suspected of causing a septic transfusion reaction in the following manner:
   • Gram stain
   • Culture on 2 blood agar plates, one incubated in CO2 at 35C, the other in air at 25C.
   • Culture in thioglycollate broth incubated at 35C (for detecting anaerobes; can also be performed on an agar plate incubated anaerobically).
   • Quantitative plate counts are performed if any of the above cultures are positive.
   The respondent points out that on page 9 of the 2006 Circular of Information it states: "Prompt recognition of a possible septic reaction is essential, with immediate discontinuation of the transfusion and aggressive therapy with broad-spectrum antimicrobials and vasopressor agents, if necessary. In addition to prompt sampling of the patient’s blood for cultures at several different temperatures, investigation should include examination of material from the blood container by Gram’s stain, and cultures of specimens from the container and the administration set." He points out that the aforementioned statement calls for blood cultures of the patient at various (unspecified) temperatures, which is not done anywhere to his knowledge, and systems in use have not been validated at temperatures other than 35C.
   
   
4. A colleague in the Atlantic Northeast reports that testing should be done according to manufacturer's instructions. The automated culture systems are optimized for certain temperatures, and these temperature ranges are the ones that should be used when looking for a contaminating organism. The Micriobiology laboratory with which the blood collector/transfusion service is working should be able to provide some guidance on this. From a practical point of view, the usual temperature studied is 35-37C.

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