Sequential intraventricular injection of tigecycline and polymyxin B in the treatment of intracranial Acinetobacter baumannii infection after trauma: a case report and review of the literature

Background:Intracranial infection after craniotomy is one of the most serious postoperative complications,especially multidrug-resistant(MDR)or extensively drug-resistant(XDR)bacterial meningitis,and strongly affects the prognosis of patients.Current treatment experience regarding these infections is scarce.Case presentation:We report a case of severe intracranial infection of XDR Acinetobacter baumannii(A.baumannii)that was treated by intravenous(IV)injection,sequential intraventricular(IVT)injection of tigecycline and polymyxin B,and other anti-infective drugs.Good results were obtained,and the patient was eventually discharged from the hospital.This case is characterized by intracranial infection.Conclusions:The polymyxin B IV+IVT pathway is an ideal treatment strategy for XDR A.baumannii.The tigecycline IVT pathway is also a safe treatment option.

Porphyromonas gingivalis Resistance to Polymyxin B Is Determined by the Lipid A 4’-Phosphatase, PGN_0524

Aim To elucidate the genetic basis for the pronounced resistance that the oral pathogen, Porphyromonas gingivalis （P. gingivalis）, exhibits towards the cationic antimicrobial peptide, polymyxin B. Methodology A genetic screen of P. gingivalis clones generated by a Tn4400-based random insertion mutagenesis strategy was performed to identify bacteria harboring novel genetic mutations that render P. gingivalis susceptible to killing by the cationic antimicrobial peptide, polymyxin B （PMB, 50μg·mL^-1）. Results P. gingivalis （ATCC 33277） is unusually resistant to the cationic antimicrobial peptide, PMB at relatively high concentrations （200μg·mL^-1）. Approximately 2,700 independent Tn4400 ＇-derived mutants ofP. gingivalis were examined for increased sensitivity to PMB killing at a relatively low dose （50 μg·mL^-1）. A single PMB-sensitive mutant was obtained in this phenotypic screen. We determined that the Tn4400＇ transposon was integrated into the gene encoding the lipid A 4＇-phosphatase, PGN 0524, demonstrating that this insertion event was responsible for its increased susceptibility of this clone to PMB-dependent killing. The resulting mutant strain, designated 0524-Tn4400＇, was highly sensitive to PMB killing relative to wild-type P. gingivalis, and exhibited the same sensitivity as the previously characterized strain, 0524KO, which bears a genetically engineered deletion in the PGN_0524 locus. Positive ion mass spectrometric structural （MALDI-TOF MS） analyses revealed that lipid A isolates from 0524-Tn4400＂ and 0524KO strains displayed strikingly similar MALDI-TOF MS spectra that were substantially different from the wildtype P gingivalis lipid A spectrum. Finally, intact 0524- Tn4400＇ and 0524KO mutant bacteria, as well as their corresponding LPS isolates, were significantly more potent in stimulating Toll-like receptor 4 （TLR4）-dependent E-selectin expression in human endothelial cells relative to intact wild-type P.. gingivalis or its corresponding LPS isolate. Conclusion The combined molecular evidence provided in this report suggests that PGN 0524, a lipid A 4＇-phosphatase, is the sole genetic element conferring the ability of the periodontopathogen, P. gingivalis, to evade the killing activity of cationic antimicrobial peptides, such as PMB. These data strongly implicate PGN_0524 as a critical virulence factor for the ability of P.. gingivalis to evade front-line host innate defenses that are dependent upon cationic antimicrobial peptide activity and TLR 4 sensing.

Direct hemoperfusion with a polymyxin B-immobilized cartridge in intestinal warm ischemia reperfusion

