Oral fosfomycin for treatment of urinary tract infection: a retrospective cohort study

Skipped wells and scientific error during fosfomycin agar dilution and broth microdilution lead to inconsistent minimal inhibitory concentrations and may be cause for reevaluating testing methods for Klebsiella pneumoniae

Despite the first-line recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are pressing barriers for optimizing its use for the treatment of non-Escherichia coli Enterobacterales UTI. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for minimal inhibitory concentration (MIC) determination is largely impractical. Using 160 clinical Klebsiella pneumoniae isolates, we sought to understand rates of skipped wells and MIC imprecision in broth microdilution (BMD) and how that compares to rates of error using AD. Though the Clinical and Laboratory Standards Institute refers to the skipped well phenomena in their recommendation against the use of BMD, there is a paucity of data on its frequency. While AD and BMD produced similar MIC50/90 values (32/256 µg/mL for AD and 64/256 µg/mL for BMD), essential agreement was poor. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells at a given concentration, as the most frequent scientific error. Growth in concentrations above the measured MIC occurred in up to 3.3% of wells and was seen within three dilutions of the MIC for BMD. Observation of single colonies either at or beyond the measured MIC for AD was also common and occurred up to 8.3% and 2.5% of the time, respectively. The frequent scientific error in both testing methods should prompt re-evaluation of AD guidelines and expansion of MIC testing methods for fosfomycin susceptibility testing, as poor agreement with another method prone to scientific error should not be the main detractor from BMD use.IMPORTANCEDespite the recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are barriers for optimizing its use. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for MIC determination is largely impractical. The use of broth microdilution (BMD) for fosfomycin testing is not recommended by the Clinical and Laboratory Standards Institute due to unsatisfactory precision and skipped wells-occurrence of no-growth in a single well before the minimal inhibitory concentration (MIC)-and trailing endpoints. We sought to understand rates of skipped wells and growth at concentrations above measured MICs in BMD and how that compares to scientific error using AD. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells for BMD and single colonies at or beyond measured MICs for AD were also common. Frequent scientific error in both methods should prompt re-evaluation of both AD and BMD for fosfomycin susceptibility testing.

The Prevalence of Multidrug-Resistant Escherichia coli in Chennai and Whole Genome Sequence Analysis of Carbapenem-Resistant Escherichia coli ST410

The current study evaluates antibiotic susceptibility and Extended Spectrum β-Lactamase (ESBL) production of 557 Escherichia coli isolates obtained from clean catch midstream urine samples using VITEK 2 compact automated microbial identification system. Different classes of drugs were used to determine the Minimum inhibitory concentration (MIC). In our study, 50.45% of isolates were ESBL producers. There is a higher incidence of UTI in females (77.4%) than in males (22.6%). The isolates reveal a high percentage of resistance to antibiotics like nalidixic acid (89.59%), ampicillin (75.76%), ticarcillin (73.43%), cefalotin (67.68%), cefixime (65.17%), ciprofloxacin (58.35%) and ceftriaxone (56.37%). An increased susceptibility pattern was observed for the isolates against drug classes like fosfomycin (98.03%) and nitrofurantoin (91.02%). Among the isolates, 395 (70.91%) were classified as Multidrug-resistant organisms based on the resistance pattern observed against three or more classes of antibiotics. One of the isolates resistant to fluoroquinolones, penicillins, penicillins along with β-lactamase inhibitor, aminoglycosides, third-generation cephalosporins and carbapenems was subjected to Whole genome sequencing (WGS). WGS data revealed the isolate to be a high-risk clone ST410, which contains antimicrobial-resistance genes (blaTEM-1B, blaCTX-M-15, blaNDM-5, aac(3)-IId, armA, gyrA(p.S83L), gyrA(p.D87N)) conferring resistance to β-lactam, cephalosporins, carbapenem, aminoglycoside and fluoroquinolone class of antibiotics. The core genome MLST was carried out using BacWGSTdb to assess the global phylogenetic relationship of the genome sequence.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01125-1.

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.

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.

Nitrofurantoin: properties and potential in treatment of urinary tract infection: a narrative review

Nitrofurantoin (NF), a wide-spectrum antibiotic accessible since 1953, is utilized widely to treat urinary tract infections as it usually stays active against drug-resistant uropathogen. The use of Nitrofurantoin has increased exponentially since new guidelines have repositioned it as first-line therapy for uncomplicated lower urinary tract infection (UTI). To, although fluoroquinolones are usually used to re-evaluate the first- and second-line therapies for treating uncomplicated UTI, their level of utilization is thought to be inappropriately excessive and will eventually have a detrimental impact; thus, we hypothesize that NF might be the best choice for this condition, because of its low frequency of utilization and its high susceptibility in common UTI pathogens. It can be concluded from this review that NF can be considered as the most effective drug in the treatment of acute urinary infection, but due to the long-term side effects of this drug, especially in elderly patients, it is essential to introduce some criteria for prescribing NF in cases of chronic UTI.

