부산대학교 도서관

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. Author summary: High genomic DNA load is a marker for the virulence of the pathogen and is associated with disease severity in bacterial infectious diseases. Recent studies have indicated that the non-surviving patients with scrub typhus had a significantly higher bacterial load than the surviving patients, and that duration of illness, presence of eschar, and hepatic enzyme levels were positively correlated with the O. tsutsugamushi DNA load in patient from northeast Thailand and South Korea. However, the severity and fatality of scrub typhus showed largely geographic variability. To further analyze the association of genomic DNA load with severity in surviving patients, the O. tsutsugamushi genomic load in blood samples of patients with scrub typhus in Hainan, China was evaluated. The results indicated that O. tsutsugamushi DNA load was associated with the genotypes, ethnic group of the patients, the highest body temperature recorded during fever onset and the total bilirubin (TBil) in the blood. However, no significant difference in O. tsutsugamushi DNA load was found between mild, moderate, and severe patient groups, nor between groups of patients with or without eschar. This research contributes to a better overall understanding of the pathogenic mechanism of O. tsutsugamushi. [ABSTRACT FROM AUTHOR]