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José A. Aínsa

Bio: José A. Aínsa is an academic researcher from University of Zaragoza. The author has contributed to research in topics: Efflux & Mycobacterium tuberculosis. The author has an hindex of 24, co-authored 60 publications receiving 2188 citations. Previous affiliations of José A. Aínsa include Norwich Research Park & Carlos III Health Institute.


Papers
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Journal ArticleDOI
TL;DR: This review highlights recent advances in the understanding of efflux-mediated drug resistance in mycobacteria, including the distribution of Efflux systems in these organisms, their substrate profiles and their contribution to drug resistance.
Abstract: Two mechanisms are thought to be involved in the natural drug resistance of mycobacteria: the mycobacterial cell wall permeability barrier and active multidrug efflux pumps. Genes encoding drug efflux transporters have been isolated from several mycobacterial species. These proteins transport tetracycline, fluoroquinolones, aminoglycosides and other compounds. Recent reports have suggested that efflux pumps may also be involved in transporting isoniazid, one of the main drugs used to treat tuberculosis. This review highlights recent advances in our understanding of efflux-mediated drug resistance in mycobacteria, including the distribution of efflux systems in these organisms, their substrate profiles and their contribution to drug resistance. The balance between the drug transport into the cell and drug efflux is not yet clearly understood, and further studies are required in mycobacteria.

285 citations

Journal ArticleDOI
TL;DR: The Tap proteins of the opportunistic organism M. fortuitum and the important pathogen M. tuberculosis are probably proton-dependent efflux pumps, although it cannot exclude the possibility that they act as regulatory proteins.
Abstract: A recombinant plasmid isolated from a Mycobacterium fortuitum genomic library by selection for gentamicin and 2-N′-ethylnetilmicin resistance conferred low-level aminoglycoside and tetracycline resistance when introduced into M. smegmatis. Further characterization of this plasmid allowed the identification of the M. fortuitum tap gene. A homologous gene in the M. tuberculosis H37Rv genome has been identified. The M. tuberculosis tap gene (Rv1258 in the annotated sequence of the M. tuberculosis genome) was cloned and conferred low-level resistance to tetracycline when introduced into M. smegmatis. The sequences of the putative Tap proteins showed 20 to 30% amino acid identity to membrane efflux pumps of the major facilitator superfamily (MFS), mainly tetracycline and macrolide efflux pumps, and to other proteins of unknown function but with similar antibiotic resistance patterns. Approximately 12 transmembrane regions and different sequence motifs characteristic of the MFS proteins also were detected. In the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP), the levels of resistance to antibiotics conferred by plasmids containing the tap genes were decreased. When tetracycline accumulation experiments were carried out with the M. fortuitum tap gene, the level of tetracycline accumulation was lower than that in control cells but was independent of the presence of CCCP. We conclude that the Tap proteins of the opportunistic organism M. fortuitum and the important pathogen M. tuberculosis are probably proton-dependent efflux pumps, although we cannot exclude the possibility that they act as regulatory proteins.

187 citations

Journal ArticleDOI
TL;DR: The antitubercular efficacy of spectinamides demonstrates that synthetic modifications to classical antibiotics can overcome the challenge of intrinsic efflux pump-mediated resistance and expands opportunities for target-based tuberculosis drug discovery.
Abstract: Although the classical antibiotic spectinomycin is a potent bacterial protein synthesis inhibitor, poor antimycobacterial activity limits its clinical application for treating tuberculosis. Using structure-based design, we generated a new semisynthetic series of spectinomycin analogs with selective ribosomal inhibition and excellent narrow-spectrum antitubercular activity. In multiple murine infection models, these spectinamides were well tolerated, significantly reduced lung mycobacterial burden and increased survival. In vitro studies demonstrated a lack of cross resistance with existing tuberculosis therapeutics, activity against multidrug-resistant (MDR) and extensively drug-resistant tuberculosis and an excellent pharmacological profile. Key to their potent antitubercular properties was their structural modification to evade the Rv1258c efflux pump, which is upregulated in MDR strains and is implicated in macrophage-induced drug tolerance. The antitubercular efficacy of spectinamides demonstrates that synthetic modifications to classical antibiotics can overcome the challenge of intrinsic efflux pump-mediated resistance and expands opportunities for target-based tuberculosis drug discovery.