AIM： To investigate the effectiveness of direct hemoperfusion with polymyxin B-immobilized fibers （DHPPMX therapy） on warm ischemia-reperfusion （I/R） injury of the small intestine.METHODS： The proximal jejunum and distal ileum of mongrel dogs were resected. Warm ischemia was performed by clamping the superior mesenteric artery （SMA） and vein （SMV） for 2 h. Blood flow to the proximal small intestine was restored 1 h after reperfusion, and the distal small intestine was used as a stoma. The experiment was discontinued 6 h after reperfusion. The dogs were divided into two groups： the DHP-PMX group （n = 6, DHP-PMX was performed for 180 min; from 10 min prior to reperfusion to 170 rain after reperfusion） and the control group （n = 5）. The rate pressure product （RPP）, SMA blood flow, mucosal tissue blood flow, and intramucosal pH （pHi） were compared between the two groups. The serum interleukin （IL）-10 levels measured 170 min after reperfusion were also compared.RESULTS： The RPP at 6 h after reperfusion was significantly higher in the PMX group than in the control group （12174 ± 1832 mmHg/min vs 8929 ± 1797 mmHg/min, P 〈 0.05）. The recovery rates of the SMA blood flow at I and 6 h after reperfusion were significantly better in the PMX group than in the control group （61%±7% vs 44% ±4%, P 〈 0.05, and 59%±5% vs 35%±5%, P 〈 0.05, respectively）. The recovery rate of the mucosal tissue blood flow and the pHi levels at 6 h after reperfusion were significantly higher in the PMX group （61%±8% vs 31%±3%, P 〈 0.05 and 7.91±0.06 vs 7.69±0.08, P 〈 0.05, respectively）. In addition, the serum IL-IO levels just before DHP-PMX removal were significantly higher in the PMX group than in the control group （1 569 ± 253 pg/mL vs 211± 40 pg/mL, P 〈 0.05）.CONCLUSION： DHP-PMX therapy reduced warm I/R injury of the small intestine. IL-10 may play a role in inhibiting I/R injury during DHP-PMX therapy.

Hemoperfusion with polymyxin B-immobilized fiber column improves liver function after ischemia-reperfusion injury

AIM： To investigate the usefulness of direct hemoperfusion with a polymyxin B-immobilized fiber column （DHP-PMX therapy） for warm hepatic ischemia-reperfusion （I/R） injury after total hepatic vascular exclusion （THVE） using a porcine model. METHODS： Eleven Mexican hairless pigs weighing 22-38 kg were subjected to THVE for 120 min and then observed for 360 min. The animals were divided into two groups randomly： the DHP-PMX group （n = 5） underwent DHP-PMX at a flow rate of 80 mL/min for 220 min （beginning 10 rain before reperfusion）, while the control group did not （n = 6）. The rate pressure product （RPP）： heart rate x end-systolic arterial blood pressure, hepatic tissue blood flow （HTBF）, portal vein blood flow （PVBF）, and serum aspartate aminotransferase （AST） levels were compared between the two groups. RESULTS： RPP and HTBF were significantly （P 〈 0.05） higher in the DHP-PMX group than in the control group 240 and 360 min after reperfusion. PVBF in the DHP-PMX group was maintained at about 70% of the flow before ischemia and differed significantly （P 〈 0.05） compared to the control group 360 min after reperfusion. The serum AST increased gradually after reperfusion in both groups, but the AST was significantly （P 〈 0.05） lower in the DHP-PMX group 360 min after reperfusion. CONCLUSION： DHP-PMX therapy reduced the hepatic warm I/R injury caused by THVE in a porcine model.

Polymyxin B hemoperfusion as a feasible therapy after source control in abdominal septic shock

BACKGROUND Polymyxin B hemoperfusion(PMX-HP)has been used as a treatment for intraabdominal septic shock by absorbing and removing endotoxins of gram-negative bacilli.AIM To investigate the clinical efficacy of PMX-HP in patients with gram-negative septic shock who underwent abdominal surgery.METHODS From January 2012 to December 2018,patients who had septic shock secondary to peritonitis were enrolled.They were classified into PMX-HP treated and control groups based on postopreative intervention using PMX-HP.The clinical outcomes were compared using 1:1 propensity score matching methods to balance the overall distribution between the two groups.RESULTS After propensity score matching,40 patients were analyzed(20 patients in the PMX group and 20 patients in the control group).The scores of total Sequential Organ Failure Assessment(SOFA)score,renal SOFA and coagulation SOFA were significantly improved in the PMX group but not in the control group.(from 11.2±5.8 to 4.7±3.5 in PMX group vs 10.0±4.0 to 8.7±7.3 in control group,P=0.047 from 2.6±1.0 to 0.7±1.0 in PMX group vs 2.6±1.5 to 2.8±1.6 in control group,P=0.000,from 1.6±1.5 to 1.3±1.3 in PMX group vs 1.2±1.2 to 2.8±1.8 in control group,P=0.014,respectively).Further,the length of intensive care unit(ICU)stay was significantly shorter in PMX group.However,no statistically significant difference was found in ICU mortality(50%in PMX group vs 50%in control group).CONCLUSION PMX-HP is a feasible adjunct treatment for peritonitis in ICU patients with peritonitis for improved organ impairment and to stabilize hemodynamics.It would be helpful to enhance clinical outcomes especially in patients with complete elimination of the source of gram-negative bacilli infection by surgical procedure accompanied with conventional treatment of sepsis.

