Intravenous fosfomycin—back to the future. Systematic review and meta-analysis of the clinical literature

Fosfomycin single- and multiple-dose pharmacokinetics in patients undergoing prolonged intermittent renal replacement therapy

BACKGROUND

Fosfomycin is used increasingly in the treatment of MDR bacteria. It is eliminated by renal excretion, but data regarding dosing recommendations for patients undergoing modern means of renal replacement therapies are scarce.

OBJECTIVES

Evaluation of the pharmacokinetics (PK) of fosfomycin in patients undergoing prolonged intermittent renal replacement therapy (PIRRT) to guide dosing recommendations.

METHODS

Fosfomycin was given in 11 (7 female) patients with severe infections undergoing PIRRT. Plasma levels were measured at several timepoints on the first day of fosfomycin therapy, as well as 5-6 days into therapy, before and after the dialyser, to calculate its clearance. Fosfomycin was measured in the collected spent dialysate.

RESULTS

The median (IQR) plasma dialyser clearance for fosfomycin was 183.4 (156.9-214.9) mL/min, eliminating a total amount of 8834 (4556-10 440) mg of fosfomycin, i.e. 73.9% (45.3%-93.5%) of the initial dose. During PIRRT, the fosfomycin half-life was 2.5 (2.2-3.4) h. Data from multiple-dose PK showed an increase in fosfomycin Cmax from 266.8 (166.3-438.1) to 926.1 (446.8-1168.0) mg/L and AUC0-14 from 2540.5 (1815.2-3644.3) to 6714 (4060.6-10612.6) mg·h/L. Dialysis intensity during the study was 1.5 L/h. T>MIC was 100% in all patients.

CONCLUSIONS

Patients undergoing PIRRT experience significant fosfomycin elimination, requiring a dose of 5 g/8 h to reach adequate plasma levels. However, drug accumulation may occur, depending on dialysis frequency and intensity.

Multicentre, randomised, open-label, phase IV-III study to evaluate the efficacy of cloxacillin plus fosfomycin versus cloxacillin alone in adult patients with methicillin-susceptible Staphylococcus aureus bacteraemia: study protocol for the SAFO trial

INTRODUCTION

Methicillin-susceptible Staphylococcus aureus (MSSA) bacteraemia is a frequent condition, with high mortality rates. There is a growing interest in identifying new therapeutic regimens able to reduce therapeutic failure and mortality observed with the standard of care of beta-lactam monotherapy. In vitro and small-scale studies have found synergy between cloxacillin and fosfomycin against S. aureus. Our aim is to test the hypothesis that cloxacillin plus fosfomycin achieves higher treatment success than cloxacillin alone in patients with MSSA bacteraemia.

METHODS

We will perform a superiority, randomised, open-label, phase IV-III, two-armed parallel group (1:1) clinical trial at 20 Spanish tertiary hospitals. Adults (≥18 years) with isolation of MSSA from at least one blood culture ≤72 hours before inclusion with evidence of infection, will be randomly allocated to receive either cloxacillin 2 g/4-hour intravenous plus fosfomycin 3 g/6-hour intravenous or cloxacillin 2 g/4-hour intravenous alone for 7 days. After the first week, sequential treatment and total duration of antibiotic therapy will be determined according to clinical criteria by the attending physician.Primary endpoints: (1) Treatment success at day 7, a composite endpoint comprising all the following criteria: patient alive, stable or with improved quick-Sequential Organ Failure Assessment score, afebrile and with negative blood cultures for MSSA at day 7. (2) Treatment success at test of cure (TOC) visit: patient alive and no isolation of MSSA in blood culture or at another sterile site from day 8 until TOC (12 weeks after randomisation).We assume a rate of treatment success of 74% in the cloxacillin group. Accepting alpha risk of 0.05 and beta risk of 0.2 in a two-sided test, 183 subjects will be required in each of the control and experimental groups to obtain statistically significant difference of 12% (considered clinically significant).

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the Ethics Committee of Bellvitge University Hospital (AC069/18) and from the Spanish Medicines and Healthcare Product Regulatory Agency (AEMPS, AC069/18), and is valid for all participating centres under existing Spanish legislation. The results will be presented at international meetings and will be made available to patients and funders.

TRIAL REGISTRATION NUMBER

The protocol has been approved by AEMPS with the Trial Registration Number EudraCT 2018-001207-37. ClinicalTrials.gov Identifier: NCT03959345; Pre-results.

Evolutionary Trajectories toward Ceftazidime-Avibactam Resistance in Klebsiella pneumoniae Clinical Isolates

From January 2019 to April 2020, 32 KPC-producing, ceftazidime-avibactam (CZA) resistant Klebsiella pneumoniae strains were isolated in a university hospital in Rome, Italy. These strains belonged to the ST512, ST101 and ST307 high-risk clones. Nine different CZA-resistant KPC-3 protein variants were identified, five of them never previously reported (KPC-66 to KPC-70). Among them, KPC-31, KPC-39, KPC-49, KPC-66, KP-68, KPC-69 and KPC-70 showed amino acid substitutions, insertions and deletions in the Ω loop of the protein. KPC-29 has the duplication, while the novel KPC-67 has the triplication of the KDD triplet in the 270-loop of the protein. Genomics performed on contemporary resistant and susceptible clones underlined that those novel mutations emerged in bla_KPC-3 genes located on conserved plasmids: in ST512, all bla_KPC-3 mutant genes were located in pKpQIL plasmids, while the three novel bla_KPC-3 mutants identified in ST101 were on FIIk-FIA(HI1)-R plasmids. Selection also promoted multiplication of the carbapenemase gene copy number by transposition, recombination, and fusion of resident plasmids. When expressed in Escherichia coli recipient cells cloned in the high-copy number pTOPO vector, the Ω loop mutated variants showed CZA-resistant phenotype associated with susceptibility to carbapenems, while KPC variants with insertions in the 270-loop showed residual activity on carbapenems. The investigation of CZA-resistance mechanisms offered the unique opportunity to study vertical, horizontal, and oblique evolutionary trajectories of K. pneumoniae high-risk clones.

Intravenous fosfomycin for the treatment of patients with bone and joint infections: a review

INTRODUCTION

Fosfomycin is a wide spectrum bactericidal antibiotic with a unique mode of action, low toxicity, and good penetration in tissues with deep-seated infections, including bone and joint infections.

AREAS COVERED

Data were extracted from 19 published articles. Three hundred and sixty-five patients, with broad age range, received intravenous fosfomycin for the treatment of bone and joint infections (including arthritis, acute and chronic osteomyelitis, discitis, periprosthetic joint infection). Fosfomycin was given as part of a combination antimicrobial therapy in the majority of patients (93.7%). The dosage of fosfomycin ranged from 4 g/day (in one case) to 24 g/day. The dosage of fosfomycin, in some cases, mostly pediatric, was calculated based on body weight, ranging from 50 mg/kg/day to 250 mg/kg/day. The duration of fosfomycin treatment ranged from a couple of days up to 3 months. The most common isolated pathogen was Staphylococcus aureus (38.9%). Three hundred patients (82.2%) were successfully treated. Fosfomycin was well tolerated, as few patients developed mild adverse events, mostly gastrointestinal discomfort, hypernatremia, skin rash, and neutropenia.

EXPERT OPINION

The available data suggests that intravenous fosfomycin may be beneficial for the treatment of patients with bone and joint infections, especially when used as part of a combination antibiotic regimen.

Combination therapy with rifampicin or fosfomycin in patients with Staphylococcus aureus bloodstream infection at high risk for complications or relapse: results of a large prospective observational cohort

OBJECTIVES

To investigate whether Staphylococcus aureus bloodstream infection (SAB) patients at high risk for complications or relapse benefit from combination therapy with adjunctive rifampicin or fosfomycin.

METHODS

In this post hoc analysis, SAB patients with native valve infective endocarditis, osteoarticular infections or implanted foreign devices were included. The co-primary endpoints were all-cause 90 day mortality and death or SAB-related late complications within 180 days. To overcome treatment selection bias and account for its time dependence, inverse probability of treatment weights were calculated and included in marginal structural Cox proportional hazard models (MSCMs).

RESULTS

A total of 578 patients were included in the analysis, of which 313 (54%) received combination therapy with either rifampicin (n = 242) or fosfomycin (n = 58). In the multivariable MSCM, combination therapy was associated with a better outcome, that is, a lower rate of death or SAB-related late complications within 180 days (HR 0.65, 95% CI 0.46-0.92). This beneficial effect was primarily seen in patients with implanted foreign devices, in which combination therapy was associated with a lower rate of death or SAB-related late complications within 180 days (HR 0.53, 95% CI 0.35-0.79) and a lower 90 day mortality (HR 0.57, 95% CI 0.36-0.91). Upon agent-specific stratification, we found no significant differences in outcomes between combination therapy containing rifampicin and fosfomycin; however, the number of patients in most subgroups was not large enough to draw firm conclusions.

