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Objectives Mortality among patients with carbapenem-resistant Acinetobacter baumannii (CRAB) infections varies between studies. We examined whether in vivo fitness of CRAB strains is associated with clinical outcomes in patients with CRAB infections. Methods Isolates were collected from patients enrolled in the AIDA trial with hospital-acquired pneumonia, bloodstream infections and/or urinary tract infections caused by CRAB. The primary outcome was 14-day clinical failure, defined as failure to meet all criteria: alive; haemodynamically stable; improved or stable Sequential Organ Failure Assessment (SOFA) score; improved or stable oxygenation; and microbiological cure of bacteraemia. The secondary outcome was 14-day mortality. We tested in vivo growth using a neutropenic murine thigh infection model. Fitness was defined based on the CFU count 24 hours after injection of an inoculum of 105 CFU. We used mixed-effects logistic regression to test the association between fitness and the two outcomes. Results The sample included 266 patients; 215 (80.8%) experienced clinical failure. CRAB fitness ranged from 5.23 to 10.08 log CFU/g. The odds of clinical failure increased by 62% for every 1-log CFU/g increase in fitness (OR 1.62, 95% CI 1.04–2.52). After adjusting for age, Charlson score, SOFA score and acquisition in the intensive care unit, fitness remained significant (adjusted OR 1.63, 95% CI 1.03–2.59). CRAB fitness had a similar effect on 14-day mortailty, although the association was not statistically significant (OR 1.56, 95% CI 0.95–2.57). It became significant after adjusting for age, Charlson score, SOFA score and recent surgery (adjusted OR 1.88, 95% CI 1.09–3.25). Conclusions In vivo CRAB fitness was associated with clinical failure in patients with CRAB infection.

Background Amoxicillin has been in use since the 1970s; it is the most widely used penicillin both alone and in combination with the β-lactamase clavulanic acid. Objectives In this narrative review, we re-examine the properties of oral amoxicillin and clavulanic acid and provide guidance on their use, with emphasis on the preferred use of amoxicillin alone. Sources Published medical literature (MEDLINE database via Pubmed). Content While amoxicillin and clavulanic acid have similar half-lives, clavulanic acid is more protein bound and even less heat stable than amoxicillin, with primarily hepatic metabolism. It is also more strongly associated with gastrointestinal side effects, including Clostridium difficile infection, and, thus, in oral combination formulations, limits the maximum daily dose of amoxicillin that can be given. The first ratio for an amoxicillin–clavulanic acid combination was set at 4:1 due to clavulanic acid's high affinity for β-lactamases; ratios of 2:1, 7:1, 14:1 and 16:1 are currently available in various regions. Comparative effectiveness data for the different ratios are scarce. Amoxicillin–clavulanic acid is often used as empiric therapy for many of the World Health Organization's Priority Infectious Syndromes in adults and children, leading to extensive consumption, when some of these syndromes could be handled with a delayed antibiotic prescription approach or amoxicillin alone. Implications Using available epidemiological and pharmacokinetic data, we provide guidance on indications for amoxicillin versus amoxicillin–clavulanic acid and on optimal oral administration, including choice of combination ratio. More data are needed, particularly on heat stability, pharmacodynamic effects and emergence of resistance in ‘real-world’ clinical settings.

Background: The objective of this study was to assess whether a zinc-impregnated polypropylene mesh (ZnMesh) has better antibacterial properties in a contaminated environment compared with a regular polypropylene mesh. Materials and methods: Thirty-eight Wistar Han rats underwent cecal ligation and puncture to induce peritonitis 24 h before implantation of an intraperitoneal ZnMesh or a regular polypropylene mesh. Primary outcome was the number of colony forming units (CFU) per sample (mesh and abdominal wall). Secondary outcomes were macroscopic (incorporation of mesh, abscesses, and adhesions on mesh surface) and histological (inflammatory cell reaction, mesh-specific parameters, and collagen deposition) parameters. All outcomes were evaluated after 30 and 90 d. Results: After 30 d, no significant difference in CFU per sample was present between the ZnMesh and control groups. After 90 d, a lower number of CFU per sample was present in the ZnMesh group compared with the control group (trypticase soy agar with 5% sheep blood: 0 log10 CFU/sample IQR: 0-1.40 versus 1.58 log10 CFU/sample IQR: 0-4.30, P = 0.012; MacConkey: 0 log10 CFU/sample IQR: 0-2.65 versus 1.18 log10 CFU/sample IQR: 0-4.04, P = 0.438). After 90 d, the percentage of adhesions on mesh surface was significantly higher in the ZnMesh group (95% IQR: 60%-100% versus 50% IQR: 23%-75%, P = 0.029). No differences were seen in other macroscopic outcomes or histology. Conclusions: A significantly lower number of CFU per sample was found in the ZnMesh group after 90 d. After 30 d, no statistically significant differences in CFU per sample were seen. This result suggests that the ZnMesh group has better antibacterial properties in a contaminated environment. However, this is at the cost of a significantly higher percentage of adhesions.

BackgroundVoriconazole exhibits in vitro activity against Candida glabrata and Candida krusei (EUCAST/CLSI epidemiological cut-off values 1/0.25 and 1/0.5 mg/L, respectively). Yet, EUCAST found insufficient evidence to set breakpoints for these species. We explored voriconazole pharmacodynamics (PD) in an in vitro dynamic model simulating human pharmacokinetics (PK).MethodsFour C. glabrata and three C. krusei isolates (voriconazole EUCAST and CLSI MICs of 0.03–2 mg/L) were tested in the PK/PD model simulating voriconazole exposures (t½ ∼6 h q12h dosing for 3 days). PK/PD breakpoints were determined calculating the PTA for exposure indices fAUC0–24/MIC associated with half-maximal activity (EI50) using Monte Carlo simulation analysis.ResultsFungal load increased from 3.60 ± 0.35 to 8.41 ± 0.24 log10 cfu/mL in the drug-free control, with a maximum effect of ∼1 log10 kill of C. glabrata and C. krusei isolates with MICs of 0.06 and 0.25 mg/L, respectively, at high drug exposures. The 72 h log10 cfu/mL change versus fAUC0–24/MIC relationship followed a sigmoid curve for C. glabrata (R2=0.85–0.87) and C. krusei (R2=0.56–0.76) with EI50 of 49 (32–76) and 52 (33–78) fAUC/MIC for EUCAST and 55 (31–96) and 80 (42–152) fAUC/MIC for CLSI, respectively. The PTAs for C. glabrata and C. krusei isolates with EUCAST/CLSI MICs ≤0.125/≤0.06 mg/L were >95%. Isolates with EUCAST/CLSI MICs of 0.25–1/0.125–0.5 would require trough levels 1–4 mg/L; isolates with higher MICs would not attain the corresponding PK/PD targets without reaching toxicity.ConclusionsThe in vitro PK/PD breakpoints for C. glabrata and C. krusei for EUCAST (0.125 mg/L) and CLSI (0.06 mg/L) bisected the WT populations. Trough levels of >4 mg/L, which are not clinically feasible, are necessary for efficacy against WT isolates.

Background The determination of the minimal effective concentration (MEC) of echinocandins against Aspergillus species is subjective, time consuming and has been associated with very major errors. Methods The MECs/MICs of 40 WT [10 each of Aspergillus fumigatus species complex (SC), Aspergillus flavus SC, Aspergillus terreus SC and Aspergillus niger SC] and 4 non-WT A. fumigatus isolates were determined with EUCAST E.Def 9.3.1 read microscopically, macroscopically, spectrophotometrically and colorimetrically in three centres. The optimal conditions for spectrophotometric (single- versus multi-point readings) and colorimetric (XTT/menadione concentration and stability, incubation time) methods were evaluated in preliminary studies using different cut-offs for the determination of macroscopic, spectrophotometric and colorimetric MIC endpoints compared with the microscopically determined MEC. Inter-centre and inter-method essential (within one 2-fold dilution) agreement (EA) and categorical agreement (CA) were determined. Results Both macroscopic and spectrophotometric endpoint readings showed poor inter-centre EA (53%–66%) and low CA (41%–88%) in distinguishing WT from non-WT A. fumigatus SC isolates, while significant differences compared with the microscopic MECs were observed for all echinocandins (EA 6%–54%). For the colorimetric method, the optimal conditions were 400 mg/L XTT/6.25 μΜ menadione, incubation for 1–2 h until the drug-free control reached an absorbance at 450/630 nm of >0.8 and use of 50% inhibition of XTT conversion as a cut-off for all species and echinocandins. All non-WT isolates had high XTT MICs >1 mg/L, whereas the overall inter-centre EA and CA were 72%–89% and 100%, respectively. Conclusions The XTT colorimetric assay improved the antifungal susceptibility testing of echinocandins against Aspergillus spp., reliably detecting non-WT isolates.

