Six-Year Review of Rickettsial Isolation from Blood Using Mammalian Cell Culture in Laos
Analysing 3,227 blood samples submitted over six years, this study achieved a 7.9% overall isolation rate for Orientia tsutsugamushi and Rickettsia typhi, rising to 17.3% when patients had a positive RDT, serology, or PCR. Buffy coat inoculation and same-day culture significantly improved success. The findings highlight modifiable pre-analytical factors that can optimise rickettsial isolation in resource-limited settings.
The original study
The Isolation of Orientia tsutsugamushi and Rickettsia typhi from Human Blood through Mammalian Cell Culture: a Descriptive Series of 3,227 Samples and Outcomes in the Lao People's Democratic Republic.
- Authors
- Ming DK, Phommadeechack V, Panyanivong P, Sengdatka D, Phuklia W, Chansamouth V, et al.
- Journal
- Journal of clinical microbiology
- Type
- Journal Article, Research Support, Non-U.S. Gov't, Review
- PMID
- 32999008
Original abstract
In the Lao People's Democratic Republic (Laos), rickettsial infections, including scrub and murine typhus, account for a significant burden of fevers. The Mahosot Hospital Microbiology Laboratory in Vientiane, Laos, routinely performs rickettsial isolation from hospitalized patients with suspected rickettsioses using mammalian cell culture systems. We review the clinical and laboratory factors associated with successful Orientia tsutsugamushi and Rickettsia typhi isolations from this laboratory over a period of 6 years between 2008 and 2014. The overall isolation success was 7.9% for all samples submitted and 17.3% for samples for which the patient had a positive O. tsutsugamushi or R. typhi rapid diagnostic test (RDT), serology, or PCR. The frequency of successful isolation was highest for samples submitted in November, at the end of the wet season (28.3%). A longer median duration of reported illness, a positive result for a concurrent Orientia or Rickettsia spp. quantitative PCR, and the use of antibiotics by the patient in the week before admission were significantly associated with isolation success (P < 0.05). Buffy coat inoculation and a shorter interval between sample collection and inoculation in the laboratory were associated with a higher frequency of isolation (both P < 0.05). This frequency was highest if cell culture inoculation occurred on the same day as blood sample collection. Factors related to the initial rickettsial bacterial concentration are likely the main contributors to isolation success. However, modifiable factors do contribute to the rickettsial isolation success, especially delays in inoculating patient samples into culture.