(P)ppGpp synthetase Rsh participates in rifampicin tolerance of persister cells in Brucella abortus in vitro

The (p)ppGpp synthetase Rsh promotes rifampicin tolerant persister cell formation in Brucella abortus by regulating the type II toxin-antitoxin module mbcTA

“…The relationships between the stringent response alarmone (p)ppGpp and persistence are dissimilar in different bacteria ( Conlon et al, 2016 ; VandenBerg et al, 2016 ; Pacios et al, 2020 ). Previous research from our laboratory indicated that B. abortus was capable of forming multi-drug tolerant persister cells ( Liu et al, 2023 ) . B. abortus displayed a biphasic killing curve with a subpopulation of surviving persister cells during different antibiotic treatment, except with gentamicin.…”

“…B. abortus displayed a biphasic killing curve with a subpopulation of surviving persister cells during different antibiotic treatment, except with gentamicin. Moreover, deletion of the gene for Rsh (Δ rsh ) resulted in decreased persistence in either exponential phase or stationary phase with rifampicin treatment for 24 h ( Liu et al, 2023 ). Therefore, we examined whether Rsh promoted persister cell production in B. abortus stationary phase during different antibiotic treatments for 36 h. Deletion of the gene for Rsh had no effect on persister cell formation in stationary phase in the presence of doxycycline ( Figure 1A ), polymyxin B ( Figure 1B ), ofloxacin ( Figure 1C ), or ampicillin ( Figure 1D ) compared with wild-type B. abortus .…”

“…These findings led us to assess whether Rsh affects persister cell production during different growth phases with different antibiotic treatments. Here, we used an analogous approach to investigate the extent to which Rsh impacted persistence in different growth phases following treatment with different antibiotics for 36 h. Wild-type and Δ rsh strains were grown to exponential (12 h) and late stationary (72 h) phases ( Liu et al, 2023 ). Aliquots were removed and cultured in TSB medium containing different antibiotics for 36 h. Similar with wild type, we found Rsh formed the time-dependent biphasic kill curves.…”

“…Persister cells may lead to relapse of infection after removal of antibiotic treatment and thus are implicated in antibiotic treatment failure ( Fisher et al, 2017 ). Persister cells in B. abortus may form experimentally upon multi-antibiotic treatment either in infected cells or when growing in culture medium ( Mode et al, 2022 ; Liu et al, 2023 ). Understanding the latent mechanisms by which B. abortus forms persister cells and elucidating the mechanisms that are involved are important for effective disease control and prevention of brucellosis.…”

“…As the (p)ppGpp synthetase Rsh was linked to persister cell formation after rifampicin exposure ( Liu et al, 2023 ), here we sought to investigate the underlying mechanism by which Rsh influences persistence in the stationary phase in B. abortus . We demonstrate that persister cell production involving Rsh is related to growth phase and antibiotic classes in B. abortus .…”