Objectives To assess the antibacterial effects of a single 3 g oral fosfomycin dose on Escherichia coli and Klebsiella pneumoniae clinical isolates within a dynamic bladder infection model. Methods An in vitro model simulating dynamic urinary fosfomycin concentrations was used. Target fosfomycin exposure (Cmax = 1984 mg/L and Tmax = 7.5 h) was validated by LC-MS/MS. Pharmacodynamic responses of 24 E. coli and 20 K. pneumoniae clinical isolates were examined (fosfomycin MIC ≤0.25–128 mg/L). Mutant prevention concentration (MPC), fosfomycin heteroresistance, fosfomycin resistance genes and fosA expression were examined. Pathogen kill and emergence of high-level resistance (HLR; MIC >1024 mg/L) were quantified. Results Following fosfomycin exposure, 20 of 24 E. coli exhibited reductions in bacterial counts below the lower limit of quantification without regrowth, despite baseline fosfomycin MICs up to 128 mg/L. Four E. coli regrew (MIC = 4–32 mg/L) with HLR population replacement. At baseline, these isolates had detectable HLR subpopulations and MPC >1024 mg/L. All E. coli isolates were fosA negative. In contrast, 17 of 20 K. pneumoniae regrew post exposure, 6 with emergence of HLR (proportion = 0.01%–100%). The three isolates without regrowth did not have a detectable HLR subpopulation after dynamic drug-free incubation. All K. pneumoniae had MPC >1024 mg/L and were fosA positive. WGS analysis and fosA expression failed to predict fosfomycin efficacy. Conclusions E. coli and K. pneumoniae isolates demonstrate discrepant responses to a single fosfomycin dose in a dynamic bladder infection in vitro model. Treatment failure against E. coli was related to an HLR subpopulation, not identified by standard MIC testing. Activity against K. pneumoniae appeared limited, regardless of MIC testing, due to universal baseline heteroresistance.

Background: Fourth-generation cephalosporins have been developed to improve their potency, that is, low minimal inhibitory concentrations (MICs) and to prevent resistance selection of derepressed AmpC-producing mutants in comparison to third-generation cephalosporins as ceftazidime. Objectives: We investigated the role of the administered cefpirome dose on the efficacy of treatment of a Klebsiella pneumoniae lung infection as well as in the selection of resistant Enterobacter cloacae isolates in the intestines of rats treated for a K. pneumoniae lung infection. Materials and Methods: Rats with K. pneumoniae lung infection received therapy with cefpirome doses of 0.4 to 50 mg/kg/day b.i.d. for 18 days. Resistance selection in intestinal E. cloacae was monitored during 43 days. Mutants were checked for β-lactamase activity, mutations in their structural ampC gene, ampD gene, and omp39-40 gene. Results: A 45% and 100% rat survival rate was obtained by administration of 3.1 and 12.5 mg/kg b.i.d. of cefpirome. A significant correlation was demonstrated in the reduction of the susceptible E. cloacae isolates with %fT>MIC at days 7, 14, 22, and 29. Cefpirome E. cloacae mutants, with increased cefpirome MICs, were obtained in only four rats. Conclusions: The treatment with cefpirome resulted in less selection of derepressed mutants in comparison to ceftazidime as shown by their low number per gram of feces and in a limited number of animals.

Objectives We used a dynamic bladder infection in vitro model with synthetic human urine (SHU) to examine fosfomycin exposures to effectively kill, or prevent emergence of resistance, among Pseudomonas aeruginosa isolates. Methods Dynamic urinary fosfomycin concentrations after 3 g oral fosfomycin were simulated, comparing single and multiple (daily for 7 days) doses. Pharmacodynamic response of 16 P. aeruginosa (MIC range 1 to >1024 mg/L) were examined. Baseline disc diffusion susceptibility, broth microdilution MIC and detection of heteroresistance were assessed. Pathogen kill and emergence of resistance over 72 h following a single dose, and over 216 h following daily dosing for 7 days, were investigated. The fAUC0–24/MIC associated with stasis and 1, 2 and 3 log10 kill were determined. Results Pre-exposure high-level resistant (HLR) subpopulations were detected in 11/16 isolates after drug-free incubation in the bladder infection model. Five of 16 isolates had >2 log10 kill after single dose, reducing to 2/16 after seven doses. Post-exposure HLR amplification occurred in 8/16 isolates following a single dose and in 11/16 isolates after seven doses. Baseline MIC ≥8 mg/L with an HLR subpopulation predicted post-exposure emergence of resistance following the multiple doses. A PK/PD target of fAUC0–24/MIC >5000 was associated with 3 log10 kill at 72 h and 7 day-stasis. Conclusions Simulated treatment of P. aeruginosa urinary tract infections with oral fosfomycin was ineffective, despite exposure to high urinary concentrations and repeated daily doses for 7 days. Emergence of resistance was observed in the majority of isolates and worsened following prolonged therapy. Detection of a baseline resistant subpopulation predicted treatment failure.

Therapeutic drug monitoring (TDM) of antibiotics has been practiced for more than half a century, but it is still not widely applied for infected patients. It has a traditional focus on limiting toxicity of specific classes of antibiotics such as aminoglycosides and vancomycin. With more patients in critical care with higher levels of sickness severity and immunosuppression as well as an increasingly obese and ageing population, an increasing risk of suboptimal antibiotic exposure continues to escalate. As such, the value of TDM continues to expand, especially for beta-lactams which constitute the most frequently used antibiotic class. To date, the minimum inhibitory concentration (MIC) of infectious microbes rather than classification in terms of susceptible and resistant can be reported. In parallel, increasingly sophisticated TDM technology is becoming available ensuring that TDM is feasible and can deliver personalized antibiotic dosing schemes. There is an obvious need for extensive studies that will quantify the improvements in clinical outcome of individual TDM-guided dosing. We suggest that a broad diagnostic and medical investigation of the TDM arena, including market analyses and analytical technology assessment, is a current priority.

Aim: This study aimed at investigating the association of gene expression of multidrug efflux pumps (MexA, MexC, MexE, and MexX), the outer membrane porin OprD, and the β-lactamase AmpC with the antimicrobial susceptibility among 44 clinical isolates of Burkholderia cepacia complex (Bcc). Results: Increased expression of ampC gene showed significant association with reduced susceptibility to chloramphenicol. In fact, reduced susceptibility to chloramphenicol was correlated with overexpression of most genes (ampC, mexC, mexE, and mexX) studied here in majority (>95%) of the Bcc isolates. Increased mexA expression showed significant association with reduced susceptibility to β-lactam antimicrobials (ceftazidime, piperacillin-tazobactam, and meropenem) and co-trimoxazole. Reduced susceptibility to meropenem also showed significant correlation with overexpression of mexC and mexX, whereas reduced susceptibility to ceftazidime was also associated with mexE overexpression. Reduced susceptibility to levofloxacin was significantly associated with overexpression of mexX. The involvement of the efflux pumps in levofloxacin and ceftazidime resistance was further inferred from the finding that the efflux pump inhibitor, carbonyl cyanide m-chlorophenylhydrazone reduced minimum inhibitory concentrations for both the antimicrobials. Conclusions: To conclude, this study explored the high-level expression of mexC, mexE, and mexX efflux pumps genes and ampC in the clinical isolates of Bcc, which can be targeted at treating infections caused by Bcc.

