Fluoroquinolones: mechanisms of action and resistance

bIdentifying the mechanism of action of new potential antibiotics is a necessary but time-consuming and costly process. Phenotypic profiling has been utilized effectively to facilitate the discovery of the mechanism of action and molecular targets of uncharacterized drugs. In this research, Raman spectroscopy was used to profile the phenotypic response of Escherichia coli to applied antibiotics. The use of Raman spectroscopy is advantageous because it is noninvasive, label free, and prone to automation, and its results can be obtained in real time. In this research, E. coli cultures were subjected to three times the MICs of 15 different antibiotics (representing five functional antibiotic classes) with known mechanisms of action for 30 min before being analyzed by Raman spectroscopy (using a 532-nm excitation wavelength). The resulting Raman spectra contained sufficient biochemical information to distinguish between profiles induced by individual antibiotics belonging to the same class. The collected spectral data were used to build a discriminant analysis model that identified the effects of unknown antibiotic compounds on the phenotype of E. coli cultures. Chemometric analysis showed the ability of Raman spectroscopy to predict the functional class of an unknown antibiotic and to identify individual antibiotics that elicit similar phenotypic responses. Results of this research demonstrate the power of Raman spectroscopy as a cellular phenotypic profiling methodology and its potential impact on antibiotic drug development research.

Section: Phenotypic Profiling By Raman Spectroscopymentioning

confidence: 72%

Phenotypic Profiling of Antibiotic Response Signatures in Escherichia coli Using Raman Spectroscopy

Athamneh

Alajlouni

Wallace

et al. 2014

“…Alanine racemase is a bacterial enzyme that catalyzes the interconversion of L-and D-alanine, which is an amino acid that represents an important component of peptidoglycan in most bacteria (51). Low concentrations of ciprofloxacin alter the structure of peptidoglycan (52). Thus, we may infer that the bacteria also overexpressed alanine racemase to repair the peptidoglycan as a defensive mechanism.…”

Section: Discussionmentioning

confidence: 99%

Structural Changes and Differentially Expressed Genes in Pseudomonas aeruginosa Exposed to Meropenem-Ciprofloxacin Combination

Siqueira

Cardoso

Caleffi-Ferracioli

et al. 2014

The effect of a meropenem-ciprofloxacin combination (MCC) on the susceptibility of multidrug-resistant (MDR) Pseudomonas aeruginosa (MRPA) clinical isolates was determined using checkerboard and time-kill curve techniques. Structural changes and differential gene expression that resulted from the synergistic action of the MCC against one of the P. aeruginosa isolates (1071-MRPA]) were evaluated using electron microscopy and representational difference analysis (RDA), respectively. The differentially expressed, SOS response-associated, and resistance-associated genes in 1071-MRPA exposed to meropenem, ciprofloxacin, and the MCC were monitored by quantitative PCR. The MCC was synergistic against 25% and 40.6% of MDR P. aeruginosa isolates as shown by the checkerboard and time-kill curves, respectively. The morphological and structural changes that resulted from the synergistic action of the MCC against 1071-MRPA were a summation of the effects observed with each antimicrobial alone. One exception included outer membrane vesicles, which were seen in a greater amount upon ciprofloxacin exposure but were significantly inhibited upon MCC exposure. Cell wall-and DNA repair-associated genes were differentially expressed in 1071-MRPA exposed to meropenem, ciprofloxacin, and the MCC. However, some of the RDA-detected, resistance-associated, and SOS response-associated genes were expressed at significantly lower levels in 1071-MRPA exposed to the MCC. The MCC may be an alternative for the treatment of MDR P. aeruginosa. The effect of this antimicrobial combination may be not only the result of a summation of the effects of meropenem and ciprofloxacin but also a result of differential action that likely inhibits protective mechanisms in the bacteria. Pseudomonas aeruginosa is a highly successful opportunistic pathogen that displays intrinsic multidrug resistance and has a great ability to acquire further resistance mechanisms (1, 2). Limited classes of antibiotics can be used for the treatment of P. aeruginosa infection (3). The emergence of multidrug-resistant (MDR) P. aeruginosa (MRPA) has prompted the search for new agents or alternative therapeutics (1, 4, 5), including antimicrobial combinations (6-9).Synergistic interactions between drugs have been investigated to improve therapeutic results, decrease the potential toxicity of antimicrobial agents, and prevent the emergence of bacterial resistance (6, 10, 11). Several studies have evaluated the effects of a meropenem-ciprofloxacin combination (MCC) in P. aeruginosa (12-14), including MDR isolates (8, 15). Despite some differences in the results, likely attributable to variations in techniques and bacterial isolates, the MCC represents a promising antipseudomonal therapeutic option (12)(13)(14). Although ␤-lactams and fluoroquinolones represent classic antimicrobials with previously known mechanisms of action, the molecular basis of synergism between these classes of drugs has not yet been elucidated.Thus, because of high rates of resistance observed in Brazilian P. ae...

