scholarly journals The Role of Efflux Pumps in the Transition from Low-Level to Clinical Antibiotic Resistance

Antibiotics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 855
Author(s):  
Anna Elisabeth Ebbensgaard ◽  
Anders Løbner-Olesen ◽  
Jakob Frimodt-Møller
Keyword(s):  
Antibiotic Resistance ◽  
Target Genes ◽  
Defense Mechanism ◽  
Efflux Pump ◽  
Spontaneous Mutation ◽  
Efflux Pumps ◽  
Infection Site ◽  
Low Level ◽  
Clinical Resistance ◽  
Level Resistance

Antibiotic resistance is on the rise and has become one of the biggest public health challenges of our time. Bacteria are able to adapt to the selective pressure exerted by antibiotics in numerous ways, including the (over)expression of efflux pumps, which represents an ancient bacterial defense mechanism. Several studies show that overexpression of efflux pumps rarely provides clinical resistance but contributes to a low-level resistance, which allows the bacteria to persist at the infection site. Furthermore, recent studies show that efflux pumps, apart from pumping out toxic substances, are also linked to persister formation and increased spontaneous mutation rates, both of which could aid persistence at the infection site. Surviving at the infection site provides the low-level-resistant population an opportunity to evolve by acquiring secondary mutations in antibiotic target genes, resulting in clinical resistance to the treating antibiotic. Thus, this emphasizes the importance and challenge for clinicians to be able to monitor overexpression of efflux pumps before low-level resistance develops to clinical resistance. One possible treatment option could be an efflux pump-targeted approach using efflux pump inhibitors.

scholarly journals Mutations that increase expression of the EmrAB-TolC efflux pump confer increased resistance to nitroxoline in Escherichia coli

2019 ◽  
Author(s):  
Fabiola Puértolas-Balint ◽  
Omar Warsi ◽  
Marius Linkevicius ◽  
Po-Cheng Tang ◽  
Dan I Andersson
Keyword(s):  
Escherichia Coli ◽  
Target Genes ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Cross Resistance ◽  
Resistance Mutations ◽  
Double Knockout ◽  
Low Level ◽  
Resistant Mutants ◽  
Level Resistance

Abstract Objectives To determine the mechanism of resistance to the antibiotic nitroxoline in Escherichia coli. Methods Spontaneous nitroxoline-resistant mutants were selected at different concentrations of nitroxoline. WGS and strain reconstruction were used to define the genetic basis for the resistance. The mechanistic basis of resistance was determined by quantitative PCR (qPCR) and by overexpression of target genes. Fitness costs of the resistance mutations and cross-resistance to other antibiotics were also determined. Results Mutations in the transcriptional repressor emrR conferred low-level resistance to nitroxoline [nitroxoline MIC (MICNOX) = 16 mg/L] by increasing the expression of the emrA and emrB genes of the EmrAB-TolC efflux pump. These resistant mutants showed no fitness reduction and displayed cross-resistance to nalidixic acid. Second-step mutants with higher-level resistance (MICNOX = 32–64 mg/L) had mutations in the emrR gene, together with either a 50 kb amplification, a mutation in the gene marA, or an IS upstream of the lon gene. The latter mutations resulted in higher-level nitroxoline resistance due to increased expression of the tolC gene, which was confirmed by overexpressing tolC from an inducible plasmid in a low-level resistance mutant. Furthermore, the emrR mutations conferred a small increase in resistance to nitrofurantoin only when combined with an nfsAB double-knockout mutation. However, nitrofurantoin-resistant nfsAB mutants showed no cross-resistance to nitroxoline. Conclusions Mutations in different genes causing increased expression of the EmrAB-TolC pump lead to an increased resistance to nitroxoline. The structurally similar antibiotics nitroxoline and nitrofurantoin appear to have different modes of action and resistance mechanisms.

scholarly journals Resistance against Membrane-Inserting MmpL3 Inhibitor through Upregulation of MmpL5 in Mycobacterium tuberculosis

2020 ◽  
Vol 64 (12) ◽  
Author(s):  
Ming Li ◽  
Samuel Agyei Nyantakyi ◽  
Mei-Lin Go ◽  
Thomas Dick
Keyword(s):  
Antibacterial Activity ◽  
Mycobacterium Tuberculosis ◽  
Mouse Model ◽  
Mannich Base ◽  
Efflux Pump ◽  
Transcriptional Repressor ◽  
Mannich Bases ◽  
Mycolic Acid ◽  
Low Level ◽  
Level Resistance