Background Temocillin plasma protein binding (PPB) in healthy individuals is reported to be ∼85% but had not been studied in patients. Objectives To obtain normative data on temocillin PPB in patients in relation to infection and impact of co-medications widely used in ICU. Methods Plasma was obtained from healthy individuals (Group #1), non-ICU patients with UTI (Group #2), ICU patients with suspected/confirmed ventriculitis (Group #3) or with sepsis/septic shock (Group #4). Total and unbound temocillin concentrations were measured in spiked samples from temocillin-naive donors (in vitro) or in plasma from temocillin-treated subjects (in vivo). The impact of diluting plasma, using pharmaceutical albumin, or adding drugs potentially competing for PPB was tested in spiked samples. Data were analysed using a modified Hill–Langmuir equation taking ligand depletion into account. Results Temocillin PPB was saturable in all groups, both in vitro and in vivo. Maximal binding capacity (Bmax) was 1.2–2-fold lower in patients. At 20 and 200 mg/L (total concentrations), the unbound fraction reached 12%–29%, 23%–42% and 32%–52% in Groups #2, #3, #4. The unbound fraction was inversely correlated with albumin and C-reactive protein concentrations. Binding to albumin was 2–3-fold lower than in plasma and non-saturable. Drugs with high PPB but active at lower molar concentrations than temocillin caused minimal displacement, while fluconazole (low PPB but similar plasma concentrations to temocillin) increased up to 2-fold its unbound fraction. Conclusions Temocillin PPB is saturable, 2–4-fold lowered in infected patients in relation to disease severity (ICU admission, hypoalbuminaemia, inflammation) and only partially reproducible with albumin. Competition with other drugs must be considered for therapeutic concentrations to be meaningful.

Nitrofurantoin is an old antibiotic and an important first-line oral antibiotic for the treatment of uncomplicated urinary tract infections. However despite its long term use for over 60 years, little information is available with respect to its dose justification and this may be the reason of highly variable recommended doses and dosing schedules. Furthermore, nitrofurantoin is not a uniform product -crystal sizes of nitrofurantoin, and therefore pharmacokinetic properties, differ significantly by product. Moreover, pharmacokinetic profiling of some products is even lacking, or difficult to interpret because of its unstable chemical properties. Pharmacokinetic and pharmacodynamic data is now slowly becoming available. This review provides an overview of nitrofurantoins antibacterial, pharmacokinetic and pharmacodynamic properties. This shows that a clear rationale of current dosing regimens is scanty.

Antimicrobial resistance is increasing and few new antibiotics are in the development pipeline. Alternative strategies to treat infectious diseases, such as combination therapy, are urgently needed. Polymyxin B is a neglected and disused antibiotic with moderate antibacterial activity. In this study, we aimed to find synergistic interactions between polymyxin B and a wide range of non-antibiotics (non-ABs) to improve its efficacy. Thirty non-AB compounds from various drug classes were screened for synergistic potential with sub-minimum inhibitory concentrations (MICs) of polymyxin B in an agar diffusion assay against Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa (3 isolates per species). Potential candidates were further studied in in vitro checkerboard assays, up to 5 isolates per species, using optical density to assess growth. Interactions were assessed with fractional inhibitory concentration index (FIC i ) analysis and surface response analysis with Loewe, Bliss and Highest Single Agent analysis using the Combenefit program. Twenty non-ABs enhanced polymyxin B activity in the agar diffusion test in one or more species. Of these, three showed a consistent synergistic effect (FIC i ≤ 0.5) in the checkerboard assay for at least one species: citalopram, sertraline and spironolactone. Surface response analyses were largely in concordance, and further assessment showed only spironolactone was synergistic with polymyxin B at clinically relevant levels. The screening strategy used showed consistent synergism in vitro between polymyxin B and some non-ABs for A. baumannii, E. coli and K. pneumoniae. The synergistic interactions found merit further exploration as alternative strategies for difficult-to-treat infections.

Background and Objective Gentamicin is an aminoglycoside antibiotic predominantly used in bloodstream infections. Although the prevalence of obesity is increasing dramatically, there is no consensus on how to adjust the dose in obese individuals. In this prospective clinical study, we study the pharmacokinetics of gentamicin in morbidly obese and non-obese individuals to develop a dosing algorithm that results in adequate drug exposure across body weights. Methods Morbidly obese subjects undergoing bariatric surgery and non-obese healthy volunteers received one intravenous dose of gentamicin (obese: 5 mg/kg based on lean body weight, non-obese: 5 mg/kg based on total body weight [TBW]) with subsequent 24-h sampling. All individuals had a normal renal function. Statistical analysis, modelling and Monte Carlo simulations were performed using R version 3.4.4 and NONMEM® version 7.3. Results A two-compartment model best described the data. TBW was the best predictor for both clearance [CL = 0.089 × (TBW/70)0.73] and central volume of distribution [Vc = 11.9 × (TBW/70)1.25] (both p

Given emerging uropathogen resistance to more recent antibiotics, old antibiotics used for uncomplicated urinary tract infection (UTI) warrant re-examination. In this study, the urinary antibacterial activities of fosfomycin and nitrofurantoin were investigated by determining the urinary inhibitory titre and urinary bactericidal titre against uropathogens in urine samples from female volunteers following administration of single-dose fosfomycin (3 g) or nitrofurantoin (50 mg q6h or 100 mg q8h). Urine samples were collected over 48 h (fosfomycin) or 6 or 8 h (nitrofurantoin), with drug levels quantified with every void. Fosfomycin concentrations ranged from

Item does not contain fulltext BACKGROUND: Use of nitrofurantoin has increased significantly since its recent repositioning as a first-line agent for uncomplicated cystitis by multiple guidelines. However, current dosing regimens were developed in an era before robust pharmacokinetic testing and may not be optimal. Furthermore, formulations have been modified over the years. OBJECTIVES: To reassess the plasma and urinary pharmacokinetic profile of macrocrystalline nitrofurantoin in two commonly used dosing regimens. METHODS: In this open-label, randomized crossover pharmacokinetic trial, 12 healthy adult female volunteers were randomized to receive oral nitrofurantoin 100 mg q8h on days 1 and 2 and, after a washout period, 50 mg q6h on days 30 and 31, or the same dosing schemes in reversed order. Urine and blood were collected at steady state and analysed by UPLC. Pharmacokinetic analysis was performed by WinNonlin. RESULTS: Plasma peak concentrations were low (mean 0.33 mg/L, SD 0.08, and 0.69 mg/L, SD 0.35, after 50 and 100 mg, respectively) and dose dependent. The AUC0-24 was higher (6.49 versus 4.43 mg.h/L, P=0.021) for the 100 mg q8h dosing regimen, but the dose-normalized AUC was similar for the two regimens. In contrast, urinary concentrations were dose independent: increasing the nitrofurantoin dose delayed the time to peak urinary concentration, while steady-state AUC0-24 values remained unchanged (943.49 and 855.95 mg.h/L at 50 mg q6h and 100 mg q8h, respectively). CONCLUSIONS: Plasma concentrations were relatively low and dose dependent. The dose-independent urinary concentrations suggest that excretion of nitrofurantoin into the urine is saturable. Pharmacodynamic studies are urgently required to determine the impact of these findings.

Background Reference antifungal susceptibility testing of echinocandins against Aspergillus spp. relies on the determination of the minimal effective concentration, which is difficult to perform, time-consuming and subjective. We developed and evaluated in a multicentre study an agar-based screening method for echinocandin susceptibility testing of Aspergillus spp. Methods Forty WT isolates [10 Aspergillus fumigatus species complex (SC), 10 Aspergillus flavus SC, 10 Aspergillus terreus SC and 10 Aspergillus niger SC] and 4 non-WT A. fumigatus isolates with or without known fks alterations were used. The optimal test conditions and stability over time were evaluated in preliminary studies monitoring colony growth. Twenty-microlitre aliquots of 1–2 McFarland inocula in 0.1% Tween 20 aqueous solution were added to each well and plates were incubated for 24/48 h at 35 ± 2°C. Subsequently, all isolates were tested blindly at three centres using four-well screening plates, containing anidulafungin, caspofungin, micafungin or no antifungal in each of the four wells, respectively. Results WT isolates produced fluffy colonies on drug-free agar wells only. The non-WT isolates produced fluffy colonies on echinocandin-containing and control agar wells. Using the echinocandin concentrations of 0.25 mg/L anidulafungin, 1 mg/L caspofungin and 0.125 mg/L micafungin, and the compact (non-fluffy) versus fluffy colony morphology endpoint, all centres successfully discriminated non-WT and WT strains even after 24 h. Among the three echinocandins, anidulafungin produced the clearest endpoints. Conclusions The four-well plate agar method is suitable for echinocandin susceptibility screening of Aspergillus spp. and can be used to detect echinocandin non-WT isolates.