“…Quinolones are good candidates because of their broad antibacterial spectrum, which includes atypical mycobacteria (16,22,25,30), together with their good tissue distribution and intracellular concentration (2). Ciprofloxacin and sparfloxacin are the only quinolones currently used against M. avium-M. intracellulare complex infection, but the incidence of strains resistant to these compounds is increasing, and there is a need for new derivatives.…”

mentioning

confidence: 99%

Prediction of Quinolone Activity against Mycobacterium avium by Molecular Topology and Virtual Computational Screening

Gozalbes

Brun-Pascaud

García-Domènech

et al. 2000

We conducted a quantitative structure-activity relationship study using a database of 158 quinolones previously tested against Mycobacterium avium-M. intracellulare complex in order to develop a model capable of predicting the activity of new quinolones against the M. avium-M. intracellulare complex in vitro. Topological indices were used as structural descriptors and were related to anti-M. avium-M. intracellulare complex activity by using the linear discriminant analysis ( Mycobacteria belonging to the Mycobacterium avium-M. intracellulare complex are responsible for opportunistic infections in immunocompromised patients, especially those with HIV infection (29), and there is a need for new drugs that can be used for treatment and prophylaxis. Quinolones are good candidates because of their broad antibacterial spectrum, which includes atypical mycobacteria (16,22,25,30), together with their good tissue distribution and intracellular concentration (2). Ciprofloxacin and sparfloxacin are the only quinolones currently used against M. avium-M. intracellulare complex infection, but the incidence of strains resistant to these compounds is increasing, and there is a need for new derivatives.In addition to in vitro and in vivo tests, which are timeconsuming for the M. avium-M. intracellulare complex, powerful methodologies for drug design and drug database screening and selection are now available (7,19). Equation systems linking structure and activity (QSAR studies) are particularly relevant, and application of the mathematical models thereby obtained to large libraries of computer-generated compounds is known as virtual computational screening (5, 24). An important feature in this method is the use of good structural descriptors that are representative of the molecular features responsible for the relevant biological activity; a very useful technique for describing molecular structure is molecular topology, a two-dimensional QSAR method which takes into account the internal atomic arrangement of compounds. The structure of each molecule is represented by specific subsets of topological indices (TIs). Klopman et al. first developed computer-based predictive models to characterize anti-M. avium-M. intracellulare complex activity (20,21,23). The aim of this study was to develop new QSAR models, based on TIs, statistical linear discriminant analysis (LDA), and multilinear regression (MLR) in order to predict the in vitro activity and MICs of quinolones against the M. avium-M. intracellulare complex. MATERIALS AND METHODSThe study involved a number of steps, which are described in the following paragraphs.Obtaining structural descriptors by molecular topology. A database of 158 quinolones with known anti-M. avium-M. intracellulare complex activities has been built up from several articles by Klopman et al. (20,21,23). Each quinolone was characterized by a set of 145 TIs specific to each molecule. We used the topological descriptors provided by MOLCONN-Z software, version 3.50 (L. H. Hall, Eastern Nazarene College, Quincy...