Clinical trial NCT05972772: Rickettsia Clearance Study
Official title: A Pharmacokinetic-pharmacodynamic Study of Early Rickettsia Clearance in Murine Typhus or Scrub Typhus Patients Treated with Doxycycline or Azithromycin
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: PHASE2
PHASE3
Conditions: Infectious Disease
Therapeutics
Keywords: Scrub Typhus
Typhus, Endemic Flea-Borne
Lead sponsor: Lao-Oxford-Mahosot Hospital Wellcome Trust Research Unit
Sponsor class: OTHER
Collaborators: name: Mahidol Oxford Tropical Medicine Research Unit
First posted: 2023-08-02
Enrollment: 72
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: Murine typhus is a disease caused by Rickettisa typhi, an obligate intracellular bacterium transmitted by rodent fleas. The disease has a worldwide distribution; however the true burden is unknown, related to its non-specific presentation and lack of access to diagnosis in many regions. A systematic review of untreated murine typhus based on observational studies of a total of 239 patients has estimated the mortality associated with the disease at between 0.4% and 3.6%.

Scrub typhus is caused by Orientia tsutsugamushi and transmitted by the larval stage of chigger mites (Trombiculidae family). It has been estimated to affect at least one million people each year. A systematic review found varying reports of the mortality associated with untreated scrub typhus ranging from 0-70% (median 6%).

Polymerase chain reaction (PCR) based diagnosis of rickettsial infections is only available in one centre (Mahosot Hospital) in Vientiane. A number of hospitals use a variety of point-of-care antibody tests to diagnose rickettsial infections however many of these have not been validated and they are of uncertain sensitivity and specificity. In 2006 results of a two year prospective study of 427 patients presenting to Mahosot Hospital with a febrile illness and negative blood cultures showed that 115 (27%) patients had an acute rickettsial infection, confirmed by serological testing. Among these patients, 41 were diagnosed with murine typhus and 63 with scrub typhus. Antibacterial agents with activity against rickettsial pathogens include doxycycline, azithromycin, chloramphenicol and rifampicin. Azithromycin is often reserved for pregnant women or children below the age of 8 years due to lasting concerns after the tetracycline-associated staining of growing bones and teeth in the past. Evidence is accumulating that doxycycline is superior to azithromycin for the treatment of rickettsial disease. Clinical treatment failures have occurred following azithromycin treatment of murine typhus. The relationship between rickettsial bacteria load and both disease severity and response to treatment has not been characterised. Rickettsial concentrations in blood are generally low, of the order of 210 DNA copies/mL blood for R. typhi and 284 DNA copies/mL blood for O. tsutsugamushi. At present, there is no standard antibiotic susceptibility testing (AST) method for R. typhi and O. tsutsugamushi. The gold standard method for AST for Rickettsia pathogens is the plaque assay which determines minimal inhibitory concentration (MICs) from the smallest antimicrobial concentration inhibiting rickettsial plaque forming unit formation. This method is laborious and time consuming, taking approximately 14-16 days based on species to yield a result. Molecular detection methods are useful for diagnosing patients infected with rickettsial pathogens and has been applied for antibiotic susceptibility testing. Antibiotic susceptibility testing based on DNA synthesis inhibition detecting by quantitative PCR (qPCR) for O. tsutsugamushi clinical isolates has been reported. However, the relationship between antibiotic susceptibility profiles and treatment response has not been studied. There is a need to develop a reliable ex vivo method to characterize the treatment response and compare susceptibility of R. typhi and O. tsutsugamushi to different agents.


Eligibility criteria: Inclusion Criteria:

* Age above or equal 18 years
* Able to take oral medication
* Rapid test positive for murine typhus or scrub typhus
* Agrees to stay in hospital for at least 36 hours and to attend for scheduled follow up visits
* Written informed consent to participate in the study
* A negative urinary pregnancy test for all women of child-bearing age

Exclusion Criteria:

* Pregnancy or breast feeding
* Previous allergic reaction to doxycycline or azithromycin
* Received more than one dose of chloramphenicol, doxycycline, tetracycline, fluoroquinolones, rifampicin or azithromycin during this hospital admission or more than one dose of any of these drugs in the week before admission
* Contraindication to doxycycline: severe hepatic impairment, known SLE
* Contraindication to azithromycin: sever hepatic impairment
* Severe typhus defined as the presence of one or more of the following:

