Identification and Characterization of Chemical Compounds that Inhibit Leucyl-tRNA Synthetase from Pseudomonas aeruginosa.

BACKGROUND: Pseudomonas aeruginosa is an opportunistic multi-drug resistance pathogen implicated as the causative agent in a high-percentage of nosocomial and community acquired bacterial infections. The gene encoding leucyl-tRNA synthetase (LeuRS) from P. aeruginosa was overexpressed in Escherichia coli and the resulting protein was characterized. METHODS: LeuRS was kinetically evaluated and the KM values for interactions with leucine, ATP and tRNA were 6.5, 330, and 3.0 µM, respectively. LeuRS was developed into a screening platform using scintillation proximity assay (SPA) technology and used to screen over 2000 synthetic and natural chemical compounds. RESULTS: The initial screen resulted in the identification of two inhibitory compounds, BT03C09 and BT03E07. IC50s against LeuRS observed for BT03C09 and BT03E07 were 23 and 15 µM, respectively. The minimum inhibitory concentrations (MIC) were determined against nine clinically relevant bacterial strains. In time-kill kinetic analysis, BT03C09 was observed to inhibit bacterial growth in a bacteriostatic manner, while BT03E07 acted as a bactericidal agent. Neither compound competed with leucine or ATP for binding LeuRS. Limited inhibition was observed in aminoacylation assays with the human mitochondrial form of LeuRS, however when tested in cultures of human cell line, BT03C09 was toxic at all concentration whereas BT03E07 only showed toxic effects at elevated concentrations. CONCLUSION: Two compounds were identified as inhibitors of LeuRS in a screen of over 2000 natural and synthetic compounds. After characterization one compound (BT03E07) exhibited broad spectrum antibacterial activity while maintaining low toxicity against human mitochondrial LeuRS as well as against human cell cultures.

Clinical Use of the Pictorial Baxter Retching Faces Scale for the Measurement of Postoperative Nausea in Children.

BACKGROUND: Because nausea is difficult to evaluate in children, vomiting is used as the objective clinical end point in managing pediatric postoperative nausea and vomiting and postdischarge nausea and vomiting (PDNV). The recently developed pictorial Baxter Retching Faces (BARF) scale has content, construct, and convergent validity in quantifying pediatric nausea intensity. We determined its clinical usefulness in assessing pediatric postoperative nausea and vomiting and PDNV, establishing the lowest age associated with consistently reliable use, the score at which patients identify a need for therapy, and the minimum clinically relevant change in scores, and examined its test-retest reliability. METHODS: We obtained subject ratings of the severity of their nausea using the BARF and visual analog scales in the preoperative, postanesthesia care unit and postdischarge phases. Changes in nausea were rated on a 5-point Likert scale, along with responses to queries of a need for rescue antiemetics at these time points. RESULTS: Children ≥6 years of age had a consistently reliable ability to use the BARF scale (132/132 [100%] vs 59/76 [77.6%] for children ≥6 and <6 years of age, respectively, Fisher exact test, P < .001). The BARF scale had excellent performance in predicting patient-perceived need for antiemetics, with a score of 4 having 80.0% sensitivity and 85.6% specificity. The minimum clinically relevant difference in BARF scores was 1.47 (95% confidence interval, 0.84-2.1). The intraclass correlation coefficient was 0.56 (95% confidence interval, 0.34-0.73).The BARF scale identified 60 of 192 (31.3%) children as having postoperative nausea in the postanesthesia care unit, with severe nausea (score >6) in 13 (6.7%). Emesis occurred in 8 (4.1%). Rescue antiemetics were administered to 16 (8.3%), including 2 with severe emesis (≥3 episodes) but in only 2 of 11 (18.2%) with severe nausea without vomiting. PDNV was reported in 39 of the 99 who returned diaries (39.4%), with nausea in 34 (34.3%), severe nausea in 15 (15.2 %), and emesis in 16 (16.2%). CONCLUSIONS: The pictorial BARF scale is easy to use in the clinical setting by children ≥6 years of age, has a minimum clinically relevant difference of 1.47, with scores of 4 or higher associated with a patient-identified need for rescue antiemetics. Assessment of postoperative nausea by the BARF scale has shown that clinically significant nausea occurs frequently in children but is not always treated unless accompanied by vomiting.

A prospective, randomized, double-blind trial of intranasal dexmedetomidine and oral chloral hydrate for sedated auditory brainstem response (ABR) testing.

BACKGROUND: Dexmedetomidine is increasingly used by various routes for pediatric sedation. However, there are few randomized controlled trials comparing the efficacy of dexmedetomidine to other commonly used sedatives. AIM: To compare the efficacy of sedation with intranasal dexmedetomidine to oral chloral hydrate for auditory brainstem response (ABR) testing. METHODS: In this double-blind, double-dummy study, children undergoing ABR testing were randomized to receive intranasal dexmedetomidine 3 mcg · kg(-1) plus oral placebo (Group IN DEX) or oral chloral hydrate 50 mg · kg(-1) plus intranasal saline placebo (Group CH). We recorded demographic data, times from sedative administration to start and completion of testing, quality of sedation, occurrence of predefined adverse events, discharge times, and return to baseline activity on the day of testing. RESULTS: Testing completion rates with a single dose of medication were higher in the IN DEX group (89% vs 66% for CH, odds ratio with 95% confidence intervals 4.04 [1.3-12.6], P = 0.018). The median [95% CI)] time to successful testing start was shorter (25 [20-29] min vs 30 [20-49] min for IN DEX and CH, respectively, log rank test P = 0.02) and the proportion of children whose parents reported a return to baseline activity on the day of testing was greater for the IN DEX than the CH group (89% vs 64%, OR [95% CI] 4.71 [1.34-16.6], P = 0.02). There were no major adverse events in either group and no significant differences in the incidence of minor events. CONCLUSION: Intranasal dexmedetomidine is an effective alternative to oral chloral hydrate sedation for ABR testing, with the advantages of a higher incidence of testing completion with a single dose, shorter time to desired sedation level, and with significantly more patients reported to return to baseline activity on the same day.