CONCLUSIONS

In patients with implanted foreign devices, combination therapy was associated with a better long-term outcome. Larger prospective studies are needed to validate these findings.

Pandrug-resistant Gram-negative bacteria: a systematic review of current epidemiology, prognosis and treatment options

BACKGROUND

The literature on the epidemiology, mortality and treatment of pandrug-resistant (PDR) Gram-negative bacteria (GNB) is scarce, scattered and controversial.

OBJECTIVES

To consolidate the relevant literature and identify treatment options for PDR GNB infections.

METHODS

A systematic search in MEDLINE, Scopus and clinical trial registries was conducted. Studies reporting PDR clinical isolates were eligible for review if susceptibility testing for all major antimicrobials had been performed. Characteristics and findings of retrieved studies were qualitatively synthesized.

RESULTS

Of 81 studies reviewed, 47 (58%) were published in the last 5 years. The reports reflected a worldwide dissemination of PDR GNB in 25 countries in 5 continents. Of 526 PDR isolates reported, Pseudomonas aeruginosa (n=175), Acinetobacter baumannii (n=172) and Klebsiella pneumoniae (n=125) were most common. PDR GNB were typically isolated in ICUs, but several studies demonstrated wider outbreak potential, including dissemination to long-term care facilities and international spread. All-cause mortality was high (range 20%-71%), but appeared to be substantially reduced in studies reporting treatment regimens active in vitro. No controlled trial has been performed to date, but several case reports and series noted successful use of various regimens, predominantly synergistic combinations, and in selected patients increased exposure regimens and newer antibiotics.

CONCLUSIONS

PDR GNB are increasingly being reported worldwide and are associated with high mortality. Several treatment regimens have been successfully used, of which synergistic combinations appear to be most promising and often the only available option. More pharmacokinetic/pharmacodynamic and outcome studies are needed to guide the use of synergistic combinations.

Elimination of fosfomycin during dialysis with the Genius system in septic patients

To assess fosfomycin (FOS) elimination in patients with sepsis and acute kidney injury (AKI) undergoing slow-extended daily dialysis (SLEDD) with the Genius system in a prospective observational study. After ethics committee approval ten patients with sepsis and AKI stage 3 underwent daily SLEDD sessions of eight hours. FOS was applied i.v. at doses of 3 × 5 g per day. FOS serum levels were measured pre- and post hemofilter before, during, and after SLEDD sessions, and instantaneous clearance was calculated. In five of the patients, we analyzed FOS levels after the first dose, in the other five patients serum levels were measured during ongoing therapy. FOS was eliminated rapidly via the hemofilter. FOS clearance decreased from 152 ± 10 mL/min (start of SLEED session) to 43 ± 38 mL/min (end of SLEDD session). In 3/5 first-dose patients after 4–6 h of SLEDD the FOS serum level fell below the EUCAST breakpoint of 32 mg/L for Enterobacterales and Staphylococcus species. In all patients with ongoing fosfomycin therapy serum levels were high and above the breakpoint at all times. FOS toxicity or adverse effects were not observed. FOS serum concentrations exhibit wide variability in critically ill patients with sepsis and AKI. FOS is eliminated rapidly during SLEDD. A loading dose of 5 g is not sufficient to achieve serum levels above the EUCAST breakpoint for common bacteria in all patients, considering that T > MIC > 70% of the dosing interval indicates sufficient plasma levels. We thus recommend a loading dose of 8 g followed by a maintenance dose of 5 g after a SLEDD session in anuric patients. We strongly recommend therapeutic drug monitoring of FOS levels in critically ill patients with AKI and dialysis therapy.

The protective role of fosfomycin in lung injury due to oxidative stress and inflammation caused by sepsis

AIM

Early and prompt treatment of sepsis by effective antibiotics against susceptible organisms may be lifesaving. However, increased antibiotic resistance and side effects of chemotherapeutic agents limiting their tolerability result in a restricted use of medications. This has led to an increased search for solution oriented novel treatments and therapeutic targets, as well as investigations on the pathogenesis and physiology of sepsis. In this study, we aimed to examine the antioxidant and anti-inflammatory effects of fosfomycin in sepsis resulting from other causes.

MAIN METHODS

Sprague Dawley rats were assigned into three groups. Randomly selected control rats received intraperitoneal saline solution only. Only caecal puncture and ligation were carried out in the caecal ligation and puncture (CLP) group, while in the CLP + fosfomycin group (CLP + FOS), together with sepsis due to caecal puncture and ligation, 500 mg/kg of FOS was administered intraperitoneally (i.p.).

KEY FINDINGS

As compared to the control group, elevated TBARS and TNF-α levels as well as increased expression of NF-kB/p65 and TLR-4 and reduced -SH levels were found in the lung tissue of CLP rats. On the other hand, TBARS and TNF-α levels were reduced and NF-kB/p65 and TLR-4 expressions were decreased together with increase in total -SH levels among CLP + FOS (500 mg/kg i.p.) rats.

SIGNIFICANCE

FOS treatment may represent a promising agent in terms of reducing the sepsis-related lung injury due to its antimicrobial effects as well as its antioxidant and anti-inflammatory properties.

Landscape of Multidrug-Resistant Gram-Negative Infections in Egypt: Survey and Literature Review

Purpose

This article is the first to review published reports on the prevalence of multidrug-resistant (MDR) gram-negative infections in Egypt and gain insights into antimicrobial resistance (AMR) surveillance and susceptibility testing capabilities of Egyptian medical centers.

Materials and Methods

A literature review and online survey were conducted.

Results

The online survey and literature review reported high prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (19–85.24% of E. coli, and 10–87% of K. pneumoniae), carbapenem-resistant Enterobacteriaceae (35–100% of K. pneumoniae and 13.8–100% of E. coli), carbapenem-resistant Acinetobacter baumannii (10–100%), and carbapenem-resistant Pseudomonas aeruginosa (15–70%) in Egypt. Risk factors for MDR Gram-negative infections were ventilated patients (67.4%), prolonged hospitalization (53.5%) and chronic disease (34.9%). Although antimicrobial surveillance capabilities were deemed at least moderate in most centers, lack of access to rapid AMR diagnostics, lack of use of local epidemiological data in treatment decision-making, lack of antimicrobial stewardship (AMS) programs, and lack of risk prediction tools were commonly reported by respondents.

Conclusion

This survey has highlighted the presence of knowledge gaps as well as limitations in the surveillance and monitoring capabilities of AMR in Egypt, with most laboratories lacking rapid diagnostics and molecular testing. Future efforts in Egypt should focus on tackling these issues via nationwide initiatives, including understanding the AMR trends in the country, capacity building of laboratories and their staff to correctly and timely identify AMR, and introducing newer antimicrobials for targeting emerging resistance mechanisms in Gram-negative species.

Population pharmacokinetics and Monte Carlo simulation for dosage optimization of fosfomycin in the treatment of osteoarticular infections in patients without renal dysfunction

Background: Fosfomycin is gaining interest in the treatment of complex osteoarticular infections (OI) due to MDR pathogens.Objective: The aims were to conduct population pharmacokinetics of fosfomycin in a cohort of OI patients receiving 16g/daily by intermittent (II) or continuous infusion (CI), and to carry out Monte Carlo simulations for dosage optimization in the treatment of these infections.Methods: Patients underwent blood sampling on day 5 of therapy (2-3 serial samples). Population pharmacokinetics and Monte Carlo simulations were performed to define the probability of target attainment (PTA) of 70% T>MIC, and the cumulative fraction of response (CFR) against common OI pathogens with dosages of 8, 12, 16, and 20g/day administered by II, extended-infusion (EI) or CI.Results: Forty-eight patients were recruited. A two-compartment open model with infusion input and first-order elimination was developed. Estimated creatinine clearance (CL_CR) was included as covariate in the final model. Monte Carlo simulations showed that optimal PTAs and CFRs (≥90%) may be achieved in three different classes of renal function by administering a daily dosage of: 2g q6h by II against S. aureus, E. coli, ESBL-producing E. Coli and MRSA; 8g by CI against CoNS, K. pneumoniae and ESBL-producing K. pneumoniae; 12g by CI against P. aeruginosa, and 16g by CI against KPC-producing K. pneumoniae Conclusion: Our study provides a strong rationale for considering fosfomycin dosages of  8-16 g daily by CI in several clinical scenarios for OI patients. Feasibility of administration by CI in an elastomeric pump makes fosfomycin a candidate for OPAT programs.

