Draft genome sequence data of multidrug-resistant Pseudomonas aeruginosa WO7 from a hospital wastewater treatment plant in Thailand

Multidrug-resistant Pseudomonas aeruginosa WO7 was isolated from an untreated water sample from a hospital wastewater treatment plant in Thailand. This report presents the draft genome sequence data of P. aeruginosa WO7. Genomic DNA was obtained from a pure culture of P. aeruginosa WO7, and paired-end reads were generated using an Illumina MiSeq sequencer. The draft genome consisted of 111 contigs with a total size of 6,784,206 base pairs, an N50 of 209,424 base pairs, and a GC content of 65.85%. The dDDH value between WO7 and Pseudomonas aeruginosa DSM 50071T was determined to be 90.7%, indicating that the strain is Pseudomonas aeruginosa. The data presented indicate the potential for bacterial classification, comparative genomics, comprehensive analysis of antimicrobial resistance, and assessment of bacterial virulence factors in P. aeruginosa. The draft genome sequence data have been deposited at the NCBI under Bioproject accession number PRJNA550309.

Effect of fosfomycin-induced hypernatremia on patients' hospital stay length and survival

BACKGROUND AND OBJECTIVE

Hypernatremia is a possible side effect of intravenous fosfomycin. The aim of this study was to investigate the effects of changes in sodium (Na) levels on hospital stay and survival in patients hospitalized in the intensive care unit receiving fosfomycin.

SUBJECTS AND METHODS

This study was conducted retrospectively on the files of patients over the age of 60, who were admitted to the Internal Medicine Intensive Care Unit. Plasma sodium levels were observed and documented over a period of 14 days. The patients were divided into two groups (Hypernatremia group Na > 145 mEq/L vs normonatremia group 135-145 mEq/L). In addition, daily sodium changes were noted for 14 days in patients.

RESULTS

The mean age of the patients was 75 years. Hospitalization days were longer for hypernatremia patients (31.5 days vs 41 days, p = 0.003). Patients with hypernatremia had an extended duration of stay in the intensive care unit. (21 days vs 31 days p = 0.002). The 1-month survival rate was 61.4% in patients with hypernatremia and 24.9% in patients without hypernatremia (p = 0.004). The absence of hypernatremia increases mortality by 2.09 times (95% CI 1.35-3.23). When discharge and mortality rates were analyzed according to sodium fluctuation, discharged patients exhibited a lower sodium fluctuation (4 min/max (-10/19) vs 6 min/max (-16/32) p < 0.001).

CONCLUSION

In conclusion, the strength of our study is that it specifically focuses on the consequences of the sodium fluctuation on patient management and provides results.

Intravenous fosfomycin in combination regimens as a treatment option for difficult-to-treat infections due to multi-drug-resistant Gram-negative organisms: A real-life experience

AIM

To investigate the efficacy of intravenous (IV) fosfomycin as combination therapy for treatment of difficult-to-treat (DTT) acute and subacute infections with multi-drug-resistant (MDR) Gram-negative bacteria (GNB), and risk factors associated with 90-day mortality.

METHODS

A retrospective, observational, monocentric study enrolled patients treated with IV fosfomycin in combination regimens (≥72 h) for proven DTT-MDR-GNB infection. Multi-variate regression analysis identified independent risk factors for 90-day mortality. A propensity score for receiving fosfomycin was performed to control for confounding factors.

RESULTS

In total, 70 patients were included in this study: 54.3% had carbapenem-resistant isolates, 31.4% had ceftazidime/avibactam-resistant isolates and 28.6% had ceftolozane/tazobactam-resistant isolates. The main pathogens were Pseudomonas aeruginosa (57.1%) and Klebsiella pneumoniae (22.9%). The most prevalent infections were nosocomial pneumonia (42.9%), osteomyelitis (17.1%) and intra-abdominal infections. All-cause 30- and 90-day mortality were 15.7% and 31.4%, respectively (18.9% and 50% considering acute DTT-MDR-GNB infections alone). Relapse at 30 days occurred in 22.9% of cases (29% with emergence of fosfomycin resistance). Mortality at 90 days was independently associated with septic shock and ceftolozane/tazobactam resistance. The relationship between resistance to ceftolozane/tazobactam and 90-day mortality was confirmed to be significant after adjustment by propensity score analysis (hazard ratio 5.84, 95% confidence interval 1.65-20.68; P=0.006).

CONCLUSIONS

Fosfomycin seems to be a promising salvage, combination treatment in DTT-MDR-GNB infections. Resistance to ceftolozane/tazobactam seems to be independently associated with treatment failure. Randomized clinical trials focusing on pathogen and infection sites are needed urgently to demonstrate the superiority of fosfomycin in combination with other agents for the resolution of DTT-MDR-GNB infections.

Comparative effectiveness and mortality of colistin monotherapy versus colistin-fosfomycin combination therapy for the treatment of carbapenem-resistant Enterobacteriaceae (CRE) infections: A propensity score analysis

BACKGROUND

Carbapenem-resistant Enterobacteriaceae (CRE) infections pose a significant threat to global health due to limited treatment options and high mortality rates. Colistin-based regimens have emerged as a primary treatment approach, but the effectiveness and mortality outcomes of colistin monotherapy versus colistin-fosfomycin combination therapy remain uncertain. This study aims to compare the effectiveness and mortality of colistin monotherapy and colistin-fosfomycin combination therapy for CRE infections. Notably, our study is the first to undertake a comprehensive examination of the effectiveness and mortality outcomes between colistin monotherapy and colistin-fosfomycin combination therapy in the context of CRE infections.

METHODS

A retrospective cohort study was conducted using data from patients diagnosed with carbapenem-resistant Enterobacteriaceae (CRE) infections at Nakornping Hospital during 2015 to 2022. Inverse probability weighting (IPW) was employed to create balanced cohorts of patients receiving either colistin monotherapy or colistin-fosfomycin combination therapy. The primary outcome measure was treatment effectiveness, assessed by 30-day mortality. Secondary outcome measures included clinical response, mortality at the end of treatment, and microbiologic response. Univariate and multivariate logistic regression analysis were employed after applying propensity score weighting using inverse probability of weighting (IPW).

RESULTS

A total of 220 patients were included in the analysis, with 67 receiving colistin monotherapy and 153 receiving colistin-fosfomycin combination therapy. Propensity score weighting using IPW balanced the baseline characteristics between the two groups. The effectiveness of treatment, as measured by 30-day mortality, was not significantly different between the colistin monotherapy group and the colistin-fosfomycin combination therapy group (adjusted odds ratio [aOR] = 1.51, 95% confidence interval [CI]: 0.60-3.78, p = 0.383). Similarly, no significant difference was observed in the mortality at the end of treatment between the two groups (aOR = 1.26, 95% CI: 0.55-2.90, p = 0.576). The clinical response (aOR = 1.48, 95% CI: 0.61-3.59, p = 0.383) and microbiologic response (aOR = 0.66, 95% CI: 0.18-2.38, p = 0.527) were similar between the colistin monotherapy and colistin-fosfomycin combination therapy groups.

CONCLUSION

The propensity score analysis among 220 matched patients showed comparable treatment effectiveness and mortality between colistin monotherapy and colistin-fosfomycin combination therapy for CRE infections. These results suggest that colistin monotherapy may be as effective as combination therapy. More prospective randomized controlled trials are needed to confirm these findings and establish optimal CRE treatment strategies.

Getting to the heart of the matter-are two agents really better than one for the treatment of staphylococcal infective endocarditis?

The recently published European Society of Cardiology guidelines for infective endocarditis management recommends daptomycin combination therapy for the treatment of staphylococcal endocarditis in severe penicillin allergy, rather than daptomycin monotherapy. We discuss the evidence base behind this recommendation, highlighting concerns regarding the lack of robust clinical studies, increased cost and logistical considerations, and adverse effects of combination therapy. Although further studies are required to elucidate the role of combination vs monotherapy in these patients, we propose a pragmatic management approach to reduce the risk of adverse antimicrobial side effects and limit costs, while aiming to maintain treatment efficacy.

In vitro activity of antibiotics potentially effective against difficult-to-treat strains of Gram-negative rods: retrospective study

Bacterial resistance surveillance is one of the main outputs of microbiological laboratories and its results are important part of antimicrobial stewardship (AMS). In this study, the susceptibility of specific bacteria to selected antimicrobial agents was tested. The susceptibility of 90 unique isolates of pathogens of critical priority obtained from clinically valid samples of ICU patients in 2017-2021 was tested. 50% of these fulfilled difficult-to-treat resistance (DTR) criteria and 50% were susceptible to all antibiotics included in the definition. 10 Enterobacterales strains met DTR criteria, and 2 (20%) were resistant to colistin (COL), 2 (20%) to cefiderocol (FCR), 7 (70%) to imipenem/cilastatin/relebactam (I/R), 3 (30%) to ceftazidime/avibactam (CAT) and 5 (50%) to fosfomycin (FOS). For Enterobacterales we also tested aztreonam/avibactam (AZA) for which there are no breakpoints yet. The highest MIC of AZA observed was 1 mg/l, MIC range in the susceptible cohort was 0.032-0.064 mg/l and in the DTR cohort (incl. class B beta-lactamase producers) it was 0.064-1 mg/l. Two (13.3%) isolates of Pseudomonas aeruginosa (15 DTR strains) were resistant to COL, 1 (6.7%) to FCR, 13 (86.7%) to I/R, 5 (33.3%) to CAT, and 5 (33.3%) to ceftolozane/tazobactam. All isolates of Acinetobacter baumannii with DTR were susceptible to COL and FCR, and at the same time resistant to I/R and ampicillin/sulbactam. New antimicrobial agents are not 100% effective against DTR. Therefore, it is necessary to perform susceptibility testing of these antibiotics, use the data for surveillance (including local surveillance) and conform to AMS standards.