  1. Reduced level of consciousness
  2. Clinical jaundice
  3. Shock (BP systolic \<80 mmHg)
  4. Unable to take oral medication
  5. Radiological evidence of pneumonia
  6. Clinical evidence for meningitis/encephalitis or the need of LP
  7. Alternative diagnosis confirmed that explains the presenting symptoms
  8. Any other syndrome which in the opinion of the admitting doctor constitutes severe typhus (reason must be stated)

Primary outcomes:
measure: Rate of clearance of R. typhi or O. tsutsugamushi from peripheral blood of patients using serial qPCR measurement
timeFrame: Within 72 hours after treatment
Secondary outcomes:
measure: Area under the plasma concentration versus time curve (AUC) of doxycycline or azithromycin for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on plasma concentrations measure up to 96 hours after the last dose. Azithromycin: Based on plasma concentrations measure up to 2 weeks after the first dose.
measure: Area under the intracellular concentration in the buffy coat versus time curve (AUC) of doxycycline or azithromycin for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on intracellular concentrations in the buffy coat measure up to 96 hours after the last dose. Azithromycin: Based on intracellular concentrations in Buffy coat measure up to 2 weeks after the first dose.
measure: Peak plasma concentration (Cmax) of doxycycline or azithromycin for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on plasma concentrations measure up to 96 hours after the last dose. Azithromycin: Based on plasma concentrations measure up to 2 weeks after the first dose.
measure: Peak of the intracellular concentration (Cmax) in the buffy coat of doxycycline or azithromycin for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on intracellular concentrations in the buffy coat measure up to 96 hours after the last dose. Azithromycin: Based on intracellular concentrations in the buffy coat measure up to 2 weeks after the first dose.
measure: Time to peak plasma concentration (Tmax) of doxycycline or azithromycin for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on plasma concentrations measure up to 96 hours after the last dose. Azithromycin: Based on plasma concentrations measure up to 2 weeks after the first dose.
measure: Time to peak of the intracellular concentration (Tmax) in the buffy coat of doxycycline or azithromycin for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on intracellular concentrations in the buffy coat measure up to 96 hours after the last dose. Azithromycin: Based on intracellular concentrations in the buffy coat measure up to 2 weeks after the first dose.
measure: Time at doxycycline or azithromycin has lost half its maximum concentration (T1/2) for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on plasma concentrations measure up to 96 hours after the last dose. Azithromycin: Based on plasma concentrations measure up to 2 weeks after the first dose.
measure: Time at doxycycline or azithromycin has lost half its maximum intracellular concentration (T1/2) for the treatment of murine typhus or scrub typhus
timeFrame: Doxycycline: Based on intracellular concentrations in the buffy coat measure up to 96 hours after the last dose. Azithromycin: Based on intracellular concentrations in the buffy coat measure up to 2 weeks after the first dose.
measure: Fever clearance time in patients with scrub typhus or murine typhus treated with doxycycline or azithromycin
timeFrame: First 7 days after treatment
measure: Frequency of serious adverse events (SAEs) after treatment
timeFrame: Day 0 to day 28
measure: Evaluation the accuracy of the new brand RDT, Rickettsia IgG/IgM Combo (Lumiquick) compared to Scrub typhus Detect IgM Rapid System (Dipstick) (InBios)
timeFrame: Day 0
measure: Evaluation the accuracy of Rickettsia IgG/IgM Combo (Lumiquick) compared to a combined gold standard of PCR assays and serology (paired samples)
timeFrame: Day 0 and Day 28
Other outcomes:
Locations:
city: Vientiane
country: Lao People's Democratic Republic
facility: Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU)
state: Vientaine
city: Vientiane Province
country: Lao People's Democratic Republic
facility: Vientiane Provincial Hospital
Study officials:
affiliation: Lao-Oxford-Mahosot Hospital Wellcome Trust Research Unit
name: Weerawat Phuklia, PhD
role: PRINCIPAL_INVESTIGATOR
References: