Objective To investigate whether ultrasound (US)-targeted microbubble (MB) destruction (UTMD) can influence the biofilm and bacteria in morphology.Methods Twenty-hour biofilms of Staphylococcus epidermidis RP62A were treated with US or UTMD.The acoustic intensity was 0.5-1.5W/cm2,the duty cycle was 50％ and the duration was 10 minutes.After treatment,the absorbance values (A570) of biofilms stained with the crystal violet were measured to assess the biofilm density.The biofilms were observed with macroscopy and light microscopy.The biofilms were examined by confocal laserscanning microscopy (CLSM) and scanning electron microscopy (SEM).Results A thick and compact biofilm was observed in the untreated control group,and there were no obvious micropores in biofilms under macrology and light micrology.Although there were no significant changes under macroscopy in both biofilms treated with US only and UTMD with 0.5 W/cm2 acoustic intensity,interestingly,many micropores could be found under microscopy.The diameters of micropores increased with increasing acoustic intensity,and the micropores in biofilms treated with UTMD were bigger than those treated with US-only in the same condition of acoustic intensity (P ＜0.05).The largest diameters of micropores were up to 1 mm in biofilms treated with UTMD using 1.5 W/cm2 (P ＜0.05).The biofilm density (A570 value) decreased with increasing of the acoustic intensity,and the values in UTMD group of 1.5 W/cm2 were the lowest (P ＜ 0.05).Micropores also could be observed under CLSM.There were no obvious dead bacteria in biofilms treated with US and UTMD compared with untreated control group (P ＞0.05).Under SEM,the shape of bacteria in biofilms treated with US and UTMD became irregular,and many rounded projection could be observed in the surface of the bacteria treated with UTMD.Conclusions US and UTMD can produce micropores in biofilms,which might help to promote antibiotic activity against biofilms

Objective To evaluate the efficacy and safety of colistimethate sodium (CMS) for the treatment of critical patients infected by pan-drug resistantAcinetobacter baumannii (PDR-AB) or pan-drug resistant Pseudomonas aeruginosa (PDR-PA).Methods 321 isolates of PDR-AB and 204 isolates of PDR-PA from critical patients admitted to 35 intensive care units (ICUs) of grade two or above were collected from the Anhui Antimicrobial Resistance Investigation Net (AHARIN) program from September 2012 to September 2015, while the minimal inhibitory concentrations (MIC) of colistin were determined by the E-test. A series of Monte Carlo simulations was performed for CMS regimens (1 MU q8h, 2 MU q8h, and 3 MU q8h, and MU meant a million of unit), and the probability of achieving a 24-hour area under the drug concentration time curve (AUC24)/MIC ratio > 60 and risk of nephrotoxicity for each dosing regimen was calculated. Each simulation was run over three CLCr ranges: < 60, ≥ 60-90, ≥ 90-120 mL/min. The probability of target attainment (PTA)for the AUC24/MIC ratio was calculated using the partial MIC value, while the cumulative fraction of response (CFR) was determined by integrating each PTA with the MIC distributions, the value greater than or equal to 90% or more than 80% was set as the optimal dosing regimen or suboptimal dosing regimen respectively. The probability of average 24-hour serum concentrations up to 4 mg/L for three dosage regimens was used to predict the risks of nephrotoxicity.Results All 321 isolates of PDR-AB and 204 isolates of PDR-PA were susceptible to colistin, the MIC50/90 against PDR-AB were 0.5mg/L and 1.0 mg/L, and those against PDR-PA were 0.5 mg/L and 1.5 mg/L, respectively. When recommended dose (1 MU q8h) was used for patients with CLCr of < 60 mL/min, high CFR value (89.78% for PDR-AB, 81.06% for PDR-PA) were obtained, but with a high risks of nephrotoxicity (> 32.51%). Moreover, low value of PTA (< 66.56%) was yielded for isolates with MIC of ≥ 1 mg/L. Recommended dose also yielded a low CFR value (56.97%-69.31% for PDR-AB, 44.76%-56.94% for PDR-PA) in patients with CLCr of ≥ 60-120 mL/min. When dose was increased to 2 MU q8h, CFR (77.45%-92.87%) and the risks of nephrotoxicity (< 0.15%) was optimal for patients with CLCr ≥ 60-120 mL/min, but low value of PTA (< 75.36%) was also yielded for isolates with MIC of ≥ 1 mg/L. The most aggressive dose of 3 MU q8h provided high CFR (> 89.24%) even in patients with CLCr ≥ 90-120 mL/min, and PTA was < 76.20% only for isolates with MIC of ≥ 1.5 mg/L, but this dosing scheme was associated with unacceptable risks of nephrotoxicity (> 33.68%).Conclusion Measurement of MIC, individualized CMS therapy and therapeutic drug-level monitoring should be considered to achieve the optimal drug exposure and ensure the safety of CMS.