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Implementation of Dual Incubation Strategies to Improve Anaerobic Culture Yield in the Clinical Laboratory

Chiamaka T. Umah, Ashleigh Riegler, Mishi Bhushan, Danielle Scarborough-Carr, Elizabeth King, Jamie Hutchinson and Megan H. Amerson-Brown
American Society for Clinical Laboratory Science August 2026, DOI: https://doi.org/10.29074/ascls.2026003355

Article Figures & Data

Figures

  • Old vs new process. A visual representation of the process used in this study. The left side of the diagram shows the old process, whereas right side shows the new process implemented in late 2022.
    Figure 1.

    Old vs new process. A visual representation of the process used in this study. The left side of the diagram shows the old process, whereas right side shows the new process implemented in late 2022.

  • Improvement in percent positivity. The bar chart shows the percent positivity of total cultures in 2022 and 2023. Using a Fisher exact text, the percentage of positive cultures in 2023 was significantly higher than the percentage of positive cultures in 2022. ***P = .0010.
    Figure 2.

    Improvement in percent positivity. The bar chart shows the percent positivity of total cultures in 2022 and 2023. Using a Fisher exact text, the percentage of positive cultures in 2023 was significantly higher than the percentage of positive cultures in 2022. ***P = .0010.

  • Comparison of facultative and obligate anaerobe percent recovery. Obligate anaerobes (gray bar) and facultative anaerobes (black bar) percentage recovery in 2022 and 2023 study periods are shown. (A) First cultures analysis. (B) Repeat cultures analysis. The repeat cultures analysis is consistent with the results of the first cultures analysis, showing an increase in anerobic organism recovery in 2023, more significantly in the obligate anaerobic organism recovery.
    Figure 3.

    Comparison of facultative and obligate anaerobe percent recovery. Obligate anaerobes (gray bar) and facultative anaerobes (black bar) percentage recovery in 2022 and 2023 study periods are shown. (A) First cultures analysis. (B) Repeat cultures analysis. The repeat cultures analysis is consistent with the results of the first cultures analysis, showing an increase in anerobic organism recovery in 2023, more significantly in the obligate anaerobic organism recovery.

  • Control charts indicating a higher average and variance owing to process change. Data were plotted for a 7-day timeframe of the datasets used during our study periods. The data indicate an increase in (A) the average of the total number of positive cultures, (B) variance in total positive cultures, (C) average strict anaerobes recovered, and (D) variance of the total strict organisms recovered. All graphs show an increase in the CL from 2022 to 2023 and a widening of the range in the UCL and LCL between 2022 and 2023 data. CL, control limit; LCL, lower CL; UCL, upper CL.
    Figure 4.

    Control charts indicating a higher average and variance owing to process change. Data were plotted for a 7-day timeframe of the datasets used during our study periods. The data indicate an increase in (A) the average of the total number of positive cultures, (B) variance in total positive cultures, (C) average strict anaerobes recovered, and (D) variance of the total strict organisms recovered. All graphs show an increase in the CL from 2022 to 2023 and a widening of the range in the UCL and LCL between 2022 and 2023 data. CL, control limit; LCL, lower CL; UCL, upper CL.

  • Heatmap showing a number of organisms identified in the study period with improved recovery in obligate anaerobes, especially in the Clostridium spp, Bacteroides spp, Prevotella spp, Fusobacterium spp, and Bilophila spp. Red indicates a highly recovered organism, whereas purple indicates a lower, not recovered organism.
    Figure 5.

    Heatmap showing a number of organisms identified in the study period with improved recovery in obligate anaerobes, especially in the Clostridium spp, Bacteroides spp, Prevotella spp, Fusobacterium spp, and Bilophila spp. Red indicates a highly recovered organism, whereas purple indicates a lower, not recovered organism.

Tables

  • Table 1.

    Differences in organism recovery

    2022 Mean (SD)2023 Mean (SD)Mean Difference, %P Value
    Total organisms0.25 (0.62)0.44 (0.88)55.07<0.0001
    Total aerobes0.01 (0.14)0.02 (0.098)66.670.0344
    Total facultative anaerobes0.071 (0.29)0.129 (0.39)58<0.0001
    Total obligate anaerobes0.16 (0.51)0.30 (0.76)60.87<0.0001

    These data show the difference in recovery of organisms in anaerobic cultures between the 2022 and 2023 datasets. The culture differences were statistically evaluated using a Mann–Whitney U test, with all categories showing significant P values less than .05.

    • Table 2.

      Difference in organism recovery among first cultures from patients

      2022 Mean (SD)2023 Mean (SD)Mean Difference, %P Value
      Total organisms1.25 (0.57)1.45 (0.78)14.810.0009
      Total aerobes0.32 (0.52)0.30 (0.52)−6.450.4754
      Total facultative anaerobes0.21 (0.46)0.24 (0.47)13.330.3865
      Total obligate anaerobes0.92 (0.69)1.15 (0.89)22.220.004

      These data show the analysis of the first culture results per anatomical site per patient using a Mann–Whitney U test. Obligate anaerobic organisms and total organisms were significantly improved in recovery from 2022 to 2023 (P < .05). There was no significant difference in the recovery of aerobic or facultative anaerobic organisms.

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      Implementation of Dual Incubation Strategies to Improve Anaerobic Culture Yield in the Clinical Laboratory
      Chiamaka T. Umah, Ashleigh Riegler, Mishi Bhushan, Danielle Scarborough-Carr, Elizabeth King, Jamie Hutchinson, Megan H. Amerson-Brown
      American Society for Clinical Laboratory Science Aug 2026, DOI: 10.29074/ascls.2026003355
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