Polymyxin B-immobilized fiber columns:A column to breathe new life into the treatment of interstitial lung disease?

Acute exacerbations of idiopathic pulmonary fibrosis(IPF) is a severe respiratory condition with high mortality rate. Direct hemoperfusion with polymyxin B-immobilized fiber columns(PMX-DHP) was originally introduced for the treatment of septic shock. Application of PMX-DHP to the treatment of acute exacerbations of IPF may improve oxygenation and survival of the patients with the disease. In addition to acute exacerbations of IPF, PMXDHP has been applied to acute respiratory failure fromvarious causes; an amyopathic dermatomyositis patient who developed rapidly progressive interstitial lung disease(ILD) with elevated anti-CADM-140/MDA5 autoantibody and a patient with severe amiodarone pulmonary toxicity. It is also demonstrated that PMX-DHP performed on the first day of steroid pulse therapy may improve the prognosis of patients with rapidly progressive ILDs in a case-control setting. PMX treatment decreases not only various circulating molecules but also inflammatory cells, in particular activated monocytes, producing such mediators. Although the incidence of acute exacerbations of IPF is too low for proper randomization, in order to test the effects of PMX-DHP on the disease, a cohort or casecontrol analytic study needs to be conducted, preferably from more than one center or research group.

Impact of Polymyxin Resistance on Virulence and Fitness among Clinically Important Gram-Negative Bacteria

Humanity is facing an enormous and growing worldwide threat from the emergence of multi-drug-resistant(MDR)Gram-negative bacteria such as Escherichia coli,Klebsiella pneumoniae,and Acinetobacter baumannii.Polymyxin B and E(colistin)constitute the last-line therapies for treating MDR Gram-negative bacteria.Polymyxin is a cationic antibacterial peptide that can destroy the outer membrane of Gram-negative bacteria.With the increasing clinical application of polymyxin,however,there have been many reports of the occurrence of polymyxin-resistant Gram-negative bacteria.This resistance is mainly mediated by the modification or complete loss of lipopolysaccharide(LPS).LPS is also a virulence factor of Gram-negative bacteria,and alterations of LPS may correlate with virulence.Although it is generally believed that the biological costs associated with drug resistance may enable benign susceptible bacteria to overcome resistant bacteria when antibiotic pressure is reduced,some studies have shown that polymyxin-resistant bacteria are associated with higher virulence and greater fitness compared with their susceptible counterparts.To predict the development of polymyxin resis-tance and evaluate interventions for its mitigation,it is important to understand the relative biological cost of polymyxin resistance compared with susceptibility.The impact of polymyxin resistance mecha-nisms on the virulence and fitness of these three Gram-negative bacteria are summarized in this review.

Polymyxin NP实验筛查肠杆菌科多黏菌素耐药菌株临床评价

目的评价Polymyxin NP实验筛查多黏菌素耐药肠杆菌科细菌的临床价值。方法采用Polymyxin NP实验对461株肠杆菌科临床分离株进行初步筛查,采用微量肉汤稀释法测定菌株对多黏菌素的最小抑菌浓度(MIC),采用纸片扩散法进行临床常用抗菌药物的体外药物敏感性试验,采用聚合酶链反应(PCR)扩增多黏菌素耐药相关基因pmrA、pmrB、phoP、phoQ、mgrB和mcr,并进行测序,采用实时定量聚合酶链反应(qRT-PCR)检测多黏菌素耐药相关双组分调控元件pmrA/pmrB、pmrD/pmrF、PhoP/PhoQ表达水平。结果461株肠杆菌科细菌中,13株多黏菌素耐药株Polymyxin NP实验在2 h内均表现为阳性,多黏菌素敏感菌株表现为阴性。13株多黏菌素耐药菌株中,10株肺炎克雷伯菌主要由mgrB基因插入突变及双组分调控系统pmrA/pmrB和PhoP/PhoQ突变或表达上调引起,1株大肠埃希菌由质粒携带的mcr-1基因介导,2株阴沟肠杆菌的耐药机制尚不清楚。多黏菌素耐药菌株和敏感菌株对多种常用抗菌药物的耐药率差异无统计学意义(P>0.05)。结论Polymyxin NP实验操作简便、结果可靠,可用于各种机制介导的多黏菌素耐药肠杆菌科细菌的临床筛查,为临床抗感染治疗和耐药防控提供依据。

