Abstract
The bacterial pathogen Bartonella quintana is passed between humans by body lice. B. quintana has adapted to both the human host and body louse vector niches, producing persistent infection with high titer bacterial loads in both the host (up to 105 colony-forming units [CFU]/ml) and vector (more than 108 CFU/ml). Using a novel custom microarray platform, we analyzed bacterial transcription at temperatures corresponding to the host (37°C) and vector (28°C), to probe for temperature-specific and growth phase-specific transcriptomes. We observed that transcription of 7% (93 genes) of the B. quintana genome is modified in response to change in growth phase, and that 5% (68 genes) of the genome is temperature-responsive. Among these transcriptional changes in response to temperature shift and growth phase was the induction of known B. quintana virulence genes and several previously unannotated genes. Hemin binding proteins, secretion systems, response regulators, and genes for invasion and cell attachment were prominent among the differentially-regulated B. quintana genes. This study represents the first analysis of global transcriptional responses by B. quintana. In addition, the in vivo experiments provide novel insight into the B. quintana transcriptional program within the body louse environment. These data and approaches will facilitate study of the adaptation mechanisms employed by Bartonella during the transition between human host and arthropod vector.
Highlights
In the last three decades, there has been a resurgence of Bartonella quintana infections, with the most severe illness occurring among immunocompromised people [1]
A cluster of growth phase-specific genes is identified in B. quintana grown in vitro on agar, at either 37uC or 28uC
Agar media was used for the analysis because we found insufficient growth of B. quintana in liquid culture at 28uC
Summary
In the last three decades, there has been a resurgence of Bartonella quintana infections, with the most severe illness occurring among immunocompromised people [1]. B. quintana is a vectorborne Gram-negative bacterium; the vector is the human body louse (Pediculus humanus humanus) [2]. 33.3% of body lice recovered from infested homeless individuals in California had PCR-detectable B. quintana DNA, underscoring the high prevalence of this potentially fatal bacterium in the human environment [3]. After introduction into the human host, B. quintana can persist in the normally sterile bloodstream for weeks or months [5]. This remarkable, prolonged persistence in the host bloodstream demonstrates the ability of B. quintana to avoid clearance by the host immune defenses [6]. Persistent B. quintana infections manifest in humans as relapsing fever, endocarditis, and potentially fatal vascular proliferative lesions
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