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Park, Shin, Yoon, Roh, Chang, and Kim: Microbial Contamination of Donated Umbilical Cord Blood
Original Article

Ann Clin Microbiol 2013;16(1):39-44.

Published online: 5 March 2013

DOI: https://doi.org/10.5145/ACM.2013.16.1.39

Microbial Contamination of Donated Umbilical Cord Blood

Jeong Su Park1, 2, 4, Sue Shin1, 2, 4, Jong Hyun Yoon1, 2, 4, Eun Youn Roh1, 2, 4, Ju Young Chang3, Eui-Chong Kim1

1Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Korea

2Department of Laboratory Medicine, Seoul National University Boramae Hospital, Seoul, Korea

3Department of Pediatrics, Seoul National University Boramae Hospital, Seoul, Korea

4Seoul Metropolitan Government Public Cord Blood Bank, Seoul, Korea

Correspondences: Jong Hyun Yoon and Sue Shin, Department of Laboratory Medicine, Seoul National University Boramae Hospital, 20 Boramae-ro 5-gil, Dongjak-gu, Seoul 156-707, Korea. (Tel) 82-2-870-2601, (Fax) 82-2-870-2620, (E-mail) slice@paran.com

Received 14 August 20125 November 2012       Accepted 5 November 2012

Copyright © 2013 The Korean Society of Clinical Microbiology

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

초록

Background

Testing for possible microorganism contamination in umbilical cord blood (UCB) is essential for validating the product safety of allogeneic cellular therapeutics. We analyzed the level of contamination and related factors at the largest public cord blood bank in Korea. In addition, we also studied the influ-ence of cryopreservation on contaminating microorganisms.

Methods

UCB was collected, transported, processed, and stored according to standard operating procedures. Microbial detection and identification was performed using a conventional automated blood culture system (BacT/ALERT; bioMérieux, France) with an inoculum of 5-10 mL plasma for pre-freezing UCB. Forty ran-domly selected non-conforming units were thawed and studied for microbiologic recovery with an inoculum of 2.5 mL.

Results

Among a total of 21,236 UCB, 677 (3.19%) were positive for culture. The most frequently identified organism was Lactobacillus spp. (17.2%), followed by Bacteroides spp. (10.1%), coagulase negative staphylococcus (6.4%), except the unidentified gram positive bacillus (21.4%). The contamination rate was higher in vaginal delivery specimens than in cesar-ean section specimens (4.1% vs. 0.7%, P＜0.001), and differed by collection center (0.7-25.4%, P＜0.001). Only 55% after-thaw cultures of non-conforming units were positive.

Conclusion

We determined the contamination rate of UCB in Korea in a large sample size. The results of this study could be used as baseline data at collection centers for quality control purposes. The low recovery rate of microorganisms after cryopreservation presents a possible way to rescue some non-con-forming cord blood units, although further study is needed to confirm the reduction of microbiological burden.

Keywords: Bacteria, Biological specimen banks, Qua-lity control, Umbilical cord blood

REFERENCES

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Fig. 1.
Proportions of origin of contaminated microorganisms according to years. Abbreviations: GI, gastrointestinal; GU, genitourinary.
acm-16-39f1.tif
Table 1.
Micro-organisms isolated from culture positive umbilical cord blood units
Potential contamination source Frequency (%)
Skin flora 11.0
  Coagulase negative staphylococcus 6.3
  Corynebacterium spp. 3.1
  Staphylococcus aureus 0.7
  Propionibacterium acnes 0.4
  Micrococcus spp. 0.4
Gastrointestinal/urogenital flora∗ 55.8
  Lactobacillus spp. 17.1
  Bacteroides spp. 10.1
  Escherichia coli 4.2
  Enterococcus spp. 4.1
  Streptococcus viridans group 3.9
  Peptostreptococcus spp. 3.4
  Prevotella spp. 3.4
  Lactococcus spp. 2.1
  Klebsiella spp. 1.9
  Clostridium spp. 1.2
Environmental contaminants∗ 5.5
  Citrobacter spp. 1.2
  Pseudomonas spp. 1.0
Unidentified Gram positive bacilli 21.3
Unidentified organisms 4.0
Missing data 2.4

∗ Species with frequency over 1.0% were presented.

