Betty H. Yagi

3-Arylpiperidines as potentiators of existing antibacterial agents

Important resistance patterns in Gram-negative pathogens include active efflux of antibiotics out of the cell via a cellular pump and decreased membrane permeability. A 3-arylpiperidine derivative (1) has been identified by high-throughput assay as a potentiator with an IC(50) approximately 90 microM. This report details the evaluation of the tether length, aryl substitution and the importance of the fluorine on antibiotic accumulation. Evaluation of various tether lengths demonstrated that the two-carbon tethered analogues are optimal. Removal of the fluorine has a modest effect on antibiotic accumulation and the defluorinated analogue 17 is equally potent to the original lead 1.

Carbon–carbon-linked (pyrazolylphenyl)oxazolidinones with antibacterial activity against multiple drug resistant gram-positive and fastidious gram-negative bacteria

In an effort to expand the spectrum of activity of the oxazolidinone class of antibacterial agents to include Gram-negative bacteria, a series of new carbon-carbon linked pyrazolylphenyl analogues has been prepared. The alpha-N-substituted methyl pyrazole (10alpha) in the C3-linked series exhibited very good Gram-positive activity with MICs <or=0.5-1 microg/mL and moderate Gram-negative activity with MICs=2-8 microg/mL against Haemophilus influenzae and Moraxella catarrhalis. This analogue was also found to have potent in vivo activity with an ED(50)=1.9 mg/kg. Beta-substitution at the C3-linked pyrazole generally results in a loss of activity. The C4-linked pyrazoles are slightly more potent than their counterparts in the C3-linked series. Most of the analogues in the C4-linked series exhibited similar levels of activity in vitro, but lower levels of activity in vivo than 10alpha. In addition, incorporation of a thioamide moiety in selected C4-linked pyrazole analogues results in an enhancement of in vitro activity leading to compounds several times more potent than eperezolid, linezolid and vancomycin. The thioamide of the N-cyanomethyl pyrazole analogue (34) exhibited an exceptional in vitro activity with MICs of <or= 0.06-0.25 microg/mL against Gram-positive pathogens and with MICs of 1 microg/mL against fastidious Gram-negative pathogens.

Synthesis and antibacterial activity of new tropone-substituted phenyloxazolidinone antibacterial agents 2. Modification of the phenyl ring — the potentiating effect of fluorine substitution on in vivo activity

Abstract Various electron-withdrawing groups were incorporated into the meta position of tropone-substituted 3-phenyl-2-oxazolidinones and their influence on antibacterial activity examined. Consideration of in vitro and in vivo test results indicated that one or two fluorine atoms flanking the para tropone appendage is the optimum arrangement for these compounds. Synthetic routes to enantiomerically enriched analogues are reported.

Synthesis and antibacterial activity of new tropone-substituted phenyloxazolidinone antibacterial agents 1. Identification of leads and importance of the tropone substitution pattern

Abstract Incorporation of a substituted tropone moiety into the para position of suitably functionalized 3-phenyl-2-oxazolidinones affords novel and potent antibacterial agents. The effect of the tropone regioisomer and its attendant substituents on antibacterial activity is discussed. Analogues such as 11c and 13b display in vitro and in vivo activity approaching that of the current clinical benchmark, vancomycin.

An in vitro time-kill assessment of linezolid and anaerobic bacteria

Linezolid is a novel oxazolidinone antibacterial agent active against staphylococci (including methicillin-resistant strains), enterococci (including vancomycin-resistant strains), streptococci (including penicillin-intermediate and -resistant Streptococcus pneumoniae), and other aerobic and facultative bacteria. The agent has also demonstrated activity against a broad spectrum of Gram-positive and Gram-negative anaerobic bacteria. Previous time-kill assessments have shown linezolid to be generally bacteriostatic against staphylococci and enterococci, and bactericidal against streptococci. In this study, an anaerobic glovebox technique was employed to conduct time-kill assessments for four strains of anaerobic Gram-positive, and seven strains of anaerobic Gram-negative bacteria. The time-kill experiment was performed using Anaerobe Broth medium. The drugs were tested at four-fold the minimum inhibitory concentration (MIC), or at the higher concentration of 8mg/L for linezolid, 2mg/L for clindamycin, and 8mg/L for metronidazole. Samples for viable count were taken at 0, 6, and 24h, and plated using the Bioscience International Autospiral DW. Exposure of samples to the aerobic environment during plating was held to less than 30min. Plates were counted after a 48h anaerobic incubation (37 degrees C). The species tested included Bacteroides fragilis (2), B. distasonis, B. thetaiotaomicron, Fusobacterium nucleatum, F. varium, Prevotella melaninogenica, Clostridium perfringens, Eubacterium lentum and Peptostreptococcus anaerobius (2). The activity of linezolid was compared to that of metronidazole and clindamycin, two standard anti-anaerobe agents. As expected, the control agents were very active in these assays. Metronidazole yielded log(10)CFU/mL reductions of 3.0 or greater for nine of ten strains; clindamycin yielded log(10)CFU/mL reductions of 2.0 or greater for six of 11 strains, and 3.0 or greater for three strains. Linezolid also produced significant in vitro killing in this model achieving log(10)CFU/mL reductions of 2.0 or greater for six of 11 strains, and 3.0 or greater for four strains. The profile of activity was similar to that of clindamycin indicating that additional developmental studies of linezolid with anaerobic bacteria are warranted.