Antibiotics efficacy in clinical and microbiological cure of uncomplicated urinary tract infection: a systematic review and network meta-analysis

PURPOSE

Fosfomycin has been used more frequently in managing uncomplicated urinary tract infections (UTIs) due to decreased compliance and increased multidrug-resistant bacteria. The aim of this network meta-analysis was to assess the efficacy of Fosfomycin compared to Nitrofurantoin, Trimethoprim-Sulfamethoxazole (TMP-SMX), and Ciprofloxacin in terms of clinical and microbiological cure alongside with other measurements.

MATERIALS AND METHODS

We searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL). We included randomized control trials (RCTs) with uncomplicated UTI patients who received Fosfomycin, Nitrofurantoin, TMP-SMX, or Ciprofloxacin and reported the clinical or microbiological cure. We used Cochrane Risk of Bias Assessment Tool to assess the included studies' quality. R-software was used for all statistical analysis. We ranked all antibiotics using the netrank function which yielded P scores. Frequentist network meta-analysis was used to assess the efficacy of all outcomes.

RESULTS

We included 13 RCTs with a total number of 3856 patients that showed Fosfomycin ranked the highest among the other antibiotics with respect to clinical cure (P-score = 0.99) and microbiological cure (P-score = 0.99) while Ciprofloxacin ranked the lowest (P-score = 0.11 and 0.02, respectively). Moreover, Ciprofloxacin yielded the highest relapse rate (P-score = 1), whereas TMP-SMX had the lowest relapse rate (P-score = 0.07). As for the adverse events, Ciprofloxacin demonstrated the highest adverse events as opposed to Fosfomycin (P-score = 0.98 and 0.05, respectively).

CONCLUSION

The network meta-analysis demonstrated that Fosfomycin is the most effective antibiotic in treating uncomplicated UTIs with respect to clinical cure, microbiological cure, and adverse events profile.

Fosfomycin as salvage therapy for persistent methicillin-resistant Staphylococcus aureus bacteremia: A case series and review of the literature

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia can be persistent and refractory; however, the optimal approach for its treatment has not been determined. Although fosfomycin (FOM) has been shown to have synergistic effects with anti-MRSA agents in vitro, clinical experience with FOM combination therapy is limited. Thus, we present cases of persistent MRSA bacteremia that improved with the addition of FOM. In case 1, a 48-year-old man with prosthetic vascular graft infection developed persistent MRSA bacteremia despite vancomycin (VCM) and daptomycin (DAP) administration. On day 46, after the first positive blood culture, we added FOM to DAP. The blood culture became negative on day 53. In case 2, an 85-year-old woman presented with pacemaker-related MRSA bacteremia. She was treated with VCM, followed by DAP and DAP plus rifampicin. However, the bacteremia persisted for 32 days because of difficulties in immediate pacemaker removal. After adding FOM to DAP, the blood culture became negative on day 38. In case 3, a 57-year-old woman developed persistent MRSA bacteremia due to pulmonary valve endocarditis and pulmonary artery thrombosis after total esophagectomy for esophageal cancer. The bacteremia continued for 50 days despite treatment with DAP, followed by VCM, VCM plus minocycline, DAP plus linezolid (LZD), and VCM plus LZD. She was managed conservatively because of surgical complications. After adding FOM to VCM on day 51, the blood culture became negative on day 58. FOM combination therapy may be effective in eliminating bacteria and can serve as salvage therapy for refractory MRSA bacteremia.

Identification of the novel fosfomycin resistance gene fosSC in Staphylococcus capitis

OBJECTIVES

Fosfomycin has regained attention for treating infections caused by methicillin-resistant Staphylococcus aureus and multidrug-resistant coagulase-negative staphylococci. In this research, our objective was to investigate the mechanisms underlying fosfomycin resistance in Staphylococcus capitis.

METHODS

The minimum inhibitory concentrations (MICs) of fosfomycin were assessed in 109 clinical S. capitis isolates by the agar dilution method. By cloning the fos-like genes into the shuttle vector, pTSSCm-Pcap, and observing the change in fosfomycin MICs, the gene function was verified. Core genome multilocus sequence typing and comparative genomics analysis were conducted to determine the population characteristics of S. capitis isolates and analyse the genetic environment of the fos-like genes.

RESULTS

We identified a novel fosfomycin resistance gene, fosSC, on the chromosome in 58 out of 109 (53.2%) S. capitis isolates. The deduced products of the fosSC genes shared 67.15-67.88% amino acid sequence identity with FosB. The RN-pT-fosSC transformants carrying fosSC showed a 512-fold increase in the fosfomycin MICs. The fosSC gene was embedded in a conserved genetic context, but IS431mec was located to the left of the fosSC gene in cluster L due to the insertion of staphylococcal cassette chromosome mec.

CONCLUSIONS

The chromosomal fosSC genes in some lineages of S. capitis explained their high-level fosfomycin resistance. Ongoing surveillance is crucial for monitoring the potential threat of horizontal transfer, which could be facilitated by the presence of mobile genetic elements surrounding the fosSC gene.

pneumoniae successfully treated with meropenem/vaborbactam and high dose of fosfomycin

OBJECTIVE

A case of post-neurosurgical ventriculitis caused by a KPC-producing Klebsiella pneumoniae (KPC-Kp) with a ceftazidime/avibactam-resistant, meropenem-susceptible phenotype is reported.

METHODS AND RESULTS

The patient had a concomitant bloodstream infection with a wild-type KPC-Kp with a ceftazidime/avibactam-susceptible, meropenem-resistant phenotype. Prolonged treatment with intravenous fosfomycin and meropenem/vaborbactam achieved clinical success. Therapeutic drug monitoring performed during the first days of treatment showed for the first time that vaborbactam efficiently penetrates cerebrospinal fluid. In contrast, meropenem was undetectable in cerebrospinal fluid at each sampling, suggesting that additional doses of meropenem may be required to appropriately prescribe meropenem/vaborbactam for central nervous system infections. Plasma and cerebrospinal fluid levels of fosfomycin were adequate, confirming the potential of this agent possibly even in the fight against multidrug-resistant organisms.

CONCLUSIONS

This case highlights the need for therapeutic drug monitoring as a crucial tool for optimizing treatment in complicated cases where the pharmacokinetic behaviour of antibiotics is difficult to predict.

Efficient degradation and detoxification of antibiotic Fosfomycin by UV irradiation in the presence of persulfate

Fosfomycin (FOS) as a widely used antibiotic has been found in abundance throughout the environment, but little effort has been devoted to its treatment. In this study, we systemically looked into the degradation of FOS by ultraviolet-activated persulfate (UV/PS) in aqueous solutions. Our findings demonstrated that FOS can be degraded efficiently under the UV/PS, e.g., >90 % of FOS was degraded with 19,200 mJ cm-2 of UV irradiance and 20 μM of PS. HO was the dominant radical responsible for FOS degradation. FOS degradation increased as PS dosage increased, and higher degradation efficiency was observed at neutral pH. Natural water constitutes either promoted (e.g., Cu2+, Fe3+, and SO42-) or inhibited (e.g., humic acid, HCO3-, and CO32-) FOS degradation to varying degrees. Hydroxyl substitution, CP bond cleavage, and coupling reactions were the major degradation pathways for FOS degradation. Finally, the toxicity evaluation revealed that FOS was toxic to E. coli and S. aureus, but the toxicity of the intermediate products of FOS to E. coli and S. aureus rapidly decreased over time after UV/PS treatment. Therefore, these findings provided a fundamental understanding of the transformation process of FOS and supplied useful information for the environmental elimination of FOS contamination and its toxicity.

Susceptibility to Fosfomycin and Nitrofurantoin of ESBL-Positive Escherichia coli and Klebsiella pneumoniae Isolated From Urine of Pediatric Patients

BACKGROUND

Pediatric urinary tract infection (UTI) caused by extended-spectrum β-lactamase (ESBL)-positive gram-negative bacilli (GNB) has limited options for oral antibiotic treatment. The purpose of this study was to investigate the susceptibility of ESBL-positive Escherichia coli and Klebsiella pneumoniae isolates from pediatric urine samples to two oral antibiotics (fosfomycin and nitrofurantoin).

METHODS

From November 2020 to April 2022, ESBL-positive E. coli and K. pneumoniae isolates from urine samples were collected at Samsung Medical Center, Seoul, Korea. Patients over 18 years of age or with malignancy were excluded. For repeated isolates from the same patient, only the first isolate was tested. Minimum inhibitory concentrations (MICs) were measured using agar (fosfomycin) or broth (nitrofurantoin) dilution methods. MIC50 and MIC90 were measured for fosfomycin and nitrofurantoin in both E. coli and K. pneumoniae.