The polymyxin antibiotics colistin (polymyxin E) and polymyxin B became available in the 1950s and thus did not undergo contemporary drug development procedures. Their clinical use has recently resurged, assuming an important role as salvage therapy for otherwise untreatable gram-negative infections. Since their reintroduction into the clinic, significant confusion remains due to the existence of several different conventions used to describe doses of the polymyxins, differences in their formulations, outdated product information, and uncertainties about susceptibility testing that has led to lack of clarity on how to optimally utilize and dose colistin and polymyxin B. We report consensus therapeutic guidelines for agent selection and dosing of the polymyxin antibiotics for optimal use in adult patients, as endorsed by the American College of Clinical Pharmacy (ACCP), Infectious Diseases Society of America (IDSA), International Society of Anti-Infective Pharmacology (ISAP), Society for Critical Care Medicine (SCCM), and Society of Infectious Diseases Pharmacists (SIDP). The European Society for Clinical Microbiology and Infectious Diseases (ESCMID) endorses this document as a consensus statement. The overall conclusions in the document are endorsed by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). We established a diverse international expert panel to make therapeutic recommendations regarding the pharmacokinetic and pharmacodynamic properties of the drugs and pharmacokinetic targets, polymyxin agent selection, dosing, dosage adjustment and monitoring of colistin and polymyxin B, use of polymyxin-based combination therapy, intrathecal therapy, inhalation therapy, toxicity, and prevention of renal failure. The treatment guidelines provide the first ever consensus recommendations for colistin and polymyxin B therapy that are intended to guide optimal clinical use.

Objectives The rise in carbapenem resistance among Gram-negative bacteria has renewed interest in colistin. Recently, the EUCAST-CLSI Polymyxin Breakpoints Working Group declared that broth microdilution (BMD) is the only valid method for colistin susceptibility testing. BMD is not easily incorporated into the routine work of clinical laboratories, and usually this test is incorporated serially, resulting in delayed susceptibility reporting. We tested a strategy of combining VITEK® 2 with a 2 μg/mL colistin agar dilution (VITEK® 2/AD) screening plate to improve performance and time to reporting of colistin susceptibility. Methods Colistin susceptibility for 364 clinical isolates was determined by VITEK® 2/AD and compared with the reference standard BMD according to the ISO 20776-1:2007 and CLSI guidelines. The EUCAST colistin susceptibility breakpoint of ≤2 μg/mL was used. Escherichia coli NCTC 13846 served as quality control strain. Agreement, very major error (VME) and major error rates were determined using ISO 20776-2:2007. Results The VME rate for VITEK® 2 alone was 30.6% (15/49, 95% CI 18.3–45.4%), and was reduced to 10.2% (5/49, 95% CI 3.4–22.2%) using the VITEK® 2/AD combined testing. The combined testing had categorical agreement with BMD of 97% (354/364, 95% CI 95.0–98.7%), and a major error (ME) rate of 1.6% (5/315, 95% CI 0.5–3.7%). Using the combined testing, even against challenging strains, 349 (95.8%, 95% CI 93.3–97.7%) colistin susceptibility results could be reported, and only 15 isolates required further analysis by BMD. Discussion Our method is simple to apply and allows rapid reporting of colistin susceptibility.

Background The Minimum Inhibitory Concentration (MIC) is a reference value for susceptibility testing of bacteria. However, the MIC is a net result of growth and killing after a certain duration of exposure under standardized favourable in vitro conditions. Killing and growth characteristics of a drug may yield more information on its activity and help to explain discrepancies between efficacy observed in vitro and in vivo. Methods The MIC of meropenem was determined for P. aeruginosa ATCC 27853 both by microdilution and the E-test in dilutions of Mueller Hinton (MH) broth from 100% to 1%. Time-kill curves were obtained for twofold dilutions of meropenem. Growth rates and kill rates at each concentration and dilution were obtained by linear regression. The Hill equation was fit to the kill rates vs concentrations. Results Growths rates decreased log linearly from 0.63/h at 100% to 0.29/h at 6% MH. Over the 100–6% MH dilution range, there was a log-linear decrease of the MIC of meropenem of both the E-test and microdilution. The EC50s decreased from 0.29 mg/L to 0.07 mg/L, which is in agreement with the MIC results. There was a log-linear relationship between MIC and EC50 for the various dilutions MH. Conclusions The availability of nutritional factors is related to the MIC, and a lower availability is related to both a lower growth rate and higher kill rate. Since nutritional factors are less abundantly available in vivo as compared to in vitro, this should be taken into account when translating in vitro to in vivo pharmacodynamics.

Objectives Fosfomycin is an established treatment for uncomplicated urinary tract infections (UTIs), yet evidence supporting susceptibility breakpoints is limited. We examine the UTI susceptibility criteria. Methods Fosfomycin susceptibility, heteroresistance and in vitro growth in a bladder infection model, after a single 3 g dose of oral fosfomycin, were bridged to human pharmacokinetics with pharmacokinetic/pharmacodynamic and Monte Carlo analyses. Data from common uropathogens (24 Escherichia coli, 20 Klebsiella pneumoniae, 4 Enterobacter cloacae, 14 Pseudomonas aeruginosa, 8 Enterococcus faecalis and 8 Enterococcus faecium) were compared and analysed to ascertain species-specific PTA. Results Glucose-6-phosphate (G6P) increased MICs of E. coli, K. pneumoniae and E. cloacae (median 2-fold dilutions 3–5), but not of P. aeruginosa and Enterococcus. Atypical E. coli lacking G6P potentiation were killed in the bladder infection model despite high MICs (32–128 mg/L). Fosfomycin heteroresistance was uncommon in E. coli (MIC > 2 mg/L) but was detected in the majority of K. pneumoniae (MIC > 1 mg/L) and P. aeruginosa (MIC >8 mg/L). For these species, baseline heteroresistance was a strong predictor for treatment failure in the model. No heteroresistance was found in Enterococcus. The fAUC/MIC targets for stasis were 1935, 3393, 9968, 2738 and 283 for typical E. coli, K. pneumoniae, E. cloacae, P. aeruginosa and E. faecalis, respectively (synthetic human urine medium alone promoted a 1 log10 kill in E. faecium). A >95% PTA for stasis was only found at MIC ≤ epidemiological cut-off (ECOFF) for E. coli (4 mg/L). For other species, PTAs were low for WT populations. Conclusions With the exception of E. coli, fosfomycin is a poor target for other uropathogen species. A reduction in oral fosfomycin UTI breakpoints is supported.

Background In hospital settings, restriction of selected classes of antibiotics is usually believed to contribute to containment of resistance development. We performed a systematic review and meta-analysis to assess the effect of restricting the use of specific antibiotic classes on the prevalence of resistant bacterial pathogens. Methods We conducted a systematic literature search in Embase and PubMed/OVID MEDLINE. We included studies until June 4, 2020 in which a restrictive antibiotic policy was applied and prevalence of resistance and use of antibiotics were reported. We calculated the overall effect of antimicrobial resistance between postintervention versus preintervention periods using pooled odds ratios (ORs) from a mixed-effects model. We stratified meta-analysis by antibiotic-pathogen combinations. We assessed heterogeneity between studies using the I2 statistic and sources of heterogeneity using meta-regression. Results We included 15 individual studies with an overall low quality of evidence. In meta-analysis, significant reductions in resistance were only observed with nonfermenters after restricting fluoroquinolones (OR = 0.77, 95% confidence interval [CI] = 0.62–0.97) and piperacillin-tazobactam (OR = 0.81, 95% CI = 0.72–0.92). High degrees of heterogeneity were observed with studies restricting carbapenem (Enterobacterales, I2 = 70.8%; nonfermenters, I2 = 81.9%), third-generation cephalosporins (nonfermenters, I2 = 63.3%), and fluoroquiolones (nonfermenters, I2 = 64.0%). Results were comparable when excluding studies with fewer than 50 bacteria. There was no evidence of publication bias for any of the antibiotic-pathogen combinations. Conclusions We could not confirm that restricting carbapenems or third-generation cephalosporins leads to decrease in prevalence of antibiotic resistance among Enterobacterales, nonfermenters, or Gram-positive bacteria in hospitalized patients. Nevertheless, reducing fluoroquinolone and piperacilline-tazobactam use may decrease resistance in nonfermenters., Restriction of selected classes of antibiotics might be useful when specifically targeting a decrease in resistance of nonfermenters. For the remaining selected antibiotic-pathogen combinations, the available evidence is insufficient to conclude that a restrictive antibiotic prescribing policy decreases bacterial resistance.

