Affordable blood culture systems from China: in vitro evaluation for use in resource-limited settings

Abstract

Background: Bloodstream infections (BSI) pose a significant threat due to high mortality rates and the challenges posed by antimicrobial resistance (AMR). In 2019, an estimated 4.95 million deaths were linked to bacterial AMR. The highest impact was seen in resource-limited settings (RLS). For diagnosis of BSI, performant continuously-monitoring blood culture systems (CMBCS) have been optimized. However, in RLS, the implementation of CMBCS is hindered by budget constraints and unsuitable environmental conditions. Manufacturers from growing economies are currently producing affordable in vitro diagnostics, which could fill the gap in capacity, but so far these are not established outside their domestic markets.

Methods: This study evaluated the performance, usability, and interchangeability of Chinese CMBCS in a laboratory setting using simulated blood cultures with a panel of 20 BSI-associated strains. Four systems were selected for the assessment: Autobio BC60, Mindray TDR60, Scenker Labstar50, and DL-biotech DL-60.

Findings: Overall, all evaluated CMBCS demonstrated good performance with high yield (96.7-100%) and specificity (97.5-100%), comparable to the reference system (bioMérieux 3D). In addition, when used as "manual" blood cultures in a conventional incubator with visual growth detection, performance was also satisfactory: yield was between 90 and 100% and specificity was 100% for all BCBs. Both the CMBCS and the BCBs were easy to use and lot-to-lot variability in BCBs was minimal. The interchangeability testing indicated that the BCBs from different brands (all except Scenker) were compatible with the various automates, further highlighting the potential for a harmonized "universal BCB."

Interpretation: Based on this in vitro study, we recommend the use of these systems in settings with challenging environments and limited resources. The Autobio system performed best for automatic detection and DL-Biotech BCBs for manual cultures respectively (combination of performance, price, usability). The appropriateness for use in RLS should still be confirmed in a field study.

Funding: The study was funded by FIND.

Keywords: Blood cultures; Continuously-monitoring blood culture systems; Evaluation study; Resource-limited settings.

Fig. 1

Set-up of 1 run: 2 ml of spiked horse blood was added to 3 BCBs of 3 lots of each manufacturer under evaluation. In addition, 1 blank (non-spiked blood) BCB was for each lot/manufacturer. 9 spiked replicates (3 replicates of 3 lots) and 3 blanks were incubated in their associated automate for continuous growth monitoring (in purple). 3 spiked replicates of lot 1 of each manufacturer and 1 blank were incubated in a conventional incubator for twice-daily visual evaluation (in turquoise). For the reference (bioMérieux) 1 lot was used. Figure created with Biorender.com.

Fig. 2

Illustration of difference in colour indicator of not grown (left: purple) and grown (right: yellow) blood culture bottle.

Fig. 3

Illustration of the labels and transparent space on the BCBs under evaluation, front and back, compared to reference (on the left).