The transcriptional analysis of Burkholderia pseudomallei upon prolonged incubation in human serum

Shirley Hii Yi Fen¹*, Mohd Khairul Nizam Mohd Khalid², Rohaidah Hashim¹, Fairuz Amran¹, Norazah Ahmad¹

1. Bacteriology unit, Infectious Diseases Research Centre, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, Jalan Setia Murni U13/52, Seksyen U13 Setia Alam, 40170 Shah Alam, Selangor.

2. IEM and Genetic unit, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, Jalan Setia Murni U13/52, Seksyen U13 Setia Alam, 40170 Shah Alam, Selangor.

*Corresponding author: Shirley Hii Yi Fen, Bacteriology unit, Infectious Diseases Research Centre, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, Jalan Setia Murni U13/52, Seksyen U13 Setia Alam, 40170 Shah Alam, Selangor. This email address is being protected from spambots. You need JavaScript enabled to view it.

CITATION: Yi Fen SH, Mohd Khalid MKN, Hashim R, Amran F, Ahmad N. The transcriptional analysis of Burkholderia pseudomallei upon prolonged incubation in human serum. International Medical Research Journal. 2023 Jun;9(1):74–87.

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ABSTRACT
Burkholderia pseudomallei causes melioidosis, an often-fatal tropical disease endemic in Southeast Asia and northern Australia. The bacteria’s ability to survive against the host immune response makes it difficult to be completely eradicated even upon appropriate treatment. In this study, we aim to evaluate B. pseudomallei’s survival and transcriptional changes upon 28-day incubation compared to 5-day in healthy human serum (HHS) by RNA sequencing. Two clinical B. pseudomallei isolates were cultured in HHS and tryptic soy broth for 28 days. RNA was extracted on the 5th and 28th day from HHS followed by RNA sequencing to identify the transcriptional adaptations of B. pseudomallei in HHS at day 28 compared to day 5. The gene expression of selected genes was validated by reverse-transcription real-time PCR. In this study, B. pseudomallei isolates were able to survive and proliferate in HHS after day 5 in contrast to declining growth in tryptic soy broth (TSB). Among the 1,657 differentially regulated genes, more than half (62%) of the up-regulated genes were of the accessory genome. The highly expressed genes were related to surface determinants especially capsular polysaccharides (CPS II and III). In addition, genes involving ATP synthase operon, acyl-homoserine lactonemediated quorum sensing system (AHL-QS) mediated secondary metabolites and secretion systems were also upregulated. These suggest that B. pseudomallei requires activation of various mechanisms for prolonged survival in HHS. This study provides an insight into the possible mechanisms utilised by B. pseudomallei for persistent survival in HHS.

KEYWORDS: B. pseudomallei, Serum, Gene expression, RNA-seq, Survival