Involvement of toxin-antitoxin modules in<i>Burkholderia cenocepacia</i>biofilm persistence

Acker, Heleen Van; Saß, Andrea; Dhondt, Inne; Nelis, Hans; Coenye, Tom

doi:10.1111/2049-632x.12177

Cited by 52 publications

(39 citation statements)

References 36 publications

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“…The RT-qPCR experiments were performed using the Perfecta SYBR green FastMix (Quanta Biosciences) on a Bio-Rad CFX96 real-time system C1000 thermal cycler, as described previously (18,19). The primer concentration was 300 nM.…”

Section: Methodsmentioning

confidence: 99%

Differential Roles of RND Efflux Pumps in Antimicrobial Drug Resistance of Sessile and Planktonic Burkholderia cenocepacia Cells

Buroni

Matthijs

Spadaro

et al. 2014

Antimicrob Agents Chemother

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Burkholderia cenocepacia is notorious for causing respiratory tract infections in people with cystic fibrosis. Infections with this organism are particularly difficult to treat due to its high level of intrinsic resistance to most antibiotics. Multidrug resistance in B. cenocepacia can be ascribed to different mechanisms, including the activity of efflux pumps and biofilm formation. In the present study, the effects of deletion of the 16 operons encoding resistance-nodulation-cell division (RND)-type efflux pumps in B. cenocepacia strain J2315 were investigated by determining the MICs of various antibiotics and by investigating the antibiofilm effect of these antibiotics. Finally, the expression levels of selected RND genes in treated and untreated cultures were investigated using reverse transcriptase quantitative PCR (RT-qPCR). Our data indicate that the RND-3 and RND-4 efflux pumps are important for resistance to various antimicrobial drugs (including tobramycin and ciprofloxacin) in planktonic B. cenocepacia J2315 populations, while the RND-3, RND-8, and RND-9 efflux systems protect biofilm-grown cells against tobramycin. The RND-8 and RND-9 efflux pumps are not involved in ciprofloxacin resistance. Results from the RT-qPCR experiments on the wild-type strain B. cenocepacia J2315 suggest that there is little regulation at the level of mRNA expression for these efflux pumps under the conditions tested. Species belonging to the Burkholderia cepacia complex (Bcc), a cluster of phylogenetically closely related and phenotypically similar Gram-negative bacteria, can cause severe respiratory tract infections in people with cystic fibrosis (1). Although there are considerable regional differences, the majority of patients with cystic fibrosis worldwide are infected with either Burkholderia multivorans or Burkholderia cenocepacia (2). Infections with B. cenocepacia are particularly difficult to treat due to their high level of resistance against a wide range of antimicrobial agents (1, 3, 4). Contributing to this is the fact that Bcc strains, including B. cenocepacia strains, readily form biofilms on various biotic and abiotic surfaces (5). While the molecular mechanisms contributing to the decreased susceptibility of cells in a biofilm have not yet been completely elucidated, protection provided by matrix components, biofilm-specific protection against oxidative stress, and biofilm-specific expression of efflux pumps are thought to play an important role (6).In the genome of B. cenocepacia strain J2315, a large number of efflux systems have been identified (7-10). The roles of some members of the resistance-nodulation-cell division (RND) efflux pump family have been investigated in more detail. The RND-3 (BCAL1674 to BCAL1676) and RND-4 (BCAL2820 to BCAL2822) efflux systems were shown to contribute to the intrinsic resistance of B. cenocepacia J2315 to various compounds and to mediate accumulation of quorum-sensing molecules in the growth medium (8). A transcriptomic analysis of RND-4 and RND-9 (BCAM1945 to BCAM1947...

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Section: Methodsmentioning

confidence: 99%

Differential Roles of RND Efflux Pumps in Antimicrobial Drug Resistance of Sessile and Planktonic Burkholderia cenocepacia Cells

Buroni

Matthijs

Spadaro

et al. 2014

Antimicrob Agents Chemother

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“…Indeed, this effect is to be expected, as discussed above and presented in Figures 3 to 5. Some of the systems that have been reported to contribute to biofilm antimicrobial tolerance include the stringent response (24), the SOS response (25), efflux pumps (26, 27), quorum sensing (28), toxin-antitoxin modules (29, 30), the elaboration of periplasmic or extracellular polysaccharides (31, 32, 33), and others (34–36). At this time it is still too early to be able to identify a consensus genetic basis for biofilm antimicrobial tolerance, but these details are certain to follow.…”