Efficacy of Single Dose of Fosfomycin Versus a Five-Day Course of Ciprofloxacin in Patients With Uncomplicated Urinary Tract Infection

Introduction and objective: Treatment has become more challenging due to an aging population, polypharmacy and high prevalence of comorbid illness, antimicrobial antibiotic allergy or sensitivity, an increase in the number of individuals with underlying immunological or structural abnormalities, as well as the frequency of multidrug-resistant infections. Many multidrug-resistant bacteria are still susceptible to nitrofurantoin and fosfomycin, two ancient medicines. Their high urine concentrations and low toxicity give them an advantage over newer medications. This study aimed to compare the efficacy of a single dose of fosfomycin versus a five-day course of ciprofloxacin in patients with uncomplicated urinary tract infections.

Methodology and data collection procedure: This randomized control trial was conducted in the Department of Medicine, Benazir Bhutto Hospital, Rawalpindi. A total of 46 patients were enrolled. Patients were divided randomly into two groups by using the lottery method. In group A, patients were given a single 3 g dose of oral fosfomycin. In group B, patients were given oral ciprofloxacin (500 mg) daily for five days. Then patients were followed-up in the Outpatient Department (OPD) for 28 days. After 28 days, patients were evaluated for resolution of symptoms (as per operational definition). Patients in whom symptoms would not be resolved were managed as per standard protocol. All this information was recorded on proforma.

Results: The average age of the patients in group A was 39.41±9.80 years while in group B that was 41.32±17.76 years. In both groups, 23 females were equally divided. The mean duration of symptoms in group A was 4.78±1.98 days while in group B was 4.95±1.29 days. The minimum duration of symptoms was three days and the maximum was 10 days. In group A, there were 15 (65.21%) patients with efficacy achieved, and among eight (34.78%) patients, efficacy was not achieved while in group B, there were 15 (65.21%) patients in which efficacy was achieved, and among eight (34.78%) patients, efficacy was not achieved. There was no significant association between efficacy and study groups as the p-value was not significant (p=0.87). 

Conclusion: The conclusion of the study was that in the treatment of simple urinary infections, a single dose of fosfomycin had equal efficacy and tolerability as a five-day course of ciprofloxacin.

Efficacy and Safety of Oral Fosfomycin-Trometamol in Male Urinary Tract Infections with Multidrug-Resistant Enterobacterales

Background: Antimicrobial drugs to treat male urinary tract infection (UTI) with multidrug-resistant Enterobacterales are limited. We studied oral fosfomycin-trometamol (FT) in this situation. The objective was to assess the clinical cure rate in patients presenting UTIs treated with oral FT. Methods: We conducted a single-center observational retrospective study from January 2017 to August 2018. The primary endpoint was clinical cure; and the secondary endpoints were incidence of recurrences, oral FT safety, and microbiological cure. Results: Sixteen male patients were included, presenting 21 UTI episodes. Fourteen patients (88%) have at least one underlying urologic disorder. We described 4 episodes of acute UTI and 17 episodes of chronic bacterial prostatitis (CBP). Sixteen out of twenty-one Enterobacterales were extended spectrum beta-lactamase (ESBL)-producers and all the patients presented a resistance to fluoroquinolones and trimethoprim/sulfamethoxazole. In acute UTI, the regimen was a daily dose of oral FT for a mean duration of 2.5 weeks (+/−7.0 days). Clinical and microbiological recovery was achieved in all patients, with no recurrence after 5.3 months follow-up on average (+/−10.4 days). In CBP, the regimen was one oral dose of fosfomycin every 24–48 h, for a mean duration of 5.5 weeks/UTI episodes (+/−15.3 days). Clinical and microbiological recovery was found in 16/17 cases. Seven of the twelve patients with CBP had relapsed and 3/12 had had a new episode of infection after an average follow-up of 5.8 months. Only 6/21 of patients presented minor or moderate adverse effects, such as digestive disorders. Conclusions: FT could be an alternative option to carbapenems in the treatment of multidrug-resistant Enterobacterales infections for male UTIs.

Antibiotic resistance pattern of uropathogenic Escherichia coli isolated from children with symptomatic urinary tract infection in Moscow, Russia

Background and Aim: Uropathogenic Escherichia coli (UPEC) is commonly involved in urinary tract infections (UTIs), which are generally treated with antibiotics. However, the emergence of multidrug-resistant (MDR) strains of UPEC has made the treatment difficult. There is thus a need to continuously assess their sensitivity to antibiotics. This study aimed to determine the antibiotic resistance patterns and MDR phenotypes of UPEC strains isolated from children diagnosed with UTIs at the Russian Children's Clinical Hospital in Moscow, Russia. Materials and Methods: Kirby–Bauer's disc diffusion method was used to study the sensitivity to antibiotics of 106 UPEC isolates from urine specimens from children (aged from 9 months to 18 years old) diagnosed with UTIs. The results were interpreted in accordance with the Clinical and Laboratory Standards Institute guidelines and the correlations of variables with the degree to which each antibiotic inhibited the UPEC strains in terms of diameter on the disc were determined using Spearman's rank correlation test. A t-test and principal component analysis were performed to visualize the correlations of the susceptibility of UPEC to antibiotics with the age and sex of the patients. Statistical significance was set at p≤0.05. Results: Among the 106 UPEC strains tested, none (0%) showed resistance to fosfomycin (FO), while 84 (79.2%) were resistant (R) to at least one antibiotic. The highest rates of resistance were observed to amoxicillin (69.8%), ampicillin (62.3%), cefazolin (39.6%), trimethoprim (TR) (37.7%), ceftriaxone (34.9%), and tetracycline (33.0%). Interestingly, 22 (20.8%) strains were R to imipenem. UPEC isolates from males aged 1-6 years were more R to antibiotics than those from the other groups, with the exception of TR, to which UPEC isolates from females aged 13-18 years old were less sensitive (S). The multidrug-resistance (MDR) index ranged between 0.00 and 0.75 and we found that more than a quarter of UPEC (31/106) had an MDR index ≥0.5 and only 22 (20.7%) strains were S to all antibiotics tested (MDR index=0). Finally, Spearman's rank correlation test showed that, with the exception of FO, there were correlations between the inhibition diameters of all other antibiotics. Conclusion: FO is the only antibiotic to which all UPECs were S and may be suggested as the first line of treatment for UPEC. Further research is needed to continue monitoring antibiotic resistance and to investigate the genetic features associated with such resistance observed in this study.

