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. 2020 Nov 30;104(2):612-621.
doi: 10.4269/ajtmh.20-0249.

Nonautomated Blood Cultures in a Low-Resource Setting: Optimizing the Timing of Blind Subculture

Sien Ombelet  1   2 , Marjan Peeters  1 , Chhundy Phe  3 , Achilleas Tsoumanis  1 , Chun Kham  3 , Syna Teav  3 , Erika Vlieghe  4 , Thong Phe  3 , Jan Jacobs  1   2
Affiliations

Nonautomated Blood Cultures in a Low-Resource Setting: Optimizing the Timing of Blind Subculture

Sien Ombelet et al. Am J Trop Med Hyg. .

Abstract

Laboratory procedures for blood cultures in a hospital in Phnom Penh were adapted to optimize detection of Burkholderia pseudomallei, an important pathogen in this setting. The effects of these changes are analyzed in this study. Blood cultures consisted of two BacT/ALERT bottles (bioMérieux, Marcy-l'Etoile, France). Growth was detected visually by daily inspection of the bottles. In 2016, the aerobic-anaerobic pair (FA/FN FAN) was substituted by an aerobic pair of BacT/ALERT FA Plus bottles. Blind subculture (BS) (subculture in the absence of visual growth) was advanced from day 3 to day 2 of incubation in July 2016. In July 2018, it was further advanced to day 1 of incubation. From July 2016 to October 2019, 9,760 blood cultures were sampled. The proportion of cultures showing pathogen growth decreased from 9.6% to 6.8% after the implementation of the laboratory changes (P < 0.001). Advancing the BS from day 3 to day 2 led to an increased proportion of pathogens detected by day 3 (92.8% versus 82.3%; P < 0.001); for B. pseudomallei, this increase was even more remarkable (92.0% versus 18.2%). Blind subculture on day 1 similarly increased the proportion of pathogens detected by day 2 (82.9% versus 69.0% overall, 66.7% versus 10.0% for B. pseudomallei; both P < 0.001). However, after implementation of day 1 subculture, a decrease in recovery of B. pseudomallei was observed (12.4% of all pathogens versus 4.3%; P < 0.001). In conclusion, earlier subculture significantly shortens time to detection and time to actionable results. Some organisms may be missed by performing an early subculture, especially those that grow more slowly.

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Conflict of interest statement

Data availability: The database for this manuscript will be made open access. Access requests for ITM research data can be made to ITM’s central point for research data access by means of submitting the completed Data Access Request Form. These requests will be reviewed for approval by ITMs Data Access Committee (https://www.itg.be/E/data-sharing-open-access).

Disclosure: Ethical approval was granted as part of the study: “Surveillance of antimicrobial resistance among consecutive blood culture isolates in tropical settings, V4.0” (IRB ITM 613/08, EC UZA 8/20/96, NECHR original protocol 009 and subsequent amendments 021, 0313, 020, 018, 141). Laboratory data were analyzed retrospectively using a coded database. Patient information was coded with restricted access to the code key. For Figure 1, we made use of two icons designed by Made by Made and Majo Ox, offered by the Noun Project on their website (https://www.thenounproject.com).

Figures

Figure 1.
Figure 1.
Procedural changes implemented during the three time periods of blood culture surveillance. The detailed results of period 1 are described in a previous publication. This figure appears in color at www.ajtmh.org.
Figure 2.
Figure 2.
Breakdown of blood cultures sampled in Sihanouk Hospital Center of Hope from July 2016 to October 2019 (periods 2 and 3). * In five episodes, two different pathogens were retrieved from the same culture.
Figure 3.
Figure 3.
Cumulative time to detection (first sign of growth) and time to colonies for all pathogens except Burkholderia pseudomallei, comparing the three periods of surveillance. Statistically significant differences between periods of surveillance are indicated with asterisks (* = P < 0.05; ** = P < 0.001). This figure appears in color at www.ajtmh.org.
Figure 4.
Figure 4.
Cumulative time to detection (first sign of growth) and time to colonies for Burkholderia pseudomallei, comparing the three periods of surveillance. Statistically significant differences between periods of surveillance are indicated with asterisks (* = P < 0.05; ** = P < 0.001). This figure appears in color at www.ajtmh.org.
See this image and copyright information in PMC

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