Methylation analysis of Klebsiella pneumoniae from Portuguese hospitals

Klebsiella pneumoniae is an important nosocomial infectious agent with a high antimicrobial resistance (AMR) burden. The application of long read sequencing technologies is providing insights into bacterial chromosomal and putative extra-chromosomal genetic elements (PEGEs) associated with AMR, but also epigenetic DNA methylation, which is thought to play a role in cleavage of foreign DNA and expression regulation. Here, we apply the PacBio sequencing platform to eight Portuguese hospital isolates, including one carbapenemase producing isolate, to identify methylation motifs. The resulting assembled chromosomes were between 5.2 and 5.5Mbp in length, and twenty-six PEGEs were found. Four of our eight samples carry blaCTX-M-15, a dominant Extended Spectrum Beta Lactamase in Europe. We identified methylation motifs that control Restriction-Modification systems, including GATC of the DNA adenine methylase (Dam), which methylates N6-methyladenine (m6A) across all our K. pneumoniae assemblies. There was a consistent lack of methylation by Dam of the GATC motif downstream of two genes: fosA, a locus associated with low level fosfomycin resistance, and tnpB transposase on IncFIB(K) plasmids. Overall, we have constructed eight high quality reference genomes of K. pneumoniae, with insights into horizontal gene transfer and methylation m6A motifs.

Recurrent neurosurgical site infection by extensively drug-resistant P. aeruginosa treated with cefiderocol: a case report and literature review

INTRODUCTION

Cefiderocol is a new siderophore cephalosporin designed to be active against extensively resistant Gram-negative bacteria; however, clinical studies are limited to complicated urinary tract infections, pneumonia, and intra-abdominal infections. To date, no data are available on neurosurgical site infections.

CASE PRESENTATION

We present a case of a patient successfully cured with Cefiderocol for a neurosurgical site infection due to extensively resistant P. aeruginosa, who had failed a previous treatment based on combined antimicrobial therapy and right parietal bone excision.

CONCLUSIONS

Cefiderocol is a promising antibiotic for complicated infections due to multidrug resistant gram-negative bacteria.

Antimicrobial prescribing for treatment of serious infections caused by Staphylococcus aureus and methicillin-resistant Staphylococcus aureus in pediatrics: an expert review

Introduction: Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), remains a significant pathogen in children. Despite evidence of decreasing prevalence, MRSA bacteremia has been closely associated with complications, including certain infections (i.e. musculoskeletal and endovascular) linked to increased treatment failures.Areas covered: This expert review summarized recent published literature on the role of treatment, dosing and administration of antibiotics used to combat serious S. aureus infections in children. The pertinent antibiotics presented were vancomycin, oxazolidinones, semi-synthetic glycopeptides, daptomycin, tigecycline, novel cephalosporins, fosfomycin and lefamulin. Vancomycin has been the most commonly used antibiotic in empiric therapy for serious MRSA infection, with new key recommendations emphasizing a different approach to dosing and therapeutic monitoring. For other antibiotics, data remain limited or clinical trials are underway.Expert opinion: MRSA remains a significant pathogen in the pediatric population. As numerous therapeutic agents are available, many agents have limited data on usage in pediatric patients. Future studies require pharmacokinetic, safety and efficacy studies in pediatric patients to ensure appropriate therapeutic treatment and outcomes. Phage therapy has been used to treat deep-seated MRSA infections and is an emerging investigational treatment option.

Antimicrobial resistance increased over an 8-year period in Enterobacteriaceae cultured from canine urine samples

OBJECTIVES

The aims of the present study were to describe the prevalence of positive urinary bacterial culture in dogs, to identify the most commonly isolated microorganisms and to analyse changes in antimicrobial susceptibility patterns over time.

MATERIAL AND METHODS

A retrospective case series was performed using culture and susceptibility results from canine urine samples collected between January 2010 and December 2017. The presence or absence of infection, identity of the bacterium with heaviest growth, and susceptibility profile were recorded for each sample. Trends in the frequency of positive culture and antimicrobial resistance were assessed by Poisson regression modelling. Prevalence rate ratio and 95% confidence interval were reported for resistance to each antimicrobial.

RESULTS

A positive urine culture was documented in 771 (22.5%) of 3420 samples. Escherichia coli was the most commonly isolated microorganism. There was no significant increase in the frequency of positive bacterial culture over the study period (prevalence rate ratio 0.98; 95% confidence interval: 0.92 to 1.0). Overall, there was an increase in antimicrobial resistance within Enterobacteriaceae from 5.2 to 35.6%. The prevalence of multidrug-resistant bacteria varied from year to year throughout the study period. However, the Poisson regression model identified a significant increase in the frequency of multidrug-resistant Enterobacteriaceae over this period, averaging approximately 22% per year (prevalence rate ratio 1.22, 95% confidence interval: 1.06 to 1.42).

CLINICAL SIGNIFICANCE

The significant increase in antimicrobial resistance observed in this study is concerning and may have implications for veterinary and public health. Appropriate measures, such as antibiotic stewardship programmes, should be implemented to address increasing antimicrobial resistance.

Therapeutic Options for Metallo-β-Lactamase-Producing Enterobacterales

The spread of metallo-β-lactamase (MBL)-producing Enterobacterales worldwide without the simultaneous increase in active antibiotics makes these organisms an urgent public health threat. This review summarizes recent advancements in diagnostic and treatment strategies for infections caused by MBL-producing Enterobacterales. Adequate treatment of patients infected with MBL-producing Enterobacterales relies on detection of the β-lactamase in the clinic. There are several molecular platforms that are currently available to identify clinically relevant MBLs as well as other important serine-β-lactamases. Once detected, there are several antibiotics that have historically been used for the treatment of MBL-producing Enterobacterales. Antimicrobials such as aminoglycosides, tetracyclines, fosfomycin, and polymyxins often show promising in vitro activity though clinical data are currently lacking to support their widespread use. Ceftazidime-avibactam combined with aztreonam is promising for treatment of infections caused by MBL-producing Enterobacterales and currently has the most clinical data of any available antibiotic to support its use. While cefiderocol has displayed promising activity against MBL-producing Enterobacterales in vitro and in preliminary clinical studies, further clinical studies will better shed light on its place in treatment. Lastly, there are several promising MBL inhibitors in the pipeline, which may further improve the treatment of MBL-producing Enterobacterales.

Current choices of antibiotic treatment for Pseudomonas aeruginosa infections

PURPOSE OF REVIEW

Pseudomonas aeruginosa is one of the most feared nosocomial pathogens. Treatment of P. aeruginosa infections is challenging because of the limited choices of antibiotics and the emergent resistance of the pathogen. The present review aims at addressing the management of P. aeruginosa infections and highlighting the novel antibiotics that show a future promising role.

RECENT FINDINGS

Novel fluoroquinolones have been recently introduced and show favorable activity. New combinations of β-lactams/β-lactamase inhibitors have been studied in various indications of infections because of P. aeruginosa. Cefiderocol, a new cephalosporin, shows very promising results against P. aeruginosa. Currently, combination therapy is only recommended in limited scenarios. Extended-infusion of β-lactams exhibit clinical benefit. Bacteriophage therapy is a growing field of interest and may have an impactful effect on the treatment of resistant P. aeruginosa.

SUMMARY

Factors that guide clinical decisions for empiric and directed P. aeruginosa therapy include the epidemiology, the patient's risk factors, the site of infection, and the available treatment options. Conventional antipseudomonal antibiotics have been used successfully for a long time, but the increase in worldwide resistance necessitates the need for newer agents. Antimicrobial stewardship is essential to preserve the new drugs and prevent future development of resistance.

Clinical syndromes and treatment location predict utility of carbapenem sparing therapies in ceftriaxone-non-susceptible Escherichia coli bloodstream infection

Background

Cefiderocol, ceftazidime-avibactam, ceftolozane-tazobactam, intravenous fosfomycin and plazomicin represent potential carbapenem sparing agents for extended-spectrum-beta-lactamase or AmpC beta-lactamase producing Escherichia coli infection. However, available data is limited in predicting the volume of carbapenem therapy which could be substituted and real-world contraindications.

Methods

We determined the number of carbapenem days of therapy (DOT) which could be substituted and frequent contraindications accounting for antimicrobial susceptibility and site of infection in an unselected cohort with ceftriaxone-non-susceptible E. coli bacteremia at a single health network from 2015 to 2016. Individual patient data was used to calculate DOT and substitution for each agent.