Predisposition of Blood group Non-secretors to Urinary tract infection with Escherichia coli Anti-microbial Resistance and Acute Kidney Injury

Urinary tract infection (UTI) causes significant renal damage and disease severity is compounded by antimicrobial resistance (AMR) and other comorbidities in the patient. Blood group antigens secreted in body fluids (secretor status) are known to play a role in bacterial adhesion and we studied its influence on AMR in UTI. A total of 2758 patients with UTI were studied with urine culture, qualitative and semiquantitative urine microscopy, serum creatinine and secretor status in saliva samples by adsorption-inhibition method. Of these, AMR from 300 patients with E. coli infection were assessed as per CLSI 2019 guidelines and extended-spectrum beta-lactamase (ESBL) genes (bla TEM, bla CTX-M, bla SHV) and NDM1 genes were studied using TaqMan probes in Real-time polymerase chain reaction. Patients with UTI were followed up for two weeks. Female patients had higher predilection (57%) for E. coli infection while patients with diabetes or non-secretors had none. In our study, ESBL producers were seen in 62% of the E. coli isolates and fosfomycin had 100% susceptibility. Non-secretors were significantly associated with acute kidney injury (AKI), AMR and ESBL genes. Multidrug-resistance (MDR) was noted in 127/160 (79.4%) ESBL and 17/18 (94%) NDM1 gene encoding strains. Quantitative urine microscopy scoring predicted AKI both at presentation and at end of follow up. ESBL producers were common in our study population and non-secretors had a significant association with AMR genes. Urine microscopy scoring system may be a useful tool to predict AKI in patients with UTI.

Predisposition of Blood group Non-secretors to Urinary tract infection with Escherichia coli Anti-microbial Resistance and Acute Kidney Injury

Urinary tract infection (UTI) causes significant renal damage and disease severity is compounded by antimicrobial resistance (AMR) and other comorbidities in the patient. Blood group antigens secreted in body fluids (secretor status) are known to play a role in bacterial adhesion and we studied its influence on AMR in UTI. A total of 2758 patients with UTI were studied with urine culture, qualitative and semiquantitative urine microscopy, serum creatinine and secretor status in saliva samples by adsorption-inhibition method. Of these, AMR from 300 patients with E. coli infection were assessed as per CLSI 2019 guidelines and extended-spectrum beta-lactamase (ESBL) genes (bla TEM, bla CTX-M, bla SHV) and NDM1 genes were studied using TaqMan probes in Real-time polymerase chain reaction. Patients with UTI were followed up for two weeks. Female patients had higher predilection (57%) for E. coli infection while patients with diabetes or non-secretors had none. In our study, ESBL producers were seen in 62% of the E. coli isolates and fosfomycin had 100% susceptibility. Non-secretors were significantly associated with acute kidney injury (AKI), AMR and ESBL genes. Multidrug-resistance (MDR) was noted in 127/160 (79.4%) ESBL and 17/18 (94%) NDM1 gene encoding strains. Quantitative urine microscopy scoring predicted AKI both at presentation and at end of follow up. ESBL producers were common in our study population and non-secretors had a significant association with AMR genes. Urine microscopy scoring system may be a useful tool to predict AKI in patients with UTI.

Fosfomycin susceptibility of uropathogens at Charlotte Maxeke Johannesburg Academic Hospital

Background

Multidrug-resistant uropathogens are becoming widespread both in community and hospital setting. Safe yet effective treatments are a priority. Fosfomycin is an antibacterial that displays good activity against most bacteria causing urinary tract infections (UTIs), including multidrug-resistant bacteria. The aim of this study was to evaluate fosfomycin susceptibility for uropathogens isolated from a microbiology laboratory at a tertiary academic hospital. In addition, this was compared to the susceptibility of other oral antimicrobials.

Methods

We conducted a retrospective analysis of laboratory reports for uropathogens isolated at Charlotte Maxeke Johannesburg Academic Hospital from September 2015 to August 2017. Antimicrobial susceptibility testing of the isolates was performed using the Kirby–Bauer disk diffusion method or the Vitek^® 2 system according to the Clinical and Laboratory Standards Institute.

Results

Overall susceptibility of fosfomycin for the 4700 Enterobacteriaceae isolates was 95.7%; 95% confidence interval (CI) 95.1–96.2. The overall susceptibility for fosfomycin against the gram-positives was 98.6%. There were 37.9% multidrug-resistant Enterobacteriaceae (MDRE) isolated during the study period. Fosfomycin displayed activity against 94.4% of extended-spectrum β-lactamase (ESBL) producers and 90.7% for carbapenem-resistant Enterobacteriaceae (CRE). None of the methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus isolates tested was fosfomycin resistant. The overall in vitro susceptibility was significantly higher for fosfomycin (p = 0.0001) compared to amoxicillin/clavulanic acid, cephalexin, cefuroxime, ciprofloxacin, trimethoprim/sulfamethoxazole and nitrofurantoin.