ABSTRACT Spiroketal indolyl Mannich bases (SIMBs) present a novel class of membrane-inserting antimycobacterials with efficacy in a tuberculosis mouse model. SIMBs exert their antibacterial activity by two mechanisms. The indolyl Mannich base scaffold causes permeabilization of bacteria, and the spiroketal moiety contributes to inhibition of the mycolic acid transporter MmpL3. Here, we show that low-level resistance to SIMBs arises by mutations in the transcriptional repressor MmpR5, resulting in upregulation of the efflux pump MmpL5.

scholarly journals Expression of Pseudomonas aeruginosa Multidrug Efflux Pumps MexA-MexB-OprM and MexC-MexD-OprJ in a Multidrug-Sensitive Escherichia coli Strain

1998 ◽  
Vol 42 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Ramakrishnan Srikumar ◽  
Tatiana Kon ◽  
Naomasa Gotoh ◽  
Keith Poole
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Crystal Violet ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Multidrug Efflux ◽  
Efflux System ◽  
E Coli ◽  
Multidrug Efflux Pumps

ABSTRACT The mexCD-oprJ and mexAB-oprM operons encode components of two distinct multidrug efflux pumps inPseudomonas aeruginosa. To assess the contribution of individual components to antibiotic resistance and substrate specificity, these operons and their component genes were cloned and expressed in Escherichia coli. Western immunoblotting confirmed expression of the P. aeruginosa efflux pump components in E. coli strains expressing and deficient in the endogenous multidrug efflux system (AcrAB), although only the ΔacrAB strain, KZM120, demonstrated increased resistance to antibiotics in the presence of the P. aeruginosa efflux genes. E. coli KZM120 expressing MexAB-OprM showed increased resistance to quinolones, chloramphenicol, erythromycin, azithromycin, sodium dodecyl sulfate (SDS), crystal violet, novobiocin, and, significantly, several β-lactams, which is reminiscent of the operation of this pump in P. aeruginosa. This confirmed previous suggestions that MexAB-OprM provides a direct contribution to β-lactam resistance via the efflux of this group of antibiotics. An increase in antibiotic resistance, however, was not observed when MexAB or OprM alone was expressed in KZM120. Thus, despite the fact that β-lactams act within the periplasm, OprM alone is insufficient to provide resistance to these agents. E. coli KZM120 expressing MexCD-OprJ also showed increased resistance to quinolones, chloramphenicol, macrolides, SDS, and crystal violet, though not to most β-lactams or novobiocin, again somewhat reminiscent of the antibiotic resistance profile of MexCD-OprJ-expressing strains ofP. aeruginosa. Surprisingly, E. coli KZM120 expressing MexCD alone also showed an increase in resistance to these agents, while an OprJ-expressing KZM120 failed to demonstrate any increase in antibiotic resistance. MexCD-mediated resistance, however, was absent in a tolC mutant of KZM120, indicating that MexCD functions in KZM120 in conjunction with TolC, the previously identified outer membrane component of the AcrAB-TolC efflux system. These data confirm that a tripartite efflux pump is necessary for the efflux of all substrate antibiotics and that the P. aeruginosa multidrug efflux pumps are functional and retain their substrate specificity in E. coli.

scholarly journals Clinically Relevant Chromosomally Encoded Multidrug Resistance Efflux Pumps in Bacteria

2006 ◽  
Vol 19 (2) ◽  
pp. 382-402 ◽  
Author(s):  
Laura J. V. Piddock
Keyword(s):  
Antibiotic Resistance ◽  
Drug Transport ◽  
Efflux Pump ◽  
Regulatory Gene ◽  
Structural Data ◽  
Efflux Pumps ◽  
Resistant Bacteria ◽  
Multiple Drug ◽  
Transporter Gene ◽  
Resistance Nodulation Division

