Ceftobiprole for Treatment of Complicated Staphylococcus aureus Bacteremia.

BACKGROUND: Ceftobiprole is a cephalosporin that may be effective for treating complicated Staphylococcus aureus bacteremia, including methicillin-resistant S. aureus. METHODS: In this phase 3, double-blind, double-dummy, noninferiority trial, adults with complicated S. aureus bacteremia were randomly assigned in a 1:1 ratio to receive ceftobiprole at a dose of 500 mg intravenously every 6 hours for 8 days and every 8 hours thereafter, or daptomycin at a dose of 6 to 10 mg per kilogram of body weight intravenously every 24 hours plus optional aztreonam (at the discretion of the trial-site investigators). The primary outcome, overall treatment success 70 days after randomization (defined as survival, bacteremia clearance, symptom improvement, no new S. aureus bacteremia-related complications, and no receipt of other potentially effective antibiotics), with a noninferiority margin of 15%, was adjudicated by a data review committee whose members were unaware of the trial-group assignments. Safety was also assessed. RESULTS: Of 390 patients who underwent randomization, 387 (189 in the ceftobiprole group and 198 in the daptomycin group) had confirmed S. aureus bacteremia and received ceftobiprole or daptomycin (modified intention-to-treat population). A total of 132 of 189 patients (69.8%) in the ceftobiprole group and 136 of 198 patients (68.7%) in the daptomycin group had overall treatment success (adjusted difference, 2.0 percentage points; 95% confidence interval [CI], -7.1 to 11.1). Findings appeared to be consistent between the ceftobiprole and daptomycin groups in key subgroups and with respect to secondary outcomes, including mortality (9.0% and 9.1%, respectively; 95% CI, -6.2 to 5.2) and the percentage of patients with microbiologic eradication (82.0% and 77.3%; 95% CI, -2.9 to 13.0). Adverse events were reported in 121 of 191 patients (63.4%) who received ceftobiprole and 117 of 198 patients (59.1%) who received daptomycin; serious adverse events were reported in 36 patients (18.8%) and 45 patients (22.7%), respectively. Gastrointestinal adverse events (primarily mild nausea) were more frequent with ceftobiprole. CONCLUSIONS: Ceftobiprole was noninferior to daptomycin with respect to overall treatment success in patients with complicated S. aureus bacteremia. (Funded by Basilea Pharmaceutica International and the U.S. Department of Health and Human Services; ERADICATE ClinicalTrials.gov number, NCT03138733.).

Sequential Treatment Failure With Aztreonam-Ceftazidime-Avibactam Followed by Cefiderocol Due to Preexisting and Acquired Mechanisms in a New Delhi Metallo-ß-lactamase-Producing Escherichia coli Causing Fatal Bloodstream Infection.

We report a fatal case of New Delhi metallo-ß-lactamase (NDM)-producing Escherichia coli in a bacteremic patient with sequential failure of aztreonam plus ceftazidime-avibactam followed by cefiderocol. Acquired resistance was documented phenotypically and mediated through preexisting and acquired mutations. This case highlights the need to rethink optimal treatment for NDM-producing organisms.

Airway Bacterial Load and Inhaled Antibiotic Response in Bronchiectasis.

Rationale: The principal underlying inhaled antibiotic treatment in bronchiectasis is that airway bacterial load drives inflammation, and therefore antibiotic treatment will reduce symptoms. Objectives: To determine the relationship between bacterial load and clinical outcomes, assess the stability of bacterial load over time, and test the hypothesis that response to inhaled antibiotics would be predicted by baseline bacterial load. Methods: We performed three studies. Studies 1 and 2 were prospective studies including adults with bronchiectasis. Study 3 was a post hoc analysis of a randomized trial of inhaled aztreonam. A priori patients were divided into low (<105 cfu/g), moderate (105-106 cfu/g), and high bacterial load (≥107 cfu/g) using quantitative sputum culture. Measurements and Main Results: Bacterial load was a stable trait associated with worse quality of life and more airway inflammation in studies 1, 2, and 3. In study 3, patients with high bacterial load showed an improvement in the primary endpoint (Quality of Life-Bronchiectasis-Respiratory Symptoms Score at Week 4) in favor of aztreonam (mean difference of 9.7 points; 95% confidence interval, 3.4-16.0; P = 0.003). The proportion of patients who achieved an increase above the minimum clinically important difference was higher in the aztreonam group at Week 4 (63% vs. 37%; P = 0.01) and at Week 12 (62% vs. 38%; P = 0.01) only in high bacterial load patients. Conclusions: Improvement of quality of life with inhaled aztreonam was only evident in patients with high bacterial load. Bacterial load may be a useful biomarker of severity of disease and treatment response.