RESULTS

There were 117 isolates from 117 patients, with a median age of 7 months (range, 0.0-18.5 years). Among 117 isolates, 92.3% (108/117) were E. coli and 7.7% (9/117) were K. pneumoniae. Isolates from the pediatric intensive care unit (PICU) and general ward (GW) was 11.1% (13/117) and 88.9% (104/117), respectively. Among 108 E. coli isolates, MIC50 and MIC90 for fosfomycin were 0.5 μg/mL and 2 μg/mL, respectively. Fosfomycin susceptibility rate was 97.2% (105/108) with a breakpoint of 128 μg/mL. Fosfomycin susceptibility rate was significantly lower in PICU isolates than in GW isolates (81.8% vs. 99.0%, P = 0.027). For nitrofurantoin, both the MIC50 and MIC90 were 16 μg/mL. Nitrofurantoin susceptibility rate was 96.3% (104/108) with a breakpoint of 64 μg/mL based on Clinical and Laboratory Standards Institute guidelines. Among the nine K. pneumoniae isolates, the MIC50 and MIC90 for fosfomycin was 2 μg/mL and 32 μg/mL, respectively. MIC50 and MIC90 for nitrofurantoin were 64 μg/mL and 128 μg/mL, respectively.

CONCLUSION

For uncomplicated UTI caused by ESBL-positive GNB in Korean children, treatment with fosfomycin and nitrofurantoin for E. coli infections can be considered as an effective oral therapy option.

Fosfomycin modifies the replication kinetics of bovine alphaherpesvirus-1 and reduces the timing of its protein expression on bovine (MDBK) and human (SH-SY5Y) cell lines

Bovine alphaherpesvirus 1 (BoAHV-1) predisposes cattle to respiratory secondary bacterial infections, which can be treated with the broad-spectrum antibiotic fosfomycin. This drug also suppresses NF-kB activity and pro-inflammatory responses. Therefore, cattle may be exposed to an interaction between the virus and the antibiotic which may have effects on it. The aim of this study was to determine the effect of calcium fosfomycin (580 µg/mL) on BoAHV-1 (moi = 0.1) replication. Two cell lines (MDBK and SH-SY5Y) were used in this study. Our results show that fosfomycin has novel properties. By MTT assay we have shown that it is non-cytotoxic for any of the cell lines. Extracellular and intracellular viral titers demonstrated that fosfomycin has a cell-type and time-dependent effect on BoAHV-1 replication. By direct immunofluorescence it was shown that it reduces the timing of BoAHV-1 protein expression, and by qPCR, we found that its effect on NF-kB mRNA expression depends on the cell type.

Fosfomycin: A potential oral option for treatment of urinary tract infections in Sri Lanka in the context of high antibiotic resistance

Introduction

Fosfomycin is an effective treatment for urinary tract infections (UTIs). It is not currently used in Sri Lanka to treat UTIs. Hence, this study was conducted to assess the fosfomycin susceptibility for E. coli in urinary isolates, with an aim to find the usability of fosfomycin in the context of high antibiotic resistance.

Methods

E. coli isolates were identified by the colony appearance and by performing biochemical tests for the urinary coliform isolates collected from two different hospitals in Western Province Sri Lanka, during the period of November 2021 to February 2022. Susceptibility to fosfomycin 200 μg disc was performed following the Clinical Laboratory Standard Institute (CLSI) disc diffusion method.

Results

A total of 101 E. coli isolates from both oncology patients (52.5%) and non-oncology patients (47.5%) were identified and included in the study. The study sample showed majority of females (63.3%). Ampicillin showed the highest resistance rate (72.2%) while fosfomycin was the only antibiotic that showed 100% in vitro susceptibility to all the tested clinical isolates. The overall presence of multidrug-resistant (MDR) and carbapenem-resistant (CR) E. coli were 47.5% and 9.9% respectively.

Conclusions

Fosfomycin is a potential antibiotic option especially for MDR and CR organisms, with 100% in vitro susceptibility. Further studies involving multiple centers, with larger sample size and clinical efficacy studies would be important to assess the potential use of fosfomycin especially for the treatment of UTI-causing MDR and CR organisms.

Plasmid-mediated fosfomycin resistance in Escherichia coli isolates of worldwide origin

OBJECTIVES

Fosfomycin is a first-line treatment for uncomplicated urinary tract infections (UTIs) in several European countries, and it is increasingly becoming the treatment of choice globally. Resistance to fosfomycin in Escherichia coli can be exerted through several mechanisms, including the acquisition of fosfomycin-modifying enzymes, of which the FosA-type enzymes are the most common. This study analysed, both phenotypically and genotypically, an international collection of E. coli strains harbouring acquired fosA genes.

METHODS

Thirty-one fosA-positive E. coli isolates were obtained from both clinical and environmental sources, from seven countries (Portugal (n = 12), Switzerland (n = 9), China (n = 3), France (n = 2), Nepal (n = 2), South Africa (n = 2), Kuwait (n = 1)). MICs were determined according to EUCAST guidelines. Whole genome sequencing (WGS) was performed on 23 isolates, and complete fosA plasmid sequences were determined for 12. Conjugation assays were performed on seven isolates.

RESULTS

All isolates exhibited high-level resistance to fosfomycin (64 to >256 mg/L). WGS of 23 isolates identified 17 sequence types (STs), and 16 harboured fosA3, four fosA4, two fosA8, and one fosA10. ESBLs, pAmpC, or carbapenemase genes were present in 15, four, and three isolates, respectively. The fosA plasmids of 12 isolates were determined and were diverse in size (∼67 kb to ∼235 kb), resistance gene carriage, and replicon types. Six fosA plasmids additionally carried ESBL or carbapenemase genes. Conjugation assays, performed on seven isolates harbouring diverse plasmids, identified that all were capable of being transmitted.

CONCLUSION

This study highlights the necessity of the surveillance and close monitoring of fosfomycin resistance in E. coli, essential to maintain the optimal use of this treatment option.

Efficacy of antibiotic combinations in an experimental sepsis model with Pseudomonas aeruginosa

This study aimed to compare the efficacy of fosfomycin, colistin, tobramycin and their dual combinations in an experimental sepsis model. After sepsis was established with a Pseudomonas aeruginosa isolate (P1), antibiotic-administered rats were divided into six groups: Fosfomycin, tobramycin, colistin and their dual combinations were administered by the intravenous or intraperitoneal route to the groups. The brain, heart, lung, liver, spleen and kidney tissues of rats were cultured to investigate bacterial translocation caused by P1. Given the antibiotics and their combinations, bacterial colony counts in liver tissues were decreased in colistin alone and colistin plus tobramycin groups compared with control group, but there were no significant differences. In addition, a non-statistical decrease was found in the spleen tissues of rats in the colistin plus tobramycin group. There was a > 2 log10 CFU/ml decrease in the number of bacterial colonies in the kidney tissues of the rats in the fosfomycin group alone, but the decrease was not statistically significant. However, there was an increase in the number of bacterial colonies in the spleen and kidney samples in the group treated with colistin as monotherapy compared to the control group. The number of bacterial colonies in the spleen samples in fosfomycin plus tobramycin groups increased compared to the control group. Bacterial colony numbers in all tissue samples in the fosfomycin plus colistin group were found to be close to those in the control group. Colistin plus tobramycin combinations are effective against P. aeruginosa in experimental sepsis, and clinical success may be achieved. New in vivo studies demonstrating the ability of P. aeruginosa to biofilm formation in tissues other than the lung are warranted in future.

Antibiotic Resistance Patterns Among Uropathogens in Female Outpatients Affected by Uncomplicated Cystitis: Focus on Fosfomycin Trometamol

OBJECTIVES

To report the resistance rate against fosfomycin trometamol among outpatient women with symptoms related to urinary tract infections over a 6-year period in a multicentre, cross-sectional study.

METHODS

Urinary samples were collected from three high-volume laboratories from January 2015 to December 2020. The pattern of resistance to fosfomycin was analysed by using the Vitek II automated system.

RESULTS

A total of 7289 urinary samples were collected and 8321 strains were analysed during the study period. The most commonly isolated uropathogen was Escherichia coli (n = 6583, 79.1%). The mean resistance rate against fosfomycin was 9.7% (range 7.1-11.3). No statistically significant difference was found between the three laboratories (P = 0.53). There was no significant increase in resistance rate during the study period. The mean resistance rate against fosfomycin was higher among extended-spectrum β-lactamase (ESBL)-producing bacteria when compared with non-ESBL-producing strains (10.8% vs. 7.9%; P < 0.001).

CONCLUSION

Uropathogens isolated from women affected by cystitis remained highly susceptible to fosfomycin. These findings confirm recommendations in international guidelines that advocate fosfomycin trometamol for empirical treatment of uncomplicated cystitis in women.

The efficacy of mesenchymal stem cell treatment and colistin-fosfomycin combination on colistin-resistant Acinetobacter baumannii sepsis model

INTRODUCTION

This study examines the role of mesenchymal stem cells (MSCs) in an experimental sepsis model developed with colistin-resistant Acinetobacter baumannii (CRAB).

MATERIALS AND METHODS

BALB-c mice were divided into treatment groups (MSC, MSC + colistin (C)-fosfomycin (F), and C-F and control groups (positive and negative)). CRAB was administered to mice through intraperitoneal injection. Three hours later, C, F, and MSC were given intraperitoneally to the treatment groups. Colistin administration was repeated every 12 h, F administration was done every 4 h, and the second dose of MSC was administered after 48 h. Mice were sacrificed at 24 and 72 h. The bacterial load was determined as colony-forming units per gram (cfu/g). Histopathological examination was conducted on the left lung, liver, and both kidneys. IL-6 and C-reactive protein (CRP) levels in mouse sera were determined by enzyme-linked immunosorbent assay.