SUMMARY Efflux pump genes and proteins are present in both antibiotic-susceptible and antibiotic-resistant bacteria. Pumps may be specific for one substrate or may transport a range of structurally dissimilar compounds (including antibiotics of multiple classes); such pumps can be associated with multiple drug (antibiotic) resistance (MDR). However, the clinical relevance of efflux-mediated resistance is species, drug, and infection dependent. This review focuses on chromosomally encoded pumps in bacteria that cause infections in humans. Recent structural data provide valuable insights into the mechanisms of drug transport. MDR efflux pumps contribute to antibiotic resistance in bacteria in several ways: (i) inherent resistance to an entire class of agents, (ii) inherent resistance to specific agents, and (iii) resistance conferred by overexpression of an efflux pump. Enhanced efflux can be mediated by mutations in (i) the local repressor gene, (ii) a global regulatory gene, (iii) the promoter region of the transporter gene, or (iv) insertion elements upstream of the transporter gene. Some data suggest that resistance nodulation division systems are important in pathogenicity and/or survival in a particular ecological niche. Inhibitors of various efflux pump systems have been described; typically these are plant alkaloids, but as yet no product has been marketed.

scholarly journals Escherichia coli Mutators Present an Enhanced Risk for Emergence of Antibiotic Resistance during Urinary Tract Infections

2004 ◽  
Vol 48 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Keith Miller ◽  
Alexander John O'Neill ◽  
Ian Chopra
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Urinary Tract ◽  
Urinary Tract Infections ◽  
Therapeutic Drug ◽  
Single Point Mutation ◽  
Low Level ◽  
Drug Concentrations ◽  
Tract Infections ◽  
Level Resistance

ABSTRACT Mutators may present an enhanced risk for the emergence of antibiotic resistance in bacteria during chemotherapy. Using Escherichia coli mutators as a model, we evaluated their ability to develop resistance to antibiotics routinely used for the treatment of urinary tract infections (UTIs). Under conditions that simulate therapeutic drug concentrations in humans, low-level resistance to trimethoprim, gentamicin, and cefotaxime emerged more frequently in mutators than normal strains. Resistance to trimethoprim in both cell types arose from a single point mutation in folA (Ile94→Leu) and cefotaxime resistance resulted from loss of outer membrane porin OmpF. The mechanisms of gentamicin resistance could not be defined, but resistance did not result from mutations in ribosomal protein L6 (rplF). Although similar mechanisms of low-level antibiotic resistance probably arise in these strains, mutators are a risk factor because the increased generation of mutants with low-level resistance enhances the opportunity for subsequent emergence of high-level resistance.

scholarly journals Aminoglycoside Cross-Resistance in Mycobacterium tuberculosis Due to Mutations in the 5′ Untranslated Region ofwhiB7

2013 ◽  
Vol 57 (4) ◽  
pp. 1857-1865 ◽  
Author(s):  
Analise Z. Reeves ◽  
Patricia J. Campbell ◽  
Razvan Sultana ◽  
Seidu Malik ◽  
Megan Murray ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Mycobacterium Tuberculosis ◽  
Untranslated Region ◽  
Regulatory Region ◽  
Cross Resistance ◽  
Drug Resistant ◽  
Second Line ◽  
Content Type ◽  
Low Level ◽  
Level Resistance

ABSTRACTSince the discovery of streptomycin's bactericidal activity againstMycobacterium tuberculosis, aminoglycosides have been utilized to treat tuberculosis (TB). Today, the aminoglycosides kanamycin and amikacin are used to treat multidrug-resistant (MDR) TB, and resistance to any of the second-line injectable antibiotics, including kanamycin, amikacin, or capreomycin, is a defining characteristic of extensively drug-resistant (XDR) TB. Resistance to kanamycin and streptomycin is thought to be due to the acquisition of unlinked chromosomal mutations. However, we identified eight independent mutations in the 5′ untranslated region of the transcriptional activatorwhiB7that confer low-level resistance to both aminoglycosides. The mutations lead to 23- to 145-fold increases inwhiB7transcripts and subsequent increased expression of botheis(Rv2416c) andtap(Rv1258c). Increased expression ofeisconfers kanamycin resistance in these mutants, while increased expression oftap, which encodes an efflux pump, is a previously uncharacterized mechanism of low-level streptomycin resistance. Additionally, high-level resistance to streptomycin arose at a much higher frequency inwhiB7mutants than in a wild-type (WT) strain. AlthoughwhiB7is typically associated with intrinsic antibiotic resistance inM. tuberculosis, these data suggest that mutations in an uncharacterized regulatory region ofwhiB7contribute to cross-resistance against clinically used second-line antibiotics. As drug resistance continues to develop and spread, understanding the mechanisms and molecular basis of antibiotic resistance is critical for the development of rapid molecular tests to diagnose drug-resistant TB strains and ultimately for designing regimens to treat drug-resistant cases of TB.