Surgical infection prophylaxis prior to left ventricular assist device implantation: A survey of clinical practice.

BACKGROUND: Short duration, antimicrobial prophylaxis that includes antistaphylococcal activity is recommended at the time of left ventricular assist device (LVAD) implantation to reduce infection-related complications. There continues to be wide variability in surgical infection prophylaxis (SIP) regimens among implantation centers. The aim of this study is to characterize current SIP regimens at different LVAD centers. METHODS: A survey study was conducted from 26 September 2017 to 25 October 2017. Surveys were distributed electronically to LVAD coordinators and infectious diseases specialists at 75 US medical centers identified as having an LVAD program. Data collection included information about antimicrobial selection, duration, Staphylococcus aureus screening, and decolonization procedures. RESULTS: We received 29 survey responses. The majority of surveys were completed by infectious diseases physicians (72.4% [21 out of 29]). Most responding centers reported LVAD programs established for greater than 10 years (20 out of 29 [69%]). Cardiac transplantation was performed in 28 out of 29 (96%) centers. Of centers reporting a defined SIP regimen for non-penicillin allergic patients (96% [28 out of 29]), 17.9% (5 out of 28) reported a four-drug regimen, 35.7% (10 out of 28) reported a three-drug regimen, and 46.4% (13 out of 28) reported a two-drug regimen, while no centers reported a single-drug regimen. Empiric fluconazole was common (50% [14 out of 28]) and 96.4% (27 out of 28) of regimens included vancomycin. Duration of antimicrobial prophylaxis (24 hours to 5 days), S. aureus screening, decolonization procedures, and alterations due to drug allergies varied across participating centers. CONCLUSIONS: Our survey results indicate wide variation in SIP regimens among participating LVAD centers. These results highlight the need for studies evaluating the implications of SIP regimens, and whether clinical factors that prolong antimicrobial duration impact postoperative infection rates.

Antibiotic therapy for chronic infection with Burkholderia cepacia complex in people with cystic fibrosis.

BACKGROUND: Cystic fibrosis (CF) a life-limiting inherited disease affecting a number of organs, but classically associated with chronic lung infection and progressive loss of lung function. Chronic infection by Burkholderia cepacia complex (BCC) is associated with increased morbidity and mortality and therefore represents a significant challenge to clinicians treating people with CF. This review examines the current evidence for long-term antibiotic therapy in people with CF and chronic BCC infection. OBJECTIVES: The objective of this review is to assess the effects of long-term oral and inhaled antibiotic therapy targeted against chronic BCC lung infections in people with CF. The primary objective is to assess the efficacy of treatments in terms of improvements in lung function and reductions in exacerbation rate. Secondary objectives include quantifying adverse events, mortality and changes in quality of life associated with treatment. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched online trial registries and the reference lists of relevant articles and reviews.Date of last search: 29 May 2019. SELECTION CRITERIA: Randomised controlled trials (RCTs) of long-term antibiotic therapy in people with CF and chronic BCC infection. DATA COLLECTION AND ANALYSIS: Two authors independently extracted data, assessed risk of bias and assessed the quality of the evidence using GRADE. MAIN RESULTS: We included one RCT (100 participants) which lasted 52 weeks comparing continuous inhaled aztreonam lysine (AZLI) and placebo in a double-blind RCT for 24 weeks, followed by a 24-week open-label extension and a four-week follow-up period. The average participant age was 26.3 years, 61% were male and average lung function was 56.5% predicted.Treatment with AZLI for 24 weeks was not associated with improvement in forced expiratory volume in one second (FEV1), mean difference 0.91% (95% confidence interval (CI) -3.15 to 4.97) (moderate-quality evidence). The median time to the next exacerbation was 75 days in the AZLI group compared to 51 days in the placebo group, but the difference was not significant (P = 0.27) (moderate-quality evidence). Similarly, the number of participants hospitalised for respiratory exacerbations showed no difference between groups, risk ratio (RR) 0.88 (95% CI 0.53 to 1.45) (moderate-quality evidence). Overall adverse events were similar between groups, RR 1.08 (95% CI 0.98 to 1.19) (moderate-quality evidence). There were no significant differences between treatment groups in relation to mortality (moderate-quality evidence), quality of life or sputum density.In relation to methodological quality, the overall risk of bias in the study was assessed to be unclear to low risk. AUTHORS' CONCLUSIONS: We found insufficient evidence from the literature to determine an effective strategy for antibiotic therapy for treating chronic BCC infection.