Conclusion

This study confirmed the high susceptibility of fosfomycin against UTI pathogens isolated at our institution. In an era of increasing antimicrobial resistance, fosfomycin represents a potential option for the treatment of UTIs at Charlotte Maxeke Johannesburg Academic Hospital.

Fosfomycin versus Nitrofurantoin for the Treatment of Lower UTI in Outpatients

Introduction Fosfomycin and nitrofurantoin are increasingly being prescribed in outpatients for the oral treatment of urinary tract infection (UTI). Although ample literature is available on the in vitro sensitivity pattern of fosfomycin and nitrofurantoin in UTI cases, clinical data are scant.

Methodology  Voided midstream urine, collected from patients ≥ 16 years of age of both genders with suspected sign and symptoms, was plated on cystine lactose electrolyte-deficient agar. Uropathogen was defined as an organism known to be associated with the signs and symptoms of UTI with > 10 ⁵ colony forming units/mL of urine. Antimicrobial susceptibility testing was determined by Kirby-Bauer disc diffusion method. Further, for fosfomycin, agar dilution method was also performed.

Results  A total of 143 patients, 47 treated with fosfomycin and 96 with nitrofurantoin, were followed for clinical outcome. The most common isolated uropathogen was Escherichiacoli . In vitro susceptibility rate of uropathogens against fosfomycin and nitrofurantoin was 99.3% and 81.2%, respectively. Overall, the clinical cure rate with fosfomycin and nitrofurantoin treatment groups was 80.85% and 90.06% respectively (not statistically significant).

Conclusion  Fosfomycin and nitrofurantoin showed good in vitro activity against uropathogens from lower UTI and can be used for empirical therapy in our area. Multiple confounding factors may have contributed to the discrepancy between in vitro susceptibility and clinical cure, which needs to be studied further.

Pharmacokinetic/pharmacodynamic analysis of oral fosfomycin against Enterobacterales, Pseudomonas aeruginosa and Enterococcus spp. in an in vitro bladder infection model: impact on clinical breakpoints

OBJECTIVES

Fosfomycin is an established treatment for uncomplicated urinary tract infections (UTIs), yet evidence supporting susceptibility breakpoints is limited. We examine the UTI susceptibility criteria.

METHODS

Fosfomycin susceptibility, heteroresistance and in vitro growth in a bladder infection model, after a single 3 g dose of oral fosfomycin, were bridged to human pharmacokinetics with pharmacokinetic/pharmacodynamic and Monte Carlo analyses. Data from common uropathogens (24 Escherichia coli, 20 Klebsiella pneumoniae, 4 Enterobacter cloacae, 14 Pseudomonas aeruginosa, 8 Enterococcus faecalis and 8 Enterococcus faecium) were compared and analysed to ascertain species-specific PTA.

RESULTS

Glucose-6-phosphate (G6P) increased MICs of E. coli, K. pneumoniae and E. cloacae (median 2-fold dilutions 3-5), but not of P. aeruginosa and Enterococcus. Atypical E. coli lacking G6P potentiation were killed in the bladder infection model despite high MICs (32-128 mg/L). Fosfomycin heteroresistance was uncommon in E. coli (MIC > 2 mg/L) but was detected in the majority of K. pneumoniae (MIC > 1 mg/L) and P. aeruginosa (MIC >8 mg/L). For these species, baseline heteroresistance was a strong predictor for treatment failure in the model. No heteroresistance was found in Enterococcus. The fAUC/MIC targets for stasis were 1935, 3393, 9968, 2738 and 283 for typical E. coli, K. pneumoniae, E. cloacae, P. aeruginosa and E. faecalis, respectively (synthetic human urine medium alone promoted a 1 log10 kill in E. faecium). A >95% PTA for stasis was only found at MIC ≤ epidemiological cut-off (ECOFF) for E. coli (4 mg/L). For other species, PTAs were low for WT populations.

CONCLUSIONS

With the exception of E. coli, fosfomycin is a poor target for other uropathogen species. A reduction in oral fosfomycin UTI breakpoints is supported.

Fosfomycin and nitrofurantoin: classic antibiotics and perspectives

Antibiotics are essential molecules for the treatment and prophylaxis of many infectious diseases. However, drugs that combat microbial infections can become a human health threat due to their high and often indiscriminate consumption, considered one of the factors of antimicrobial resistance (AMR) emergence. The AMR crisis, the decrease in new drug development by the pharmaceutical industry, and reduced economic incentives for research have all reduced the options for treating infections, and new strategies are necessary, including the return of some traditional but "forgotten" antibiotics. However, prescriptions for these older drugs including nitrofurantoin and oral fosfomycin, have been based on the results of pioneer studies, and the limited knowledge generated 50-70 years ago may not be enough. To avoid harming patients and further increasing multidrug resistance, systematic evaluation is required, mainly for the drugs prescribed for community-acquired infections, such as urinary tract infections (UTI). Therefore, this review has the objective of reporting the use of two classic drugs from the nitrofuran and phosphonic acid classes for UTI control nowadays. Furthermore, we also explore new approaches used for these antibiotics, including new combination regimes for spectral amplification, and the prospects for reducing bacterial resistance in the fight against bacteria responsible for UTI.

