Background

Enterohepatic Helicobacter-like organisms (HLO) have been recognized as causes of human infection since 1984, primarily as a cause of bacteremia and cellulitis in immunocompromised individuals, but the spectrum of illness due to HLO has expanded based on numerous reports from Japan.

Methods

We report 4 epidemiologically unrelated immunocompetent patients with HLO bacteremia diagnosed within a 2-year period. Three patients had cellulitis and 1 patient had unexplained fever. 16S ribosomal deoxyribonucleic acid (rDNA) sequence analysis of 2 isolates suggested that they were Helicobacter cinaedi, and whole-genome sequencing showed that they differed only slightly from reference strains.

Conclusions

We believe that this syndrome is more common than reported, but it is easily overlooked because the skin lesions resemble streptococcal cellulitis and respond very rapidly to β-lactam antibiotics, and the organism is difficult to isolate from the blood. All HLO in our series were isolated from blood using the ESP system and were not detected in 2 other widely used commercial blood culture systems.

Droplet digital PCR (ddPCR) is a quantitative assay that requires DNA fragmentation to maximize reaction efficiency. Here, we measured the proportion of mitochondrial DNA (mtDNA) carrying the "common deletion," a rare event, to compare quantification sensitivities between alternative DNA fragmentation methods (sonication and QIAshredder spin columns) against enzymatic digestion (traditionally used). QIAshredder showed the highest sensitivity when compared to sonication, followed by digestion. Also, both sonication and QIAshredder fragmentation had shorter processing times than enzymatic digestion; therefore, QIAshredder fragmentation and sonication are alternative DNA processing methods that maximize ddPCR quantification for the detection of rare events.

Cell-free mitochondiral DNA (mtDNA) is an immunogenic molecule associated with many inflammatory conditions. We evaluated the relationship between cell-free mtDNA in cerebrospinal fluid (CSF) and neurocognitive performance and inflammation during HIV infection. In a cross-sectional analysis, we evaluated the association of mtDNA levels with clinical assessments, inflammatory markers, and neurocognitive performance in 28 HIV-infected individuals. In CSF, we measured mtDNA levels by droplet digital PCR, and soluble CD14 and CD163, neurofilament light, and neopterin by ELISA. In blood and CSF, we measured soluble IP-10, MCP-1, TNF-α, and IL-6 by ELISA, and intracellular expression of IL-2, IFN-γ, and TNF-α in CD4(+) and CD8(+) T cells by flow cytometry. We also evaluated the relationship between CSF pleocytosis and mtDNA longitudinally in another set of five individuals participating in an antiretroviral treatment (ART) interruption study. Cell-free CSF mtDNA levels strongly correlated with neurocognitive performance among individuals with neurocognitive impairment (NCI) (r = 0.77, p = 0.001). CSF mtDNA also correlated with levels of IP-10 in CSF (r = 0.70, p = 0.007) and MCP-1 in blood plasma (r = 0.66, p = 0.01) in individuals with NCI. There were no significant associations between inflammatory markers and mtDNA in subjects without NCI, and levels of mtDNA did not differ between subjects with and without NCI. MtDNA levels preceded pleocytosis and HIV RNA following ART interruption. Cell-free mtDNA in CSF was strongly associated with the severity of neurocognitive dysfunction and inflammation only in individuals with NCI. Our findings suggest that within a subset of subjects cell-free CSF mtDNA is associated with inflammation and degree of NCI.