Results

There were 108 episodes of E. coli bacteremia resulting in 67.2 carbapenem DOT/100 patient-days of antimicrobial therapy administered. Ceftazidime-avibactam could be used to substitute 36.2 DOT/100 patient-days (54%) for inpatient definitive therapy, ceftolozane-tazobactam for 34.7 DOT/100 patient-days (52%), cefiderocol for 27.1 DOT/100 patient-days (40%), fosfomycin for 23.3 DOT /100 patient-days (35%) and plazomicin for 27.1 DOT/100 patient-days (40%). Non-urinary tract source of infection was the most frequent contraindication to fosfomycin (25), plazomicin (26) and cefiderocol (26). Use in outpatient parenteral antimicrobial therapy (OPAT) programs accounted for 40% of DOT, all of which could be substituted if stability data allowed for ceftazidime-avibactam and ceftolozane-tazobactam.

Conclusions

All tested agents could be used to replace a significant volume of carbapenem therapy. Establishing stability of these agents for use in OPAT is required for maximizing their use as carbapenem sparing agents while randomized clinical data is awaited for some of these agents in resistant E. coli bacteremia.

Cure of Limb-Threatening XDR Pseudomonas aeruginosa Infection: Combining Genome Sequencing, Therapeutic Drug Level Monitoring, and Surgical Debridement

We describe a case of limb-threatening osteomyelitis and metalware infection with carbapenemase-producing extensively drug-resistant Pseudomonas aeruginosa successfully cured with aggressive surgical debridement and combined intravenous fosfomycin and colistin. Real-time therapeutic drug monitoring was used to maximize probability of efficacy and minimize potential for toxicity.

Evaluation of BD Phoenix and Microscan WalkAway for determination of fosfomycin susceptibility in Staphylococcus aureus

We evaluate the performance of BD Phoenix (BD Diagnostic; Hunt Valley, MD) and MiscroScan WalkAway (Beckman Coulter Inc; Carlsbad, CA) systems versus reference agar dilution method for fosfomycin susceptibility determination in 200 Staphylococcus aureus clinical isolates. Both methods exhibit ≤89.0% of categorica agreement and ≥63.3% of very major error. All commercial antimicrobial susceptibility systems show poor concordance with reference method.

Case series of carbapenemase-producing Enterobacteriaceae osteomyelitis: Feel it in your bones

OBJECTIVES

Limited data have been reported regarding osteomyelitis due to carbapenemase-producing Enterobacteriaceae (CPE), including co-infections with extended-spectrum β-lactamase (ESBL)-producing micro-organisms.

METHODS

We conducted a retrospective study in a reference centre for bone and joint infections from 2011 to 2019 among patients infected with CPE.

RESULTS

Nine patients (mean age 46.8 ± 16.6 years), including three with infected implants, were identified. Infections were mostly polymicrobial (n = 8/9), including Staphylococcus aureus (n = 6/9). CPE were mainly OXA-48-type, associated with ESBL-producing Enterobacteriaceae (n = 8/9), of which 5/9 isolates were Klebsiella pneumoniae. Control of the infection was achieved in seven cases.

CONCLUSIONS

CPE osteomyelitides are essentially polymicrobial and fluoroquinolone-resistant infections, highlighting the need for efficient surgery with implant removal.

Effective Treatment for Uncomplicated Urinary Tract Infections with Oral Fosfomycin, Single Center Four Year Retrospective Study

Fosfomycin represents a relatively old antibiotic, but it is experiencing a comeback in recent years. According to some studies, the increasing therapeutic use of this drug led to a rapid increase in the levels of resistance in bacteria causing urinary tract infection. In the presented study, levels of resistance to fosfomycin in more than 3500 bacterial isolates before and after fosfomycin introduction into therapeutic use in the Czech Republic and the clinical efficacy of treatment in 300 patients using this drug were assessed. The results show that the resistance levels to fosfomycin in Escherichia coli isolates before and after the drug registration were not significantly different (3.4% and 4.4%, respectively). In some other Gram-negative rods, such as otherwise susceptible Enterobacter, resistance to fosfomycin increased significantly from 45.6% to 76.6%. Fosfomycin treatment of urinary tract infections showed an excellent seven-day clinical efficacy (79.7%). However, when used to treat recurrent or complicated urinary tract infections, fosfomycin treatment was associated with high levels of infection relapse, leading to relapse in a total of 20.4% of patients during the first two months. This indicates that fosfomycin exhibits good efficacy only for the treatment of uncomplicated urinary tract infections

The role of fosfomycin for multidrug-resistant gram-negative infections

PURPOSE OF REVIEW

In the last decade, an increasing interest in using fosfomycin for the treatment of multidrug-resistant gram-negative (MDR-GNB) infections have been registered, especially when none or only a few other active alternatives remained available.

RECENT FINDINGS

Fosfomycin may remain active against a considerable proportion of MDR-GNB. In observational studies, a possible curative effect of oral fosfomycin monotherapy has been described for uncomplicated urinary tract infections (UTI) and bacterial prostatitis caused by MDR-GNB, whereas intravenous fosfomycin has been mostly used in combination with other agents for various type of severe MDR-GNB infections. The ZEUS randomized controlled trial (RCT) has started to provide high-level evidence about the possible use of fosfomycin for complicated UTI caused by extended-spectrum β-lactamase-producing GNB, but no results of large RCT are currently available to firmly guide the use of fosfomycin for carbapenem-resistant GNB.

SUMMARY

Fosfomycin is an important therapeutic option for MDR-GNB infections. Further pharmacokinetic/pharmacodynamic and clinical research is needed to optimize its use.

Fosfomycin for bacterial prostatitis: a review

There has been growing interest in fosfomycin for the treatment of bacterial prostatitis due to evidence suggesting that it achieves adequate prostatic concentrations for antimicrobial effect, has activity against resistant micro-organisms, and has a low-toxicity profile. This review evaluated the current clinical evidence for fosfomycin in acute and chronic bacterial prostatitis to elucidate the clinical implications of fosfomycin in an era of increasing antimicrobial resistance. PubMed, Scopus, EMBASE, Web of Science, Google Scholar and ClinicalTrials.gov were searched for studies published in the English language from January 1984 to November 2019. The inclusion criteria were met if the study reported the use of fosfomycin (more than one dose) to treat bacterial prostatitis. Ten observational studies were identified that met the inclusion criteria. The evidence for the use of fosfomycin in acute bacterial prostatitis is sparse. The majority of the available evidence is for chronic bacterial prostatitis caused by Escherichia coli. Despite the implementation of variable dosing regimens, extended courses of fosfomycin appear to be safe and effective in achieving clinical and microbiological cure. In these studies, the use of fosfomycin was restricted to cases of treatment failure, intolerance to first-line therapy, or multi-resistant organisms. However, given the development of resistant organisms and the undesirable adverse effects of many first-line therapeutic options, fosfomycin has the potential to be considered as an effective first-line alternative for acute and chronic bacterial prostatitis in the future. Further studies, including randomized controlled trials, would be helpful to firmly establish its optimal dosing regimen, efficacy and place in therapy.

Ceftazidime-Avibactam in Combination With Fosfomycin: A Novel Therapeutic Strategy Against Multidrug-Resistant Pseudomonas aeruginosa

Previously, by targeting penicillin-binding protein 3, Pseudomonas-derived cephalosporinase (PDC), and MurA with ceftazidime-avibactam-fosfomycin, antimicrobial susceptibility was restored among multidrug-resistant (MDR) Pseudomonas aeruginosa. Herein, ceftazidime-avibactam-fosfomycin combination therapy against MDR P. aeruginosa clinical isolate CL232 was further evaluated. Checkerboard susceptibility analysis revealed synergy between ceftazidime-avibactam and fosfomycin. Accordingly, the resistance elements present and expressed in P. aeruginosa were analyzed using whole-genome sequencing and transcriptome profiling. Mutations in genes that are known to contribute to β-lactam resistance were identified. Moreover, expression of blaPDC, the mexAB-oprM efflux pump, and murA were upregulated. When fosfomycin was administered alone, the frequency of mutations conferring resistance was high; however, coadministration of fosfomycin with ceftazidime-avibactam yielded a lower frequency of resistance mutations. In a murine infection model using a high bacterial burden, ceftazidime-avibactam-fosfomycin significantly reduced the P. aeruginosa colony-forming units (CFUs), by approximately 2 and 5 logs, compared with stasis and in the vehicle-treated control, respectively. Administration of ceftazidime-avibactam and fosfomycin separately significantly increased CFUs, by approximately 3 logs and 1 log, respectively, compared with the number at stasis, and only reduced CFUs by approximately 1 log and 2 logs, respectively, compared with the number in the vehicle-treated control. Thus, the combination of ceftazidime-avibactam-fosfomycin was superior to either drug alone. By employing a "mechanism-based approach" to combination chemotherapy, we show that ceftazidime-avibactam-fosfomycin has the potential to offer infected patients with high bacterial burdens a therapeutic hope against infection with MDR P. aeruginosa that lack metallo-β-lactamases.