scholarly journals Two resistance nodulation division-family efflux pumps inChromobacteriumspecies and their role in antibiotic resistance and tolerance

2019 ◽  
Author(s):  
Saida Benomar ◽  
Kara C Evans ◽  
Robert L Unckless ◽  
Josephine R Chandler
Keyword(s):  
Antibiotic Resistance ◽  
Efflux Pump ◽  
Bacterial Species ◽  
Efflux Pumps ◽  
Resistance Mechanisms ◽  
Antibiotic Resistant ◽  
Burkholderia Thailandensis ◽  
New Information ◽  
Resistance Nodulation Division ◽  
Culture Growth

ABSTRACTVery little is known of the antibiotic resistance mechanisms of members of theChromobacteriumgenus. In previous studies ofChromobacterium subtsugae(formerlyC. violaceum) strain CV017, we identified a resistance nodulation division (RND)-family efflux pump (CdeAB-OprM). Here, we show thecdeAB-oprMgenes are widely distributed in members of theChromobacteriumgenus. We use antimicrobial susceptibility testing with a CV017cdeAB-oprMmutant to show the products of these genes confers resistance to a variety of antibiotics including ciprofloxacin, a clinically important antibiotic. We also identified a related RND-family pump,cseAB-oprN, in the genome of CV017 and otherC. subtsugaespecies, that is not present in other members of theChromobacteriumgenus. We demonstrate that CdeAB-OprM and CseAB-OprN are both transcriptionally induced in CV017 cells treated with sub-lethal antibiotic concentrations and they are important for induction of tolerance to different antibiotics. While CdeAB-OprM has a broad antibiotic specificity, the CseAB-OprN system is highly specific for a ribosome-targeting antibiotic produced by the saprophytic bacteriumBurkholderia thailandensis,bactobolin. Finally, we use a previously developedB. thailandensis-C. subtsugaeCV017 co-culture model to demonstrate that adding sub-lethal bactobolin at the beginning of co-culture growth increases the ability of CV017 to compete withB. thailandensisin a manner that is dependent on the CseAB-OprN system. Our results provide new information on the antibiotic resistance mechanisms ofChromobacteriumspecies and highlight the importance of efflux pumps during competition with other bacterial species.IMPORTANCEThis study describes two closely related efflux pumps in members of theChromobacteriumgenus, which includes opportunistic but often-fatal pathogens and species with highly versatile metabolic capabilities. Efflux pumps remove antibiotics from the cell and are important for antibiotic resistance. One of these pumps is broadly distributed in theChromobacteriumgenus and increases resistance to clinically relevant antibiotics. The other efflux pump is present only inChromobacterium subtsugaeand is highly specific for bactobolin, an antibiotic produced by the soil saprophyteBurkholderia thailandensis. We demonstrate these pumps can be activated to increase resistance by their antibiotic substrates, and that this activation is important forC. subtsugaeto survive in a laboratory competition experiment withB. thailandensis.These results have implications for managing antibiotic-resistantChromobacteriuminfections, bioengineering ofChromobacteriumspecies, and for understanding the evolution of efflux pumps.

scholarly journals EFFLUX PUMP OVEREXPRESSION PROFILING IN ACINETOBACTER BAUMANNII AND STUDY OF NEW 1-(1-NAPHTHYLMETHYL)-PIPERAZINE ANALOGS AS POTENTIAL EFFLUX INHIBITORS

2021 ◽  
Author(s):  
Morgane Choquet ◽  
Elodie Lohou ◽  
Etienne Pair ◽  
Pascal Sonnet ◽  
Catherine Mullie
Keyword(s):  
Antibiotic Resistance ◽  
Acinetobacter Baumannii ◽  
Inhibitory Activity ◽  
Efflux Pump ◽  
Parent Compound ◽  
Efflux Pumps ◽  
Quinoline Derivative ◽  
Genes Encoding ◽  
Efflux Pump Inhibitors ◽  
Therapeutic Alternatives

