Several questions were posed for those of you who are participating in Hematopoietic Cell collection and/or processing regarding your experience with positive cultures of Hematopoietic Cell Therapy components. Here are the questions:

• For those of you who are participating in Hematopoietic Cell collection and/or processing, what is your experience with positive cultures of Hematopoietic Cell Therapy components?
• What is your rate of positive cultures for aerobic bacteria, anaerobic bacteria, and fungi?
• For those of you with positive culture results, have you done any root cause analysis to determine the reason for positive cultures?
• Does anyone do their processing in a Class 100,000 environment, assuring you purity of less than 100 particles, which are 0.5 microns or larger, per cubic foot (or better)?

I am certain that several e-Network members would appreciate knowing what others are experiencing and how they deal with positive culture results.

1. These questions and the corresponding responses were submitted by a sole institution:

A member reported that positive cultures occur at his facility less than 0.1% of the time and are usually contaminants. In 11 years and with thousands of specimens, this institution has yet to find something worth worrying about. They do put patients on prophylactic antibiotics when a positive component is reinfused, but almost nobody at his institution thinks this is truly essential.

They report having seen about 3 or 4 positives out of some thousands of collections, usually a skin-derived staph epidermidis of little to no significance. They do not routinely culture for anaerobes. Their feeling is that, in general, culturing, except for procedural QA purposes, is largely a waste of time and money.

It is the reporting institution's opinion that you cannot do meaningful root cause analysis on rare events like this. The contaminating organisms most probably came from the skin or the environment and not the blood or marrow in most, if not all cases. The number of organisms is tiny because marrows and PBSCs are processed and either administered or cryopreserved quickly. There really is no time for serious levels of contamination to develop. The reporting member knows of no documented cases of infection or sepsis due to infusion of fresh or cryopreserved stem cells in the literature, but he has never made an exhaustive search and would be interested in other folks' experience.

The reporting institution does NOT, and they comment that in their opinion, this would be largely unnecessary for routine stem cell work.

EDITOR's NOTE: The following reference, from the web site of the Scottish Society of Contamination Control, might be of interest to those of you who want to know more about the various kinds of "ENVIRONMENTS" from class 100 to class 100,000 (and beyond!).

ADDENDA July 16, 2001

5. A physician-scientist has provided permission to share the following excerpt from his book chapter which addresses transfusion reactions associated with hematopoietic stem cell reinfusion. This chapter will appear in Dr. Mark Popovsky's upcoming revision of the AABB text on Transfusion Reactions:

"Other reactions observed in recipients of non-cryopreserved marrow and PBSC. Stroncek et al (10) observed that symptoms such as nausea, vomiting, chills and fever, headache and dyspnea and post-infusional hematuria were seen far less frequently in recients of non-cryopreserved marrow than in those receiving cryopreserved marrows. Nonetheless, there was a 7-20% incidence of nausea associated with marrow infusion, up to 15% incidence of emesis, and 5% incidence of headache and dyspnea. Hence, infusion of cellular products, even unmanipulated is associated with a finite rate of transient, self-limited reactions. Of note, bacterial cultures of marrow, even unmanipulated, show a significant rate of bacterial contamination (up to 5-20% in bone marrows, about a log less in PBSC collections, and mostly gram positive skin flora). (10), (11), (12) The degree to which bacteria contribute to the infusional symptoms is unclear, although the Stroncek report noted a significantly higher rate of fever and chills in the highly manipulated marrow infusions that also had higher rates of bacterial contamination. Finally, procedures should be in place to prevent iatrogenic contamination of the infused component by non-sterile conditions in the storage tank (13)."

6. Another network member wrote that his institution processes 2,000 products a year with cultures performed post processing on every product. The rate of positive cultures for aerobic bacteria, anaerobic bacteria, and fungi is very low, along the lines of the 0.1% reported by the above institution Most of the positives are "contaminants" and these generally are not reported as a true positive, but it is the physician's decision to use the product and to follow up with antibiotics. A second culture is done on a back-up specimen whenever a report of a positive sample is issued and these secondary cultures are usually negative, confirming the contamination. The member commented that since most people process products in "closed systems" you would expect very low contamination from processing. The member commented that they do NOT do their processing in a Class 100,000 environment, assuring purity of less than 100 particles, which are 0.5 microns or larger, per cubic foot (or better), but that this day is probably coming.

ADDENDA July 17, 2001

7. A blood banker in Ohio wrote that "routine sterility testing is prudent (and mandated) even though positive cultures are rare, so that patients can be placed on a prophylactic antibiotic regimen as soon as any growth is observed. Recalling my experience from Georgetown, and in discussions with others, most centers only test for aerobic bacterial and fungal contaminants since the introduction of anerobes is extremely unlikely. There is no real tracking data on contamination but rates are about 1-2%. Most contaminants are skin flora and can be attributed to the personal involved in collection, processing or sterility testing. Having a fairly extensive environmental monitoring program in place is often the only way to pinpoint the cause of the contamination. Some centers are building class 100,000 facilities for their processing labs if they intend to do more than minimally manipulated procedures. However the majority of facilities favor a class 100 biosafety cabinet within an unclassified (unfilitered) environment. A more controlled environment is needed for any products that require extensive open container manipulations or a culture period before infusion."

Please submit comments, additional data, and if you feel so compelled, additional opinions, either supporting or refuting the above opinions to the
e-Network Forum.

Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator