1.
Durcik, Martina, et al.
(författare)
New Dual Inhibitors of Bacterial Topoisomerases with Broad-Spectrum Antibacterial Activity and In Vivo Efficacy against Vancomycin-Intermediate Staphylococcus aureus
2023
Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 66:6, s. 3968-3994
Tidskriftsartikel (refereegranskat) abstract
A new series of dual low nanomolar benzothiazole inhibitors of bacterial DNA gyrase and topoisomerase IV were developed. The resulting compounds show excellent broad-spectrum antibacterial activities against Gram-positive Enterococcus faecalis, Enterococcus faecium and multidrug resistant (MDR) Staphylococcus aureus strains [best compound minimal inhibitory concentrations (MICs): range, <0.03125–0.25 μg/mL] and against the Gram-negatives Acinetobacter baumannii and Klebsiella pneumoniae (best compound MICs: range, 1–4 μg/mL). Lead compound 7a was identified with favorable solubility and plasma protein binding, good metabolic stability, selectivity for bacterial topoisomerases, and no toxicity issues. The crystal structure of 7a in complex with Pseudomonas aeruginosa GyrB24 revealed its binding mode at the ATP-binding site. Expanded profiling of 7a and 7h showed potent antibacterial activity against over 100 MDR and non-MDR strains of A. baumannii and several other Gram-positive and Gram-negative strains. Ultimately, in vivo efficacy of 7a in a mouse model of vancomycin-intermediate S. aureus thigh infection was also demonstrated.
2.
Pietsch, Franziska, et al.
(författare)
Ciprofloxacin selects for RNA polymerase mutations with pleiotropic antibiotic resistance effects
2017
Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press. - 0305-7453 .- 1460-2091. ; 72:1, s. 75-84
Tidskriftsartikel (refereegranskat) abstract
ObjectivesResistance to the fluoroquinolone drug ciprofloxacin is commonly linked to mutations that alter the drug target or increase drug efflux via the major AcrAB-TolC transporter. Very little is known about other mutations that might also reduce susceptibility to ciprofloxacin. We discovered that an Escherichia coli strain experimentally evolved for resistance to ciprofloxacin had acquired a mutation in rpoB, the gene coding for the β-subunit of RNA polymerase. The aim of this work was to determine whether this mutation, and other mutations in rpoB, contribute to ciprofloxacin resistance and, if so, by which mechanism.MethodsIndependent lineages of E. coli were evolved in the presence of ciprofloxacin and clones from endpoint cultures were screened for mutations in rpoB. Ciprofloxacin-selected rpoB mutations were identified and characterized in terms of effects on susceptibility and mode of action.ResultsMutations in rpoB were selected at a high frequency in 3 out of 10 evolved lineages, in each case arising after the occurrence of mutations affecting topoisomerases and drug efflux. All ciprofloxacin-selected rpoB mutations had a high fitness cost in the absence of drug, but conferred a competitive advantage in the presence of ciprofloxacin. RNA sequencing and quantitative RT–PCR analysis showed that expression of mdtK, encoding a multidrug efflux transporter, was significantly increased by the ciprofloxacin-selected rpoB mutations. The susceptibility phenotype was shown to depend on the presence of an active mdtK and a mutant rpoB allele.ConclusionsThese data identify mutations in RNA polymerase as novel contributors to the evolution of resistance to ciprofloxacin and show that the phenotype is mediated by increased MdtK-dependent drug efflux.
3.
Brandis, Gerrit, 1985-, et al.
(författare)
Comprehensive phenotypic characterization of rifampicin resistance mutations in Salmonella provides insight into the evolution of resistance in Mycobacterium tuberculosis
2015
Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press. - 0305-7453 .- 1460-2091. ; 70:3, s. 680-685
Tidskriftsartikel (refereegranskat) abstract
ObjectivesMutations in the β-subunit of RNA polymerase (RNAP), encoded by rpoB, are responsible for rifampicin resistance (RifR). Although many mutations in rpoB can reduce susceptibility, only a few are frequent amongst RifR clinical Mycobacterium tuberculosis (MTB) isolates. It has been suggested that there is a negative correlation between the fitness costs of RifR mutations and their respective clinical frequency, but so far comparable fitness cost measurements have only been conducted for a very limited number of RifR mutations. We tested this hypothesis using Salmonella and Mycobacterium smegmatis as model organisms.MethodsWe constructed 122 different RifR mutations in Salmonella. MICs and relative fitness costs in the presence and absence of rifampicin were determined for each mutant, including for a smaller number of RifRM. smegmatis strains. Results were compared with available mutation frequency data from clinical MTB isolates.Results(i) RifR mutations frequently found in MTB isolates have a fitness cost in Salmonella Typhimurium and M. smegmatis. (ii) Clinically frequent RifR mutations have a high rifampicin MIC. (iii) There is a strong correlation between the magnitude of the fitness cost of a RifR mutation in Salmonella Typhimurium or M. smegmatis and the frequency with which that mutation is associated with secondary (putative compensatory) mutations in RNAP of clinical MTB isolates.ConclusionsThis suggests that the success of RifR mutations in clinical MTB isolates may be dependent not only on a low initial fitness cost, but rather the results of three factors: (i) a high rifampicin MIC; (ii) a relatively low initial fitness cost; and (iii) the ability to additionally acquire compensatory mutations selected to further reduce fitness cost.
4.
Abdulkarim, Farhad, et al.
(författare)
Homologous recombination between the tuf genes of Salmonella typhimurium
1996
Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 260:4, s. 506-522
Tidskriftsartikel (refereegranskat) abstract
The genes coding for the translation factor EF-Tu, tufA and tufB are separated by over 700 kb on the circular chromosome of Salmonella typhimurium. The coding regions of these genes have 99% identity at the nucleotide level in spite of the presumed ancient origin of the gene duplication. Sequence comparisons between S. typhimurium and Escherichiacoli suggest that within each species the two tuf genes are evolving inconcert. Here we show that each of the S. typhimurium tuf genes cantransfer genetic information to the other. In our genetic system thetransfers are seen as non-reciprocal, i.e. as gene conversion events.However, the mechanism of recombination could be reciprocal, with sisterchromosome segregation and selection leading to the isolation of aparticular class of recombinant. The amount of sequence informationtransferred in individual recombination events varies, but can be close tothe entire length of the gene. The recombination is RecABCD-dependent,and is opposed by MutSHLU mismatch repair. In the wild-type, this typeof recombination occurs at a rate that is two or three orders of magnitudegreater than the nucleotide substitution rate. The rate of recombinationdiffers by six orders of magnitude between a recA and a mutS strain.Mismatch repair reduces the rate of this recombination 1000-fold. The rateof recombination also differs by one order of magnitude depending onwhich tuf gene is donating the sequence selected for. We discuss threeclasses of model that could, in principle, account for the sequencetransfers: (1) tuf mRNA mediated recombination; (2) non-allelic reciprocalrecombination involving sister chromosomes; (3) non-allelic geneconversion involving sister chromosomes, initiated by a double-strandbreak close to one tuf gene. Although the mechanism remains to bedetermined, the effect on the bacterial cells is tuf gene sequencehomogenisation. This recombination phenomenon can account for theconcerted evolution of the tuf genes.
5.
Abdulkarim, Farhad, et al.
(författare)
Missense substitutions lethal to essential functions of EF-Tu
1991
Ingår i: Biochimie. - : Elsevier BV. - 0300-9084 .- 1638-6183. ; 73:12, s. 1457-1464
Tidskriftsartikel (refereegranskat) abstract
We have used a simple selection and screening method to isolate function defective mutants of EF-Tu. From 28 mutants tested, 12 different missense substitutions, individually lethal to some essential function of EF-Tu, were identified by sequencing. In addition we found a new non-lethal missense mutation. The frequency of isolation of unique mutations suggests that this method can be used to easily isolate many more. The lethal mutations occur in all three structural domains of EF-Tu, but most are in domain II. We aim to use these mutants to define functional domains on EF-Tu.
