Detection and Quantitation of Candidatus Riesia Pediculola in Human Lice
Background: Candidatus Riesia pediculicola is a gram-negative obligate intracellular bacterium, which is the primary endosymbiont of human lice The presence of Riesia is crucial in providing the lice with essential B vitamins, nicotinic acid, pantothenic acid, and beta-biotin. Several genes responsible for pantothenic acid synthesis are encoded on the Riesia plasmid. We tested whether the Riesia plasmid is always present in different samples of human head and body lice and whether the plasmid copy numbers differs with the life stage and sex.
Methods: Head and body human lice were identified morphologically and their sex and life stage was recorded. DNA was extracted from each louse using the QIAamp DNA Mini Kit (Qiagen) and concentration determined using Nanodrop (Fisher Scientific). The integrity of each extract was determined by targeting 159-bp louse chromosome and 101-bp louse mitochondrial gene amplified by EvaGreen PCR. Two quantitative PCR (qPCR) assays were developed and amplification conditions were optimized for detection of Riesia plasmid and Riesia chromosome genes. Testing was performed for individual DNA samples in duplicate followed by melting curve analysis of each amplicon to verify the absence of secondary PCR products. Relative gene Riesia copy numbers were determined and statistical analysis was done using t-test.
Results: All 81 DNA louse samples extracted (35 head lice and 46 body lice) tested positive for louse chromosome and mitochondrial gene fragments by EvaGreen PCR. Relative copy number of Riesia plasmid gene was similar in male, female and nymphs of head lice from Georgia, USA and its average (+ standard deviation) ranged from 1.72 + 1.0 to 2.8 + 2.46. Likewise, relative copy number of Riesia plasmid gene was similar in male, female and nymphs of body lice from Russia but its average (ranged from 1.25 + 0.86 to 2.37 + 2.61) was slightly lower compared to head lice (P=0.03), though it had comparable ratio.
Conclusions: Riesia was ubiquitous and its plasmid content is similar in human and body lice from different geographic regions and throughout different stages of lice. Whether its copy numbers vary following feeding needs further investigation.
Southeastern Microbiology Summit (SMS)
Braswell, Sarah E., E. A. Tiugaeva, Helaina D. Capps, Lance A. Durden, Marina E. Eremeeva.
"Detection and Quantitation of Candidatus Riesia Pediculola in Human Lice."
Environmental Health Sciences Faculty Presentations.