Expert Consensus on Polymyxin Antimicrobial Susceptibility Testing and Clinical Interpretation

The polymyxins are important antimicrobial agents against antibiotic-resistant gram-negative bacilli.In 2020,the Clinical and Laboratory Standards Institute modified the clinical breakpoints for polymyxin susceptibility test by eliminating the"susceptible"interpretive category,only reporting intermediate(≤2 mg/L)and resistant(≥4 mg/L).However,the European Committee on Antimicrobial Susceptibility Testing recommended the use of clinical breakpoints of W2 mg/L as susceptible and>2 mg/L as resistant.The first-line laboratorians and clinicians in China have been perplexed by the inconsistence of international polymyxin clinical breakpoints and discouraged by the difficulty of conducting polymyxin susceptibility testing.Therefore,it is urgently needed to make it clear for the laboratorians in China to know how to accurately carry out polymyxin susceptibility testing and standardize the interpretation of susceptibility testing results.To this end,the experts from relevant fields were convened to formulate this consensus statement on the testing and clinical interpretation of polymyxin susceptibility.Relevant recommendations are proposed accordingly for laboratorians and clinicians to streamline their daily work.

Preliminary study on the safety and efficacy of a new polymyxin B-immoblized resin column in treatment of LPS-induced sepsis beagles

Background:This study aims to assess the safety and efficacy of direct hemoperfu-sion using a new polymyxin B-immobilized resin column(disposable endotoxin ad-sorber,KCEA)in an endotoxin/lipopolysaccharide(LPS)-induced sepsis model.Methods:Eighteen beagles were randomized into 1 intervention group(KCEA group,n=6)and 2 control groups(sham group and model group,n=6 each).Sepsis was in-duced by continuous intravenous application of 0.5 mg/kg body weight of endotoxin for 60 min.An extracorporeal hemoperfusion device made with KCEA for endotoxin adsorption was used.Model group beagles received standard treatment with fluids and vasoactive drugs,KCEA group beagles received standard treatment and direct hemoperfusion of KCEA for 2 h,and sham group beagles were treated with standard treatment and direct hemoperfusion of a sham column for 2 h.Results:Good blood compatibility of KCEA was confirmed by assessing clinical pa-rameters.Blood endotoxin peak levels in the KCEA group were significantly lower,resulting in a significant suppression of IL-6,TNF-αand procalcitonin,which improved mean arterial pressure and significantly lowered vasopressor demand,thereby pro-tecting organ function and improving survival time and rate.In the KCEA group,MAP was significantly higher over 6 h than those recorded both in the sham group and model group.The 7-day survival rates of the KCEA,sham and model groups were 50%,0%and 0%,respectively.Conclusion:KCEA hemoadsorption was effective at detoxifying circulatory endotoxin and inflammatory mediators and contributed to the decreased mortality rate in the sepsis beagles.

Differential Role of Two-Component Regulatory Systems (<i>phoPQ</i>and <i>pmrAB</i>) in Polymyxin B Susceptibility of <i>Pseudomonas aeruginosa</i>

Polymyxins are often considered as a last resort to treat multidrug resistant P. aeruginosa but polymyxin resistance has been increasingly reported worldwide in clinical isolates. Polymyxin resistance in P. aeruginosa is known to be associated with alterations in either PhoQ or PmrB. In this study, mutant strains of P. aeruginosa carrying amino acid substitution, a single and/or dual inactivation of PhoQ and PmrB were constructed to further understand the roles of PhoQ and PmrB in polymyxin susceptibility. Polymyxin B resistance was caused by both inactivation and/or amino acid substitutions in PhoQ but by only amino acid substitutions of PmrB. Alterations of both PhoQ and PmrB resulted in higher levels of polymyxin B resistance than alteration of either PhoQ or PmrB alone. These results were confirmed by time-killing assays suggesting that high-level polymyxin resistance in P. aeruginosa is caused by alterations of both PhoQ and PmrB.