Characteristics of fosA-carrying plasmids in E. coli and Klebsiella spp. isolates originating from food and environmental samples

OBJECTIVES

Fosfomycin is an important antibiotic for the treatment of MDR Enterobacteriaceae infections. High susceptibility rates are, however, threatened by the spread of plasmids encoding fosfomycin-modifying enzymes. In this study, we sought to characterize the genetic context of fosA in plasmids from Escherichia coli and Klebsiella spp. isolates recovered from food, wastewater and surface water in Switzerland.

METHODS

E. coli and Klebsiella spp. isolates collected between 2012 and 2019 in Switzerland were screened for fosfomycin resistance. Presence of fosA was verified by PCR and sodium phosphonoformate (PPF) disc potentiation testing, and transferability was tested using conjugation assays. Whole-genome sequences including complete fosA-containing plasmids were determined using long- and short-read sequencing.

RESULTS

In 11 E. coli and two Klebsiella spp. isolates, high-level fosfomycin resistance was mediated by plasmids containing fosA3 (n = 12) or fosA8 (n = 1). Four isolates harboured a near-identical 45 kb IncN plasmid with fosA3, while replicon types varied in the remaining plasmids. The fosA genes were typically embedded in IS26-bounded transposition units and frequently located in the proximity of blaCTX-M transposition units.

CONCLUSIONS

Although fosfomycin resistance rates are currently low, the presence of fosA-encoding plasmids circulating in the Enterobacteriaceae population suggests that fosfomycin resistance may rapidly spread upon increased selection pressure. Transposition mobility of fosA and co-location on plasmids with other resistance genes may further promote its dissemination.

Oral fosfomycin for treating lower urinary tract infections due to multidrug-resistant Escherichia coli in female adolescents

Fosfomycin trometamol (FT) has shown promising in vitro activity against multidrug-resistant (MDR) uropathogens; however, clinical data are limited in pediatric patients. We conducted a retrospective study to describe the clinical and microbiological outcomes of uncomplicated lower urinary tract infections (LUTIs) due to MDR Escherichia coli treated with oral FT in female adolescents. A total of 70 outpatients, with a median age of 13 years (range 12-16 years), were included. FT was initiated as definitive treatment of UTIs in all patients due to documented resistance against alternative oral agents. All patients received a single dose of 3 g oral FT. The post-treatment clinical and microbiological cure rates were 97% (68/70) and 94% (66/70), respectively. Only two (3%) patients reported mild, self-limited diarrhea. UTI relapse occurred in two (3%) patients. Our results suggest that oral FT might be an alternative option for outpatient treatment of uncomplicated LUTIs due to MDR E. coli in female adolescents.

Unraveling Mechanisms and Epidemic Characteristics of Nitrofurantoin Resistance in Uropathogenic Enterococcus faecium Clinical Isolates

Purpose

Multidrug-resistant (MDR) Enterococcus faecium is an important nosocomial pathogen causing urinary tract infection, and the reapplication of nitrofurantoin (NIT) in the clinic has attracted great attention. This study aims to explore the NIT resistance mechanisms and epidemiological characteristics of E. faecium clinical isolates.

Patients and Methods

A total of 633 E. faecium clinical isolates was obtained from urine samples in a clinical teaching hospital during 2017–2018. Among them, 40 NIT-resistant strains, and a similar number of -intermediate and -susceptible strains were isolated. The minimum inhibitory concentrations (MICs) of NIT were detected by agar dilution method. The prevalence and mutations of nitroreductase-encoding genes ef0404 and ef0648 were explored by polymerase chain reaction (PCR), followed by efflux pump inhibition test and quantitative real-time PCR (qRT-PCR) to investigate the resistance mechanisms of NIT. Furthermore, the epidemiological characteristics were detected by multilocus sequence typing (MLST).

Results

The carrying rates of nitroreductase in NIT-susceptible, -intermediate, and -resistant isolates were 100%, 50%, and 20%, respectively. After exposure to the efflux pump inhibitor, the MIC of 12 E. faecium decreased by ≥4-fold. However, the efflux pump genes efrAB, emeA, and oqxAB were not overexpressed in NIT-resistant E. faecium isolates. Moreover, MLST analysis revealed that all the NIT-resistant isolates belonged to CC17, of which 30 (75%) were associated with ST78.

Conclusion

This study has established for the first time that the absence of EF0404 and EF0648 is the main mechanism of NIT resistance in E. faecium. Our findings are likely to fill the knowledge gap pertaining to the NIT resistance mechanism in E. faecium and provide important insights for molecular epidemiological characteristics analysis.