6.
Abdulkarim, Farhad, et al.
(författare)
Mutations to kirromycin resistance occur in the interface of domains I and III of EF-Tu.GTP
1994
Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 352, s. 118-122
Tidskriftsartikel (refereegranskat) abstract
The antibiotic kirromycin inhibits protein synthesis by binding to EF-Tu and preventing its release from the ribosome after GTP hydrolysis.We have isolated and sequenced a collection of kirromycin resistant tuf mutations and identified thirteen single amino acid substitutions at sevendifferent sites in EF-Tu. These have been mapped onto the 3D structures of EF-Tu’GTP and EF-Tu.GDP. In the active GTP form of EF-Tu themutations cluster on each side of the interface between domains I and III. We propose that this domain interface is the binding site for kirromycin.
7.
Andersson, Dan, et al.
(författare)
Antibiotikaresistens: är den reversibel?
1998
Ingår i: Smittskydd: Smittskyddsinstitutets tidskrift. - 1401-0690. ; 4:1, s. 3-5
Recension (övrigt vetenskapligt/konstnärligt)
8.
Andersson, Dan I., et al.
(författare)
Antibiotic resistance and its cost : is it possible to reverse resistance?
2010
Ingår i: Nature Reviews Microbiology. - : Springer Science and Business Media LLC. - 1740-1526 .- 1740-1534. ; 8:4, s. 260-271
Forskningsöversikt (refereegranskat) abstract
Most antibiotic resistance mechanisms are associated with a fitness cost that is typically observed as a reduced bacterial growth rate. The magnitude of this cost is the main biological parameter that influences the rate of development of resistance, the stability of the resistance and the rate at which the resistance might decrease if antibiotic use were reduced. These findings suggest that the fitness costs of resistance will allow susceptible bacteria to outcompete resistant bacteria if the selective pressure from antibiotics is reduced. Unfortunately, the available data suggest that the rate of reversibility will be slow at the community level. Here, we review the factors that influence the fitness costs of antibiotic resistance, the ways by which bacteria can reduce these costs and the possibility of exploiting them.
9.
Andersson, D.I, et al.
(författare)
Antibiotikaresistens här för att stanna?
1998
Ingår i: Läkartidningen. - 0023-7205 .- 1652-7518. ; 95:37, s. 3940-3944
Forskningsöversikt (övrigt vetenskapligt/konstnärligt)
10.
Arrazuria, Rakel, et al.
(författare)
Variability of murine bacterial pneumonia models used to evaluate antimicrobial agents
2022
Ingår i: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 13
Forskningsöversikt (refereegranskat) abstract
Antimicrobial resistance has become one of the greatest threats to human health, and new antibacterial treatments are urgently needed. As a tool to develop novel therapies, animal models are essential to bridge the gap between preclinical and clinical research. However, despite common usage of in vivo models that mimic clinical infection, translational challenges remain high. Standardization of in vivo models is deemed necessary to improve the robustness and reproducibility of preclinical studies and thus translational research. The European Innovative Medicines Initiative (IMI)-funded "Collaboration for prevention and treatment of MDR bacterial infections" (COMBINE) consortium, aims to develop a standardized, quality-controlled murine pneumonia model for preclinical efficacy testing of novel anti-infective candidates and to improve tools for the translation of preclinical data to the clinic. In this review of murine pneumonia model data published in the last 10 years, we present our findings of considerable variability in the protocols employed for testing the efficacy of antimicrobial compounds using this in vivo model. Based on specific inclusion criteria, fifty-three studies focusing on antimicrobial assessment against Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii were reviewed in detail. The data revealed marked differences in the experimental design of the murine pneumonia models employed in the literature. Notably, several differences were observed in variables that are expected to impact the obtained results, such as the immune status of the animals, the age, infection route and sample processing, highlighting the necessity of a standardized model.