Potential of fosfomycin in treating multidrug-resistant infections in children

In an era of increasing antimicrobial resistance, there are limited treatment options available to treat multidrug-resistant organisms in paediatric patients. Fosfomycin is an antibiotic defined as 'critically important' by The World Health Organization due to its potential efficacy against multidrug-resistant bacteria and is increasingly cited in the international literature as a promising antimicrobial for combating sepsis in an era of increasing antimicrobial resistance. With broad-spectrum cover that includes both Gram-positive and Gram-negative organisms and both parenteral and oral formulations available, fosfomycin provides a promising treatment option for paediatric patients. This review summarises fosfomycin's spectrum of activity, published efficacy in paediatric patients, safety considerations and pharmacokinetic data, as well as identifying current clinical trials delineating pharmacokinetic parameters and safety parameters in neonatal sepsis which will provide further information regarding the use of fosfomycin in neonatal and paediatric infections. Limitations regarding the current standards for fosfomycin susceptibility definitions, variations in dosing regimens and the potential mechanisms for resistance are also discussed.

Shorter Total Length of Stay After Intraperitoneal Fosfomycin, Metronidazole, and Molgramostim for Complicated Appendicitis: A Pivotal Quasi-Randomized Controlled Trial

Background: We aimed to investigate the difference in the total length of hospital stay (LOS) after intraperitoneal vs. intravenous antibiotic treatment in patients with complicated appendicitis.

Methods: We conducted a quasi-randomized prospective clinical trial. The intervention group received 4 g fosfomycin, 1 g metronidazole, and 50 μg recombinant human granulocyte-macrophage colony-stimulating factor intraperitoneally, which was left in the abdominal cavity, immediately after laparoscopic appendectomy. Postoperatively, this group received antibiotics orally. The control group received intravenous antibiotics both during surgery and postoperatively. We primarily evaluated total LOS within 30 days. Furthermore, we evaluated harms and adverse events, Gastrointestinal Quality of Life Index, postoperative complications, and convalescence. Participants were followed for 30 days postoperatively.

Results: A total of 12 participants concluded the trial. The total LOS was significantly shorter in the intervention group (six participants, median 13 h; range 2–21 h) than in the control group (six participants, median 84 h; range 67–169 h), p = 0.017. Comparable harms and Gastrointestinal Quality of Life Index scores were found in the two groups. The time to return to normal activities was median 6 and 10 days for the intervention and the control group, respectively. There were no serious adverse events related to the trial nor any complications in the intervention group. In the control group, two patients developed intraabdominal abscesses.

Conclusions: The intervention group had a significantly shorter total LOS. The study was not powered to assess differences in complications, but the results indicate that the intervention seems to be a safe regimen, which can be investigated further to treat patients with complicated appendicitis.

Identifiers: EudraCT no. 2017-004753-16.

ClinicalTrials:https://clinicaltrials.gov/ct2/show/NCT03435900?term=NCT03435900&draw=2&rank=1">draw=2&rank=1.

Molecular Characterization of β-Lactam Resistance and Antimicrobial Susceptibility to Possible Therapeutic Options of AmpC-Producing Multidrug-Resistant Proteus mirabilis in a University Hospital of Split, Croatia

This study was performed to elucidate genetic relatedness and molecular resistance mechanisms of AmpC-producing multidrug-resistant Proteus mirabilis isolates in University Hospital of Split (UHS), and define efficient antibiotics in vitro. A total of 100 nonrepeated, consecutive, amoxicillin/clavulanate- and cefoxitin-resistant P. mirabilis isolates were collected, mostly from urine (44%) and skin and soft-tissue samples (30%). They were all positive in cefoxitin Hodge test and negative for extended spectrum beta-lactamase production. Pulsed field gel electrophoresis identified four clusters and two singletons, with 79% of isolates in dominant cluster. Molecular characterization and I-CeuI analysis of representatives revealed bla_CMY-16 gene located on chromosome, and insertion element ISEcp1 positioned 110 pb upstream of bla_CMY-16 starting codon. They also harbored bla_TEM-1, except one with bla_TEM-2. They were all resistant to trimethoprim-sulfamethoxazole, all but one to quinolones, and 81% to all aminoglycosides, while 77% were susceptible (S) and 22% intermediate (I) to piperacillin/tazobactam, and 4% were S and 68% I to cefepime. Only 15% were S to ceftolozane/tazobactam. Meropenem, ertapenem, ceftazidime/avibactam, temocillin, and fosfomycin were 100% efficient in vitro. This is the first report of bla_CMY-16 gene in P. mirabilis from hospital samples in Croatia. The findings are in accordance with Italian and Greek reports. The clonal nature of outbreak suggests the high potential of clonal spread. Alternative agents should be considered to spare carbapenem usage.

The pharmacodynamics of fosfomycin against Staphylococcus aureus studied in an in vitro model of infection

OBJECTIVES

The pharmacodynamics of intravenous fosfomycin have not been described for Gram-positive pathogens such as Staphylococcus aureus (S. aureus). This paper described the dominant pharmacodynamic index for fosfomycin against S. aureus and its size for antibacterial effect.

METHODS

A single-compartment dilutional in vitro pharmacokinetic model was used to provide fosfomycin exposures against S. aureus, three methicillin-susceptible S. aureus (MSSA), two methicillin-resistant S. aureus (MRSA); fosfomycin MICs were 2 mg/L (one strain), 4 mg/L (one strain), 8 mg/L (two strains) and 16 mg/L (one strain). For all simulations, a fosfomycin half-life of 2.5 hours was modelled. Cmax/MICs from 0-74.8, AUC/MICs from 0-750 and T>MIC 0-100% were simulated. The primary end-points were changes in bacterial load after 24 hours and changes in population profiles after 48 hours.

RESULTS

Log AUC/MIC R² = 0.55 and log Cmax/MIC R² = 0.66 were related to S. aureus log reduction in viable count at 24 hours; T>MIC was poorly related. Cmax/MIC for a 24 hour static, -1 log drop and -2 log drop were 3.0 ± 1.7, 4.6 ± 2.4 and 6.6 ± 3.8, respectively. AUC/MIC for a 24 hour static, -1 log drop and -2 log drop were 26.4 ± 11.8, 42.8 ± 21.8 and 66.6 ± 39.1. Emergence of resistance as indicated by > 2 log growth on MICx8 recovery media was maximal at AUC/MIC ratios of 10-40 and was suppressed at AUC/MIC ratios of ≥ 250.

CONCLUSIONS

The dominant pharmacodynamic index for fosfomycin against S. aureus was Cmax/MIC in terms of reduction of bacterial load and AUC/MIC in terms of suppressing emergence of resistance. AUC/MIC ratios of 20-75 were associated with a -1 log reduction in bacterial load and AUC/MIC of 10-40 maximally increased emergence of resistance.

In vitro synergistic activity of fosfomycin in combination with meropenem, amikacin and colistin against OXA-48 and/or NDM-producing Klebsiella pneumoniae

Objective: Carbapenemase-producing Klebsiella pneumoniae (CPKp) infections are increasing worldwide. We investigated the in vitro synergistic activity of fosfomycin (FOS) with meropenem (MRP), amikacin (AMK) and colistin (COL) against OXA-48 and/or New Delhi metallo-beta-lactamase (NDM)-producing Kp blood isolates. Materials and Methods: Seventeen CPKp blood isolates were studied. The broth microdilution method was used for COL, MRP and AMK susceptibilities, while agar dilution for FOS. Synergy was tested by agar dilution chequerboard technique and also was confirmed by a time-kill assay for FOS/MRP and FOS/COL using three representative isolates that were found to be synergistic. Results: FOS in combination with MRP was found to be the most synergistic (15/17 strains, 88%), while 29% and 41% with AMK and COL, respectively. Antagonism was only determined in 2 isolates with the COL/FOS. Conclusions: The MRP/FOS combination demonstrated synergistic activity against CRKp, especially against the two common enzyme-producing isolates in Turkey (OXA-48 and NDM).

Guidelines of the Association of Anesthesiologists-Intensivists, the Interregional Non-Governmental Organization Alliance of Clinical Chemotherapists and Microbiologists, the Interregional Association for Clinical Microbiology and Antimicrobial Chemotherapy (IACMAC), and NGO Russian Sepsis Forum Diagnostics and antimicrobial therapy of the infections caused by multiresistant microorganisms

Introduction. Strains of microorganisms resistant to antimicrobial agents are commonly found in medical units throughout most regions of the world, including Russia. This leads to lower antimicrobial therapy efficacy when treating nosocomial infections. In this regard, the timely implementation of adequate antibiotic therapy is of great importance.