Table 2.
Contamination rate of umbilical cord blood unit according to collection center
Collection center Culture positive units (N) Stored units (N) Contamination rate (%) Vaginal delivery rate (%)
A 28 1,795 1.6 77.5
B 65 1,721 3.8 61.4
C 11 1,063 1.0 59.4
D 20 786 2.5 77.6
E 17 766 2.2 75.2
F 12 669 1.8 78.3
G 31 599 5.2 67.8
H 127 501 25.3∗ 73.7
I 15 485 3.1 84.5
J 29 483 6.0 51.1
K 26 473 5.5 82.9
L 7 414 1.7 70.0
M 10 385 2.6 75.8
N 9 364 2.5 79.1
O 6 360 1.7 66.7
P 15 347 4.3 74.1
Q 20 320 6.3 70.3
R 2 309 0.6 74.8

∗ H center vs. other centers, P＜0.001.

Table 3.
Univariate analysis for parameters associated with the contamination of cord blood units
Culture positive Culture negative P
Type of delivery, N (%)
  Vaginal delivery 634 (4.1) 14,987 (95.9) ＜0.001
  Cesarean section 37 (0.7) 5,420 (99.3)
Collection center, N (%)
  H center∗ 127 (25.3) 374 (74.7) ＜0.001
  Other centers 550 (2.7) 20,176 (97.3)
Maternal age (years)† 31 (29-34) 31 (29-33) 0.728
Gestational age (months)† 39 (39-40) 39 (38-40) 0.067
Birth weight (kg)† 3.35 (3.12-3.60) 3.34 (3.10-3.60) 0.852
Volume of cord blood (mL)† 105.8 (95.2-118.9) 108.0 (96.6-122.0) ＜0.001
Processing time (hours)† 25 (22-29) 26 (23-30) 0.003
White blood cell (×103/uL)† 10.7 (9.3-12.9) 10.6 (8.9-12.6) 0.006
Platelet (×103/uL)† 210 (186-238) 208 (183-234) 0.089
Hemoglobin (g/dL)† 11.6 (10.8-12.4) 11.7 (10.9-12.6) 0.125
Nucleated RBC (/100 WBC)† 2.2 (1.2-4.7) 2.0 (1.0-3.9) ＜0.001

∗ See Table 2; † The values are presented as the median and interquartile range.

Table 4.
Multivariate logistic regression for parameters associated with the contamination of cord blood units
Beta coefficient Odds ratio 95% Confidence interval P
Vaginal delivery∗ 1.938 6.942 4.891-9.854 ＜0.001
H center† 2.548 12.777 10.160-16.068 ＜0.001
Volume of cord blood (mL) -0.007 0.993 0.988-0.998 0.003
Processing time (hours) -0.011 0.989 0.979-1.000 0.048
Hemoglobin (g/dL) -0.06 0.942 0.882-1.005 0.069
Nucleated RBC (/100 WBC) 0.02 1.02 1.006-1.033 0.004

∗ Cesarean section was set as the reference group; † See Table 2; Other centers were set as the reference group.

Table 5.
Discordant culture results of contaminated cord blood units between pre-freeze and post-thaw
ID No. Pre-freeze Post-thaw
06-1 ID-unknown No growth
06-2 ID-unknown No growth
06-4 Citrobacter freundii Klebsiella pneumoniae
  Klebsiella pneumoniae Citrobacter freundii
    Enterococcus casseliflavus
06-6 Unknown gram positive rod No growth
06-8 Streptococcus viridans group No growth
06-9 Unknown gram positive rod No growth
06-10 Coagulase negative staphylococcus No growth
07-1 Bifidobacterium spp. No growth
07-4 Bacteroides ovatus Pediococcus pentosaceus
07-5 Bacteroides merdae No growth
07-7 Neisseria flavescens No growth
  Streptococcus viridans group  
07-8 Coagulase negative staphylococcus No growth
08-1 Escherichia coli Klebsiella pneumoniae
08-2 Bacteroides vulgatus Lactobacillus spp.
08-4 Corynebacterium spp. No growth
08-5 Lactobacillus spp. No growth
08-6 Coagulase negative staphylococcus No growth
08-7 Peptostreptococcus anaerobius Lactobacillus spp.
08-9 Bacteroides uniformis No growth
08-10 Prevotella bivia No growth
09-2 Corynebacterium spp. No growth
09-6 Lactobacillus spp. No growth
09-9 Lactobacillus spp. Escherichia coli
09-10 Corynebacterium spp. No growth

Abbreviation: ID, identification.

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