Simplified Aztreonam Dosing in Patients with End-Stage Renal Disease: Results of a Monte Carlo Simulation.

The manufacturer-recommended aztreonam dosing for patients with creatinine clearance values of <10 ml/min/1.73 m2 is complex. It is not known whether simpler posthemodialysis dosing administered once daily or thrice weekly can reliably achieve pharmacodynamic goals. We found that 1 or 2 g administered once daily after hemodialysis had >90% probability of target attainment up to MICs of 4 or 8 mg/liter, respectively. Thrice-weekly dosing should generally be avoided, except in nonsevere infections with MICs of ≤0.5 mg/liter.

Efficacy and safety of delafloxacin compared with vancomycin plus aztreonam for acute bacterial skin and skin structure infections: a Phase 3, double-blind, randomized study.

BACKGROUND: Delafloxacin is an investigational anionic fluoroquinolone in development for oral or intravenous administration for the treatment of infections caused by Gram-positive (including MRSA), Gram-negative, atypical and anaerobic organisms. OBJECTIVES: To establish the non-inferiority of delafloxacin compared with vancomycin plus aztreonam for the treatment of acute bacterial skin and skin structure infections and to compare the safety of the two antimicrobials. PATIENTS AND METHODS: A Phase 3, multicentre, randomized, double-blind, active-controlled study with 660 patients compared delafloxacin 300 mg or vancomycin 15 mg/kg plus aztreonam 2 g each administered twice daily intravenously for 5-14 days. Non-inferiority was evaluated by objective response (≥20% erythema reduction) at 48-72 h after initiation of study drug, investigator subjective assessment of outcome and microbiological responses. Clinical Trials Registration: NCT01811732. EudraCT number: 2012-001767-71. RESULTS: In the ITT analysis set, the objective response was 78.2% in the delafloxacin arm and 80.9% in the vancomycin/aztreonam arm (mean treatment difference, -2.6%; 95% CI, -8.78% to 3.57%). Investigator-assessed cure was similar between the two groups at follow-up (52.0% versus 50.5%) and late follow-up (70.4% versus 66.6%). Bacterial eradication of MRSA was 100% and 98.5% in the delafloxacin group and the vancomycin/aztreonam group, respectively. Frequency of treatment-emergent adverse events in the delafloxacin and vancomycin/aztreonam groups was similar. Treatment-emergent adverse events leading to study drug discontinuation were higher in the vancomycin/aztreonam group compared with the delafloxacin group (4.3% versus 0.9%). CONCLUSIONS: Delafloxacin, an anionic fluoroquinolone, was statistically non-inferior to vancomycin/aztreonam at 48-72 h following the start of therapy and was well tolerated as monotherapy in the treatment of acute bacterial skin and skin structure infections.

Repurposing an old drug: aztreonam as a new treatment strategy for gonorrhoea.

Objectives: To determine whether aztreonam is still an effective drug for the treatment of gonorrhoea. Methods: Observational study of patients with gonorrhoea diagnosed by urine multiplex PCR, with a past medical history of allergy to ß-lactams or relapse after treatment with a third-generation cephalosporin. Patients received a single 1 g dose of aztreonam in accordance with the manufacturer's instructions. Results: Five patients (four males, one female) were enrolled, comprising two who were allergic to ß-lactams and three previously treated with cephalosporins who relapsed. Median age was 38 years (range 23-51). Following treatment with aztreonam all were cured without any adverse event. All the men were free of symptoms, and the woman tested negative for gonorrhoea 1 month after treatment. Conclusion: Aztreonam appears to be an effective alternative to cephalosporins in the treatment of uncomplicated gonorrhoea, particularly when patients are suspected of being infected by strains with reduced susceptibility to ceftriaxone or are known to be allergic to penicillin.

In vitro and in vivo Pharmacodynamics of Colistin and Aztreonam Alone and in Combination against Multidrug-Resistant Pseudomonas aeruginosa.