RESULTS

Among the treatment groups, the C-F group had the lowest colony count in the lung (1.24 ± 1.66 cfu/g) and liver (1.03 ± 1.08 cfu/g). The highest bacterial clearance was observed at 72 h compared to 24 h in the MSC-treated groups (p = 0.008). The MSC + C-F group showed the lowest histopathological score in the liver and kidney (p = 0.009). In the negative control group, the IL-6 level at the 24th hour was the lowest (p < 0.001). Among the treatment groups, the CRP level was the lowest in the MSC + C-F group at 24 and 72 h.

CONCLUSION

In a CRAB sepsis model, adding MSCs to a colistin-fosfomycin treatment may be beneficial in terms of reducing bacterial loads and preventing histopathological damage.

Fosfomycin-induced agranulocytosis: a case report and review of the literature

BACKGROUND

The intravenous form of fosfomycin, a bactericide antibiotic used to treat multiresistant bacterial infections is little prescribed. The most common reported adverse effects are hypokaliemia and hypernatremia. We describe a case of agranulocytosis, a rarely described side effect that may be fatal.

CASE PRESENTATION

A 45 year-old woman was admitted to the intensive care unit for post-surgical meningitis following meningioma resection. Meropenem and vancomycin were first introduced. A DRESS-syndrom with meropenem was suspected. Neutropenia was diagnosed three days after the introduction of parenteral fosfomycin and agranulocytosis four days later. Eosinophilia was also observed. A bone marrow aspiration was performed showing a disappearance of the neutrophil granulocyte line and a significant eosinophilia. Meropenem was discontinued. Fosfomycin was maintained and filgrastim was added. As filgrastim had no effect, the relationship with fosfomycin was suspected, so it was then withheld. An increase of the neutrophil count was observed. Because of the complexity of the case, the unfavorable course of the illness and the urgent need for revision surgery, a rechallenge with fosfomycin was done followed by a decrease of the neutrophil count.

CONCLUSION

This is the third paper reporting agranulocytosis induced by fosfomycin, and the first detailed description of a case. Based on chronological and semiological criteria and bibliographic data, the event was qualified as probable with the Naranjo adverse drug probability scale. Literature data is scarce. The summary of product characteristics mentions that only a few cases of transient neutropenia and agranulocytosis have been reported. An analysis of the FDA Adverse Event Reporting System Database highlighted a higher than expected frequency of agranulocytosis in patients treated with fosfomycin. Parenteral fosfomycin is often used in patients receiving other medications, so that it is rarely the only suspect. In our case, the results of the bone marrow aspiration, the sudden drop of the neutrophil count with concomitant eosinophilia and the absence of improvement despite the dose decrease, point towards an immuno-allergic mechanism. However, the overlap between the suspected DRESS induced by meropenem and the agranulocytosis do not allow to conclude with certainty on the causality. Awareness should be raised about this side effect.

Small molecule inhibitors of the fosfomycin resistance enzyme FosM from Mycobacterium abscessus

Fosfomycin is a safe broad-spectrum antibiotic that has not achieved widespread use because of the emergence of fosfomycin-modifying enzymes. Inhibition of fosfomycin-modifying enzymes could be used to help combat pathogens like Mycobacterium abscessus. Our previous work identified several inhibitors for the enzyme FosB from Staphylococcus aureus. We have tested those same compounds for inhibition of FosM, the fosfomycin-modifying enzyme from M. abscessus. The work described here will be used as the basis for more detailed studies into the inhibition of FosM.

Stability Study of Fosfomycin in Elastomeric Pumps at 4 °C and 34 °C: Technical Bases for a Continuous Infusion Use for Outpatient Parenteral Antibiotic Therapy

BACKGROUND

Fosfomycin acts against aerobic Gram-/+ bacteria by blocking the synthesis of peptidoglycan. Its use has been currently re-evaluated for intravenous administration for the treatment of systemic infections by multidrug-resistant bacteria. Concentration-/time-dependent activity has been suggested, with potential clinical advantages from prolonged or continuous infusion. Nevertheless, little is known about Fosfomycin stability in elastomeric pumps. The aim of the present work was stability investigation before administration at 4 °C and during administration at 34 °C.

METHODS

InfectoFos® (InfectoPharm s.r.l., Milan, Italy) preparation for intravenous use in elastomeric pumps at 4 °C and 34 °C was analyzed following EMA guidelines for drug stability. Samples were analyzed with an ultra-high performance liquid chromatography coupled with tandem mass spectrometry method on a LX50® UHPLC system equipped with a QSight 220® (Perkin Elmer, Milan, Italy) tandem mass spectrometer.

RESULTS

Fosfomycin in elastomeric preparation is stable for at least 5 days at a storage temperature of 4 °C and 34 °C.

CONCLUSIONS

The results suggest Fosfomycin eligibility for continuous infusion even in the context of outpatient parenteral antibiotic therapy. Therefore, this approach should be tested in clinical and pharmacokinetic studies, in order to evaluate the possible gains in the pharmacokinetic profile and the clinical effectiveness.

Effectiveness of fosfomycin-based antimicrobial prophylaxis for transrectal ultrasound-guided prostate biopsy: A Korean multicenter study

PURPOSE

Recent studies have highlighted increasing infectious complications due to fluoroquinolone (FQ)-resistant organisms in men undergoing transrectal ultrasound-guided prostate biopsy (TRUSPB). This study investigated whether fosfomycin (FM)-based antibiotic prophylaxis reduces infections after TRUSPB and identified risk factors for infective complications.

MATERIALS AND METHODS

A multicenter study was conducted in the Republic of Korea from January 2018 to December 2021. Patients undergoing prostate biopsy with FQ or FM-based prophylaxis were included. The primary outcome was the post-biopsy infectious complication rate after FQ (group 1) or FM-based antibiotic prophylaxis with FM alone (group 2) or FQ and FM (group 3). Risk factors for infectious complications after TRUSPB were secondary outcomes.

RESULTS

Patients (n=2,595) undergoing prostate biopsy were divided into three groups according to the type of prophylactic antibiotics. Group 1 (n=417) received FQ before TRUSPB. Group 2 (n=795) received FM only and group 3 (n=1,383) received FM and FQ before TRUSPB. The overall post-biopsy infectious complication rate was 1.27%. The infectious complication rates were 2.4%, 1.9%, and 0.5% in groups 1, 2, and 3, respectively (p=0.002). In multivariable analysis, predictors of post-biopsy infectious complications included an association with health care utilization (adjusted odds ratio [OR], 4.66; 95% confidence interval [CI], 1.74-12.4; p=0.002) and combination antibiotic prophylaxis (FQ and FM) (adjusted OR, 0.26; 95% CI, 0.09-0.69; p=0.007).

CONCLUSIONS

In comparison with monotherapy with FM or FQ, combination antibiotic prophylaxis (FQ and FM) showed a lower rate of infectious complications after TRUSPB. Utilization of health care was an independent risk factor for infectious complications after TRUSPB.

Population plasma and urine pharmacokinetics and the probability of target attainment of fosfomycin in healthy male volunteers

PURPOSE

A population pharmacokinetic model of fosfomycin was developed in healthy volunteers after intravenous administration, and different dosing regimens were evaluated in terms of the probability of target attainment for Escherichia coli using both plasma and urinary pharmacokinetic/pharmacodynamic targets.

METHODS

Eight healthy men received fosfomycin as both intermittent 8 g q8h and continuous infusion 1 g/h with a loading dose of 8 g in a crossover study design. Dense sampling was conducted during both regimens. Population pharmacokinetic modelling was performed using NONMEM. Monte Carlo simulations were conducted to evaluate the Probability of Target Attainment (PTA) of different dosing regimens using bactericidal (AUC_24h/MIC of 83 and 75%T_>MIC) and bacteriostatic (AUC_24h/MIC of 25) plasma targets and bacteriostatic (AUC_24h/MIC of 3994) urine target.

RESULTS

A total of 176 plasma and 86 urine samples were available for PK analysis. A two-compartment model with a urine compartment best described the data. Glomerular filtration rate (GFR) showed a significant correlation with renal clearance and was implemented in the final model. Simulation results show that the dose of 4 g q8h reached 100% of PTA using bactericidal and bacteriostatic targets for MIC up to 16 mg/L.

CONCLUSION

For the clinical breakpoint of 32 mg/L, the standard dosing regimen (4 g q8h) might not be sufficient to reach the bactericidal target. Higher dosing of 8 g q8h as an intermittent infusion or 0.75 g/h as a continuous infusion might be required. Continuous infusion resulted in better attainment of the %T_>MIC target than intermittent infusion.

Single-dose fosfomycin could prevent infectious complications after retrograde intrarenal surgery: A prospective study

BACKGROUND

In this study, we aimed to show the protective effect of a single-dose Fosfomycin from infective complications against the standard usage of cephalosporine before retrograde intrarenal surgery.

MATERIAL

A total of 186 patients who underwent retrograde intrarenal surgery between 2020 and 2021, included the study. Patients were divided into two groups: group 1(n=49), patients who received an oral dose of 3g Fosfomycin tromethamine powder administered 4-6h before the operation; and group 2 (n=137): patients who received Cephalosporin 30min before surgery and an additional dose 6h after surgery.