A Pattern of Antibiotic Resistance in Gram-Negative Rods Causing Urinary Tract Infection in Adults

Background and aim Gram-negative rods (GNR) are the most common pathogens associated with urinary tract infections (UTI). The resistance of these gram-negative rods to various antibiotics is increasing with time. The study aimed to determine the pattern of resistance to antibiotics in GNR causing urinary tract infection in adults. Material and methods This is a cross-sectional study conducted during six months (1st December 2019 to 1st June 2020) among adult patients admitted to Russells Hall Hospital Dudley, UK. Urine cultures of 156 patients admitted with urinary tract infection were collected and reviewed. Sources of urine included midstream urine (MSU), catheter specimen urine (CSU), and others from nephrostomy bags and urine bags. Sensitivity and resistance were checked using Clinical and Laboratory Standards Institute (CLSI) guidelines. Results were analyzed using SPSS version 13.  Results Altogether 156 patients were included in the study. Males were 40.4% of the patients were males, and 59.6% were females. The mean age was 78 with a standard deviation (SD) of 13.15. Most of the samples (67.3%) were urine MSU, 23.1% catheter urine, and 9.6% were others, like from nephrostomy bags or unspecified. Resistance to amoxicillin was found in 61.7%, trimethoprim in 36.2%, nitrofurantoin in 13.2%, ciprofloxacin in 25.6%, fosfomycin in 10.7%, co-amoxiclav in 36.2%, gentamicin in 12.8%, piperacillin-tazobactam in 7.1%, cephalexin in 44.4%, and meropenem in 0% of patients. Conclusion Resistance to gram-negative rods causing urinary tract infection is increasing; a particular concern is increased resistance to beta-lactams, trimethoprim, and quinolones.

Impact of reflex fosfomycin susceptibility testing on the utilization of carbapenems for definitive extended-spectrum β-lactamase Escherichia coli urinary tract infection treatment

Purpose

A protocol was started within a large health system to automatically test all confirmed extended-spectrum beta-lactamase (ESBL)–producing Escherichia coli urine isolates for susceptibility to fosfomycin, an antibiotic not routinely included in such testing in most institutions. This study assessed the effectiveness of the protocol at reducing carbapenem use for the definitive treatment of ESBL E. coli urinary tract infection (UTI) through several endpoints.

Methods

Eighty and 99 patients were compared pre- and postintervention, respectively. The primary outcome was the proportion of patients who received definitive carbapenem therapy. Key secondary outcomes included median total carbapenem days of therapy (DOT), discharge on intravenous UTI antibiotics, and median total antibiotic DOT.

Results

Preprotocol vs postprotocol definitive carbapenem use was seen in 59 of 80 patients (73.8%) and 71 of 99 patients (71.7%) (95% confidence interval [CI] for difference, -11.1% to 15.1%; P = 0.76). The rates of step-down to oral agents pre- and postintervention were 15 of 59 (25.4%) and 35 of 71 (49.3%) (P = 0.004). Median carbapenem DOT in those receiving carbapenems decreased from 8 to 4 days (95% CI, -5 to -1 days; P = 0.001). Median total DOT decreased from 10 to 8 days (95% CI, -3 to -1 days; P = 0.002).

Conclusion

Implementation of a laboratory policy to automatically test ESBL positive E. coli for fosfomycin susceptibility did not reduce the percentage of patients receiving at least 1 dose of carbapenem treatment. It did result in a larger percentage reduction in step-down use of intravenous antibiotics for UTI prior to discharge, reduction in carbapenem DOT, and reduction in total antibiotic DOT.

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

Streptomyces from traditional medicine: sources of new innovations in antibiotic discovery

Given the increased reporting of multi-resistant bacteria and the shortage of newly approved medicines, researchers have been looking towards extreme and unusual environments as a new source of antibiotics. Streptomyces currently provides many of the world's clinical antibiotics, so it comes as no surprise that these bacteria have recently been isolated from traditional medicine. Given the wide array of traditional medicines, it is hoped that these discoveries can provide the much sought after core structure diversity that will be required of a new generation of antibiotics. This review discusses the contribution of Streptomyces to antibiotics and the potential of newly discovered species in traditional medicine. We also explore how knowledge of traditional medicines can aid current initiatives in sourcing new and chemically diverse antibiotics.

Oral and Intravenous Fosfomycin for the Treatment of Complicated Urinary Tract Infections

Oral fosfomycin is approved in Canada for the treatment of acute uncomplicated cystitis. Several studies have reported “off label” use of oral fosfomycin in the treatment of patients with complicated lower urinary tract infection (cLUTI). This review summarizes the available literature describing the use of oral fosfomycin in the treatment of patients with cLUTI. Collectively, these studies support the use of a regimen of 3 grams of oral fosfomycin administered once every 48 or 72 hours for a total of 3 doses for patients who have previously failed treatment with another agent, are infected with a multidrug-resistant (MDR) pathogen, or cannot tolerate first-line treatment due to intolerance or adverse effects. Additionally, a Phase 2/3 clinical trial, known as the ZEUS study, assessed the efficacy and safety of intravenous (IV) fosfomycin versus piperacillin-tazobactam in the treatment of patients with complicated upper urinary tract infection (cUUTI) or acute pyelonephritis (AP) including in patients with concomitant bacteremia. IV fosfomycin was reported to be noninferior to piperacillin-tazobactam in treating patients with cUUTI and AP; however, when outcomes were independently evaluated according to baseline diagnosis (i.e., cUUTI versus AP), IV fosfomycin was superior to piperacillin-tazobactam in the treatment of patients with cUUTI and demonstrated superior microbiological eradication rates, across all resistant phenotypes including extended-spectrum β-lactamase- (ESBL-) producing Escherichia coli and Klebsiella spp. and carbapenem-resistant (CRE), aminoglycoside-resistant, and MDR Gram-negative bacilli (primarily Enterobacterales). Based on the ZEUS study, IV fosfomycin dosed at 6 grams every 8 hours for 7 days (14 days in patients with concurrent bacteremia) appears to be a safe and effective therapeutic option in treating patients with upper urinary tract infections, particularly those with cUUTI caused by antimicrobial-resistant Enterobacterales.