151 citations

Journal ArticleDOI
TL;DR: The inventory of the drug transporters subfamily, included in the major facilitator superfamily (MFS), encoded by the complete genome of Mycobacterium tuberculosis, revealed 16 open reading frames encoding putative drug efflux pumps belonging to MFS, and it is demonstrated that two of them function asDrug efflux proteins.
Abstract: Both intrinsic and acquired multidrug resistance play an important role in the insurgence of tuberculosis. Detailed knowledge of the molecular basis of drug recognition and transport by multidrug transport systems is required for the development of new antibiotics that are not extruded or of inhibitors that block the multidrug transporter and allow traditional antibiotics to be effective. We have undertaken the inventory of the drug transporters subfamily, included in the major facilitator superfamily (MFS), encoded by the complete genome of Mycobacterium tuberculosis (MTB). These proteins were identified on the basis of their characteristic stretches of amino acids and transmembrane segments (TMS) number. Genome analysis and searches of homology between the identified transporters and proteins characterized in other organisms revealed 16 open reading frames encoding putative drug efflux pumps belonging to MFS. In the case of two of them, we also have demonstrated that they function as drug efflux proteins.

134 citations

Journal ArticleDOI
TL;DR: It is concluded that P55 is a membrane protein implicated in aminoglycoside and tetracycline efflux in mycobacteria.
Abstract: The Mycobacterium bovis P55 gene, located downstream from the gene that encodes the immunogenic lipoprotein P27, has been characterized. The gene was identical to the open reading frame of the Rv1410c gene in the genome of Mycobacterium tuberculosis H37Rv, annotated as a probable drug efflux protein. Genes similar to P55 were present in all species of the M. tuberculosis complex and other mycobacteria such as Mycobacterium leprae and Mycobacterium avium. By Western blotting, P55 was located in the membrane fraction of M. bovis. When transformed into Mycobacterium smegmatis after cloning, P55 conferred aminoglycoside and tetracycline resistance. The levels of resistance to streptomycin and tetracycline conferred by P55 were decreased in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone and the pump inhibitors verapamil and reserpine. M. smegmatis cells expressing the plasmid-encoded P55 accumulated less tetracycline than the control cells. We conclude that P55 is a membrane protein implicated in aminoglycoside and tetracycline efflux in mycobacteria.

128 citations


Cited by
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Journal Article
TL;DR: Evidence is presented substantiating the proposal that an internal tandem gene duplication event gave rise to a primordial MFS protein before divergence of the family members.
Abstract: In 1998 we updated earlier descriptions of the largest family of secondary transport carriers found in living organisms, the major facilitator superfamily (MFS). Seventeen families of transport proteins were shown to comprise this superfamily. We here report expansion of the MFS to include 29 established families as well as five probable families. Structural, functional, and mechanistic features of the constituent permeases are described, and each newly identified family is shown to exhibit specificity for a single class of substrates. Phylogenetic analyses define the evolutionary relationships of the members of each family to each other, and multiple alignments allow definition of family-specific signature sequences as well as all wellconserved sequence motifs. The work described serves to update previous publications and allows extrapolation of structural, functional and mechanistic information obtained with any one member of the superfamily to other members with limitations determined by the degrees of sequence divergence.