RESULTS

The median age and stone size were significantly higher in the cephalosporin group (P=0.006 and P=0.008, respectively). There was no statistically significant difference between the groups in terms of postoperative fever and postoperative UTI (P=0.408 and P=0.438). Additionally, no patient developed sepsis. and no adverse event was seen in either group. Preoperative urinary tract infection (UTI) and previous Extracorporeal Shock Wave lithotripsy (ESWL) were independent risk factors and increased postoperative infectious complications (O.R. 2.929 95% C.I. 0.723, P<0.001, and O.R. 2.860 95% C.I. 0.985, P=0.004, respectively).

CONCLUSION

Infectious is still one of the important complications after RIRS, and preoperative UTI is an independent risk factors for infections. Fosfomycin monotherapy could be sufficient and is also effective in patients with preoperative culture positive.

The Combination of Daptomycin with Fosfomycin is More Effective than Daptomycin Alone in Reducing Mortality of Vancomycin-Resistant Enterococcal Bloodstream Infections: A Retrospective, Comparative Cohort Study

INTRODUCTION

High-dose daptomycin-based combinations are recommended for vancomycin-resistant Enterococcus (VRE) bloodstream infection (BSI). Preclinical data have shown a synergistic effect of daptomycin/fosfomycin combinations against VRE. However, clinical studies comparing daptomycin monotherapy with daptomycin/fosfomycin combinations are unavailable.

METHODS

An observational study of VRE-BSI was performed between 2010-2021 on patients receiving daptomycin monotherapy (≥ 8 mg/kg) or daptomycin combined with intravenous fosfomycin. Patients treated with concomitant β-lactam combinations were excluded. The primary outcome was in-hospital mortality. Outcomes were analyzed using multivariable logistic regression and augmented inverse probability weighting (AIPW) analyses.

RESULTS

Among 224 patients, 176 received daptomycin monotherapy, and 48 received fosfomycin combinations. The median daptomycin and fosfomycin doses were 9.8 mg/kg and 12 g/day, respectively. In-hospital mortality was 77.3% and 47.9% in the daptomycin monotherapy and fosfomycin combination groups (P < 0.001), respectively. Multivariable logistic regression analysis predicted lower mortality with fosfomycin combination treatment (adjusted odds ratio, 0.35; 95% confidence interval (CI), 0.17-0.73; P = 0.005). AIPW demonstrated a 17.8% reduced mortality with fosfomycin combinations (95% CI, - 30.6- - 4.9%; P = 0.007). The survival benefit was significant, especially among patients with a lower Pitt bacteremia score or fosfomycin minimum inhibitory concentration (MIC) ≤ 64 mg/l. Fosfomycin combination resulted in higher hypernatremia (10.4% vs. 2.8%, P = 0.04) and hypokalemia (33.3% vs. 15.3%, P = 0.009) compared to daptomycin monotherapy.

CONCLUSION

The combination of high-dose daptomycin with fosfomycin improved the survival rate of patients with VRE-BSI compared to daptomycin alone. The benefit of the combination was most pronounced for VRE with fosfomycin MIC ≤ 64 mg/l and for patients with a low Pitt bacteremia score.

First trimester pregnancy exposure to fosfomycin and risk of major congenital anomaly: a comparative study in the EFEMERIS database

PURPOSE

Fosfomycin trometamol has been recommended as first-line bactericidal antibiotic for urinary tract infections in pregnant women since 2015 in France. However, studies assessing fosfomycin safety in pregnancy are sparse. This study aimed to assess the risk of major Congenital Anomaly (CA) after fosfomycin exposure during the first trimester of pregnancy.

METHODS

We performed a comparative study in EFEMERIS, the French database including expecting mothers covered by the French Health Insurance System of Haute-Garonne from July 1st, 2004 to December 31th, 2018. EFEMERIS contains prescribed and dispensed reimbursed medications during pregnancy and pregnancy outcomes. Logistic regressions have been conducted to compare three groups: (1) pregnancies exposed at least once to fosfomycin; (2) pregnancies exposed at least once to nitrofurantoin; and (3) pregnancies exposed neither to fosfomycin nor to nitrofurantoin, another antibiotic prescribed for urinary infections, before and during pregnancy.

RESULTS

A total of 2724 (2.0%) pregnant women received at least one fosfomycin prescription during the first trimester, 650 (0.5%) received nitrofurantoin during the first trimester, and 133,502 (97.5%) pregnant women were not exposed to fosfomycin nor to nitrofurantoin. First trimester pregnancy exposure to fosfomycin was not associated with an increased risk of major CA, compared to first trimester exposure to nitrofurantoin (2.0% versus 2.5%; OR_a = 0.80 [0.44-1.47]), or to pregnancies unexposed to fosfomycin and nitrofurantoin (2.0% versus 2.1%; OR_a = 0.97 [0.73-1.30]).

CONCLUSION

This is the first large comparative study assessing fosfomycin safety in pregnancy. It does not exhibit an increased risk of major CA after fosfomycin exposure during the first trimester of pregnancy.

Isolation of Hafnia paralvei co-harbouring blaNDM-1 and blaVIM-1 in a woman who underwent allogeneic hematopoietic stem cell transplantation

Metallo-β-lactamases (MBL) are a threat to public health, since they dramatically limit the use of β-lactams. We report the isolation of a multidrug-resistant Hafnia paralvei strain from urine and a rectal swab of a female patient after allogeneic hematopoietic stem cell transplantation for myelodysplastic syndrome. Antimicrobial susceptibility testing yielded resistance to trimethoprim/sulfamethoxazole, colistin, fosfomycin and all β-lactams, except cefiderocol. Whole genome sequencing revealed the presence of plasmid-encoded NDM-1 and VIM-1 carbapenemases. This finding highlights the importance of epidemiological surveillance and new therapeutic options for MBL.

[Urinary tract infections in older adults: Etiology and antimicrobial susceptibilities in a southern area of Spain]

INTRODUCTION

Urinary tract infection (UTI) is one of the most prevalent diseases in clinical practice and increases in patients older than 65years compared to middle-aged patients. In order to improve empirical treatment, the etiology and antibiotic sensitivity profile of the most frequent bacteria that produce UTIs in older people have been studied.

MATERIAL AND METHODS

Cross-sectional, descriptive and retrospective study in which isolated micro-organisms with significant counts in urine samples from patients with UTI were included. The global etiology and according to sex were analyzed. Only one urine sample per patient and UTI episode was considered.

RESULTS

Regarding the origin of the sample, the highest proportion was in primary care with 4853 urine cultures (51.6% of positive urine cultures), followed by hospital care with 3565 urine cultures (46.4% of positive urine cultures) and 94 urine cultures in nursing homes elderly (2% positive urine cultures). Escherichia coli was the most isolated micro-organism both in the population as a whole (54%) and in each of the analyzed groups. It was observed that E.coli isolated in women was significantly higher than in men (χ², P=.044). Their sensitivity was: 80% fosfomycin and 75% amoxicillin-clavulanic acid.

CONCLUSIONS

E.coli continues to be the most frequently isolated micro-organism in UTI. Empirical treatment of UTI in our environment should include fosfomycin or amoxicillin-clavulanic acid, regardless of the health care unit and gender.

How I manage bacterial prostatitis

BACKGROUND

Bacterial prostatitis is a highly prevalent infection responsible for significant morbidity among men. The diagnosis and treatment for bacterial prostatitis remains complicated. The difficulty in diagnosis is in part owing to the paucity of high-quality evidence that guides a clinician's interpretation of patients' history, physical examination, and laboratory findings. Treatment is challenging because of the few antimicrobials capable of prostate penetration, growing antimicrobial resistance limiting effective treatment options, and the high risk of recurrence.

OBJECTIVES

We aimed to provide a useful resource for clinicians in effectively diagnosing and managing acute bacterial prostatitis (ABP) and chronic bacterial prostatitis (CBP).

SOURCES

A PubMed literature search on prostatitis was performed with no restrictions on publication date.

CONTENT

The epidemiology, pathophysiology, diagnosis, and treatment for ABP and CBP are explored using a clinical vignette as relevant context.

IMPLICATIONS

Bacterial prostatitis can be diagnosed through a focused history and microbiological investigations. The Meares-Stamey 4-glass test or modified 2-glass test can help confirm the diagnosis if uncertainty exists. Typical uropathogens are common contributors to bacterial prostatitis but there is growing interest in exploring the role atypical and traditional non-pathogenic organisms may have. Fluoroquinolones remain first-line therapy, followed by trimethoprim-sulfamethoxazole (TMP-SMX) or doxycycline if the pathogen is susceptible. Fosfomycin has emerged as a repurposed and useful agent because of the increasing incidence of multidrug-resistant pathogens. Selection of appropriate antimicrobial regimens can be challenging and is dependent on the host, chronicity of symptoms, uropathogens' susceptibilities, antimicrobials' side effect profile, and the presence of prostatic abscesses or calcifications. ABP can typically be treated similar to other complicated urinary tract infections. However, CBP requires prolonged therapy, with a minimum of 4 weeks and up to 12 weeks of therapy.

Prescription Pattern of Intravenous Fosfomycin in a Provincial Hospital in Thailand

BACKGROUND

In Thailand, active antibiotics against Gram-negative bacteria are limited. The re-emergence of intravenous (IV) fosfomycin is an alternative. IV fosfomycin has broad-spectrum activity, relative safety, and availability. The limitations of the clinical use of IV fosfomycin include the lack of susceptibility reports and unclear dosing. Therefore, this study was designed to examine the prescription pattern of IV fosfomycin in Chonburi Hospital, a provincial hospital in Thailand.