BACKGROUND: Reports of Pseudomonas aeruginosa with high antimicrobial resistance have steadily emerged, threatening the utility of a mainstay in antipseudomonal therapy. This study evaluated the antimicrobial activities of various combination therapies against P. aeruginosa with high antimicrobial resistance, including multidrug-resistant P. aeruginosa (MDRP) using an in vitro and in vivo study. METHODS: We evaluated 24 combination therapies, including colistin, aztreonam, meropenem, ceftazidime, ciprofloxacin, amikacin, rifampicin, arbekacin and piperacillin against 15 MDRP isolates detected at Aichi Medical University Hospital with the break-point checkerboard method. Based on the results of the in vitro study, we evaluated antimicrobial activity against highly antimicrobial-resistant P. aeruginosa with an in vivo murine thigh infection model. RESULTS: The combination regimens including colistin and aztreonam showed higher antimicrobial activity against the 15 MDRP isolates. In the in vivo study, the high-dose colistin monotherapy (16 mg/kg every 12 h) achieved greater log10 CFU changes than the normal-dose colistin regimen (8 mg/kg every 12 h) against 5 P. aeruginosa isolates, including 2 MDRP isolates (p < 0.05). Aztreonam monotherapy (400 mg every 8 h) yielded bacterial densities similar to untreated control mice for the MDRP isolate evaluated. The combination therapy with a higher dose of colistin had superior antimicrobial activity against 5 P. aeruginosa with colistin (MIC 0.5 µg/ml) and aztreonam (MIC ≥128 µg/ml) than colistin monotherapy. CONCLUSION: The data suggest that the combination treatment of colistin and aztreonam could be the most useful for treating highly resistant P. aeruginosa with a higher susceptibility to colistin, including MDRP infections.

Biopharmaceutical Characterization of Nebulized Antimicrobial Agents in Rats. 4. Aztreonam.

The aim of this study was to determine aztreonam (ATM) membrane permeability using Calu-3 cells and its plasma and pulmonary epithelial lining fluid (ELF) pharmacokinetics in rats after intratracheal nebulization and intravenous administration (15 mg · kg(-1)). ATM exhibits low Calu-3 permeability (0.07 ± 0.02 × 10(-6) cm · s(-1)), and a high area under the ELF/unbound plasma concentration time curve between 0 and infinity (AUCELF/AUCu,plasma) ratio of 1,069 was observed after nebulization in rats. These results confirm that ATM is a low-permeability molecule and a good candidate for nebulization.

A review of the pharmacokinetics and pharmacodynamics of aztreonam.

The monobactam aztreonam is currently being re-examined as a therapeutic agent in light of the global spread of carbapenem resistance in aerobic Gram-negative bacilli and aztreonam's stability to Ambler class B metallo-ß-lactamases. Of particular interest are the pharmacokinetic and pharmacodynamic properties of aztreonam alone and in combination with ß-lactamase inhibitors. The choice of inhibitor may vary depending on the spectrum of ß-lactamases produced by Enterobacteriaceae. The monobactam ring is also being used to produce new developmental monobactams. Thus, a greater understanding of aztreonam pharmacokinetics and dynamics is of great relevance in drug development. This review summarizes the pharmacokinetic profile of aztreonam in man and its pharmacodynamics in human and pre-clinical studies when studied alone and with ß-lactamase inhibitors.

A Phase III, randomized, controlled, non-inferiority trial of ceftaroline fosamil 600 mg every 8 h versus vancomycin plus aztreonam in patients with complicated skin and soft tissue infection with systemic inflammatory response or underlying comorbidities.