Extended-spectrum-β-lactamase (ESBL)-producing strains are increasing worldwide, limiting therapeutic options. Taniborbactam (VNRX-5133) is a newly developed β-lactamase inhibitor with a wide spectrum of activity covering both serine and metallo enzymes. We therefore evaluated cefepime-taniborbactam activity against ESBL-producing isolates and determined the concentrations to be used in MIC determinations in the clinical laboratory. The in vitro activity of cefepime (0.06 to 256 mg liter-1) combined with taniborbactam (0.03 to 32mg liter21) against 129 clinically and molecularly well-documented ESBL-producing isolates (42 Escherichia coli, 39 Klebsiella pneumoniae, 28 Pseudomonas aeruginosa, 16 Enterobacter cloacae, 2 Citrobacter freundii, and 2 Enterobacter aerogenes) was tested with a broth microdilution checkerboard method based on the ISO standard. The MICs of cefepime alone and in combination, together with percentage resistance at different concentrations of taniborbactam, were calculated for each species and resistance mechanism. The median (range)/MIC90of cefepime was 32 (0.125 to 256)/256mg liter-1for all Enterobacterales isolates (n = 101), with 72% being resistant, and 32 (8 to 256)/128mg liter-1for the 28 P. aeruginosa isolates, with 86% being resistant. The median (range)/90th percentile concentration of taniborbactam required to restore Enterobacterales susceptibility to cefepime (MIC ≤1mg liter-1) was 0.06 (≤0.03 to 32)/4mg liter-1and P. aeruginosa susceptibility to increased exposure to cefepime (MIC ≤8mg liter-1) 1 (≤0.032 to 32)/32mg liter-1. At a fixed concentration of 4mg liter21 of taniborbactam, cefepime median (range)/MIC90were reduced to 0.125 (0.06 to 4)/1mg liter-1for Enterobacterales with no resistant isolates found, and to 8 (2 to 64)/16mg liter-1for P. aeruginosa isolates, where 36% remained resistant. The combination cefepime-taniborbactam demonstrated a potent activity against ESBL isolates, restoring susceptibility of all Enterobacterales and two-thirds of P. aeruginosa isolates.

Posaconazole is more active than fluconazole against Candida albicans in vitro and is approved for the treatment of oropharyngeal candidiasis but not for that of invasive candidiasis (IC). Here, we explored the efficacy of posaconazole against C. albicans in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model of IC and determined the probability of pharmacodynamic target attainment for the oral solution and intravenous (i.v.)/tablet formulations. Three clinical C. albicans isolates (posaconazole MICs, 0.008 to 0.25 mg/liter) were studied in the in vitro PK/PD dilution model simulating steady-state posaconazole PK. The in vitro exposure-effect relationship, area under the 24-h free drug concentration curve (fAUC0-24)/MIC, was described and compared with in vivo outcome in animals with IC. PK/PD susceptibility breakpoints and trough levels required for optimal treatment were determined for EUCAST and CLSI 24-h/48-h (CLSI24h/CLSI48h) methods using the fAUC0-24/MIC associated with half-maximal activity (EI50) and Monte Carlo simulation analysis for oral solution (400mg every 12 hours [q12h]) and i.v./tablet formulations (300mg q24h). The in vitro mean (95% confidence interval [CI]) EI50 was 330 (183 to 597) fAUC0-24/MIC for CLSI24h and 169 (92 to 310) for EUCAST/CLSI48h methods, which are close to the near-stasis in vivo effect. The probability of target attainment for EI50was estimated; for the wild-type isolates (MIC≤0.06 mg/liter), it was low for the oral solution and higher than 95% for the i.v./tablet formulations for the EUCAST/CLSI48h methods but not for the CLSI 24-h method. Non-wild-type isolates with EUCAST/ CLSI48h MICs of 0.125 and 0.25 mg/liter would require trough levels of >1.2 and >2.4 mg/liter, respectively. Posaconazole i.v./tablet formulations may have a role in the therapy of invasive infections by wild-type C. albicans isolates, provided that a steady state is reached quickly. A PK/PD susceptibility breakpoint at the epidemiological cutoff (ECV/ECOFF) of 0.06 mg/liter was determined.

The post-antibiotic effect (PAE) of ceftazidime-avibactam

Objectives To describe the population genetics and antibiotic resistance gene distribution of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates causing infections in three Mediterranean countries. Methods Isolates were collected during the 2013–17 AIDA clinical trial in six hospitals in Israel, Greece and Italy. WGS, bioinformatic characterization and antibiotic resistance profiling were performed. Results In the 247 CRAB isolates characterized in this study, ST distribution varied by country: 29/31 (93.5%) Greek isolates, 34/41 (82.9%) Italian isolates and 70/175 (40.0%) Israeli isolates belonged to ST2. The identified ST2 isolates included eight distinct clades: 2C, 2D and 2H were significantly more common in Italy, while 2F was unique to Greece. The uncommon ST3 was not present among Greek isolates and constituted only 5/41 (12%) Italian isolates. On the other hand, it was much more common among Israeli isolates: 78/175 (44.6%) belonged to ST3. The vast majority of isolates, 240/247 (97.2%), were found to harbour acquired carbapenemases, primarily blaOXA-23. The chromosomal oxaAb (blaOXA-51-like) and ampC genes characteristic of this organism were also ubiquitous. Most (96.4%) ST3 isolates carried a broad-host-range plasmid IncP1α. Conclusions The geographical differences in CRAB populations support the theory that clonal spread of CRAB leads to endemicity in hospitals and regions. The close association between antibiotic resistance genes and clades, and between plasmids and STs, suggest that de novo creation of MDR A. baumannii is rare. The clustering of antibiotic resistance genes and plasmids that is unique to each clade/ST, and nearly uniform within clades/STs, suggests that horizontal transmission is rare but crucial to the clade’s/ST’s success.

[Scope] These ESCMID guidelines address the targeted antibiotic treatment of third-generation cephalosporin-resistant Enterobacterales (3GCephRE) and carbapenem-resistant Gram-negative bacteria, focusing on the effectiveness of individual antibiotics and on combination versus monotherapy., [Methods] An expert panel was convened by ESCMID. A systematic review was performed including randomized controlled trials and observational studies, examining different antibiotic treatment regimens for the targeted treatment of infections caused by the 3GCephRE, carbapenem-resistant Enterobacterales, carbapenem-resistant Pseudomonas aeruginosa and carbapenem-resistant Acinetobacter baumannii. Treatments were classified as head-to-head comparisons between individual antibiotics and between monotherapy and combination therapy regimens, including defined monotherapy and combination regimens only. The primary outcome was all-cause mortality, preferably at 30 days and secondary outcomes included clinical failure, microbiological failure, development of resistance, relapse/recurrence, adverse events and length of hospital stay. The last search of all databases was conducted in December 2019, followed by a focused search for relevant studies up until ECCMID 2021. Data were summarized narratively. The certainty of the evidence for each comparison between antibiotics and between monotherapy and combination therapy regimens was classified by the GRADE recommendations. The strength of the recommendations for or against treatments was classified as strong or conditional (weak)., [Recommendations] The guideline panel reviewed the evidence per pathogen, preferably per site of infection, critically appraising the existing studies. Many of the comparisons were addressed in small observational studies at high risk of bias only. Notably, there was very little evidence on the effects of the new, recently approved, β-lactam/β-lactamase inhibitors on infections caused by carbapenem-resistant Gram-negative bacteria. Most recommendations are based on very-low- and low-certainty evidence. A high value was placed on antibiotic stewardship considerations in all recommendations, searching for carbapenem-sparing options for 3GCephRE and limiting the recommendations of the new antibiotics for severe infections, as defined by the sepsis-3 criteria. Research needs are addressed., These guidelines were supported in part by ESCMID.

