Methods for detecting Gemmata spp. bacteremia in the microbiology laboratory

Gemmata bacteria are fastidious, Gram-negative and aerobic. The only representatives are Gemmata obscuriglobus and Gemmata massiliana. These Planctomycetes appear to be a part of human digestive tract microbiome, and G. massiliana has been isolated from water. Further specific detection in the blood of two patients with febrile neutropenia suggests that Gemmata bacteremia may remain under-documented. The objective of this study was to develop an effective protocol to document Gemmata spp. bacteremia in the laboratory. Using mock-infected and control blood specimens, three methods for detecting Gemmata bacteremia, namely, automated microbial detection, culture on solid medium, and quantitative polymerase chain reaction (PCR), have been developed and studied.

Gemmata spp. were undetected by automated blood culture system but culturing mock-infected blood on Caulobacter agar detected ≥ 10² G. obscuriglobus bacteria/mL and ≥ 10⁴ G. massiliana bacteria/mL. Specific real-time PCR detected 10² Gemmata bacteria/mL. These protocols may be used to investigate the epidemiology of Gemmata spp. bacteremia.