Overexpression of efflux pumps extruding antibiotics currently used for the treatment of Acinetobacter baumannii infections has been described as an important mechanism causing antibiotic resistance. The first aim of this work was to phenotypically evaluate the overexpression of efflux pumps on a collection of 124 ciprofloxacin resistant A. baumannii strains. An overexpression of genes encoding one or more efflux pumps was obtained for 19 out of the 34 strains with a positive phenotypic efflux (56%). The most frequent genes overexpressed were those belonging to the RND family, with adeJ being the most prevalent (50%). Interestingly, efflux pump genes coding for MATE and MFS families were also overexpressed quite frequently: abeM (32%) and abaQ (26%). The second aim was to synthesize 1-(1-NaphthylMethyl)-Piperazine analogs as potential new efflux pump inhibitors and biologically evaluate them against strains with a positive phenotypic efflux. Quinoline and pyridine analogs were found to be more effective than their parent compound 1-(1-NaphthylMethyl)-Piperazine. Stereochemistry also played an important part in the inhibitory activity as quinoline derivative ( R )-3a was identified as being the most effective and less cytotoxic. Its inhibitory activity was also correlated to the number of efflux pumps expressed by a strain. The results obtained in this work suggest that quinoline analogs of 1-(1-NaphthylMethyl)-Piperazine are promising leads in the development of new anti- Acinetobacter baumannii therapeutic alternatives, in combination with antibiotics for which an efflux-mediated resistance is suspected.

scholarly journals The analysis of the role of MexAB-OprM on quorum sensing homeostasis shows that the apparent redundancy of Pseudomonas aeruginosa multidrug efflux pumps allows keeping the robustness and the plasticity of this intercellular signaling network

2020 ◽  
Author(s):  
Manuel Alcalde-Rico ◽  
Jorge Olivares-Pacheco ◽  
Nigel Halliday ◽  
Miguel Cámara ◽  
José Luis Martínez
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Quorum Sensing ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Multidrug Efflux ◽  
Intrinsic Resistance ◽  
Bacterial Physiology ◽  
Multidrug Efflux Pumps ◽  
Depth Analysis

AbstractMultidrug efflux pumps are key determinants for antibiotic resistance. Besides contributing to intrinsic resistance, their overexpression is frequently a cause of the increased resistance acquired during therapy. In addition to their role in resistance to antimicrobials, efflux pumps are ancient and conserved elements with relevant roles in different aspects of the bacterial physiology. It is then conceivable that their overexpression might cause a burden that will be translated into a fitness cost associated with the acquisition of resistance. In the case of Pseudomonas aeruginosa, it has been stated that overexpression of different efflux pumps is linked to the impairment of the quorum sensing (QS) response. Nevertheless, the causes of such impairment are different for each analyzed efflux pump. In this study, we performed an in-depth analysis of the QS-mediated response of a P. aeruginosa antibiotic resistant mutant that overexpresses MexAB-OprM. Although previous work claimed that this efflux pump extrudes the QS signal 3-oxo-C12-HSL, we show otherwise. Our results suggest that the observed attenuation in the QS response when overexpressing this pump is related to a reduced availability of intracellular octanoate, one of the precursors of the biosynthesis of alkyl quinolone QS signals. The overexpression of other P. aeruginosa efflux pumps has been shown to also cause a reduction in intracellular levels of QS signals or their precursors impacting on these signaling mechanisms. However, the molecules involved are distinct for each efflux pump, indicating that they can differentially contribute to the P. aeruginosa quorum sensing homeostasis.ImportanceThe success of bacterial pathogens to cause disease relies on their virulence capabilities as well as in their resistance to antibiotic interventions. In the case of the important nosocomial pathogen Pseudomonas aeruginosa, multidrug efflux pumps participate in the resistance/virulence crosstalk since, besides contributing to antibiotic resistance, they can also modulate the quorum sensing (QS) response. We show that mutants overexpressing the MexAB-OprM efflux pump, present an impaired QS response due to the reduced availability of the QS signal precursor octanoate, not because they extrude, as previously stated, the QS signal 3-oxo-C12-HSL. Together with previous studies, this indicates that, although the consequences of overexpressing efflux pumps are similar (impaired QS response), the mechanisms are different. This ‘apparent redundancy’ of RND efflux systems can be understood as a P. aeruginosa strategy to keep the robustness of the QS regulatory network and modulate its output in response to different signals.

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