Optimisation of blood components sterility testing: impact of small volumes in analytical sensitivity

Daria Vay, Franca Gotta, Laura Carrabba, Roberta Mazzeo, Andrea Rocchetti

Author address: 

Azienda Ospedaliera SS. Antonio e Biagio e Cesare Arrigo, Alessandria, Italy, EU, Microbiology and Virology Unit, Alessandria, Italy

Abstract: 

Background: sterility testing of blood components is pivotal to prevent bacterial and/or fungal transfusion-transmitted infections. This is particularly challenging for lymphocyte apheresis, hematopoietic stem cells, platelet concentrates, cord blood and serum, for which very small volumes (from 0.5 to 1 ml) are inoculated into culture bottles. Aim of this study was to find and validate the most effective and rapid method in detecting a possible contamination of blood components.

Materials/methods: 15 strains were used, 13 from ATCC®: Aspergillus brasiliensis 16404; Aspergillus niger 16888; Candida albicans 10231; Bacillus subtilis subsp.spizizenii 6633; Bacteroides fragilis 25285; Campylobacter jejuni 33560; Clostridium sporogenes 19404; Cutibacterium acnes 11827; Haemophilus influenzae 49247; Neisseria gonorrhoeae 49226; Pseudomonas aeruginosa 9027; Staphylococcus aureus subsp. aureus 6538; Streptococcus pyogenes 19615; and two strains from clinical samples: Corynebacterium striatum; Micrococcus luteus; Colonies of each strain grown on chocolate agar were resuspended in separate tubes containing sterile saline solution until a standard turbidity of 1.0 McFarland (equivalent to about 3x108 CFU/ml) was obtained. From these tubes, a series of four 1:100 dilutions were made, resulting in a final concentration of ~3x100 CFU/ml (3 CFU/ml) of inoculum. The final suspension was inoculated into BD Bactec plus Aerobic, Anaerobic, Pediatric and Mycosis (the latter only for Candida albicans and Aspergillus spp.), with a volume of 1 ml and 0.5 ml.

Results: among bottles inoculated with 1 ml: 6/15 (40%) Aerobic, 5/15 (33.3%) Anaerobic and 8/15 (53.3%) Pediatric were positive. In the 0.5 ml group: 3/15 (20%) Aerobic, 4/15 (26.6%) Anaerobic and 5/15 (33.3%) Pediatric were positive. Time to positivity: for the 1 ml group: the 6 Aerobic bottles flagged positive in a mean time of 60.1 hours with a standard deviation of ±43.1 hours; the 5 Anaerobic bottles in 58.8 ±51.9 hours; the 8 Pediatric bottles in 31.9 ±27.6 hours. For the 0.5 ml group: 81.3 ±78.4 hours for the 3 Aerobic bottles; 50.8 ±45.9 hours for the 4 Anaerobic bottles; 24.2 ±15.2 hours for the Pediatric bottles.

Conclusions: this study showed how the combined use of both pediatric and anaerobic bottles improves detection of possible contamination even dealing with small volumes of blood components.

Presenter email address: [email protected]

2020

abstract No: 

2316

Full conference title: 

European Congress of Clinical Microbiology and Infectious Diseases 2020
    • ECCMID 30th (2020)