Polymyxin B effects on motility parameters of cryopreserved bull semen

Objective:To evaluate the effect of adding different values of polymyxin B (PMB) to bull semen on various motility parameters of post-thawed semen such as total motility, progressive motility and velocity parameters using kinetic parameters of sperm by Computer Assisted Sperm Analysis.Methods: Gram negative bacteria release lipopolysaccharide, which induces the apoptotic pathway. Antibiotics are added to semen in order to prevent bacterial contaminations in bovine semen. These antibiotics kill the bacteria especially gram negative bacteria. Therefore, their endotoxins are released during bacteriolysis and bind to the head region and midpiece of sperm. PMB is a bactericidal antibiotic against multidrug resistant gram-negative bacteria and is able to neutralize the toxic effects of the released endotoxin. This study was performed on 3-year old Taleshi bulls. Results:The results showed both positive and negative significant effects of PMB on semen quality. Total motility and progressive motility were significantly increased (P<0.0001) by 100 μg per mL of PMB (55.2% and 48.8% respectively) against the control groups (43.5% and 37.7%, respectively). Moreover, they were significantly decreased (P<0.0001) by 1000 μg per mL of PMB (35.2% and 28.8% respectively) against the control groups (43.5% and 37.7% respectively) in above-mentioned parameters. In Computer Assisted Semen Analyzer, parameter VAP was significantly decreased (P<0.04) in 1000 μg (69.6 μm/s) against the control group (78.7 μm/s). Finally, using PMB in processing cryopreserved bull semen is advised, but before using it, the rate of endotoxins must be measured.Conclusions: We advise using PMB after measuring endotoxin concentration;In vitro,in vivoand in field fertilization, adding other sperm evaluation factors such as acrosomal integrity, DNA integrity, mitochondrial function to PMB treated semen.

Prevalence of polymyxin-induced nephrotoxicity and its predictors in critically ill adult patients:A meta-analysis

BACKGROUND Polymyxin-induced nephrotoxicity is a major safety concern in clinical practice due to long-term adverse outcomes and high mortality.AIM To conducted a systematic review and meta-analysis of the prevalence and potential predictors of polymyxin-induced nephrotoxicity in adult intensive care unit(ICU)patients.METHODS PubMed,EMBASE,the Cochrane Library and Reference Citation Analysis database were searched for relevant studies from inception through May 30,2022.The pooled prevalence of polymyxin-induced nephrotoxicity and pooled risk ratios of associated factors were analysed using a random-effects or fixed-effects model by Stata SE ver.12.1.Additionally,subgroup analyses and meta-regression were conducted to assess heterogeneity.RESULTS A total of 89 studies involving 12234 critically ill adult patients were included in the meta-analysis.The overall pooled incidence of polymyxin-induced nephrotoxicity was 34.8%.The pooled prevalence of colistin-induced nephrotoxicity was not higher than that of polymyxin B(PMB)-induced nephrotoxicity.The subgroup analyses showed that nephrotoxicity was significantly associated with dosing interval,nephrotoxicity criteria,age,publication year,study quality and sample size,which were confirmed in the univariable meta-regression analysis.Nephrotoxicity was significantly increased when the total daily dose was divided into 2 doses but not 3 or 4 doses.Furthermore,older age,the presence of sepsis or septic shock,hypoalbuminemia,and concomitant vancomycin or vasopressor use were independent risk factors for polymyxin-induced nephrotoxicity,while an elevated baseline glomerular filtration rate was a protective factor against colistin-induced nephrotoxicity.CONCLUSION Our findings indicated that the incidence of polymyxin-induced nephrotoxicity among ICU patients was high.It emphasizes the importance of additional efforts to manage ICU patients receiving polymyxins to decrease the risk of adverse outcomes.

Polymyxin B Alleviates Angiotensin II-Induced Stress Fiber Formation and Cellular Hypertrophy

Polymyxin B is widely used antibiotic in the clinic for resistant Gram-negative infections. In addition, polymyxin B-immobilized hemoperfusion cartridge has been used for endotoxin removal therapy in patients with septic shock. The aim of this study was to investigate the anti-fibrotic and anti-cellular hypertrophic effects of polymyxin B, and further to explore its possible mechanism. Polymyxin B (3, 10 μM) significantly inhibited stress fiber formation induced by angiotensin II (Ang II) in rat heart-derived H9c2 cells. Furthermore, polymyxin B (1 - 10 μM) showed a potent inhibitory effect on Ang II-induced cellular hypertrophy in H9c2 cells. Under the mechanism study, the inhibitory activities of polymyxin B against kinases involved in cellular hypertrophy such as AKT1, CAMK, GRK5, GSK3β, MLCK, PKC, PKD2, AMPK, ROCK2, p70S6K, SGK1were evaluated. Polymyxin B possesses a potent G protein related kinase 5 (GKR5) inhibitory activity with IC50 value of 1.1 μM, and has an ATP non-competitive inhibitory mode. Taken together, these results indicate that polymyxin B alleviates Ang II-induced stress fiber formation and cellular hypertrophy, and propose that one mechanism underlying these effects involves inhibition of the GRK5 pathway.