MATERIALS AND METHODS

A retrospective descriptive study involving in-patients aged ≥18 years who received IV fosfomycin between February 2019 and January 2020. Data were collected from the electronic patient records.

RESULTS

Of 265 patients, 254 (95.8%) and 11 (4.2%) received IV fosfomycin for treatment and prophylaxis, respectively. IV fosfomycin was prescribed for empirical and definitive treatment. All 166 organisms were Gram-negative bacteria (GNB), including Enterobacterales (47.0%), Acinetobacter baumannii (44.0%), and Pseudomonas aeruginosa (9.0%). Moreover, 141 (87.6%) isolates were carbapenem-resistant GNB (CR-GNB). The most commonly used IV fosfomycin regimen contained colistin or aminoglycosides. Furthermore, 35.3% of the combination regimens contained one active antibiotic. The appropriate dosage of IV fosfomycin for treating urinary tract infection was 71.8%. The 14-day all-cause mortality rate in CR-GNB was 45.0%.

CONCLUSION

IV fosfomycin is reserved for secondary use in treating nosocomial infection with resistant GNB. It is used synergistically with other antibiotics. At least one active antibiotic and the optimal fosfomycin dosage should be considered. An antimicrobial stewardship program should be implemented for the optimal use of fosfomycin.

The novel fosfomycin resistance gene fosY is present on a genomic island in CC1 methicillin-resistant Staphylococcus aureus

Fosfomycin has gained attention as a combination therapy for methicillin-resistant Staphylococcus aureus infections. Hence, the detection of novel fosfomycin-resistance mechanisms in S. aureus is important. Here, the minimal inhibitory concentrations (MICs) of fosfomycin in CC1 methicillin-resistant S. aureus were determined. The pangenome analysis and comparative genomics were used to analyse CC1 MRSA. The gene function was confirmed by cloning the gene into pTXΔ. A phylogenetic tree was constructed to determine the clustering of the CC1 strains of S. aureus. We identified a novel gene, designated fosY, that confers fosfomycin resistance in S. aureus. The FosY protein is a putative bacillithiol transferase enzyme sharing 65.9-77.5% amino acid identity with FosB and FosD, respectively. The function of fosY in decreasing fosfomycin susceptibility was confirmed by cloning it into pTXΔ. The pTX-fosY transformant exhibited a 16-fold increase in fosfomycin MIC. The bioinformatic analysis showed that fosY is in a novel genomic island designated RI_fosY (for "resistance island carrying fosY") that originated from other species. The global phylogenetic tree of ST1 MRSA displayed this fosY-positive ST1 clone, originating from different regions, in the same clade. The novel resistance gene in the fos family, fosY, and a genomic island, RI_fosY, can promote cross-species gene transfer and confer resistance to CC1 MRSA causing the failure of clinical treatment. This emphasises the importance of genetic surveillance of resistance genes among MRSA isolates.

Comparison of amikacin with fosfomycin as an add-on to ciprofloxacin for antibiotic prophylaxis in transrectal prostate biopsy: A single-center retrospective study

PURPOSE

To assess the effect of ciprofloxacin (CP) and fosfomycin compared with CP and amikacin in patients with a fluoroquinolone (FQ)-resistant rectal flora who have undergone transrectal ultrasound-guided prostate biopsy (TRUSPB).

MATERIALS AND METHODS

In total, 516 patients with FQ-resistant rectal flora based on rectal swab cultures were divided into two groups according to prophylactic antibiotics. Patients in both groups were administered CP (400 mg, intravenous [IV], twice daily) on the same day as TRUSPB and 1 day after biopsy. The amikacin group (n=260) was administered a single injection of amikacin (1 g, IV) 1 hour before TRUSPB, whereas the fosfomycin group (n=256) was administered fosfomycin (3 g, orally) the night before the procedure. The primary endpoint was the rate of infectious complications in the two groups.

RESULTS

Overall, 13 patients (2.5%) reported infectious complications: 12 patients (4.62%) in the amikacin group compared with 1 patient (0.39%) in the fosfomycin group (risk ratio, 0.09; 95% confidence interval [CI], 0.01-0.65), respectively, which was a statistically significant difference (p=0.017). This corresponds to a number needed to treat of 24 patients (95% CI, 15-65) to prevent one infectious complication. In the multivariate analysis to assess variables related to infectious complications, prophylactic antibiotics with added fosfomycin was associated with infectious complications (odds ratio, 0.060; 95% CI, 0.008-0.459).

CONCLUSIONS

In the era of FQ resistance, CP and fosfomycin may reduce the rate of infectious complications compared with CP and amikacin prophylaxis.

Experimental Clarification of PRPS-1 Structural Essentials

Phosphoribosyl pyrophosphate synthetase-1 (PRPS-1; EC 2.7.6.1.) catalyzes the binding of phosphate-group to ribose 5-phosphate, forming the 5-phosphoribosyl-1-pyrophosphate, which is necessary for the salvage pathways of purine and pyrimidine, pyridine nucleotide cofactors - NAD and NADP, the amino acids histidine and tryptophan biosynthesis. We aimed to investigate the impact of the different effectors on the activity of PRPS-1, to check the activity of the enzyme in vitro in a wide range of pHs and investigate some structural essentials of the enzyme, isolated from brain and liver. Molecular docking analyses were used to delineate the essentials of PRPS-1 structure, to find out the existence of enzyme effectors. Previously created by us kit was used for determination of the activity of PRPS-1 based on the formation of the inorganic phosphates (λ = 700 nm, Cary 60, Agilent, USA). Effectors impact on the activity of PRPS-1 was evaluated. In silico results of the effectors were later proven by in vitro experiments. For the first time biochemical essentials, including the existence of the multiple pockets, involvement of the amino acids into the processes of interactions with the effectors, evolutional of the sequence conservation, tissue depended V_max differences were identified.

Genomic analysis of Fosfomycin resistance in multi-drug resistant uropathogens and comparison of in-vitro susceptibility methods uropathogens

BACKGROUND AND OBJECTIVES

Urinary tract infection is one of the most common bacterial infections causing high morbidity and mortality. The alarming rise of multidrug-resistant uropathogens worldwide forced the clinician to rethink the old drugs like Fosfomycin for its therapeutic management. Our objective was to compare agar dilution, disc diffusion and E-test method for antimicrobial susceptibility testing of Fosfomycin against different drug-resistant uropathogens.

MATERIALS AND METHODS

Consecutive 181 uropathogens were tested for Fosfomycin susceptibility using agar dilution, disc diffusion and E-test. Results were interpreted using Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. Whole genome sequencing analysis was done on the 4 XDR/PDR Fosfomycin resistant Klebsiella pneumoniae isolates.

RESULTS

Escherichia coli was found as the most common (62.4%) uropathogen followed by Klebsiella pneumoniae (21%). Considering agar dilution as the gold standard, 6.1% of isolates were resistant to Fosfomycin. Following CLSI breakpoints, the susceptibility of Escherichia coli, Klebsiella pneumoniae, other Enterobacterales and Pseudomonas aeruginosa were 92.9%, 92.1%, 100%, 100%; whereas using EUCAST breakpoints the susceptibility rates were 85.7%, 86.9%, 92.9%, and 100%, respectively. The essential agreement, categorical agreement, major error, and very major error for E-test/disc diffusion for all the organisms were 91.2%/Not Applicable, 95%/93.9%, 1.8%/4.7%, 9.1%/9.1%, respectively. Whole-genome sequencing showed mutation UhpT gene as well as the presence of plasmid-mediated fosA5 or fosA6 genes conferring Fosfomycin resistance.

CONCLUSION

This result supports very low resistance of Enterobacterales against Fosfomycin; hence should be considered a valuable option to treat multidrug-resistant uropathogens. Disc diffusion was observed to be a convenient method for Fosfomycin susceptibility testing compared to agar dilution.

Resistance to fosfomycin is increasing and is significantly associated with extended-spectrum β-lactamase-production in urinary isolates of Escherichia coli

Fosfomycin has become a therapeutic option in urinary tract infections. Our objective was to evaluate the in vitro activity of fosfomycin against Escherichia coli isolated from urine samples in 2013, 2018 and 2021. We also determined a putative association between fosfomycin resistance and extended-spectrum β-lactamases (ESBL) production. Fosfomycin activity was evaluated against 7367, 8128 and 5072 Escherichia coli urinary isolates in 2013, 2018 and 2021, respectively. We compare the prevalence of fosfomycin-resistant strains among the ESBL- and non-ESBL-producing isolates. MICs of fosfomycin, cefotaxime, and cefotaxime-clavulanate were determined by a microdilution method. 302 ESBL-producers were selected to determine MICs of fosfomycin by agar dilution and genes encoding ESBLs were detected by PCR. Among the total of ESBL-producing strains, 14.3%, 20.8% and 20% were resistant to fosfomycin in 2013, 2018 and 2021, respectively, whereas fosfomycin resistance in non-ESBL producers was 3.5%, 4.05% and 5.53% for each year (P ≤ 0.001). In the 302 selected ESBL-producing isolates, CTX-M was the main ESBL (228 isolates), being 50.7% CTX-M-15. Resistance to fosfomycin among these ESBL-producing strains was associated (P = 0.049) with isolates that produced the CTX-M type. Our data show that fosfomycin resistance is increasing in Escherichia coli urinary isolates and it is related to ESBL-production. A follow-up of fosfomycin resistance is required.

