Predatory Bacteria Attenuate Klebsiella pneumoniae Burden in Rat Lungs

Abstract

Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus are predatory bacteria that naturally—and obligately—prey on other Gram-negative bacteria, and their use has been proposed as a potential new approach to control microbial infection. The ability of predatory bacteria to prey on Gram-negative human pathogens in vitro is well documented; however, the in vivo safety and efficacy of predatory bacteria have yet to be fully assessed. In this study, we examined whether predatory bacteria can reduce bacterial burden in the lungs in an in vivo mammalian system. Initial safety studies were performed by intranasal inoculation of rats with predatory bacteria. No adverse effects or lung pathology were observed in rats exposed to high concentrations of predatory bacteria at up to 10 days postinoculation. Enzyme-linked immunosorbent assay (ELISA) of the immune response revealed a slight increase in inflammatory cytokine levels at 1 h postinoculation that was not sustained by 48 h. Additionally, dissemination experiments showed that predators were efficiently cleared from the host by 10 days postinoculation. To measure the ability of predatory bacteria to reduce microbial burden in vivo, we introduced sublethal concentrations of Klebsiella pneumoniae into the lungs of rats via intranasal inoculation and followed with multiple doses of predatory bacteria over 24 h. Predatory bacteria were able to reduce K. pneumoniae bacterial burden, on average, by more than 3.0 log10 in the lungs of most rats as measured by CFU plating. The work presented here provides further support for the idea of developing predatory bacteria as a novel biocontrol agent.

Examining the efficacy of intravenous administration of predatory bacteria in rats

“…Recently, we demonstrated the ability of predatory bacteria to attenuate bacterial burden in vivo within the lungs of rats 19 . In this study, we extend this approach to determine if predatory bacteria can reduce bacterial burden introduced directly into the rat vasculature.…”

Bacterial predation under changing viscosities

“…Although their association with the human body is not firmly established, their ability to prey on pathogenic gramnegative bacteria and the low immune responses they generate (Monnappa et al, 2016;Shatzkes, Singleton, et al, 2017) have made them a focus of interest for the development of novel antimicrobial strategies Shatzkes, Connell, et al, 2017). Their application in vivo shows they can curb certain infections in mucus-lined habitats (Shatzkes et al, 2016;Willis et al, 2016;De Dios Caballero et al, 2017), further increasing the need to understand their behaviour under body cavity-relevant conditions. We thus explored the behaviour of three different BALOs under various viscosities and temperatures.…”

“…It has been shown that constructed habitats largely change BALO predatory dynamics (Hol et al, 2016;Dattner et al, 2017), but our results suggest that the macro-molecular environment also alters predator-prey interactions. This is relevant to the applications of BALOs against pathogenic bacteria as BALOs have been tested as possible treatments for lung infections, whereby they should be active in mucus, and in plasma (Shatzkes et al, 2016;Baker et al, 2017), two habitats totally different in terms of spatial structure as well as in macromolecular composition.…”

“…Furthermore, the ability of BALOs to prey on a large variety of prey bacteria, including plant and animal (including human) pathogens comprising antibioticresistant strains (Dashiff et al, 2011;Kadouri et al, 2013), is generating a growing interest in their potential as living antibiotics in medicine and aquaculture (Lambert and Sockett, 2013;Negus et al, 2017) and, unrelatedly, for industrial applications (Martínez et al, 2016;Qiu et al, 2016;Yu et al, 2017). Lately, BALOs have been shown to prey in serum, in mammalian cell cultures and to curb some infections in vivo in animal models (Shatzkes et al, 2016;Baker et al, 2017;De Dios Caballero et al, 2017). These habitats largely vary in viscosity: For example, the mucosal lining covering the respiratory, gastrointestinal and reproductive tracts, and wounds are all environments of viscosities 10 2 -10 6 times higher than that of water (Lai et al, 2009;Hickey et al, 2011;Zanin et al, 2016).…”

Antibiotic disturbance affects aquatic microbial community composition and food web interactions but not community resilience

“…Interestingly, the increment of Bdellovibrionaceae occurred only in the AB++ treatment. This family is notorious for preying on other bacteria, and organisms of this family have often been suggested as potential natural antimicrobials because of their preference for gram‐negative antibiotic‐resistant bacteria (Shatzkes et al, ; Sockett & Lambert, ). Our results can be considered an indirect confirmation of those findings, as Bdellovibrionaceae have an ecological advantage in treatment AB++, where they seem to find their ideal growth conditions.…”