Influence of polymyxin intravenous drip combined with aerosol inhalation on the inflammatory response process in patients with Acinetobacter baumannii infectious VAP

Objective: To explore the influence of polymyxin intravenous drip combined with aerosol inhalation on the inflammatory response process in patients with Acinetobacter baumannii infectious VAP. Methods: A total of 60 patients with Acinetobacter baumannii infectious VAP who received hospitalization in the hospital between January 2014 and January 2017 were collected and divided into control group and observation group by random number table, 30 cases in each group. Control group of patients received conventional therapy, observation group of patients received conventional therapy + polymyxin intravenous drip combined with aerosol inhalation, and the therapy lasted for 2 weeks. The differences in serum levels of acute phase proteins, oxidative stress indexes and inflammatory response indexes were compared between the two groups before and after treatment. Results: Before treatment, the differences in serum levels of acute phase proteins, oxidative stress indexes and inflammatory response indexes were not statistically significant between the two groups of patients. After 2 weeks of treatment, serum acute phase protein PA level of observation group was higher than that of control group while CRP and CER levels were lower than those of control group;serum oxidative stress indexes MDA and LHP levels were lower than those of control group while SOD level was higher than that of control group;serum inflammatory response indexes IL-1, IL-6, IL-8 and TNF-α levels were lower than those of control group. Conclusion: Polymyxin intravenous drip combined with aerosol inhalation can inhibit the systemic inflammatory response process and promote the disease recovery in patients with Acinetobacter baumannii infectious VAP.

Nystatin-Neomycin-Polymyxin B Combination:Efficacy and Tolerance as 1st-Line Local Treatment of Infectious Vaginitis

Objective: To evaluate the efficacy and tolerance of a local treatment combining two antibacterials and one antifungal in patients with a clinical presentation suggesting infectious vaginitis. Patients and methods: 169 patients presenting with clinical criteria for vaginitis were included in an open, multicenter trial. Vaginal samples were taken for microbiological analyses and a triple-combination product of nystatin, neomycin and polymyxin B was then started as local treatment, without waiting for the test results. The treatment was continued with the usual dosage (1 vaginal capsule at bedtime for 12 days) for vaginal infections in the scope of the combination product with approved labeling. A second vaginal sample was performed at the end of the treatment. The main efficacy criterion was the clinical success rate (cure or improvement of the clinical signs and symptoms) according to the investigator.Results: 93 patients were included in the efficacy population. Non-exclusively fungal vaginitis (strictly bacterial or bacterial + fungal) represented 31.2% of the cases. The clinical success rate was 97.8% according to the investigator and 95.7% according to the patients. The microbiological success rate was 81.3%, with no differences between etiologies (Candida spp., bacteria or both). The combination product was well-tolerated, despite the local inflammation before treatment. Discussion and conclusion: Given the etiological diversity of vaginitis, this trial supports the efficacy of a triple-combination product (nystatin, neomycin, polymyxin B) as a first-line local treatment of Candida, bacterial or mixed vaginitis.

Enhancement of polymyxin B1 production by an artificial microbial consortium of Paenibacillus polymyxa and recombinant Corynebacterium glutamicum producing precursor amino acids

Polymyxin B,produced by Paenibacillus polymyxa,is used as the last line of defense clinically.In this study,exogenous mixture of precursor amino acids increased the level and proportion of polymyxin B1 in the total of polymyxin B analogs of P.polymyxa CJX518-AC(PPAC)from 0.15 g/L and 61.8%to 0.33 g/L and 79.9%,respectively.The co-culture of strain PPAC and recombinant Corynebacterium glutamicum-leu01,which produces high levels of threonine,leucine,and isoleucine,increased polymyxin B1 production to 0.64 g/L.When strains PPAC and C.glu-leu01 simultaneously inoculated into an optimized medium with 20 g/L peptone,polymyxin B1 production was increased to 0.97 g/L.Furthermore,the polymyxin B1 production in the co-culture of strains PPAC and C.glu-leu01 increased to 2.21 g/L after optimized inoculation ratios and fermentation medium with 60 g/L peptone.This study provides a new strategy to improve polymyxin B1 production.