Background Population external validity is the extent to which an experimental study results can be generalized from a specific sample to a defined population. In order to apply the results of a study, we should be able to assess its population external validity. We performed an investigator-initiated randomized controlled trial (RCT) (AIDA study), which compared colistin-meropenem combination therapy to colistin monotherapy in the treatment of patients infected with carbapenem-resistant Gram-negative bacteria. In order to examine the study’s population external validity and to substantiate the use of AIDA study results in clinical practice, we performed a concomitant observational trial. Methods The study was conducted between October 1st, 2013 and January 31st, 2017 (during the RCTs recruitment period) in Greece, Israel and Italy. Patients included in the observational arm of the study have fulfilled clinical and microbiological inclusion criteria but were excluded from the RCT due to receipt of colistin for > 96 h, refusal to participate, or prior inclusion in the RCT. Non-randomized cases were compared to randomized patients. The primary outcome was clinical failure at 14 days of infection onset. Results Analysis included 701 patients. Patients were infected mainly with Acinetobacter baumannii [78.2% (548/701)]. The most common reason for exclusion was refusal to participate [62% (183/295)]. Non-randomized and randomized patients were similar in most of the demographic and background parameters, though randomized patients showed minor differences towards a more severe infection. Combination therapy was less common in non-randomized patients [31.9% (53/166) vs. 51.2% (208/406), p = 0.000]. Randomized patients received longer treatment of colistin [13 days (IQR 10–16) vs. 8.5 days (IQR 0–15), p = 0.000]. Univariate analysis showed that non-randomized patients were more inclined to clinical failure on day 14 from infection onset [82% (242/295) vs. 75.5% (307/406), p = 0.042]. After adjusting for other variables, non-inclusion was not an independent risk factor for clinical failure at day 14. Conclusion The similarity between the observational arm and RCT patients has strengthened our confidence in the population external validity of the AIDA trial. Adding an observational arm to intervention studies can help increase the population external validity and improve implementation of study results in clinical practice. Trial registration The trial was registered with ClinicalTrials.gov, number NCT01732250 on November 22, 2012.

Extended-spectrum-β-lactamase (ESBL)-producing strains are increasing worldwide, limiting therapeutic options. Taniborbactam (VNRX-5133) is a newly developed β-lactamase inhibitor with a wide spectrum of activity covering both serine and metallo enzymes. We therefore evaluated cefepime-taniborbactam activity against ESBL-producing isolates and determined the concentrations to be used in MIC determinations in the clinical laboratory. The in vitro activity of cefepime (0.06 to 256 mg liter(−1)) combined with taniborbactam (0.03 to 32 mg liter(−1)) against 129 clinically and molecularly well-documented ESBL-producing isolates (42 Escherichia coli, 39 Klebsiella pneumoniae, 28 Pseudomonas aeruginosa, 16 Enterobacter cloacae, 2 Citrobacter freundii, and 2 Enterobacter aerogenes) was tested with a broth microdilution checkerboard method based on the ISO standard. The MICs of cefepime alone and in combination, together with percentage resistance at different concentrations of taniborbactam, were calculated for each species and resistance mechanism. The median (range)/MIC(90) of cefepime was 32 (0.125 to 256)/256 mg liter(−1) for all Enterobacterales isolates (n = 101), with 72% being resistant, and 32 (8 to 256)/128 mg liter(−1) for the 28 P. aeruginosa isolates, with 86% being resistant. The median (range)/90th percentile concentration of taniborbactam required to restore Enterobacterales susceptibility to cefepime (MIC ≤1 mg liter(−1)) was 0.06 (≤0.03 to 32)/4 mg liter(−1) and P. aeruginosa susceptibility to increased exposure to cefepime (MIC ≤8 mg liter(−1)) 1 (≤0.032 to 32)/32 mg liter(−1). At a fixed concentration of 4 mg liter(−1) of taniborbactam, cefepime median (range)/MIC(90) were reduced to 0.125 (0.06 to 4)/1 mg liter(−1) for Enterobacterales with no resistant isolates found, and to 8 (2 to 64)/16 mg liter(−1) for P. aeruginosa isolates, where 36% remained resistant. The combination cefepime-taniborbactam demonstrated a potent activity against ESBL isolates, restoring susceptibility of all Enterobacterales and two-thirds of P. aeruginosa isolates.

Posaconazole exhibits in-vitro activity against Candida glabrata and Candida krusei. Epidemiological cut-off values set by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and the Clinical and Laboratory Standards Institute (CLSI) are 1/1 and 0.5/0.5 mg/L, respectively, but clinical breakpoints have not been established to date. This study explored the pharmacodynamics (PD) of posaconazole in a validated one-compartment in-vitro pharmacokinetic (PK)/PD model, and determined the probability of PK/PD target attainment (PTA) for the available formulations. Five C. glabrata and three C. krusei isolates with posaconazole minimum inhibitory concentrations (MICs) of 0.06–2 and 0.03–0.25 mg/L, respectively, were tested in the PK/PD model simulating different time–concentration profiles of posaconazole. The exposure–effect relationship fAUC0–24/MIC was described for EUCAST/CLSI methods, and PTA was calculated in order to determine PK/PD susceptibility breakpoints for oral solution (400 mg q12h), and intravenous (i.v.)/tablet formulations (300 mg q24h). Fungicidal activity (~2log kill) was found against the most susceptible C. glabrata isolate alone, and against all three C. krusei isolates. The corresponding EUCAST/CLSI PK/PD targets (fAUC0–24/MIC) were 102/79 for C. glabrata and 12/8 for C. krusei. Mean PTA was high (>95%) for C. glabrata isolates with EUCAST/CLSI MICs ≤0.03/≤0.03 mg/L for oral solution and ≤0.125/≤0.125 mg/L for i.v. and tablet formulations for the wild-type population. For C. krusei isolates, mean PTA was high (>95%) for EUCAST/CLSI MICs ≤0.25/≤0.5 mg/L for oral solution and ≤1/≤2 mg/L for i.v. and tablet formulations for the wild-type population. The use of posaconazole to treat C. glabrata infections is questionable. Intravenous and tablet formulations may be therapeutic options for the treatment of C. krusei infections, and oral exposure can be optimized with therapeutic drug monitoring (trough levels >0.6–0.9 mg/L).

Background Pharmacokinetic (PK)–pharmacodynamic (PD) indices relate measures of drug exposure to antibacterial effect. Clinical PK–PD studies aim to correlate PK–PD indices with outcomes in patients. Optimization of dosing based on pre-clinical studies means that PK–PD relationships are difficult to establish; therefore studies need to be designed and reported carefully to validate pre-clinical findings. Objectives To describe the methodological features of clinical antibacterial and antifungal PK–PD studies that reported the relationship between PK–PD indices and clinical or microbiological responses. Methods Studies published between 1980 and 2015 were identified through systematic searches. Methodological features of eligible studies were extracted. Results We identified 85 publications containing 97 PK–PD analyses. Most studies were small, with fewer than 100 patients. Around a quarter were performed on patients with infections due to a single specific pathogen. In approximately one-third of studies, patients received concurrent antibiotics/antifungals and in some other studies patients received other treatments that may confound the PK–PD–outcome relationship. Most studies measured antimicrobial concentrations in blood/serum and only four measured free concentrations. Most performed some form of regression, time-to-event analysis or used the Hill/Emax equation to examine the association between PK–PD index and outcome. Target values of PK–PD indices that predict outcomes were investigated in 52% of studies. Target identification was most commonly done using recursive partitioning or logistic regression. Conclusions Given the variability in conduct and reporting, we suggest that an agreed set of standards for the conduct and reporting of studies should be developed.

Oral fosfomycin trometamol is licensed as a single oral dose for the treatment of uncomplicated urinary tract infections, with activity against multidrug-resistant uropathogens. The impact of interindividual variability in urinary concentrations on antimicrobial efficacy, and any benefit of giving multiple doses, is uncertain. We therefore performed pharmacodynamic profiling of oral fosfomycin, using a dynamic bladder infection in vitro model, to assess high and low urinary exposures following a single oral dose and three repeat doses given every 72 h, 48 h, and 24 h against 16 clinical isolates with various MICs of fosfomycin (8 Escherichia coli, 4 Enterobacter cloacae, and 4 Klebsiella pneumoniae isolates). Baseline fosfomycin high-level-resistant (HLR) subpopulations were detected prior to drug exposure in half of the isolates (2 E. coli, 2 E. cloacae, and 4 K. pneumoniae isolates; proportion, 1 × 10(−5) to 5 × 10(−4)% of the total population). Fosfomycin exposures were accurately reproduced compared to mathematical modeling (linear regression slope, 1.1; R(2), 0.99), with a bias of 3.8% ± 5.7%. All 5/5 isolates with MICs of ≤1 μg/ml had no HLR and were killed, whereas 8/11 isolates with higher MICs regrew regardless of exposure to high or low urinary concentrations. A disk diffusion zone of

