Survival of Brucella abortus S19 and other Brucella spp. in the presence of oxidative stress and within macrophages

Abstract

The evolutionary “success” of the genus Brucella depends on the ability to persist both in the environment as well as inside of even activated macrophages of the animal host. For that, the Brucellae produce catalase and superoxide dismutase to defend against oxidative stress. Since the deletion of the mglA gene in the B. abortus S19 vaccine strain resulted not only in an increased tolerance to H2O2 but also in the induction of cytokines in macrophages, we here investigated the effect of oxidative stress (Fe2+ and H2O2) on the survival of B. abortus S19 and the isogenic B. abortus S 19 ∆mglA 3.14 deletion mutant in comparison with B. neotomae 5K33, Brucella strain 83/13, and B. microti CCM4915. These Brucellae belong to different phylogenetic clades and show characteristic differences in the mgl-operon. From the various Brucellae tested, B. abortus S19 showed the highest susceptibility to oxidative stress and the lowest ability to survive inside of murine macrophages. B. abortus S19 ∆mglA 3.14 as well as B. neotomae, which also belongs to the classical core clade of Brucella and lacks the regulators of the mgl-operon, presented the highest degree of tolerance to H2O2 but not in the survival in macrophages. The latter was most pronounced in case of an infection with B. 83/13 and B. microti CCM4915. The various Brucellae investigated here demonstrate significant differences in tolerance against oxidative stress and different survival in murine macrophages, which, however, do not correlate directly.

Evidence of a Viable but Nonculturable (VBNC) Phase in B. abortus S19 under Oxidative Stress (H2O2, -Fe2+, Bleach) and under Non-Oxidative Inhibitory Conditions (Isopropanol, Erythritol, Selenite)

“…In addition to our previous findings about a VBNC phase in Brucella abortus S19 [ 1 ], our results presented here yield further evidence on the formation of a VBNC state in Brucella . The rise of the ATP (RLU-LUMI)/CFU quotients showed that under conditions of different types of oxidative stress (Fe 2+ , H 2 O 2 , bleach), the numbers of colony forming units dropped more quickly with the increase of ATP (RLU-LUMI) values.…”

“…The experiments for testing oxidative stress were carried out in standardized aqueous systems [ 1 ].…”

“…Oxidative stress, caused by Fe 2+ , H 2 O 2 , or bleach acts via release of active oxygen radicals (O 2 − , OH − ). Investigations into the effects of Fe 2+ in the presence (Fenton effect) or absence of H 2 O 2 on the survival of various Brucella species have already started [ 1 , 2 ].…”

“…Because the first information about a VBNC Brucella resulted from our previous study [ 1 ], we here conducted a study in which we investigated the effects of iron, H 2 O 2 , and bleach, respectively, on the survival of B. abortus S19, B. abortus S19 ∆mglA 3.14, and B. neotomae 5K33, including in comparison to non-oxidative inhibitory substances, with special attention given to ATP–CFU imbalances.…”

Using ferrous-oxidizing bacteria to enhance the performance of a pH neutral all-iron flow battery

“…Furthermore, Brucella as a facultative parasite possesses more catalase and/or superoxide dismutase (SOD) expression quantity as it needs to resist oxidative stress caused by macrophages. 46 , 47 This reason explains the strong resistance of Brucella to ROS attack.…”