Asp50Glu mutation in MurA results in fosfomycin resistance in Enterococcus faecium

OBJECTIVES

Enterococcus faecium is one of the important pathogens causing nosocomial infection, which can be resistant to fosfomycin by obtaining the plasmid-encoded fosfomycin resistance genes, and the mutation of MurA protein encoded by chromosome is a newly discovered fosfomycin resistance mechanism in recent years.

METHODS

In this study, we found a fosfomycin-resistant clinical isolate of E. faecium Efm_1415 with fosfomycin MIC of 512 mg/L, carrying Asp50Glu mutant of MurA protein, which was never reported before. To study the role and mechanism of this mutant protein in fosfomycin resistance, we used gene cloning, protein expression, and purification, steady-state kinetic, fosfomycin inhibition assay, and next-generation sequencing (NGS) to investigate the functions, characters, and enzymatic kinetic properties of MurA protein.

RESULTS

The results revealed that the Asp50Glu MurA can mediate a 4-fold increase in the fosfomycin MIC of the host bacteria. Compared with the wild-type MurA, the affinity of the Asp50Glu MurA to the substrates was increased, and the enzyme activity cannot be inhibited by the concentration of fosfomycin less than 100 mg/L.

CONCLUSIONS

The research on the mutant MurA had gained a new understanding of the fosfomycin resistance mechanisms and helped to find new antibiotics with MurA enzyme as the target of action.

Characterization of the cobalamin-dependent radical S-adenosyl-l-methionine enzyme C-methyltransferase Fom3 in fosfomycin biosynthesis

Fosfomycin is a clinically used broad-spectrum antibiotic that has the structure of an oxirane ring with a phosphonic acid substituent and a methyl substituent. In nature, fosfomycin is produced by Streptomyces spp. and Pseudomonas sp., but biosynthesis of fosfomycin significantly differs between the two bacteria, especially in the incorporation mechanism of the methyl group. It has been proposed that the cobalamin-dependent radical S-adenosyl-l-methionine (SAM) enzyme Fom3 is responsible for the methyl-transfer reaction in Streptomyces fosfomycin biosynthesis. In this chapter, we describe the experimental methods to characterize Fom3. We performed the methylation reaction with the purified recombinant Fom3, revealing that Fom3 recognizes a cytidylylated 2-hydroxyethylphosphonate as a substrate and catalyzes stereoselective methylation of the sp³ carbon at the C2 position to afford cytidylylated (S)-2-hydroxypropylphosphonate. Reaction analysis using deuterium-labeled substrates showed that the 5'-deoxyadenosyl radical generated by reductive cleavage of SAM stereoselectively abstracts the pro-R hydrogen atom of the CH bond at the C2 position of cytidylylated 2-hydroxyethylphosphonate. Therefore, the C-methylation reaction catalyzed by Fom3 proceeds with inversion of the configuration at the C2 position. Experimental methods to elucidate the chemical structures of the substrate and products and the stereochemical course in the Fom3-catalyzed reaction could give information to progress investigation of cobalamin-dependent radical SAM C-methyltransferases.

Synergistic activity and molecular modelling of fosfomycin combinations with some antibiotics against multidrug resistant Helicobacter pylori

Antibiotic resistance represents the main challenge of Helicobacter pylori infection worldwide. This study investigates the potential bactericidal effects of fosfomycin combinations with clarithromycin, metronidazole, ciprofloxacin, amoxicillin, rifampicin, and doxycycline against thirty-six H. pylori strains using the checkerboard and time-kill assay methods. The results showed that ≥ 50% of the strains were resistant to the six antibiotics. Remarkably, only six strains exerted resistance to these antibiotics, with the minimum inhibitory concentrations (MICs) ranges of (3.2–12.8 mg/l), (32–256 mg/l), (3.2–51.2 mg/l), (3.2–25.6 mg/l), (1.6–3.2 mg/l), and (25.6 > 51.2 mg/l), respectively. The seven antibiotics were evaluated through in silico studies for their permeability and ability to bind UDP-N-acetylglucosamine1-carboxyvinyltransferase (MurA) of H. pylori. The results indicated that fosfomycin exhibited the highest predicted membrane permeability (membrane ∆G insert = − 37.54 kcal/mol) and binding affinity (docking score = − 5.310 kcal/mol) for H. pylori MurA, compared to other tested antibiotics. The combinations of fosfomycin with these antibiotics exerted synergistic interactions (Fractional inhibitory concentration, FIC index < 1) against the six strains. Importantly, the combinations of fosfomycin with clarithromycin, doxycycline and rifampicin achieved bactericidal effects (reduction ≥ 3.0 Log₁₀ cfu/ml) against the most resistant H. pylori strain. Notably, these effects increased with presence of metronidazole, which enhanced the activity of the fosfomycin combination with amoxicillin from a weak inhibition to bactericidal effect. This study provides evidence that the combination of fosfomycin with either clarithromycin, amoxicillin, doxycycline, or rifampicin (especially with the presence of metronidazole) could be a promising option for treating MDR H. pylori infection.

Structural and functional characterization of fosfomycin resistance conferred by FosB from Enterococcus faecium

The Gram-positive pathogen Enterococcus faecium is one of the leading causes of hospital-acquired vancomycin resistant enterococci (VRE) infections. E. faecium has extensive multidrug resistance and accounts for more than two million infections in the United States each year. FosB is a fosfomycin resistance enzyme found in Gram-positive pathogens like E. faecium. Typically, the FosB enzymes are Mn²⁺ -dependent bacillithiol (BSH) transferases that inactivate fosfomycin through nucleophilic addition of the thiol to the antibiotic. However, our kinetic analysis of FosB^Ef shows that the enzyme does not utilize BSH as a thiol substrate, unlike the other well characterized FosB enzymes. Here we report that FosB^Ef is a Mn²⁺ -dependent L-cys transferase. In addition, we have determined the three-dimensional X-ray crystal structure of FosB^Ef in complex with fosfomycin at a resolution of 2.0 Å. A sequence similarity network (SSN) was generated for the FosB family to investigate the unexpected substrate selectivity. Three non-conserved residues were identified in the SSN that may contribute to the substrate selectivity differences in the family of enzymes. Our structural and functional characterization of FosB^Ef establishes the enzyme as a potential target and may prove useful for future structure-based development of FosB inhibitors to increase the efficacy of fosfomycin.

Potential Inhibitors Targeting Escherichia coli UDP-N-Acetylglucosamine Enolpyruvyl Transferase (MurA): An Overview

Antibiotic resistance is one of the biggest challenges that is escalating and affecting humanity across the globe. To overcome this increasing burden of resistance, discovering novel hits by targeting the enzymes involved in peptidoglycan (murein) biosynthesis has always been considered better in antimicrobial drug discovery. UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) enzyme has been identified as essential for Escherichia coli survival and catalyzes the early-stage step in bacterial cell wall synthesis. The present article gives a brief overview of the role of enzymes in peptidoglycan synthesis and MurA enzyme (previously known as MurZ in E. coli), in particular, including its structural and active site features. This review also provides an insight into the current knowledge of the reported MurA inhibitors, their mechanism of action and drawbacks of these hits that hinder their clinical trials, which would be helpful for synthesis and discovering potent molecules.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12088-021-00988-6.

A Real-world Study on Prescription Pattern of Fosfomycin in Critical Care Patients

Background

This study presents a real-world scenario for prescription pattern, efficacy, and safety data on the current clinical use of intravenous fosfomycin in critically ill patients in Indian settings.

Patients and methods

This was a retrospective cohort study conducted for a period of 10 months among critically ill patients admitted to hospital's critical care unit. The primary objective of the study was to analyze the prescription pattern of intravenous fosfomycin, and the secondary objective was to evaluate the safety profile and patient outcomes.

Results

A total of 309 patients were enrolled, and they were diagnosed with bacteremia (45.3%), pneumonia (15.85%), septic shock (14.24%), and urinary tract infections (UTI) (13.91%). The average dose of fosfomycin given was 11.7 ± 4.06 gm/day. The average duration of the therapy was 4.85 ± 3.59 days with a median duration of 4 days. Fosfomycin was given at 8 hourly dosing frequency to maximum (45.6%) cases. Hypokalemia was the most observed adverse event. The overall survival was seen in 55% of patients.

Conclusion

Our data suggest that UTI, infection caused by Escherichia coli, and a daily dose of >12 g were associated with better clinical outcomes. The overall survival of critically ill patients receiving fosfomycin was 55%.

How to cite this article

Zirpe KG, Mehta Y, Pandit R, Pande R, Deshmukh AM, Patil S, et al. A Real-world Study on Prescription Pattern of Fosfomycin in Critical Care Patients. Indian J Crit Care Med 2021;25(9):1055–1058.

Investigation of In-vitro Efficacy of Intravenous Fosfomycin in Extensively Drug-Resistant Klebsiella pneumoniae Isolates and Effect of Glucose 6-Phosphate on Sensitivity Results

BACKGROUND

The aim of this study was to determine the in vitro efficacy of intravenous (IV) fosfomycin against extensively drug-resistant Enterobacterales strains and the effect of glucose 6-phosphate (G6-P) on sensitivity results.

MATERIAL METHOD

Thirty-two extensively drug-resistant Klebsiella pneumonia strains were included in the study. Detection of the carbapenemase genes was performed using the Gene-Xpert® System Carba R® kit. Susceptibility of IV fosfomycin was assessed using the agar dilution method. The agar dilution method was repeated using Muller-Hinton Agar medium without G6-P to assess the effect of G6-P on sensitivity results.