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.

Prediction of trimethoprim/sulfamethoxazole resistance in community-onset urinary tract infections

OBJECTIVES

This study aimed to predict trimethoprim/sulfamethoxazole (SXT) resistance in patients with community-onset urinary tract infection (UTI) due to Enterobacteriaceae based on patient-specific risk factors.

METHODS

This was a retrospective case-control study in Prisma Health facilities in central South Carolina, USA, including three community hospitals, affiliated emergency departments and ambulatory clinics, including adult patients with community-onset UTI due to Enterobacteriaceae (1 April 2015 to 29 February 2016). Multivariate logistic regression was used to examine risk factors for SXT resistance.

RESULTS

Among 351 unique patients with community-onset UTI, 71 (20.2%) had SXT-resistant Enterobacteriaceae urinary isolates. Overall, median age was 64 years and 252 (71.8%) were female. A multivariate model identified prior urinary infection/colonisation with SXT-resistant Enterobacteriaceae (OR=8.58, 95% CI 3.92-18.81; P<0.001) and SXT use within past 12 months (OR=2.58, 95% CI 1.13-5.89; P=0.02) as predictors of SXT resistance among urinary isolates. Most patients with UTI (285; 81.2%) had no risk factors for SXT resistance. SXT resistance rates increased from 13% in the absence of risk factors to 31% in patients with prior SXT use, 66% in those with prior urinary infection/colonisation with SXT-resistant Enterobacteriaceae and 73% in the presence of both risk factors.

CONCLUSION

SXT resistance in Enterobacteriaceae urinary isolates may be predicted based on prior urine culture results and SXT use within the previous year. Utilisation of a patient-specific antibiogram may allow empirical SXT use in patients with community-onset UTI in the absence of risk factors for resistance.

Treatment of urinary tract infections in the era of antimicrobial resistance and new antimicrobial agents

Urinary tract infections (UTIs) caused by antibiotic-resistant Gram-negative bacteria are a growing concern due to limited treatment options. Knowledge of the common uropathogens in addition to local susceptibility patterns is essential in determining appropriate empiric antibiotic therapy of UTIs. The recommended first-line empiric antibiotic therapy for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females is a 5-day course of nitrofurantoin, a 3-g single dose of fosfomycin tromethamine, or a 5-day course of pivmecillinam. High rates of resistance for trimethoprim-sulfamethoxazole and ciprofloxacin preclude their use as empiric treatment of UTIs in several communities, particularly if patients who were recently exposed to them or in patients who are at risk of infections with extended-spectrum β-lactamases (ESBLs)-producing Enterobacteriales. Second-line options include oral cephalosporins such as cephalexin or cefixime, fluoroquinolones and β-lactams, such as amoxicillin-clavulanate. Current treatment options for UTIs due to AmpC- β -lactamase-producing Enterobacteriales include nitrofurantoin, fosfomycin, pivmecillinam, fluoroquinolones, cefepime, piperacillin-tazobactam and carbapenems. Treatment oral options for UTIs due to ESBLs-E coli include nitrofurantoin, fosfomycin, pivmecillinam, amoxicillin-clavulanate, finafloxacin, and sitafloxacin while pivmecillinam, fosfomycin, finafloxacin, and sitafloxacin are treatment oral options for ESBLs- Klebsiella pneumoniae. Parenteral treatment options for UTIs due to ESBLs-producing Enterobacteriales include piperacillin-tazobactam (for ESBL-E coli only), carbapenems including meropenem/vaborbactam, imipenem/cilastatin-relebactam, and sulopenem, ceftazidime-avibactam, ceftolozane-tazobactam, aminoglycosides including plazomicin, cefiderocol, fosfomycin, sitafloxacin, and finafloxacin. Ceftazidime-avibactam, meropenem/vaborbactam, imipenem/cilastatin-relebactam, colistin, fosfomycin, aztreonam and ceftazidime-avibactam, aztreonam and amoxicillin-clavulanate, aminoglycosides including plazomicin, cefiderocol, tigecycline are treatment options for UTIs caused by carbapenem-resistant Enterobacteriales (CRE). Treatment options for UTIs caused by multidrug resistant (MDR)-Pseudomonas spp. include fluoroquinolones, ceftazidime, cefepime, piperacillin-tazobactam, carbapenems including imipenem-cilastatin/relebactam, meropenem, and fosfomycin, ceftolozane-tazobactam, ceftazidime-avibactam, aminoglycosides including plazomicin, aztreonam and ceftazidime-avibactam, cefiderocol, and colistin. It is important to use the new antimicrobials wisely for treatment of UTIs caused by MDR-organisms to avoid resistance development.

