Effects of cryopreservation on the results of nucleic acid detection and culture of Bordetella pertussis in nasopharyngeal swab specimens
10.3760/cma.j.cn114452-20240607-00302
- VernacularTitle:低温保存对鼻咽拭子标本中百日咳博德特菌核酸检测和细菌培养结果的影响
- Author:
Zhiyun LIU
1
;
Chunzhen HUA
;
Jinsi ZHOU
;
Ying YANG
;
Yumei MI
;
Mingming ZHOU
;
Jianping LI
;
Wei LI
;
Xuechao ZHANG
Author Information
1. 杭州市富阳区中医院儿科，富阳 311400
- Publication Type:Journal Article
- Keywords:
Bordetella pertussis;
Polymerase chain reaction;
Cultivate;
Cryopreservation
- From:
Chinese Journal of Laboratory Medicine
2025;48(2):265-269
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the effects of cryopreservation on the results of nucleic acid detection and culture for Bordetella pertussis in residual culture-positive nasopharyngeal swab specimens, aiming to provide the basis for specimens preservation, transport and centralized detection. Methods:In this cross-sectional study, the residual nasopharyngeal swab specimens which were culture-positive for Bordetella pertussis were collected in the Children′s Hospital, Zhejiang University School of Medicine from January to August in 2022. The specimens were placed at ?20 ℃ and?70 ℃ by random number table method, respectively. Re-detection by culture and PCR for Bordetella pertussis were conducted after these specimens were frozen for 114.3±31.9 days. The specimens were grouped according to the cryopreservation temperature and the semi-quantitative results by bacteria culture. The positive rates of the results were compared with χ 2 test between groups. Results:A total of 244 nasopharyngeal swabs specimens were included and 166 were culture-positive after cryopreservation, the positive rate decreased by 32%. Among them, the positive rate of re-culture of specimens containing low bacterial loads decreased by 56% after cryopreservation. However, there was no significant difference in the positive rate of culture between the specimens freezing at ?70 ℃ and ?20 ℃ (χ2=1.65, P=0.20). The positive rate of DNA detection decreased by 10.6% (88.9% vs 78.3%) after cryopreservation. The positive rate of the ?70 ℃ storage group was significantly higher than that of the ?20 ℃ group (χ2=5.11, P=0.02). The positive rate of the re-detection of DNA of nasopharyngeal swabs with low bacteria loads in ?70 ℃ storage group was significantly higher than that of the ?20 ℃ group (χ2=4.86, P=0.03). While for the samples with a bacterial load of "+" or more, there was no significant difference in the positive rate of DNA detection after cryopreservation between the ?20 ℃ and -70 ℃ (χ2=1.25, P=0.26) groups. The positive rate of nasopharyngeal swab culture after cryopreservation was 68.0% (166/244), which was significantly lower than the DNA detection positive rate of 78.3% (191/244, χ2=6.52, P=0.01). Conclusions:Cryopreservation nasopharyngeal swabs specimens could be used for Bordetella pertussis culture and nucleic acid detection. The bacterial load in the original sample affects the positive detection rate after cryopreservation. Cryopreservation has less influence on the positive rate of the result of nucleic acid detection when compared with culture. Preservation at ?70 ℃ is superior to ?20 ℃.
