Strategies of bacteria screening in cellular blood components

Abstract

Since the impressive reduction of transfusion-transmitted virus infections, bacterial infections by blood transfusion represent the most important infection risk. Platelet concentrates are the current focus of attention, as they are stored under temperature conditions which allow growth of contaminating bacteria up to 10(10) and more microbes per platelet bag. This paper does not consider the pathogen reduction methods but will assess suitable screening methods. Beside conventional microbiological approaches or surrogate markers, several efficient methods able to detect bacterial contamination in platelets are available on the market. They need to be divided into two different methodological principles: the cultivation methods and rapid methods. Cultivation or incubation methods require some time for signal production as they depend on growth of microbes. Thus, they have to be combined with early sampling, i.e., the sample to be examined has to be drawn from the blood component 1 day after donation. Their advantage is the relatively uncomplicated implementation into the logistics of blood banks. Because of the initially very low count of bacteria after donation, a certain small sampling error in application of that strategy remains. Rapid methods are able to produce the diagnosis within a short time. Therefore, they allow postponing of sample drawing, ideally up to the time immediately before transfusion. However, this procedure causes logistic complications. On the other hand, late sampling combined with a rapid method will prevent the transfusion of highly contaminated platelet concentrates leading to acute septic shock up to the death of the patient. Considering the sum of different aspects including the supply of patients, the potential improvement of microbial safety of platelet concentrates is comparable in both strategies.

Novel Flow Cytometry–Based Screening for Bacterial Contamination of Donor Platelet Preparations Compared with Other Rapid Screening Methods

“…The consensus of some studies is to use a late sampling strategy in combination with rapid detection methods (3,23 ). Another approach to prevent transfusion-transmitted bacterial infection is the use of PRT; however, concerns remain regarding the effectiveness, cost, and risks of PRT (1,24,25 ).…”

“…We believe these methods are currently the best solution to avoid transfusion of contaminated PLTs. The prevention of transfusion of highly contaminated blood products may not always avoid reactions to low concentrations of bacterial endotoxins or exotoxins in the recipient, but the consequences are generally less severe (23 ). Table 2 summarizes the specifications of the currently available rapid detection methods compared to the BacT/Alert culture system and the new BactiFlow assay.…”

The Pan Genera Detection Immunoassay: a Novel Point-of-Issue Method for Detection of Bacterial Contamination in Platelet Concentrates

“…The consensus of several studies is a late-sampling strategy in combination with rapid detection methods (9,18), offering the possibility of sample drawing at a later stage to overcome the risk of sampling error due to initially low bacterial count or slow-growing bacterial species. Decisions regarding bacterial testing strategies always have to balance the requirements for rapid detection and assay sensitivity (27).…”

Diagnostic Methods for Platelet Bacteria Screening: Current Status and Developments

“…These essential strategies for preventing bacterial contamination of blood components include careful donor selection, selection of the punction site, effective skin disinfection, separation of the first volume from the blood donation (pre-donation sampling, also called diversion) and the consistent monitoring of the bag systems, including monitoring of additional connections to the bag by the so-called sterile connecting device. Policies regarding these precautionary measures have already been implemented in Germany [1,2,3,4,5,6,7]. …”

“…These national guidelines were introduced to monitor bacterial contamination of blood components as part of routine quality control to establish standardized methods for bacterial testing [6]. The standardized protocols included the time of sampling (expiry date + 3 days), the sample quantity (0.4 × root of monthly produced blood component per production facility), sampling procedure, microbiological control (aerobic and anaerobic cultivation using 4-10 ml sample each with incubation at 30-37 °C for 14 days if conventional liquid culture is performed and 7 days if an automated system is used), identification of contaminating micro-organisms, and performing a second culture as a confirmatory test using material from the same blood bag [1,5,8]. As a result of the obtained and analyzed data; statement V16 was revised and adopted as statement V43 in 2012 by the AKB.…”