1,996 citations

Journal ArticleDOI
01 Jan 2004-Drugs
TL;DR: Fluoroquinolones and β-lactams of the latest generations are likely to select for overproduction mutants of these pumps and make the bacteria resistant in one step to practically all classes of antibacterial agents.
Abstract: Drug efflux pumps play a key role in drug resistance and also serve other functions in bacteria. There has been a growing list of multidrug and drug-specific efflux pumps characterized from bacteria of human, animal, plant and environmental origins. These pumps are mostly encoded on the chromosome, although they can also be plasmid-encoded. A previous article in this journal provided a comprehensive review regarding efflux-mediated drug resistance in bacteria. In the past 5 years, significant progress has been achieved in further understanding of drug resistance-related efflux transporters and this review focuses on the latest studies in this field since 2003. This has been demonstrated in multiple aspects that include but are not limited to: further molecular and biochemical characterization of the known drug efflux pumps and identification of novel drug efflux pumps; structural elucidation of the transport mechanisms of drug transporters; regulatory mechanisms of drug efflux pumps; determining the role of the drug efflux pumps in other functions such as stress responses, virulence and cell communication; and development of efflux pump inhibitors. Overall, the multifaceted implications of drug efflux transporters warrant novel strategies to combat multidrug resistance in bacteria.

1,118 citations

Journal ArticleDOI
TL;DR: This review focuses on chromosomally encoded pumps in bacteria that cause infections in humans, and suggests that resistance nodulation division systems are important in pathogenicity and/or survival in a particular ecological niche.
Abstract: 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.

1,078 citations

Journal ArticleDOI
TL;DR: An account of the recent explosion of actinobacterial genomics data is provided and an attempt to place this in a biological and evolutionary context.
Abstract: Summary: Actinobacteria constitute one of the largest phyla among Bacteria and represent gram-positive bacteria with a high G+C content in their DNA. This bacterial group includes microorganisms exhibiting a wide spectrum of morphologies, from coccoid to fragmenting hyphal forms, as well as possessing highly variable physiological and metabolic properties. Furthermore, Actinobacteria members have adopted different lifestyles, and can be pathogens (e.g., Corynebacterium, Mycobacterium, Nocardia, Tropheryma, and Propionibacterium), soil inhabitants (Streptomyces), plant commensals (Leifsonia), or gastrointestinal commensals (Bifidobacterium). The divergence of Actinobacteria from other bacteria is ancient, making it impossible to identify the phylogenetically closest bacterial group to Actinobacteria. Genome sequence analysis has revolutionized every aspect of bacterial biology by enhancing the understanding of the genetics, physiology, and evolutionary development of bacteria. Various actinobacterial genomes have been sequenced, revealing a wide genomic heterogeneity probably as a reflection of their biodiversity. This review provides an account of the recent explosion of actinobacterial genomics data and an attempt to place this in a biological and evolutionary context.

1,026 citations

Journal ArticleDOI
Keith Poole1
TL;DR: Given the clinical significance of multidrug (and drug-specific) exporters, efflux must be considered in formulating strategies/approaches to treating drug-resistant infections, both in the development of new agents less impacted by efflux and in targeting efflux directly with efflux inhibitors.
Abstract: Antibiotic resistance continues to plague antimicrobial chemotherapy of infectious disease. And while true biocide resistance is as yet unrealized, in vitro and in vivo episodes of reduced biocide susceptibility are common and the history of antibiotic resistance should not be ignored in the development and use of biocidal agents. Efflux mechanisms of resistance, both drug specific and multidrug, are important determinants of intrinsic and/or acquired resistance to these antimicrobials, with some accommodating both antibiotics and biocides. This latter raises the spectre (as yet generally unrealized) of biocide selection of multiple antibiotic-resistant organisms. Multidrug efflux mechanisms are broadly conserved in bacteria, are almost invariably chromosome-encoded and their expression in many instances results from mutations in regulatory genes. In contrast, drug-specific efflux mechanisms are generally encoded by plasmids and/or other mobile genetic elements (transposons, integrons) that carry additional resistance genes, and so their ready acquisition is compounded by their association with multidrug resistance. While there is some support for the latter efflux systems arising from efflux determinants of self-protection in antibiotic-producing Streptomyces spp. and, thus, intended as drug exporters, increasingly, chromosomal multidrug efflux determinants, at least in Gram-negative bacteria, appear not to be intended as drug exporters but as exporters with, perhaps, a variety of other roles in bacterial cells. Still, given the clinical significance of multidrug (and drug-specific) exporters, efflux must be considered in formulating strategies/approaches to treating drug-resistant infections, both in the development of new agents, for example, less impacted by efflux and in targeting efflux directly with efflux inhibitors.

979 citations