The objective of the guidelines: To provide summarized information on contemporary approaches to microbiological diagnostics and the assessment of results, as well as the principles of rational use of antimicrobial and antifungal agents, including treatment of infections caused by multiple drug-resistant strains of microorganisms.

Subjects and methods. These guidelines are based on published data obtained in the course of randomized trials, as well as information presented in the provisions of international guidelines supported by high-level evidence. The guidelines were prepared by a working group of Russian experts with extensive experience in research and practical work in this area. On October 11, 2019, the final version of the guidelines was reviewed and approved at a joint meeting of the working group and representatives of the public organizations which initiated the development of these guidelines (Association of Anesthesiologists-Intensivists, the Interregional Non-Governmental Organization Alliance of Clinical Chemotherapists and Microbiologists, the Interregional Association for Clinical Microbiology and Antimicrobial Chemotherapy (IACMAC), NGO Russian Sepsis Forum).

Conclusion. The guidelines reflect an interdisciplinary consensus of approaches to the diagnostics and antibiotic therapy of infections caused by multiresistant microorganisms. The provisions set forth should be used to decide on the strategy of empirical and etiotropic therapy of the most severe infections.

Oral fosfomycin for the treatment of lower urinary tract infections among kidney transplant recipients-Results of a Spanish multicenter cohort

Oral fosfomycin may constitute an alternative for the treatment of lower urinary tract infections (UTIs) in kidney transplant recipients (KTRs), particularly in view of recent safety concerns with fluroquinolones. Specific data on the efficacy and safety of fosfomycin in KTR are scarce. We performed a retrospective study in 14 Spanish hospitals including KTRs treated with oral fosfomycin (calcium and trometamol salts) for posttransplant cystitis between January 2005 and December 2017. A total of 133 KTRs developed 143 episodes of cystitis. Most episodes (131 [91.6%]) were produced by gram-negative bacilli (GNB), and 78 (54.5%) were categorized as multidrug resistant (including extended-spectrum β-lactamase-producing Enterobacteriaceae [14%] or carbapenem-resistant GNB [3.5%]). A median daily dose of 1.5 g of fosfomycin (interquartile range [IQR]: 1.5-2) was administered for a median of 7 days (IQR: 3-10). Clinical cure (remission of UTI-attributable symptoms at the end of therapy) was achieved in 83.9% (120/143) episodes. Among those episodes with follow-up urine culture, microbiological cure at month 1 was achieved in 70.2% (59/84) episodes. Percutaneous nephrostomy was associated with a lower probability of clinical cure (adjusted odds ratio: 10.50; 95% confidence interval: 0.98-112.29; P = 0.052). In conclusion, fosfomycin is an effective orally available alternative for treating cystitis among KTRs.

Performance of disk diffusion and broth microdilution for fosfomycin susceptibility testing of multidrug-resistant clinical isolates of Enterobacterales and Pseudomonas aeruginosa

OBJECTIVES

This study aimed to evaluate the susceptibility of clinical isolates of Enterobacterales and Pseudomonas aeruginosa to fosfomycin and to determine the concordance of disk diffusion (DD) and broth microdilution (BMD) with agar dilution (AD) for fosfomycin susceptibility testing.

METHODS

The activity of fosfomycin against 225 clinical isolates of Escherichia coli (n = 64), Klebsiella pneumoniae (n = 68), Enterobacter spp. (n = 28) and P. aeruginosa (n = 65) was tested by AD, DD and BMD. For DD, results were recorded considering and not considering colonies growing within the inhibition halo as recommended by the CLSI and EUCAST, respectively. Escherichia coli breakpoints were used for all Enterobacterales. Results were reported as categorical agreement (CA), major error (ME; false-resistant), very major error (VME; false-susceptible) and minor error (any other discrepancies).

RESULTS

Fosfomycin susceptibility of all tested species was >90% by AD. Following CLSI guidelines, DD was the only method reaching ≥90% CA with AD for E. coli and K. pneumoniae, albeit yielding 6% ME. Neither DD nor BMD achieved acceptable CA percentages for Enterobacter spp. Following EUCAST guidelines, none of the methods had CA ≥ 90%. For Enterobacterales, the best performance of DD is achieved when read as indicated by EUCAST but interpreted according the CLSI breakpoints (>97% CA; 0% VME; ≤2% ME). For P. aeruginosa, BMD yielded the best results (89% CA; 0% VME; 11% ME).

CONCLUSION

Neither DD or BMD provide accurate results owing to unacceptable ME and VME percentages even when performed as intended by the guidelines.

The plasma pharmacokinetics of fosfomycin and metronidazole after intraperitoneal administration in patients undergoing appendectomy for uncomplicated appendicitis

We aimed to investigate the pharmacokinetics of fosfomycin and metronidazole after intraperitoneal administration of the combination of fosfomycin and metronidazole in patients undergoing laparoscopic appendectomy for uncomplicated appendicitis. We included eight otherwise healthy men undergoing laparoscopic appendectomy. The trial treatment was administered at the end of the surgical procedure and left in the abdominal cavity. Trial drugs consisted of 4 g fosfomycin and 1 g metronidazole in a total volume of 500.2 mL. Blood samples were collected prior to and ½, 1, 2, 4, 8, 12 and 24 h after administration. High-performance liquid chromatography-mass spectrometry was used for the measurement of plasma concentrations, and pharmacokinetic calculations were undertaken. Antimicrobial susceptibility testing was undertaken on isolates from intraoperatively collected specimens. The median maximal concentration for fosfomycin in plasma was 104.4 mg/L, median time point for the maximal concentration was 1.5 h, median half-life 3.0 h, and median area under the curve 608 mg*h/L. The median maximal concentration for metronidazole in plasma was 13.6 mg/L, median time point for the maximal concentration was 2.0 h, median half-life 7.3 h, and median area under the curve was 164 mg*h/L. All aerobic bacteria were susceptible to fosfomycin, and all anaerobes were susceptible to metronidazole. Plasma concentrations of fosfomycin and metronidazole were in line with concentrations reported from pharmacokinetic studies after intravenous administration and were within therapeutic ranges.

Fosfomycin in severe infections due to genetically distinct pan-drug-resistant Gram-negative microorganisms: synergy with meropenem

Background

In vitro and clinical studies using parenteral fosfomycin have suggested the possibility of using this drug against infections caused by MDR microorganisms. The aim of this study was to describe a case series of patients treated with fosfomycin who had severe infections caused by pan-drug-resistant Gram-negative bacteria.

Methods

We describe a prospective series of cases of hospitalized patients with infections caused by Gram-negative bacteria resistant to β-lactams and colistin, treated with 16 g of fosfomycin daily for 10-14 days. Isolates were tested for antimicrobial susceptibility and synergism of fosfomycin with meropenem. We tested for resistance genes and performed typing using PCR and WGS.

Results

Thirteen patients received fosfomycin (seven immunosuppressed); they had bloodstream infections (n = 11; 85%), ventilator-associated pneumonia (n = 1; 8%) and surgical site infection (n = 1; 8%), caused by Klebsiella pneumoniae (n = 9), Serratia marcescens (n = 3) and Pseudomonas aeruginosa (n = 1). Overall, eight (62%) patients were cured. Using time-kill assays, synergism between fosfomycin and meropenem occurred in 9 (82%) of 11 isolates. Typing demonstrated that K. pneumoniae were polyclonal. Eight patients (62%) had possible adverse events, but therapy was not discontinued.

Conclusions

Fosfomycin may be safe and effective against infections caused by pan-drug-resistant Gram-negative microorganisms with different antimicrobial resistance mechanisms and there seems to be synergism with meropenem.

Colistin-sparing approaches with newer antimicrobials to treat carbapenem-resistant organisms: Current evidence and future prospects

Antimicrobial resistance is on the rise across the globe. Increasing incidence of infections due to carbapenem resistance organisms is becoming difficult to treat, due to the limited availability of therapeutic agents. Very few agents such as colistin, fosfomycin, tigecycline and minocycline are widely used, despite its toxicity. However, with the availability of novel antimicrobials, beta-lactam/beta-lactamase inhibitor-based and non-beta-lactam-based agents could be of great relief. This review covers three important aspects which include (i) current management of carbapenem-resistant infections, (ii) determination of specific types of carbapenemases produced by multidrug-resistant and extensively drug-resistant Gram-negative pathogens and (iii) the currently available novel beta-lactam/beta-lactamase inhibitors and non-beta-lactam-based agents' laboratory findings, clinical outcome and implications.

