Dong Chai

Colistin resistance of Acinetobacter baumannii: clinical reports, mechanisms and antimicrobial strategies

Colistin is the last resort for treatment of multidrug-resistant Acinetobacter baumannii. Unfortunately, resistance to colistin has been reported all over the world. The highest resistance rate was reported in Asia, followed by Europe. The heteroresistance rate of A. baumannii to colistin is generally higher than the resistance rate. The mechanism of resistance might be loss of lipopolysaccharide or/and the PmrAB two-component system. Pharmacokinetic/pharmacodynamic studies revealed that colistin monotherapy is unable to prevent resistance, and combination therapy might be the best antimicrobial strategy against colistin-resistant A. baumannii. Colistin/rifampicin and colistin/carbapenem are the most studied combinations that showed promising results in vitro, in vivo and in the clinic. New peptides showing good activity against colistin-resistant A. baumannii are also being investigated.

Effectiveness and safety of macrolides in cystic fibrosis patients: a meta-analysis and systematic review

OBJECTIVES To evaluate the efficacy and safety of macrolides in cystic fibrosis (CF). METHODS Randomized controlled trials (RCTs) of macrolides for the treatment of CF published in PubMed, the Cochrane Library and Embase were searched. Application of inclusion and exclusion criteria, data extraction, and assessment of methodological quality were independently performed in duplicate. The primary efficacy outcome was the impact on the deterioration of lung function (changes in FEV(1) and FVC). Safety outcomes included adverse events and mortality. RESULTS Eight RCTs (seven with azithromycin and one with clarithromycin) were found in the systematic review and six RCTs with azithromycin (654 patients) were included in the meta-analysis. Azithromycin treatment showed a significant increase in FEV(1)% (3.22%, 95% CI = 1.38-5.06, P = 0.0006, I(2) = 0%) and FVC% (3.23%, 95% CI = 1.62-4.85, P < 0.0001, I(2) = 0%) compared with placebo. In individuals with baseline Pseudomonas aeruginosa colonization, both FEV(1)% (4.80%, 95% CI = 1.66-7.94, P = 0.003, I(2) = 42%) and FVC% (4.74%, 95% CI = 1.92-7.57, P = 0.001, I(2) = 0%) increased significantly. The incidence rates of the main side effects (cough, headache, abdominal pain, vomiting, nausea and diarrhoea) were not significantly different between the azithromycin-treated group and the placebo group. The RCT of clarithromycin, involving 18 patients, showed its effects on clinical improvement; however, the small sample size made comparisons with azithromycin difficult. CONCLUSIONS Long-term use of azithromycin can improve lung function, especially for P. aeruginosa-colonized CF patients. There was no evidence of increased adverse events with azithromycin. More data are needed to verify the best azithromycin regimen and to evaluate other macrolides in CF patients.

Weight-adjusted versus fixed dose of linezolid for Chinese healthy volunteers of higher and lower body weight: a Phase I pharmacokinetic and pharmacodynamic study

Objectives: The objective was to evaluate the pharmacokinetic and pharmacodynamic properties of a single intravenous fixed dose compared with a weight-adjusted dose of linezolid. Methods: A Phase I, comparative clinical trial was conducted involving 20 healthy male Chinese volunteers, assigned into low weight (LW) (50 kg < weight ≤ 55 kg) and high weight (HW) (≥ 80 kg) groups. All subjects were administrated single dose of linezolid (600 mg/30 min) and, after 72 h washout period, another single-dose (10 mg/kg/30 min). Plasma linezolid concentrations were measured by liquid chromatography-tandem mass spectrometry. A Monte Carlo simulation was used to evaluate the probability of pharmacodynamic target attainment (PTA). Results: With 600 mg dose, plasma concentrations in LW group were much higher than that in HW group. A persistent serum inhibitory activity was observed in LW group; the inhibitory activity was lower in HW group. The PTA in HW group was lower than in LW group. For 10 mg/kg dose, both HW and LW groups had similar plasma concentrations. The HW and LW groups had similar serum inhibitory effects. The PTA in HW and LW groups also showed no difference. Conclusions: Our findings suggest that a weight-adjusted, 10 mg/kg regimen of linezolid may be more appropriate than fixed dosing for patients of different body weight.

Immediate hematological toxicity of linezolid in healthy volunteers with different body weight: a phase I clinical trial

Linezolid is an important therapeutic option for infections from multi-drug resistant Gram-positive pathogens. However, prolonged linezolid treatment (>14 days) is considered to increase the risk of hematological adverse events. We aimed to evaluate the hematological safety profile of an i.v. single dose of linezolid in healthy volunteers of different body weight. We conducted a phase I clinical trial involving 20 healthy male Chinese volunteers that received an i.v. single dose of linezolid (600 mg). The study participants were assigned to two groups: low-weight (LW) group: 50 kg <body weight ⩽55 kg and high-weight (HW) group: ⩾80 kg. A significant decrease in the hemoglobin (Hb) levels and red blood cell (RBC) count was observed at the end of administration of the study drug in both groups. White blood cell (WBC) count was simultaneously decreased in the HW group. In the LW group, Hb levels and RBC count were also significantly decreased at 5, 7 and 24 h. In the HW group, both values were significantly decreased at 5 h. At 48 h all values were normal. The observed decreases were numerically higher in the LW group compared with the HW group. Yet, no statistical significance was noted. No difference was observed in the platelet count in both the groups. Our findings suggest that linezolid-associated hematological toxicity may also occur shortly after the i.v. administration of the drug in both LW and HW healthy volunteers. Early initiated continuous monitoring of hematological values and linezolid dosage adjustment for body weight are recommended.