OBJECTIVES: Increasing the ceftaroline fosamil dose beyond 600 mg every 12 h may provide additional benefit for patients with complicated skin and soft tissue infections (cSSTIs) with severe inflammation and/or reduced pathogen susceptibility. A Phase III multicentre, randomized trial evaluated the safety and efficacy of ceftaroline fosamil 600 mg every 8 h in this setting. METHODS: Adult patients with cSSTI and systemic inflammation or comorbidities were randomized 2:1 to intravenous ceftaroline fosamil (600 mg every 8 h) or vancomycin (15 mg/kg every 12 h) plus aztreonam (1 g every 8 h) for 5-14 days. Clinical cure was assessed at the test of cure (TOC) visit (8-15 days after the final dose) in the modified ITT (MITT) and clinically evaluable (CE) populations. Non-inferiority was defined as a lower limit of the 95% CI around the treatment difference greater than -10%. An MRSA-focused expansion period was initiated after completion of the main study. Clinicaltrials.gov registration numbers NCT01499277 and NCT02202135. RESULTS: Clinical cure rates at TOC demonstrated non-inferiority of ceftaroline fosamil 600 mg every 8 h versus vancomycin plus aztreonam in the MITT and CE populations: 396/506 (78.3%) versus 202/255 (79.2%) patients (difference -1.0%, 95% CI -6.9, 5.4) and 342/395 (86.6%) versus 180/211 (85.3%) patients (difference 1.3%, 95% CI -4.3, 7.5), respectively. In the expansion period, 3/4 (75%) patients treated with ceftaroline fosamil were cured at TOC. The frequency of adverse events was similar between groups. CONCLUSIONS: Ceftaroline fosamil 600 mg every 8 h was effective for cSSTI patients with evidence of systemic inflammation and/or comorbidities. No new safety signals were identified.

Expanded Gram-Negative Antimicrobial Prophylaxis Reduces Surgical Site Infections in Hip Arthroplasty.

BACKGROUND: A first-generation cephalosporin is the recommended antibiotic prophylaxis for implants. However, this standard does not address the increasing prevalence and virulence of gram-negative pathogens infecting patients. We found that gram-negative bacilli caused 30% of our surgical site infections (SSIs) following hip procedures, whereas only 10% of knee SSIs were caused by gram-negative bacilli. To address this, we instituted Expanded Gram-Negative Antimicrobial Prophylaxis (EGNAP) for our hip arthroplasty patients. The purpose of this study is to measure the effect of EGNAP on the SSI rates following primary total hip arthroplasty. METHODS: The study consisted of 10,084 total patients. Before July 2012, all patients were administered 1 g of cefazolin. After July 2012, our protocol was adjusted by adding the EGNAP with either gentamicin or aztreonam to hip patients (group 1) and not to the knee arthroplasty patients (group 2). RESULTS: Group 1 consisted of the 5389 primary hip arthroplasty patients. Of these patients, 4122 (before July 2012) did not receive weight-based high-dose gentamicin and 1267 (after July 2012) did. Before the introduction of EGNAP, group 1 SSI rate was 1.19% (49/4122). After July 2012 when EGNAP was added, the overall group 1 SSI rate decreased to 0.55% (7/1267) (P = .05). During the study period, there was not a significant difference in SSI rate of knee arthroplasty (group 2): 1.08% vs 1.02% (P = .999). CONCLUSIONS: The addition of EGNAP for hip arthroplasty is a safe and effective method to decrease SSIs. LEVEL OF EVIDENCE: III. Case-control study.

Quality of Life Questionnaire-Bronchiectasis: final psychometric analyses and determination of minimal important difference scores.

BACKGROUND: The Quality of Life-Bronchiectasis (QOL-B), a self-administered, patient-reported outcome measure assessing symptoms, functioning and health-related quality of life for patients with non-cystic fibrosis (CF) bronchiectasis, contains 37 items on 8 scales (Respiratory Symptoms, Physical, Role, Emotional and Social Functioning, Vitality, Health Perceptions and Treatment Burden). METHODS: Psychometric analyses of QOL-B V.3.0 used data from two double-blind, multicentre, randomised, placebo-controlled, phase III trials of aztreonam for inhalation solution (AZLI) in 542 patients with non-CF bronchiectasis and Gram-negative endobronchial infection. RESULTS: Excellent internal consistency (Cronbach's α ≥0.70) and 2-week test-retest reliability (intraclass correlation coefficients ≥0.72) were demonstrated for each scale. Convergent validity with 6 min walk test was observed for Physical and Role Functioning scores. No floor or ceiling effects (baseline scores of 0 or 100) were found for the Respiratory Symptoms scale (primary endpoint of trials). Baseline Respiratory Symptoms scores discriminated between patients based on baseline FEV1% predicted in only one trial. The minimal important difference score for the Respiratory Symptoms scale was 8.0 points. AZLI did not show efficacy in the two phase III trials. QOL-B responsivity to treatment was assessed by examining changes from baseline QOL-B scores at study visits at which protocol-defined pulmonary exacerbations were reported. Mean Respiratory Symptoms scores decreased 14.0 and 14.2 points from baseline for placebo-treated and AZLI-treated patients with exacerbations, indicating that worsening respiratory symptoms were reflected in clinically meaningful changes in QOL-B scores. CONCLUSIONS: Previously established content validity, reliability and responsivity of the QOL-B are confirmed by this final validation study. The QOL-B is available for use in clinical trials and routine clinical practice.