RESULTS

All strains in the study produced carbapenemases and were resistant to all drugs tested, including carbapenems, piperacillin-tazobactam, ceftriaxone, and ceftazidime. Fosfomycin resistance was detected in 3 (9.3%) strains. When the sensitivity test was repeated without G6-P, fosfomycin resistance was detected in 82.7% of the fosfomycin-susceptible strains. The Gene-Xpert® System showed NDM-1 in 46.8%, OXA-48 in 18.7%, KPC in 3.1%, and NDM-1 + OXA-48 in 21.8% of the strains. OXA-48 was detected in one of the resistant strains, and none of the viable genes were detected in two of the resistant strains.

CONCLUSION

This study shows that IV fosfomycin is a potentially important treatment alternative for infections caused by common resistant strains. Accurate results may not be obtained unless G6-P is used in the agar dilution method for in vitro susceptibility studies of fosfomycin.

Antimicrobial Susceptibilities of Urinary Extended-spectrum β-lactamase Escherichia coli to Fosfomycin

Objectives

Escherichia coli (E. coli)-induced urinary tract infection (UTI) is a common infection associated with frequent use of antibiotics and the increase in global antibiotic resistances. We aimed to determine the susceptibility profile of extended-spectrum β-lactamase (ESBL) producing E. coli isolated from the urinary samples to fosfomycin and other antibiotics.

Methods

We retrospectively analyzed urine samples with ESBL-producing E. coli isolates obtained between January 2018 and December 2019 in the Microbiology Section, Salmaniya Medical Complex, Bahrain. We collected and analyzed all the E. coli urinary isolates' data and their antibiotic susceptibility patterns.

Results

The study included 3044 E. coli isolates with 50.6% obtained in 2018 and 49.4% in 2019; 38.1% (1161 isolates) were ESBL E. coli, and 0.7% (21 isolates) were carbapenem-resistant ^{Enterobacteriaceae} (CRE). There were 1161 (38.1%) isolates with ESBL-producing E. coli, with 37.3% isolated in 2018 and 39.0% isolated in 2019. The antibiotic susceptibility of ESBL-producing E. coli during the study period showed susceptibility to trimethoprim/sulfamethoxazole in 46.1% of isolates (50.2% in 2018 dropped to 41.9% in 2019), to ciprofloxacin in 49.0% of isolates (49.5% in 2018 dropped to 48.4% in 2019), to nitrofurantoin in 91.8% of isolates (94.3 in 2018 dropped to 89.3% in 2019), and to fosfomycin in 97.6% of isolates (98.8% in 2018 dropped to 96.3% in 2019).

Conclusions

ESBL-producing E. coli is an important cause of UTI in Bahrain. Fosfomycin is a very effective oral antimicrobial that retains high efficacy against ESBL-producing E. coli, which helps decrease the need for parenteral therapy and, consequently, hospitalization.

Antimicrobial Susceptibilities of Urinary Extended-spectrum β-lactamase Escherichia coli to Fosfomycin

OBJECTIVES

Escherichia coli (E. coli)-induced urinary tract infection (UTI) is a common infection associated with frequent use of antibiotics and the increase in global antibiotic resistances. We aimed to determine the susceptibility profile of extended-spectrum β-lactamase (ESBL) producing E. coli isolated from the urinary samples to fosfomycin and other antibiotics.

METHODS

We retrospectively analyzed urine samples with ESBL-producing E. coli isolates obtained between January 2018 and December 2019 in the Microbiology Section, Salmaniya Medical Complex, Bahrain. We collected and analyzed all the E. coli urinary isolates' data and their antibiotic susceptibility patterns.

RESULTS

The study included 3044 E. coli isolates with 50.6% obtained in 2018 and 49.4% in 2019; 38.1% (1161 isolates) were ESBL E. coli, and 0.7% (21 isolates) were carbapenem-resistant ^{Enterobacteriaceae} (CRE). There were 1161 (38.1%) isolates with ESBL-producing E. coli, with 37.3% isolated in 2018 and 39.0% isolated in 2019. The antibiotic susceptibility of ESBL-producing E. coli during the study period showed susceptibility to trimethoprim/sulfamethoxazole in 46.1% of isolates (50.2% in 2018 dropped to 41.9% in 2019), to ciprofloxacin in 49.0% of isolates (49.5% in 2018 dropped to 48.4% in 2019), to nitrofurantoin in 91.8% of isolates (94.3 in 2018 dropped to 89.3% in 2019), and to fosfomycin in 97.6% of isolates (98.8% in 2018 dropped to 96.3% in 2019).

CONCLUSIONS

ESBL-producing E. coli is an important cause of UTI in Bahrain. Fosfomycin is a very effective oral antimicrobial that retains high efficacy against ESBL-producing E. coli, which helps decrease the need for parenteral therapy and, consequently, hospitalization.

Comparison of a combined regimen of fosfomycin and ciprofloxacin with ciprofloxacin alone as antimicrobial prophylaxis for transrectal prostate biopsy in the era of high fluoroquinolone-resistant rectal flora

Background

To assess the prophylactic effect of fosfomycin (FM) and ciprofloxacin combinations for infectious complications of transrectal ultrasound-guided prostate biopsy (TRUSPB) compared to that of ciprofloxacin alone.

Methods

In total, 1,578 patients were enrolled and were divided into two groups according to the prophylactic antibiotics. Group 1 (n = 1234) received ciprofloxacin on the day of the biopsy and for an additional 1–2 days, whereas Group 2 (n = 334) was given FM in addition to ciprofloxacin in the same manner as Group 1. The primary outcome was overall infectious complications within 1 month of TRUSPB. The secondary outcome was the risk factors of infectious complications after TRUSPB.

Results

Infectious complications occurred in 31 patients (2.5%) and 1 patient (0.3%) in Groups 1 and 2, respectively. Our results indicated that fluoroquinolone (FQ) and FM significantly reduced the risk of infectious complications compared to FQ (relative risk: 0.12; 95% confidence interval 0.02–0.87, P = 0.015). Based on the multivariate analysis, previous antibiotic exposure (odds ratio [OR] = 3.59, P = 0.026), and the addition of FM (OR = 0.12, P = 0.038) were associated with infectious complications. Based on the rectal swab, FQ resistance was 28.0% (n = 294) in total. FQ resistance in the FQ and FM group was higher than that in the FQ group (n = 178, 54.9% vs. n = 116, 16.0%, P < 0.001).

Conclusion

The combination of ciprofloxacin and FM exhibited reduced infectious complications after TRUSPB compared with ciprofloxacin monotherapy and may be applicable in the era of the high abundance of FQ-resistant rectal flora.

Synthesis and evaluation of fosfomycin group end-capped packing materials for hydrophilic interaction liquid chromatography

Hydrophilic interaction liquid chromatography (HILIC) plays an important role in the analysis of compounds having high polarity. In this study, fosfomycin (F) was chosen as a new end-capping reagent, owing to the facile hydrolysis reaction of its epoxy group. Zirconia coated silica (ZrO₂/SiO₂) materials having good chemical and physical stability were prepared. D-glucose-6-phosphate (G) and D-fructose1,6-bisphosphate (FDP) were modified onto the inner and outer surfaces of the ZrO₂/SiO₂ microbeads. The new end-capping reagent (F) was then bonded onto the surface of the modified material through Lewis acid-base interactions. The properties (morphology, Zr content, pore size, pore volume, and carbon content) of the stationary phases (SPs) were characterized. Finally, the resulting end-capped SPs were employed to separate alkaloids and benzoic acids. Multiple interactions, including HILIC, electrostatic repulsion, ion exchange and hydrogen bonding, contributed to the retention of the analytes on the SPs. On the F-FDP-ZrO₂/SiO₂ column, a theoretical plate number of 31,700 plates/m and an asymmetry factor of 1.63 were achieved for berberine, exhibiting good chromatographic performance. Furthermore, the FDP-ZrO₂/SiO₂ column showed good acid-base stability and good potential for the analysis of benzoic acid in Sprite and ginsenoside separations. Thus, the results indicated the significant potential of using F as an end-capping reagent.

Efficacy and safety of intravenous fosfomycin for the treatment of difficult-to-treat Gram-negative bacterial infections

We reviewed the efficacy and safety of intravenous (IV) fosfomycin for the treatment of infections caused by Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR). Data were retrospectively retrieved for all hospitalized patients who received IV fosfomycin for ≥48 h for the treatment of a DTR GNB between September 27, 2017 and January 31, 2020. A total of 30 patients were included, of which 63.3% were males, and the median age was 63.5 years (IQR 46-73). The median Charlson Comorbidity Score was 6 (IQR 3.8-9). The urinary tract (56.7%) was the most frequent site of infection, and the most frequent target organisms were Klebsiella pneumoniae (56.7%), and Escherichia coli (23.3%). The majority (76.%) received IV fosfomycin in combination with other antibacterial agents. Clinical improvement was observed in 22 (73.3%), eradication of baseline pathogens in 20 (66.7%), 30-day all-cause mortality in 7 (23.3%), and documented emergent resistance to fosfomycin in 5 (16.7%) patients. Treatment-related adverse events were infrequent and generally mild or moderate in severity. In conclusion, IV fosfomycin is a potentially efficacious and safe treatment option for the treatment of DTR GNB infections. Randomized trials are urgently required to confirm the utility of IV fosfomycin as monotherapy and in combination with other agents.