Scrub typhus along the Thai-Kampuchean border: new treatment regimen

The efficacy and tolerability of antibiotics in scrub typhus: An updated network meta-analysis of randomized controlled trials

INTRODUCTION

Inadequate treatment of scrub typhus results in severe complications such as septic shock and is also associated with a high median mortality rate of 6%. However, there has been no conclusive evidence about the superiority of different antibiotics in managing scrub typhus in terms of efficacy and tolerability.

METHODS

The current network meta-analysis (NMA) was conducted using the frequentist method. The included participants were pediatric and adult patients infected with scrub typhus. The primary outcome was the cure rate in the patients included. The subgroup analysis was done according to pediatric or adult patients.

RESULTS

Overall, 14 randomized controlled trials (RCTs) with 1264 participants were included in this study. The NMA revealed that all the investigated antibiotics were associated with cure rates similar to those of doxycycline. The chloramphenicol and minocycline were ranked to be associated with the highest cure rate in the pediatric subgroup and adult subgroup, respectively. Second-generation quinolones, including ofloxacin and ciprofloxacin and chloramphenicol were associated with significantly lower adverse event rates than doxycycline.

CONCLUSION

The current update NMA provides evidence for the efficacy of chloramphenicol and minocycline in scrub typhus management. However, future large-scale RCTs with longer follow-up times are warranted.

TRIAL REGISTRATION

PROSPERO CRD42020222410. The current study was approved by the Institutional Review Board of the Tri-Service General Hospital, National Defense Medical Center (TSGHIRB No. B-109-29).

Efficacy and Safety of Antibiotics for Treatment of Scrub Typhus: A Network Meta-analysis

IMPORTANCE

Antibiotics have been used for many years to treat scrub typhus, but their efficacy and safety have not been studied thoroughly.

OBJECTIVE

To compare and rank different antibiotics to identify which one can safely eliminate Orientia tsutsugamushi and efficiently alleviate fever in patients with scrub typhus.

DATA SOURCES

An electronic search of PubMed and Embase was conducted, from database inception to July 12, 2019. The study was conducted from July 12 to September 2, 2019.

STUDY SELECTION

Randomized clinical trials and retrospective studies that evaluated the use of antibiotics for treatment in patients diagnosed with scrub typhus caused by O tsutsugamushi were included. Records of articles in English were considered eligible. Studies were assessed independently by 2 reviewers, with disagreement resolved by consensus. Of 6408 studies initially identified, 10 randomized clinical trials and 4 retrospective study met the criteria for further analysis.

DATA EXTRACTION AND SYNTHESIS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses extension statement for systematic reviews incorporating network meta-analyses of health care interventions. Data were independently extracted by 2 reviewers and synthesized with frequentist random-effects network meta-analyses.

MAIN OUTCOMES AND MEASURES

The primary outcome was efficacy of the antibiotic, considered as the number of patients who achieved complete healing with an antibiotic. Safety, defined as the prevalence of adverse events associated with the antibiotics, was the secondary outcome, and defervescence time was the tertiary outcome. P scores (scale of 0 to 1, with 1 indicating superiority to other treatments) were used to rank the efficacy, safety, and defeverescence time of the antibiotics.

RESULTS

Three searches for articles in Embase and PubMed identified 10 randomized clinical trials (888 participants) and 4 retrospective studies (323 participants) for further analyses. No particular treatment regimen showed a significant advantage or disadvantage with regard to efficacy or safety. However, meta-analysis of retrospective studies indicated that clarithromycin (P score = 0.8730) alleviated fever more efficiently than other antibiotics.

CONCLUSIONS AND RELEVANCE

No treatment regimen reported in this network meta-analysis showed a significant advantage or disadvantage with regard to efficacy or safety. However, clarithromycin might be a better choice than the other drugs for alleviating fever.

Molecular epidemiology of Orientia tsutsugamushi in Cambodia and Central Vietnam reveals a broad region-wide genetic diversity

Scrub typhus is an acute infectious disease caused by an obligate intracellular bacterium Orientia tsutsugamushi following the bite of infected trombiculid mites of the genus Leptotrombidium. This zoonotic disease is a major cause of febrile illness in the Asia-Pacific region, with a large spectrum of clinical manifestations from unapparent or mild disease to fatal disease. O. tsutsugamushi is characterized by a very high genomic plasticity and a large number of antigenic variants amongst strains. The 56-kDa type specific antigen (TSA) gene, encoding the major antigenic protein, was used as reference to investigate the genetic relationships between the strains and to genotype O. tsutsugamushi isolates. The open reading frame of the 56-kDa TSA gene of 41 sequences (28 Cambodian and 13 Vietnamese strains) from patient samples were sequenced and used for genotyping. The 28 Cambodian isolates clustered into 5 major groups, including Karp (43.5%), JG-v (25%), Kato/TA716 (21.5%), TA763 (3.5%) and Gilliam (3.5%). Karp (77%), TA763 (15.5%) and JG-v (7.5%) strains were identified amongst the 13 Vietnamese isolates. This is the first countrywide genotyping description in Cambodia and in Central Vietnam. These results demonstrate the considerable diversity of genotypes in co-circulation in both countries. The genotyping result might raise awareness amongst Cambodian and Vietnamese clinicians of the high genetic diversity of circulating O. tsutsugamushi strains and provides unique and beneficial data for serological and molecular diagnosis of scrub typhus infections as well as raw materials for future studies and vaccine development.