Pharmacokinetics/pharmacodynamics of a ß-lactam and ß-lactamase inhibitor combination: a novel approach for aztreonam/avibactam.

OBJECTIVES: The combination of aztreonam/avibactam has promising activity against MDR Gram-negative pathogens producing metallo-ß-lactamases (MBLs), such as New Delhi MBL-1. Pharmacokinetic (PK)/pharmacodynamic (PD) understanding of this combination is critical for optimal clinical dose selection. This study focuses on the determination of an integrated PK/PD approach for aztreonam/avibactam across multiple clinical Enterobacteriaceae strains. METHODS: Six clinical Enterobacteriaceae isolates expressing MBLs and ESBLs were studied in an in vitro hollow-fibre infection model (HFIM) using various dosing regimens simulating human-like PK for aztreonam/avibactam. The neutropenic murine thigh infection model was used for in vivo validation against two bacterial strains. RESULTS: MIC values of aztreonam/avibactam for the isolates ranged from 0.125 to 8 mg/L. Using a constant infusion of avibactam at 4 mg/L, the aztreonam PK/PD index was observed as % fT >MIC. Studies performed in the presence of a fixed dose of aztreonam revealed that the efficacy of avibactam correlates best with percentage of time above a critical threshold concentration of 2-2.5 mg/L. These conclusions translated well to the efficacy observed in the murine thigh model, demonstrating in vivo validation of the in vitro PK/PD target. CONCLUSIONS: PK/PD evaluations for aztreonam/avibactam in HFIM yielded a single target across strains with a wide MIC range. This integrated approach could be easily applied for forecasting clinically efficacious doses for ß-lactam/ß-lactamase inhibitor combinations.

In vitro activities of ceftazidime-avibactam and aztreonam-avibactam against 372 Gram-negative bacilli collected in 2011 and 2012 from 11 teaching hospitals in China.

Ceftazidime-avibactam, aztreonam-avibactam, and comparators were tested by reference broth microdilution against 372 nonrepetitive Gram-negative bacilli (346 unselected plus 26 selected meropenem-nonsusceptible Enterobacteriaceae isolates) collected from 11 teaching hospitals in China in 2011 and 2012. Meropenem-nonsusceptible isolates produced extended-spectrum ß-lactamases (ESBLs; e.g., CTX-M-14/3), AmpCs (e.g., CMY-2), and/or carbapenemases (e.g., KPC-2 and NDM-1). Avibactam potentiated the activity of ceftazidime against organisms with combinations of ESBLs, AmpCs, and KPC-2. Aztreonam-avibactam was active against all ß-lactamase producers (including producers of NDM-1 and IMP-4/8) except blaOXA-containing Acinetobacter baumannii and some Pseudomonas aeruginosa isolates.

Evaluation of double- and triple-antibiotic combinations for VIM- and NDM-producing Klebsiella pneumoniae by in vitro time-kill experiments.

Combination therapy is recommended for infections with carbapenemase-producing Klebsiella pneumoniae. However, limited data exist on which antibiotic combinations are the most effective. The aim of this study was to find effective antibiotic combinations against metallo-beta-lactamase-producing K. pneumoniae (MBL-KP). Two VIM- and two NDM-producing K. pneumoniae strains, all susceptible to colistin, were exposed to antibiotics at clinically relevant static concentrations during 24-h time-kill experiments. Double- and triple-antibiotic combinations of aztreonam, ciprofloxacin, colistin, daptomycin, fosfomycin, meropenem, rifampin, telavancin, tigecycline, and vancomycin were used. Synergy was defined as a ≥2 log10 decrease in CFU/ml between the combination and its most active drug after 24 h, and bactericidal effect was defined as a ≥3 log10 decrease in CFU/ml after 24 h compared with the starting inoculum. Synergistic or bactericidal activity was demonstrated for aztreonam, fosfomycin, meropenem, and rifampin in double-antibiotic combinations with colistin and also for aztreonam, fosfomycin, and rifampin in triple-antibiotic combinations with meropenem and colistin. Overall, the combination of rifampin-meropenem-colistin was the most effective regimen, demonstrating synergistic and bactericidal effects against all four strains. Meropenem-colistin, meropenem-fosfomycin, and tigecycline-colistin combinations were not bactericidal against the strains used. The findings of this and other studies indicate that there is great potential of antibiotic combinations against carbapenemase-producing K. pneumoniae. However, our results deviate to some extent from those of previous studies, which might be because most studies to date have included KPC-producing rather than MBL-producing strains. More studies addressing MBL-KP are needed.

