Genomic bacterial load associated with bacterial genotypes and clinical characteristics in patients with scrub typhus in Hainan Island, Southern China

PLoS Negl Trop Dis. 2023 Apr 21;17(4):e0011243. doi: 10.1371/journal.pntd.0011243. eCollection 2023 Apr.

Abstract

Scrub typhus, caused by mite-borne Orientia tsutsugamushi (O. tsutsugamushi), is a major febrile disease in the Asia-Pacific region. The DNA load of O. tsutsugamushi in the blood was previously found to be significantly higher in patients with fatal disease than those with non-fatal disease and correlated with the duration of illness, presence of eschar, and hepatic enzyme levels. In this prospective observation study, we analyzed the association of bacterial DNA load with clinical features, disease severity, and genotype using real-time PCR targeting the 56 kDa TSA gene of O. tsutsugamushi in the blood samples of 117 surviving patients with scrub typhus who had not received appropriate antibiotic treatment. The median O. tsutsugamushi DNA load was 3.11×103 copies/mL (range, 44 to 3.3×106 copies/mL). The severity of patients was categorized as mild, moderate, and severe based on the number of dysfunctional organs, and no significant difference in O. tsutsugamushi DNA load was found among these groups. Patients infected with the Karp group showed a significantly higher O. tsutsugamushi DNA load than those in the Gilliam (P < 0.05) and TA763 (P < 0.01) groups. Patients belonging to the Li ethnic group showed a significantly higher DNA load than those in the Han ethnic groups. The blood bacterial DNA load of patients showed no significant difference between groups divided by gender, age, with or without eschar, or the season of disease onset. The highest body temperature recorded during fever onset was positively correlated with O. tsutsugamushi DNA load (ρ = 0.272, P = 0.022). Correlation analyses indicated that the serum total bilirubin level was positively correlated with O. tsutsugamushi DNA load. In conclusion, the findings in this study demonstrated the association of DNA load of O. tsutsugamushi with the severity and genotype in patients with scrub typhus in Hainan, China.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Load
  • China / epidemiology
  • DNA, Bacterial / genetics
  • Genomics
  • Genotype
  • Humans
  • Orientia tsutsugamushi* / genetics
  • Prospective Studies
  • Scrub Typhus* / microbiology

Substances

  • DNA, Bacterial

Grants and funding

This study was supported by the Hainan Provincial Natural Science Foundation of China (http://dost.hainan.gov.cn/) grant No. 820RC628 (awarded to FY), 820QN267 (awarded to GW), 820QN412 (awarded to MX), 821QN258 (awarded to RP), 821QN0896 (awarded to YH) and 822MS076 (awarded to GW), the Key Research and Development Plan of Hainan Province (http://dost.hainan.gov.cn/) grant No. ZDYF2022SHFZ085 (awarded to FY) and ZDYF2022SHFZ098 (awarded to LZ), the Education Department of Hainan Province (http://edu.hainan.gov.cn/) grant No. Hnky021-40 (awarded to CT), the National Natural Science Foundation of China (https://isisn.nsfc.gov.cn/pmpweb/login) grant No. 82060378(awarded to FY), 81860367(awarded to FY), the Open Foundation of Key Laboratory of Tropical Translational Medicine of Ministry of Education, Hainan Medical University (https://ttm.hainmc.edu.cn/) grant No. 2021TTM005 (awarded to LZ), HYPY201919(awarded to YH), the Major Science and Technology Program of Hainan Province (http://dost.hainan.gov.cn/) grant No. ZDKJ202003 (awarded to FY) and ZDKJ2021035 (awarded to CH), Hainan Province Clinical Medical Center (http://wst.hainan.gov.cn/swjw/) QWYH202175 (awarded to MX) and donations from the Lee Wan Keung Charity Foundation Limited, Marina Man-Wai Lee, and the Hong Kong Hainan Commercial Association South China Microbiology Research Fund (awarded to JF-WC). The funding sources had no role in the study design, data collection, analysis, interpretation, or writing of this report.