A polymyxin B loaded hypoxia-responsive liposome with improved biosafety for efficient eradication of bacterial biofilms

Biofilm-associated bacterial infection brings serious threats to global public health owing to serious antibiotic resistance.It is urgently needed to develop innovative strategies to combat biofilm-associated bacterial infections.Polymyxins stand out as the last line of defense against Gram-negative bacteria.However,serious nephrotoxicity of polymyxins severely limits their clinical utility.Herein,a hypoxia-responsive liposome is designed as the nanocarrier of polymyxin B(PMB)to combat biofilms developed by Gram-negative bacteria.A metronidazole modified lipid(hypoxia-responsive lipid(HRLipid))is synthesized to fabricate hypoxia-responsive liposomes(HRLip).PMB loaded hypoxia-responsive liposomes(HRL-PMB)is then prepared to mitigate the nephrotoxicity of PMB while preserving its excellent bactericidal activity.HRL-PMB shows very low hemolysis and cytotoxicity due to liposomal encapsulation of PMB.PMB can be readily released from HRL-PMB in response to hypoxic biofilm microenvironment,exerting its bactericidal activity to realize biofilm eradication.The excellent in vivo antibiofilm ability of HRL-PMB is confirmed by a Pseudomonas aeruginosa infected zebrafish model and a P.aeruginosa pneumonia infection model.Meanwhile,HRL-PMB can greatly reduce the nephrotoxicity of PMB after intravenous injection.The hypoxia-sensitive liposomes held great promise to improve the biosafety of highly toxic antibiotics while preserving their intrinsic bactericidal ability,which may provide an innovative strategy for combating biofilm-associated infections.

Chinese consensus guidelines for therapeutic drug monitoring of polymyxin B,endorsed by the Infection and Chemotherapy Committee of the Shanghai Medical Association and the Therapeutic Drug Monitoring Committee of the Chinese Pharmacological Society

Polymyxin B,which is a last-line antibiotic for extensively drug-resistant Gram-negative bacterial infections,became available in China in Dec.2017.As dose adjustments are based solely on clinical experience of risk toxicity,treatment failure,and emergence of resistance,there is an urgent clinical need to perform therapeutic drug monitoring(TDM)to optimize the use of polymyxin B.It is thus necessary to standardize operating procedures to ensure the accuracy of TDM and provide evidence for their rational use.We report a consensus on TDM guidelines for polymyxin B,as endorsed by the Infection and Chemotherapy Committee of the Shanghai Medical Association and the Therapeutic Drug Monitoring Committee of the Chinese Pharmacological Society.The consensus panel was composed of clinicians,pharmacists,and microbiologists from different provinces in China and Australia who made recommendations regarding target concentrations,sample collection,reporting,and explanation of TDM results.The guidelines provide the first-ever consensus on conducting TDM of polymyxin B,and are intended to guide optimal clinical use.

LPS adsorption and inflammation alleviation by polymyxin B-modified liposomes for atherosclerosis treatment

Chronic inflammation is critical in the onset and progression of atherosclerosis(AS).The lipopolysaccharide(LPS)level in the circulation system is elevated in AS patients and animal models,which is correlated with the severity of AS.Inspired by the underlying mechanism that LPS could drive the polarization of macrophages toward the M1 phenotype,aggravate inflammation,and ultimately contribute to the exacerbation of AS,LPS in the circulation system was supposed to be the therapeutic target for AS treatment.In the present study,polymyxin(PMB)covalently conjugated to PEGylated liposomes(PLPs)were formulated to adsorb LPS through specific interactions between PMB and LPS.In vitro,the experiments demonstrated that PLPs could adsorb LPS,reduce the polarization of macrophages to M1 phenotype and inhibit the formation of foam cells.In vivo,the study revealed that PLPs treatment reduced the serum levels of LPS and pro-inflammatory cytokines,decreased the proportion of M1-type macrophages in AS plaque,stabilized AS plaque,and downsized the plaque burdens in arteries,which eventually attenuated the progression of AS.Our study highlighted LPS in the circulation system as the therapeutic target for AS and provided an alternative strategy for AS treatment.