Preventing sepsis development in complicated urinary tract infections

Introduction: Urinary tract infections (UTIs) are the most prevalent infections in the community and the most common reason for antimicrobial prescribing in ambulatory care. A UTI is defined as complicated when urinary tract anatomical abnormalities or urinary devices are present, when it is recurrent and when associated with immunodeficiency. Complicated UTIs (cUTIs) have a higher risk of treatment failure and often require longer antimicrobial treatment courses. cUTIs, especially those which are healthcare-associated, are often due to multidrug resistant organisms (MDROs).Areas covered: This article will review the available evidence in relation to prevention of sepsis in cUTI, evaluating the risk factors associated with sepsis development. Published articles from January 2005 to September 2019 on UTIs and sepsis prevention in complicated UTIs were identified by using MEDLINE (National Library of Medicine Bethesda MD) and by reviewing the references of retrieved articles.Expert opinion: Prevention of sepsis relies on prompt and timely diagnosis of cUTI, early identification of the causative organism, removal of obstructions and source control, proper and adequate empirical/targeted antimicrobial treatment. In particular, source control, i.e. removal of urinary obstructions, infected stents, urinary catheters, nephrostomies, and drainage of hydronephrosis/abscess, is essential for preventing the development and progression of sepsis.

Fosfomycin for Injection (ZTI-01) Versus Piperacillin-tazobactam for the Treatment of Complicated Urinary Tract Infection Including Acute Pyelonephritis: ZEUS, A Phase 2/3 Randomized Trial

BACKGROUND

ZTI-01 (fosfomycin for injection) is an epoxide antibiotic with a differentiated mechanism of action (MOA) inhibiting an early step in bacterial cell wall synthesis. ZTI-01 has broad in vitro spectrum of activity, including multidrug-resistant Gram-negative pathogens, and is being developed for treatment of complicated urinary tract infection (cUTI) and acute pyelonephritis (AP) in the United States.

METHODS

Hospitalized adults with suspected or microbiologically confirmed cUTI/AP were randomized 1:1 to 6 g ZTI-01 q8h or 4.5 g intravenous (IV) piperacillin-tazobactam (PIP-TAZ) q8h for a fixed 7-day course (no oral switch); patients with concomitant bacteremia could receive up to 14 days.

RESULTS

Of 465 randomized patients, 233 and 231 were treated with ZTI-01 and PIP-TAZ, respectively. In the microbiologic modified intent-to-treat (m-MITT) population, ZTI-01 met the primary objective of noninferiority compared with PIP-TAZ with overall success rates of 64.7% (119/184 patients) vs 54.5% (97/178 patients), respectively; treatment difference was 10.2% (95% confidence interval [CI]: -0.4, 20.8). Clinical cure rates at test of cure (TOC, day 19-21) were high and similar between treatments (90.8% [167/184] vs 91.6% [163/178], respectively). In post hoc analysis using unique pathogens typed by pulsed-field gel electrophoresis, overall success rates at TOC in m-MITT were 69.0% (127/184) for ZTI-01 versus 57.3% (102/178) for PIP-TAZ (difference 11.7% 95% CI: 1.3, 22.1). ZTI-01 was well tolerated. Most treatment-emergent adverse events, including hypokalemia and elevated serum aminotransferases, were mild and transient.

CONCLUSIONS

ZTI-01 was effective for treatment of cUTI including AP and offers a new IV therapeutic option with a differentiated MOA for patients with serious Gram-negative infections.

CLINICAL TRIAL REGISTRATION

NCT02753946.

Treatment Options for Carbapenem-resistant Gram-negative Bacterial Infections

Antimicrobial resistance has become one of the greatest threats to public health, with rising resistance to carbapenems being a particular concern due to the lack of effective and safe alternative treatment options. Carbapenem-resistant gram-negative bacteria of clinical relevance include the Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii, and more recently, Stenotrophomonas maltophilia. Colistin and tigecycline have been used as first-line agents for the treatment of infections caused by these pathogens; however, there are uncertainties regarding their efficacy even when used in combination with other agents. More recently, several new agents with activity against certain carbapenem-resistant pathogens have been approved for clinical use or are reaching late-stage clinical development. They include ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, plazomicin, eravacycline, and cefiderocol. In addition, fosfomycin has been redeveloped in a new intravenous formulation. Data regarding the clinical efficacy of these new agents specific to infections caused by carbapenem-resistant pathogens are slowly emerging and appear to generally favor newer agents over previous best available therapy. As more treatment options become widely available for carbapenem-resistant gram-negative infections, the role of antimicrobial stewardship will become crucial in ensuring appropriate and rationale use of these new agents.

Optimizing therapy in carbapenem-resistant Enterobacteriaceae infections

PURPOSE OF REVIEW

In the absence of randomized clinical trial data, questions remain regarding the optimal treatment of carbapenem-resistant Enterobacteriaceae (CRE) infections. CRE have historically been susceptible to polymyxins, tigecycline or aminoglycosides (mostly gentamicin), and these antibiotics have long been considered the drugs of choice for CRE infections, although varying rates of resistance to all have been reported. This review looks at data from clinical studies assessing the outcomes of CRE infections treated with different antibiotic regimens.

RECENT FINDINGS

The recently approved fixed-dose combination agent, ceftazidime-avibactam (CAZ-AVI), is active against KPC and OXA-48-producing Enterobacteriaceae. The limited clinical data available on CAZ-AVI indicate that it is associated with survival benefits relative to other commonly used regimens, although development of resistance is a concern. New drugs active against CRE isolates (including the recently approved meropenem-vaborbactam) are in different stages of development.

SUMMARY

CAZ-AVI and meropenem-vaborbactam seem destined to become the backbone of target therapy for high-risk patients with severe infections caused by susceptible CRE strains. However, empirical therapy should be based on risk factors to be defined in the near future, whereas the necessity of combinations with CAZ-AVI requires further studies. Polymyxins are still important options for low-risk patients with susceptible CRE infections, but also for high-risk patients in regions where metallo-β-lactamase-producing CRE predominate because CAZ-AVI and meropenem-vaborbactam are both ineffective against these strains.

Susceptibility of ESBL Escherichia coli and Klebsiella pneumoniae to fosfomycin in the Netherlands and comparison of several testing methods including Etest, MIC test strip, Vitek2, Phoenix and disc diffusion

Objectives

Fosfomycin susceptibility testing is complicated and prone to error. Before using fosfomycin widely in patients with serious infections, acquisition of WT distribution data and reliable susceptibility testing methods are crucial. In this study, the performance of five methods for fosfomycin testing in the routine laboratory against the reference method was evaluated.

Methods

Ten laboratories collected up to 100 ESBL-producing isolates each (80 Escherichia coli and 20 Klebsiella pneumoniae). Isolates were tested using Etest, MIC test strip (MTS), Vitek2, Phoenix and disc diffusion. Agar dilution was performed as the reference method in a central laboratory. Epidemiological cut-off values (ECOFFs) were determined for each species and susceptibility and error rates were calculated.

Results

In total, 775 E. coli and 201 K. pneumoniae isolates were tested by agar dilution. The ECOFF was 2 mg/L for E. coli and 64 mg/L for K. pneumoniae. Susceptibility rates based on the EUCAST breakpoint of ≤32 mg/L were 95.9% for E. coli and 87.6% for K. pneumoniae. Despite high categorical agreement rates for all methods, notably in E. coli, none of the alternative antimicrobial susceptibility testing methods performed satisfactorily. Due to poor detection of resistant isolates, very high error rates of 23.3% (Etest), 18.5% (MTS), 18.8% (Vitek2), 12.5% (Phoenix) and 12.9% (disc diffusion) for E. coli and 22.7% (Etest and MTS), 16.0% (Vitek2) and 12% (Phoenix) for K. pneumoniae were found. None of the methods adequately differentiated between WT and non-WT populations.

Conclusions

Overall, it was concluded that none of the test methods is suitable as an alternative to agar dilution in the routine laboratory.

The Role of fosA in Challenges with Fosfomycin Susceptibility Testing of Multispecies Klebsiella pneumoniae Carbapenemase-Producing Clinical Isolates

With multidrug-resistant (MDR) Enterobacterales on the rise, a nontoxic antimicrobial agent with a unique mechanism of action such as fosfomycin seems attractive. However, establishing accurate fosfomycin susceptibility testing for non-Escherichia coli isolates in a clinical microbiology laboratory remains problematic. We evaluated fosfomycin susceptibility by multiple methods with 96 KPC-producing clinical isolates of multiple strains and species collected at a single center between 2008 and 2016. In addition, we assessed the presence of fosfomycin resistance genes from whole-genome sequencing (WGS) data using NCBI's AMRFinder and custom HMM search. Susceptibility testing was performed using a glucose-6-phosphate-supplemented fosfomycin Etest and Kirby-Bauer disk diffusion (DD) assays, and the results were compared to those obtained by agar dilution. Clinical Laboratory and Standards Institute (CLSI) breakpoints for E. coli were applied for interpretation. Overall, 63% (60/96) of isolates were susceptible by Etest, 70% (67/96) by DD, and 88% (84/96) by agar dilution. fosA was detected in 80% (70/88) of previously sequenced isolates, with species-specific associations and alleles, and fosA-positive isolates were associated with higher MIC distributions. Disk potentiation testing was performed using sodium phosphonoformate to inhibit fosA and showed significant increases in the zone diameter of DD testing for isolates that were fosA positive compared to those that were fosA negative. The addition of sodium phosphonoformate (PPF) corrected 10/14 (71%) major errors in categorical agreement with agar dilution. Our results indicate that fosA influences the inaccuracy of susceptibility testing by methods readily available in a clinical laboratory compared to agar dilution. Further research is needed to determine the impact of fosA on clinical outcomes.