There are limited treatment options for enterococcal urinary tract infections, especially vancomycin-resistant Enterococcus (VRE). Oral fosfomycin is a potential option, although limited data are available guiding dosing and susceptibility. We undertook pharmacodynamic profiling of fosfomycin against E. faecalis and E. faecium isolates using a dynamic in vitro bladder infection model. Eighty-four isolates underwent fosfomycin agar dilution susceptibility testing (E. faecalis MIC(50/90) 32/64 μg/ml; E. faecium MIC(50/90) 64/128 μg/ml). Sixteen isolates (including E. faecalis ATCC 29212 and E. faecium ATCC 35667) were chosen to reflect the MIC range and tested in the bladder infection model with synthetic human urine (SHU). Under drug-free conditions, E. faecium demonstrated greater growth restriction in SHU compared to E. faecalis (E. faecium maximal growth 5.8 ± 0.6 log(10) CFU/ml; E. faecalis 8.0 ± 1.0 log(10) CFU/ml). Isolates were exposed to high and low fosfomycin urinary concentrations after a single dose, and after two doses given over two days with low urinary concentration exposure. Simulated concentrations closely matched the target (bias 2.3%). E. faecalis isolates required greater fosfomycin exposure for 3 log(10) kill from the starting inoculum compared with E. faecium. The ƒAUC(0-72)/MIC and ƒ%T > MIC(0-72) for E. faecalis were 672 and 70%, compared to 216 and 51% for E. faecium, respectively. There was no rise in fosfomycin MIC postexposure. Two doses of fosfomycin with low urinary concentrations resulted in equivalent growth inhibition to a single dose with high urinary concentrations. With this urinary exposure, fosfomycin was effective in promoting suppression of regrowth (>3 log(10) kill) in the majority of isolates.

Objectives In vitro models showing synergism between polymyxins and carbapenems support combination treatment for carbapenem-resistant Gram-negative (CRGN) infections. We tested the association between the presence of in vitro synergism and clinical outcomes in patients treated with colistin plus meropenem. Methods This was a secondary analysis of AIDA, a randomized controlled trial comparing colistin with colistin–meropenem for severe CRGN infections. We tested in vitro synergism using a checkerboard assay. Based on the fractional inhibitory concentration (ΣFIC) index for each colistin–meropenem combination, we categorized results as synergistic, antagonistic or additive/indifferent. The primary outcome was clinical failure at 14 days. Secondary outcomes were 14- and 28-day mortality and microbiological failure. Results The sample included 171 patients with infections caused by carbapenem-resistant Acinetobacter baumannii (n = 131), Enterobacteriaceae (n = 37) and Pseudomonas aeuruginosa (n = 3). In vitro testing showed synergism for 73 isolates, antagonism for 20 and additivism/indifference for 78. In patients who received any colistin plus meropenem, clinical failure at 14 days was 59/78 (75.6%) in the additivism/indifference group (reference category), 54/73 (74.0%) in the synergism group (adjusted odds ratio (aOR) 0.76, 95% CI 0.31–1.83), and 11/20 (55%) in the antagonism group (aOR 0.77, 95% CI 0.22–2.73). There was no significant difference between groups for any secondary outcome. Comparing the synergism group to patients treated with colistin monotherapy, synergism was not protective against 14-day clinical failure (aOR 0.52, 95% CI 0.26–1.04) or 14-day mortality (aOR1.09, 95% CI 0.60–1.96). Discussion In vitro synergism between colistin and meropenem via checkerboard method did not translate into clinical benefit.

CLSI and EUCAST susceptibility breakpoints for voriconazole and Candida albicans differ by one dilution (≤0.125 and ≤0.06 mg/liter, respectively) whereas the epidemiological cutoff values for EUCAST (ECOFF) and CLSI (ECV) are the same (0.03 mg/liter). We therefore determined the pharmacokinetic/pharmacodynamic (PK/PD) breakpoints of voriconazole against C. albicans for both methodologies with an in vitro PK/PD model, which was validated using existing animal PK/PD data. Four clinical wild-type and non-wild-type C. albicans isolates (voriconazole MICs, 0.008 to 0.125 mg/liter) were tested in an in vitro PK/PD model. For validation purposes, mouse PK were simulated and in vitro PD were compared with in vivo outcomes. Human PK were simulated, and the exposure-effect relationship area under the concentration-time curve for the free, unbound fraction of a drug from 0 to 24 h (fAUC(0–24))/MIC was described for EUCAST and CLSI 24/48-h methods. PK/PD breakpoints were determined using the fAUC(0–24)/MIC associated with half-maximal activity (EI(50)) and Monte Carlo simulation analysis. The in vitro 24-h PD EI(50) values of voriconazole against C. albicans were 2.5 to 5 (1.5 to 17) fAUC/MIC. However, the 72-h PD were higher at 133 (51 to 347) fAUC/MIC for EUCAST and 94 (35 to 252) fAUC/MIC for CLSI. The mean (95% confidence interval) probability of target attainment (PTA) was 100% (95 to 100%), 97% (72 to 100%), 83% (35 to 99%), and 49% (8 to 91%) for EUCAST and 100% (97 to 100%), 99% (85 to 100%), 91% (52 to 100%), and 68% (17 to 96%) for CLSI for MICs of 0.03, 0.06, 0.125, and 0.25 mg/liter, respectively. Significantly, >95% PTA values were found for EUCAST/CLSI MICs of ≤0.03 mg/liter. For MICs of 0.06 to 0.125 mg/liter, trough levels 1 to 4 mg/liter would be required to attain the PK/PD target. A PK/PD breakpoint of C. albicans voriconazole at the ECOFF/ECV of 0.03 mg/liter was determined for both the EUCAST and CLSI methods, indicating the need for breakpoint harmonization for the reference methodologies.

Purpose Tobramycin is an aminoglycoside antibiotic of which the 24 h exposure correlates with efficacy. Recently, we found that clearance of the aminoglycoside gentamicin correlates with total body weight (TBW). In this study, we investigate the full pharmacokinetic profile of tobramycin in obese and non-obese individuals with normal renal function. Methods Morbidly obese individuals (n = 20) undergoing bariatric surgery and non-obese healthy volunteers (n = 8), with TBW ranging 57–194 kg, received an IV dose of tobramycin with plasma concentrations measured over 24 h (n = 10 per individual). Statistical analysis, modelling and simulations were performed using NONMEM. Results In a two-compartment model, TBW was the best predictor for central volume of distribution (p

Objectives To determine trends, seasonality and the association between community antibiotic use and antimicrobial resistance (AMR) in Escherichia coli and Klebsiella pneumoniae in urinary tract infections. Methods We analysed Dutch national databases from January 2008 to December 2016 regarding antibiotic use and AMR for nitrofurantoin, trimethoprim, fosfomycin and ciprofloxacin. Antibiotic use was expressed as DDD/1000 inhabitant-days (DID) and AMR was expressed as the percentage of resistance from total tested isolates. Temporal trends and seasonality were analysed with autoregressive integrated moving average (ARIMA) models. Each antibiotic use–resistance combination was cross-correlated with a linear regression of the ARIMA residuals. Results The trends of DID increased for ciprofloxacin, fosfomycin and nitrofurantoin, but decreased for trimethoprim. Similar trends were found in E. coli and K. pneumoniae resistance to the same antibiotics, except for K. pneumoniae resistance to ciprofloxacin, which decreased. Resistance levels peaked in winter/spring, whereas antibiotic use peaked in summer/autumn. In univariate analysis, the strongest and most significant cross-correlations were approximately 0.20, and had a time delay of 3–6 months between changes in antibiotic use and changes in resistance. In multivariate analysis, significant effects of nitrofurantoin use and ciprofloxacin use on resistance to these antibiotics were found in E. coli and K. pneumoniae, respectively. There was a significant association of nitrofurantoin use with trimethoprim resistance in K. pneumoniae after adjusting for trimethoprim use. Conclusions We found a relatively low use of antibiotics and resistance levels over a 9 year period. Although the correlations were weak, variations in antibiotic use for these four antibiotics were associated with subsequent variations in AMR in urinary pathogens.