Section: Mechanisms Of Biofilm Antimicrobial Tolerancementioning

confidence: 99%

Antimicrobial Tolerance in Biofilms

2015

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The tolerance of microorganisms in biofilms to antimicrobial agents is examined through a meta-analysis of literature data. A numerical tolerance factor comparing the rates of killing in the planktonic and biofilm states is defined to provide a quantitative basis for the analysis. Tolerance factors for biocides and antibiotics range over three orders of magnitude. This variation is not explained by taking into account the molecular weight of the agent, the chemistry of the agent, the substratum material, or the speciation of the microorganisms. Tolerance factors do depend on the areal cell density of the biofilm at the time of treatment and on the age of the biofilm as grown in a particular experimental system. This suggests that there is something that happens during biofilm maturation, either physical or physiological, that is essential for full biofilm tolerance. Experimental measurements of antimicrobial penetration times in biofilms range over orders of magnitude, with slower penetration (>12 min) observed for reactive oxidants and cationic molecules. These agents are retarded through the interaction of reaction, sorption, and diffusion. The specific physiological status of microbial cells in a biofilm contributes to antimicrobial tolerance. A conceptual framework for categorizing physiological cell states is discussed in the context of antimicrobial susceptibility. It is likely that biofilms harbor cells in multiple states simultaneously (e.g., growing, stress-adapted, dormant, inactive) and that this physiological heterogeneity is an important factor in the tolerance of the biofilm state.

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“…For example, transcriptome analysis of dormant E. coli cells identified mqsR as the most highly induced gene in persister cells as compared with nonpersisters (67). In B. cenocepacia, several toxins were found to be up-regulated in biofilms as compared with planktonic cells, and overexpression of these toxins contributed to persistence in biofilms after treatment with tobramycin or ciprofloxacin (68). Although overproduction of almost any toxin may increase persistence, only two TA pairs have been shown to decrease persistence upon deletion (69,70).…”

Section: Ta Modulesmentioning

confidence: 99%

The Role of Efflux and Physiological Adaptation in Biofilm Tolerance and Resistance

Acker

Coenye

2016

Journal of Biological Chemistry

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Microbial biofilms demonstrate a decreased susceptibility to antimicrobial agents. Various mechanisms have been proposed to be involved in this recalcitrance. We focus on two of these factors. Firstly, the ability of sessile cells to actively mediate efflux of antimicrobial compounds has a profound impact on resistance and tolerance, and several studies point to the existence of biofilm-specific efflux systems. Secondly, biofilm-specific stress responses have a marked influence on cellular physiology, and contribute to the occurrence of persister cells. We provide an overview of the data that demonstrate that both processes are important for survival following exposure to antimicrobial agents.Microbial biofilms are surface-attached communities, consisting of cells embedded in an extracellular polymeric matrix that is at least partially composed of polymers produced by the microorganism themselves (1). Biofilms are omnipresent in natural and man-made environments (1, 2), and biofilm-associated bacteria are involved in a wide range of infections, including respiratory tract infections in cystic fibrosis (CF) 2 patients, chronically infected wounds, and device-related infections (3, 4). One of the hallmarks of these biofilm-associated infections is the frequent failure of antimicrobial chemotherapy. Although it is often postulated that sessile cells are more resistant to antimicrobial agents, these cells typically do not grow better than planktonic cells in the presence of antibiotics; for example, biofilm-associated and stationary-phase planktonic Burkholderia cepacia complex bacteria showed similar susceptibilities to antibiotics (5). However, it is much more difficult to kill biofilm-associated cells than planktonic cells (6), and various mechanisms that potentially could be involved in this have been described in the literature (see Refs. 7 and 8 for recent reviews as well as Refs. 9 and 10 in this minireview series). Avoiding exposure to (sufficiently high concentrations of) antibiotics, and the presence of a small population of specialized survivor cells that are tolerant toward particular antimicrobial agents (i.e. they are not killed upon exposure to the product) are two important mechanisms that will be discussed in this review.

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Involvement of toxin-antitoxin modules inBurkholderia cenocepaciabiofilm persistence

Cited by 52 publications

References 36 publications

Differential Roles of RND Efflux Pumps in Antimicrobial Drug Resistance of Sessile and Planktonic Burkholderia cenocepacia Cells

Differential Roles of RND Efflux Pumps in Antimicrobial Drug Resistance of Sessile and Planktonic Burkholderia cenocepacia Cells

Antimicrobial Tolerance in Biofilms

The Role of Efflux and Physiological Adaptation in Biofilm Tolerance and Resistance

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