Prognosis of urinary tract infection caused by KPC-producing Klebsiella pneumoniae: The impact of inappropriate empirical treatment

INTRODUCTION

There is scarce information on the prognosis of urinary tract infections (UTI) caused by KPC carbapenemase-producing Klebsiella pneumoniae (KPC-Kp).

OBJETIVE

To investigate the association between KPC-Kp aetiology and clinical failure and all cause mortality and to explore the impact of inappropriate empirical treatment.

MATERIAL AND METHODS

This is a retrospective observational study of hospitalized patients with UTI due to K. pneumoniae. We explored clinical failure at day 21 and 30-day all-cause mortality using different models of adjusted analysis.

RESULTS

We analyzed 142 episodes of UTI; 46 episodes (32.4%) were due to KPC-Kp and 96 episodes (67.6%) were due to non-KPC-Kp strains (62 wild type and 34 EBSL producer). Clinical failure was more frequent in the KPC-Kp group (41.3% vs. 15.6%, p = 0.001). KPC-Kp aetiology and inappropriate empirical therapy were associated in the non-adjusted analysis with clinical failure. When analysed in separate adjusted models, both were found to be associated; inappropriate empirical treatment (OR 2.51; 95% CI, 1.03-6.12; p = 0.04) and KPC-Kp (OR 2.73; 95% CI, 1.03-7.22; p = 0.04) were associated with increased risk of failure. All-cause 30-day mortality was higher in patients with KPC-Kp UTI (39.1% vs. 15.6%, p = 0.002). Bacteraemia was more frequent in patients with KPC-Kp etiology (23.9% vs. 10.4%; p = 0.034). In both cases, the association was not confirmed in the adjusted analysis.

CONCLUSION

KPC-Kp UTI is associated with higher clinical failure and may be due to an increase in inappropriate empirical treatment.

Treatment Options for Colistin Resistant Klebsiella pneumoniae: Present and Future

Multidrug-resistant (MDR) Klebsiella pneumoniae represents an increasing threat to human health, causing difficult-to-treat infections with a high mortality rate. Since colistin is one of the few treatment options for carbapenem-resistant K. pneumoniae infections, colistin resistance represents a challenge due to the limited range of potentially available effective antimicrobials, including tigecycline, gentamicin, fosfomycin and ceftazidime/avibactam. Moreover, the choice of these antimicrobials depends on their pharmacokinetics/pharmacodynamics properties, the site of infection and the susceptibility profile of the isolated strain, and is sometimes hampered by side effects. This review describes the features of colistin resistance in K. pneumoniae and the characteristics of the currently available antimicrobials for colistin-resistant MDR K. pneumoniae, as well as the characteristics of novel antimicrobial options, such as the soon-to-be commercially available plazomicin and cefiderocol. Finally, we consider the future use of innovative therapeutic strategies in development, including bacteriophages therapy and monoclonal antibodies.

Current clinical use of intravenous fosfomycin in ICU patients in two European countries

PURPOSE

In Europe, intravenous fosfomycin (IV) is used particularly in difficult-to-treat or complex infections, caused by both Gram-positive and Gram-negative pathogens including multidrug-resistant strains. Here, we investigated the efficacy and safety of intravenous fosfomycin under real-life conditions.

METHODS

Prospective, multi-center, and non-interventional study in patients with bacterial infections from 20 intensive care units (ICU) in Germany and Austria (NCT01173575).

RESULTS

Overall, 209 patients were included (77 females, 132 males, mean age: 59 ± 16 years), 194 of which were treated in intensive care (APACHE II score at the beginning of fosfomycin therapy: 23 ± 8). Main indications (± bacteremia or sepsis) were infections of the CNS (21.5%), community- (CAP) and hospital-acquired pneumonia (HAP)/ventilator-associated pneumonia (VAP, 15.3%), bone and joint infections (BJI, 11%), abdominal infections (11%), and bacteremia (10.5%). Most frequently identified pathogens were S. aureus (22.3%), S. epidermidis (14.2%), Enterococcus spp. (10.8%), E. coli (12.3%) and Klebsiella spp. (7.7%). At least one multidrug-resistant (MDR) pathogen was isolated from 51 patients (24.4%). Fosfomycin was administered with an average daily dose of 13.7 ± 3.5 g over 12.4 ± 8.6 days, almost exclusively (99%) in combination with other antibiotics. The overall clinical success was favorable in 81.3% (148/182) of cases, and in 84.8% (39/46) of patients with ≥ 1 MDR pathogen. Noteworthy, 16.3% (34/209) of patients developed at least one, in the majority of cases non-serious, adverse drug reaction during fosfomycin therapy.

CONCLUSION

Our data suggest that IV fosfomycin is an effective and safe combination partner for the treatment of a broad spectrum of severe bacterial infections in critically ill patients.

The "Old" and the "New" Antibiotics for MDR Gram-Negative Pathogens: For Whom, When, and How

The recent expansion of multidrug resistant and pan-drug-resistant pathogens poses significant challenges in the treatment of healthcare associated infections. An important advancement, is a handful of recently launched new antibiotics targeting some of the current most problematic Gram-negative pathogens, namely carbapenem-producing Enterobacteriaceae (CRE) and carbapenem-resistant P. aeruginosa (CRPA). Less options are available against carbapenem-resistant Acinetobacter baumannii (CRAB) and strains producing metallo-beta lactamases (MBL). Ceftazidime-avibactam signaled a turning point in the treatment of KPC and partly OXA- type carbapenemases, whereas meropenem-vaborbactam was added as a potent combination against KPC-producers. Ceftolozane-tazobactam could be seen as an ideal beta-lactam backbone for the treatment of CRPA. Plazomicin, an aminoglycoside with better pharmacokinetics and less toxicity compared to other class members, will cover important proportions of multi-drug resistant pathogens. Eravacycline holds promise in the treatment of infections by CRAB, with a broad spectrum of activity similar to tigecycline, and improved pharmacokinetics. Novel drugs and combinations are not to be considered "panacea" for the ongoing crisis in the therapy of XDR Gram-negative bacteria and colistin will continue to be considered as a fundamental companion drug for the treatment of carbapenem-resistant Enterobacteriaceae (particularly in areas where MBL predominate), for the treatment of CRPA (in many cases being the only in vitro active drug) as well as CRAB. Aminoglycosides are still important companion antibiotics. Finally, fosfomycin as part of combination treatment for CRE infections and P. aeruginosa, deserves a greater attention. Optimal conditions for monotherapy and the "when and how" of combination treatments integrating the novel agents will be discussed.

In vitro investigation of synergy among fosfomycin and parenteral antimicrobials against carbapenemase-producing Enterobacteriaceae

Intravenous fosfomycin is undergoing clinical development in the United States for treatment of complicated urinary tract infections (cUTIs) and may be prescribed as a component of dual antibiotic regimens against carbapenemase-producing Enterobacteriaceae (CPE). Fosfomycin, aztreonam, cefepime, ceftazidime, ceftazidime/avibactam, ceftolozane/tazobactam, meropenem, piperacillin/tazobactam, and tobramycin minimum inhibitory concentrations (MICs) were determined by gradient diffusion strip (GDS) against CPE isolates (N = 49). The GDS cross method was used to assess antibiotic interactions between fosfomycin and the aforementioned parenteral antibiotics. The resultant fractional inhibitory concentration index was used to classify interactions. Fosfomycin-containing combinations were evaluated only if nonsusceptible to the second agent. The fosfomycin MIC₅₀ was ≥1024 mg/L by GDS. Synergy or additivity was detected in 80 (22%) fosfomycin-containing combinations. Antagonism was not observed. Ceftolozane/tazobactam most frequently displayed synergy [8 (16.3%) isolates]. When CPE are isolated, clinical laboratories should consider performing GDS synergy tests to identify favorable antibiotic interactions.