Inhaled antibiotics: dry or wet?

Dry powder inhalers (DPIs) delivering antibiotics for the suppressive treatment of Pseudomonas aeruginosa in cystic fibrosis patients were developed recently and are now increasingly replacing time-consuming nebuliser therapy. Noninferiority studies have shown that the efficacy of inhaled tobramycin delivered by DPI was similar to that of wet nebulisation. However, there are many differences between inhaled antibiotic therapy delivered by DPI and by nebuliser. The question is whether and to what extent inhalation technique and other patient-related factors affect the efficacy of antibiotics delivered by DPI compared with nebulisers. Health professionals should be aware of the differences between dry and wet aerosols, and of patient-related factors that can influence efficacy, in order to personalise treatment, to give appropriate instructions to patients and to better understand the response to the treatment after switching. In this review, key issues of aerosol therapy are discussed in relation to inhaled antibiotic therapy with the aim of optimising the use of both nebulised and DPI antibiotics by patients. An example of these issues is the relationship between airway generation, structural lung changes and local concentrations of the inhaled antibiotics. The pros and cons of dry and wet modes of delivery for inhaled antibiotics are discussed.

Effectiveness of antibiotic combination therapy as evaluated by the Break-point Checkerboard Plate method for multidrug-resistant Pseudomonas aeruginosa in clinical use.

Multidrug-resistant Pseudomonas aeruginosa (MDRP) strains are defined as having resistance to the following 3 groups of antibiotics: carbapenems, aminoglycosides, and fluoroquinolones. Antibiotic combinations have demonstrated increased activity in vitro compared with a single agent. As an in vitro method of determining the combination activity of antibiotics, the Break-point Checkerboard Plate (BC-plate) can be used routinely in clinical microbiology laboratories. We evaluated the effectiveness of the BC-plate for MDRP infections in clinical settings. We retrospectively selected cases of MDRP infection treated with combination therapy of antibiotics in Tokyo Medical University Hospital (1015 beds), Tokyo, Japan, from November 2010 to October 2012. A total of 28 MDRP strains were clinically isolated from 28 patients during the study period. This study design is a case series of MDRP infection. Six infections among the 28 patients were treated based on the results of the BC-plate assay, and the 6 strains tested positive for MBL. One patient had pneumonia, 3 had urinary tract infections, 1 had vertebral osteomyelitis, and 1 had nasal abscess. The combination of aztreonam with amikacin demonstrated the most frequently recognized in vitro effect (5 patients). Next, aztreonam with ciprofloxacin and piperacillin with amikacin revealed equivalent in vitro effects (3 patients, respectively). The clinical cure rate was 83.3% (5/6 patients). Antibiotic combination therapy based on the results of the BC-plate assay might indicate the effective therapy against MDRP infection in clinical settings.

Confronting multidrug-resistant Klebsiella meningitis after mid-clival Cerebrospinal Fluid leak repair: a therapeutic odyssey.

A man in his 40s with type 2 diabetes mellitus had persistent right-sided watery nasal discharge for 6 months following cerebrospinal fluid (CSF) leak repair at another hospital, prompting his visit to us due to recurring symptoms. Imaging revealed a CSF leak from the mid-clivus for which revision endoscopic CSF leak repair was done. Regrettably, he developed postoperative meningitis caused by multidrug-resistant (MDR) Klebsiella pneumoniaeManaging this complex case was a challenging task due to the pathogen's resistance to conventional drugs and the scarcity of scientific evidence. We initiated a culture-guided combination regimen with ceftazidime, avibactam, aztreonam and tigecycline. This decision stemmed from meticulous literature review and observed antibiotic synergy while testing for this organism.After 4 weeks of vigilant treatment, the patient's symptoms improved significantly, and CSF cultures were sterile. We present our approach to effectively confront and manage a challenging instance of postoperative MDR bacterial meningitis.