Efficacy of Linezolid and Fosfomycin in Catheter-Related Biofilm Infection Caused by Methicillin-Resistant Staphylococcus aureus

As long-standing clinical problems, catheter-related infections and other chronic biofilm infections are more difficult to treat due to the high antibiotic resistance of biofilm. Therefore, new treatments are needed for more effective bacteria clearance. In this study, we evaluated the antibacterial activities of several common antibiotics alone and their combinations against biofilm-embedded methicillin-resistant staphylococcus aureus (MRSA) infections, both in vitro and in vivo. In brief, fosfomycin, levofloxacin, and rifampin alone or in combination with linezolid were tested in vitro against planktonic and biofilm-embedded MRSA infection in three MRSA stains. The synergistic effects between linezolid and the other three antibiotics were assessed by fractional inhibitory concentration index (FICI) and time-kill curves, where the combination of linezolid plus fosfomycin showed the best synergistic effect in all strains. For further evaluation in vivo, we applied the combination of linezolid and fosfomycin in a catheter-related biofilm rat model and found that viable bacteria counts in biofilm were significantly reduced after treatment (P < 0.05). In summary, we have shown here that the combination of linezolid and fosfomycin treatment had improved therapeutic effects on biofilm-embedded MRSA infection both in vitro and in vivo, which provided important basis for new clinical therapy development.

Development and validation of a highly sensitive LC‐MS/MS method for quantitation of bivalirudin in human plasma: application to a human pharmacokinetic study

A sensitive, specific and simple LC-MS/MS method was developed for the identification and quantification of bivalirudin in human plasma using diazepam as an internal standard (IS). The API-4000 LC-MS/MS was operated under multiple-reaction monitoring mode using electrospray ionization. The sample preparation consisted of an easy protein precipitation sample pretreatment with methanol. Chromatographic separation was achieved on a Zorbax Eclipse plus C18 100 × 2.1 mm column with a mobile phase of water-methanol-0.1% formic acid. The analytes were detected with a triple quadrupole Quantum Access with positive ionization. Ions monitored in the multiple-reaction monitoring mode were m/z 1091 → 650 for bivalirudin (at 2.70 min) and m/z 285 → 193 for diazepam (at 3.85 min). The developed method was validated in human plasma with a lower limit of quantitation of 20 µg/L for bivalirudin. A linear response function was established for the range of concentrations 20-10,000 µg/L (r > 0.998) for bivalirudin. The intra- and inter-day precision values for bivalirudin met the acceptance criteria as per US Food and Drug Administration guidelines. Bivalirudin was stable in the battery of stability studies, viz. bench-top, freeze-thaw cycles and long-term stability. The developed assay method was applied to an intravenous administration study in humans.

Single‐dose pharmacokinetics and safety of iptakalim hydrochloride in Chinese healthy volunteers

Objectives  To investigate the safety, pharmacokinetics and food effect of iptakalim in healthy adult Han Chinese volunteers.

Penetration of ciprofloxacin and amikacin into the alveolar epithelial lining fluid of rats with pulmonary fibrosis

ABSTRACT We determined the concentration-time profiles of ciprofloxacin and amikacin in serum and alveolar epithelial lining fluid (ELF) of rats with or without pulmonary fibrosis and investigated the effect of pulmonary fibrosis on the capacity for penetration of antimicrobials into the ELF of rats. Pulmonary fibrosis was induced in rats with a single intratracheal instillation of bleomycin. After intravenous injection of ciprofloxacin or amikacin, blood and bronchoalveolar lavage fluid samples were collected. Urea concentrations in serum and lavage fluid were determined using an enzymatic assay. Ciprofloxacin and amikacin concentrations were determined by high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry, respectively. The mean ratio of ELF to plasma concentrations of ciprofloxacin at each time point in the normal group did not significantly differ from that in the pulmonary fibrosis group. However, the ratio of the ciprofloxacin area under the concentration-time curve from 0 to 24 h (AUC0–24) in ELF to the AUC0–24 in plasma was 1.02 in the normal group and 0.76 in the pulmonary fibrosis group. The mean ELF-to-plasma concentration ratios of amikacin at each time point in the normal group were higher than those in the pulmonary fibrosis group, reaching a statistically significant difference at 1, 2, and 4 h. The ratio of the AUC0–24 in ELF to the AUC0–24 in plasma was 0.49 in the normal group and 0.27 in the pulmonary fibrosis group. In conclusion, pulmonary fibrosis can influence the penetration of antimicrobials into the ELF of rats and may have a marked effect on the penetration of amikacin than that of ciprofloxacin.

Clinical features, epidemiology and outcomes of infective endocarditis at a general hospital in China: A 10-year survey

This study retrospectively investigated the epidemiology, treatment and outcome of infective endocarditis (IE) in Peoples Liberation Army (PLA) General Hospital from 1997-2007. Totally, 65 cases were included. The results showed that bacteria were isolated from 63.08% of the IE cases. Staphylococcus was the main pathogen causing IE (43.9%), followed by Streptococcus (41.5%). Surgical treatment was performed for 81.5% (53/65) of the IE patients. The most common surgery was aortic valve replacement conducted for 58.18% of the IE patients. Six patients (9.23%) died during hospitalization. Antimicrobial agents including penicillin, vancomycin and quinolones were most frequently utilized. We concluded that early diagnosis, timely surgery and appropriate utilization of antibiotics can improve the prognosis of IE patients.