IntroductionWith the widespread use of electronic health records and handheld electronic devices in hospitals, informatics-based antimicrobial stewardship interventions hold great promise as tools to promote appropriate antimicrobial drug prescribing. However, more research is needed to evaluate their optimal design and impact on quantity and quality of antimicrobial prescribing.Methods and analysisUse of smartphone-based digital stewardship applications (apps) with local guideline directed empirical antimicrobial use by physicians will be compared with antimicrobial prescription as per usual as primary outcome in three hospitals in the Netherlands, Sweden and Switzerland. Secondary outcomes will include antimicrobial use metrics, clinical and process outcomes. A multicentre stepped-wedge cluster randomised trial will randomise entities defined as wards or specialty regarding time of introduction of the intervention. We will include 36 hospital entities with seven measurement periods in which the primary outcome will be measured in 15 participating patients per time period per cluster. At participating wards, patients of at least 18 years of age using antimicrobials will be included. After a baseline period of 2-week measurements, six periods of 4 weeks will follow in which the intervention is introduced in 6 wards (in three hospitals) until all 36 wards have implemented the intervention. Thereafter, we allow use of the app by everyone, and evaluate the sustainability of the app use 6 months later.Ethics and disseminationThis protocol has been approved by the institutional review board of each participating centre. Results will be disseminated via media, to healthcare professionals via professional training and meetings and to researchers via conferences and publications.Trial registration numberClinicalTrials.gov registry (NCT03793946). Stage; pre-results.

Objectives: The aim was to analyse the population pharmacokinetics of colistin and to explore the relationship between colistin exposure and time to death. Methods: Patients included in the AIDA randomized controlled trial were treated with colistin for severe infections caused by carbapenem-resistant Gram-negative bacteria. All subjects received a 9 million units (MU) loading dose, followed by a 4.5 MU twice daily maintenance dose, with dose reduction if creatinine clearance (CrCL) < 50 mL/min. Individual colistin exposures were estimated from the developed population pharmacokinetic model and an optimized two-sample per patient sampling design. Time to death was evaluated in a parametric survival analysis. Results: Out of 406 randomized patients, 349 contributed pharmacokinetic data. The median (90% range) colistin plasma concentration was 0.44 (0.14–1.59) mg/L at 15 minutes after the end of first infusion. In samples drawn 10 hr after a maintenance dose, concentrations were >2 mg/L in 94% (195/208) and 44% (38/87) of patients with CrCL ≤120 mL/min, and >120 mL/min, respectively. Colistin methanesulfonate sodium (CMS) and colistin clearances were strongly dependent on CrCL. High colistin exposure to MIC ratio was associated with increased hazard of death in the multivariate analysis (adjusted hazard ratio (95% CI): 1.07 (1.03–1.12)). Other significant predictors included SOFA score at baseline (HR 1.24 (1.19–1.30) per score increase), age and Acinetobacter or Pseudomonas as index pathogen. Discussion: The population pharmacokinetic model predicted that >90% of the patients had colistin concentrations >2 mg/L at steady state, but only 66% at 4 hr after start of treatment. High colistin exposure was associated with poor kidney function, and was not related to a prolonged survival.

Introduction. Quantification of bacterial load in tissue homogenates in in vivo pharmacodynamic studies is cumbersome and time-consuming.Aim. We therefore developed a new method for quantifying bacterial load in tissue homogenates of animals treated with a β-lactam and β-lactamase inhibitor using growth curves.Methods. The log10 colony-forming units (c.f.u.) ml-1 of 184 thigh and lung homogenates from female CD-1 mice infected intranasally and intramuscularly with 4 Pseudomonas aeruginosa, 4 Klebsiella pneumoniae, 3 Enterobacter cloacae and 2 Escherichia coli strains treated with a β-lactam drug and tazobactam were calculated using the standard approach of serial quantitative cultures and analysis of growth curves. Growth curves were obtained with continuous (every 10 min) monitoring of optical density at 630 nm (OD630) after 20 µl tissue homogenates were inoculated in total volume of 200 µl Mueller-Hinton broth in 96-well microtitration plates and incubated at 37 °C for 18 h.Results. The best correlation between log10 c.f.u. ml-1 determined with the serial quantitative cultures and growth curves was found at the time point corresponding to an OD630 of 0.25 increase above the baseline OD (average of first five timepoints) (R2=0.918-0.999). The median (range) differences between the two methods was -0.19 (-1.79-1.69) with 86-97 % of all isolates and species being within 1 log10 c.f.u. ml-1 with 1 h hands-on-time and

Background Population pharmacokinetic (popPK) models for antibiotics are used to improve dosing strategies and individualize dosing by therapeutic drug monitoring. Little is known about the differences in results of parametric versus nonparametric popPK models and their potential consequences in clinical practice. We developed both parametric and nonparametric models of imipenem using data from critically ill patients and compared their results. Methods Twenty-six critically ill patients treated with intravenous imipenem/cilastatin were included in this study. Median estimated glomerular filtration rate (eGFR) measured by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation was 116 mL/min/1.73 m2 (interquartile range 104–124) at inclusion. The usual dosing regimen was 500 mg/500 mg four times daily. On average, five imipenem levels per patient (138 levels in total) were drawn as peak, intermediate, and trough levels. Imipenem concentration-time profiles were analyzed using parametric (NONMEM 7.2) and nonparametric (Pmetrics 1.5.2) popPK software. Results For both methods, data were best described by a model with two distribution compartments and the CKD-EPI eGFR equation unadjusted for body surface area as a covariate on the elimination rate constant (Ke). The parametric population parameter estimates were Ke 0.637 h−1 (between-subject variability [BSV]: 19.0% coefficient of variation [CV]) and central distribution volume (Vc) 29.6 L (without BSV). The nonparametric values were Ke 0.681 h−1 (34.0% CV) and Vc 31.1 L (42.6% CV). Conclusions Both models described imipenem popPK well; the parameter estimates were comparable and the included covariate was identical. However, estimated BSV was higher in the nonparametric model. This may have consequences for estimated exposure during dosing simulations and should be further investigated in simulation studies. Electronic supplementary material The online version of this article (10.1007/s40262-020-00859-1) contains supplementary material, which is available to authorized users.

There are limited treatment options for enterococcal urinary tract infections, especially vancomycin-resistant Enterococcus (VRE). Oral fosfomycin is a potential option, although limited data are available guiding dosing and susceptibility. We undertook pharmacodynamic profiling of fosfomycin against E. faecalis and E. faecium isolates using a dynamic in vitro bladder infection model. Eighty-four isolates underwent fosfomycin agar dilution susceptibility testing (E. faecalis MIC50/90 32/64 μg/ml; E. faecium MIC50/90 64/128 μg/ml). Sixteen isolates (including E. faecalis ATCC 29212 and E. faecium ATCC 35667) were chosen to reflect the MIC range and tested in the bladder infection model with synthetic human urine (SHU). Under drug-free conditions, E. faecium demonstrated greater growth restriction in SHU compared to E. faecalis (E. faecium maximal growth 5.8 ± 0.6 log10 CFU/ml; E. faecalis 8.0 ± 1.0 log10 CFU/ml). Isolates were exposed to high and low fosfomycin urinary concentrations after a single dose, and after two doses given over two days with low urinary concentration exposure. Simulated concentrations closely matched the target (bias 2.3%). E. faecalis isolates required greater fosfomycin exposure for 3 log10 kill from the starting inoculum compared with E. faecium The ƒAUC0-72/MIC and ƒ%T > MIC0-72 for E. faecalis were 672 and 70%, compared to 216 and 51% for E. faecium, respectively. There was no rise in fosfomycin MIC postexposure. Two doses of fosfomycin with low urinary concentrations resulted in equivalent growth inhibition to a single dose with high urinary concentrations. With this urinary exposure, fosfomycin was effective in promoting suppression of regrowth (>3 log10 kill) in the majority of isolates.

CRISPR-Cas9 systems are enriched in human pathogenic bacteria and have been linked to cytotoxicity by an unknown mechanism. Here, we show that upon infection of human cells, Campylobacter jejuni secretes its Cas9 (CjeCas9) nuclease into their cytoplasm. Next, a native nuclear localization signal enables CjeCas9 nuclear entry, where it catalyzes metal-dependent nonspecific DNA cleavage leading to cell death. Compared to CjeCas9, native Cas9 of Streptococcus pyogenes (SpyCas9) is more suitable for guide-dependent editing. However, in human cells, native SpyCas9 may still cause some DNA damage, most likely because of its ssDNA cleavage activity. This side effect can be completely prevented by saturation of SpyCas9 with an appropriate guide RNA, which is only partially effective for CjeCas9. We conclude that CjeCas9 plays an active role in attacking human cells rather than in viral defense. Moreover, these unique catalytic features may therefore make CjeCas9 less suitable for genome editing applications.