An in vitro experimental study of the effect of fosfomycin in combination with amikacin, ciprofloxacin or meropenem on biofilm formation by multidrug-resistant urinary isolates of Escherichia coli

Background. This study was conducted to understand the effect of fosfomycin in combination with amikacin, ciprofloxacin or meropenem on biofilm formation by multidrug-resistant urinary isolates of Escherichia coli.Methods. Fifty urinary tract multidrug-resistant E. coli isolates that were known biofilm producers were studied. The MIC was determined using the agar dilution method for amikacin, ciprofloxacin, meropenem and fosfomycin. The fractional inhibitory concentration was determined for the combination of antibiotics followed by a time-kill assay. A tissue culture plate method was used to study the effect of the combination of antibiotics on biofilm formation.Results. The MICs of the isolates tested ranged from 0.25 to 32 µg ml^-1 for fosfomycin, 1 to 1024 µg ml^-1 for ciprofloxacin, 4 to 1024 µg ml^-1 for amikacin, and 0.25 to 512 µg ml^-1 for meropenem. The combination of fosfomycin with meropenem showed 68 % synergy, fosfomycin with amikacin 58 % synergy and fosfomycin with ciprofloxacin 6 % synergy. The combination also reduced the MIC of each antibiotic and none showed an antagonistic effect. Biofilm inhibition was best observed with the combination of fosfomycin with meropenem.Conclusion. The combination of fosfomycin with amikacin and fosfomycin with meropenem yielded a high percentage of synergy alongside an increased capacity to reduce biofilm formation when compared to combination with ciprofloxacin against multidrug-resistant E. coli. Fosfomycin in combination with other classes of antimicrobial agents has potential beneficial effects.

Shortening duration of ertapenem in outpatient parenteral antimicrobial therapy for complicated urinary tract infections: A retrospective study

Background

The incidence of multi-drug resistant ESBL-associated urinary tract infections (UTIs) is increasing globally. Patients with abnormal renal tract anatomy and other co-morbidities are at increased risk of complicated UTI and ESBL-associated infections. The duration and safety of OPAT for this cohort of patients is unknown.

Objectives

This study aims to provide an evidence base to support decision-making regarding duration of antibiotic treatment for complicated UTIs.

Methods

We retrospectively reviewed all patients receiving ertapenem with or without adjunctive fosfomycin for complicated UTIs in the OPAT service of our tertiary infectious diseases hospital. All data had been collected prospectively as part of routine clinical care. Our primary outcomes were microbiological and clinical cure of UTI.

Results

We identified 33 treatment episodes of ertapenem use for UTIs. 76% episodes related to pyelonephritis or urosepsis diagnoses. Renal tract abnormalities or prior urological surgery were present in 45% of patients. The median duration of appropriate parenteral antibiotic therapy in our study was 6 days. Clinical cure was achieved with short-course parenteral treatment alone in 81% of patients and this increased to 96% when adjunctive fosfomycin was used. There was a single treatment failure resulting in hospital admission.

Conclusions

Short duration ertapenem via OPAT with or without adjunctive fosfomycin is safe and effective for the treatment of complicated UTIs. Further studies are required to inform optimal treatment strategies and publication of guidelines in this field.

Fosfomycin for treatment of multidrug-resistant pathogens causing urinary tract infection: A real-world perspective and review of the literature

Among 47 patients with urinary tract infections (UTIs) due to multidrug-resistant (MDR) bacteria, treatment with fosfomycin resulted in clinical cure rates of 87% and 94% at 48 hours and 14 days, respectively. Response rates did not vary across pathogens. Our retrospective, observational findings support fosfomycin treatment against MDR pathogens causing UTIs.

Experience with fosfomycin in the treatment of complicated urinary tract infections caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae

Background

The aim of this study was to evaluate the efficacy of fosfomycin in the treatment of complicated urinary tract infections (cUTIs) caused by extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae.

Methods

We retrospectively evaluated 42 ambulatory patients with cUTIs caused by ESBL-producing Enterobacteriaceae at the Outpatient Internal Medicine Clinic of the University Clinical Hospital Centre Zagreb in the period from June 2012 to June 2014. ESBL production was confirmed by double disk synergy test according to Jarlier. In vitro susceptibility to fosfomycin of ESBL-producing Escherichia coli, Klebsiella pneumoniae and Citrobacter freundii isolates was tested according to the European Committee on Antimicrobial Susceptibility Testing methodology.

Results

In 42 patients with cUTIs, 43 urinary pathogens susceptible to fosfomycin were isolated in the urine cultures, including 34 E. coli ESBL, seven K. pneumoniae ESBL and two C. freundii ESBL isolates. On average, patients had 2.2 complicating factors (CFs) and received 3.6 fosfomycin doses per treatment course. The overall microbiological cure was 50%, clinical cure was 71% and ESBL eradication rate was 74%. Patients with between zero and one CFs received significantly fewer fosfomycin doses than patients with two or more CFs (p = 0.022). Three kidney transplant patients achieved microbiological cure following prolonged fosfomycin administration. No statistically significant correlation was found between the presence of individual CFs and treatment outcome.

Conclusions

Fosfomycin may be a valid option for oral treatment of cUTIs caused by ESBL-producing pathogens. The optimal duration of fosfomycin treatment for cUTIs remains to be determined.

Fosfomycin efficacy and emergence of resistance among Enterobacteriaceae in an in vitro dynamic bladder infection model

Background

Urinary tract infections (UTIs) are among the most common bacterial infections and a frequent indication for antibiotic use. Fosfomycin, an important oral antibiotic for outpatient UTIs, remains a viable option for MDR uropathogens. We aimed to perform pharmacodynamic profiling simulating urinary concentrations to assess the adequacy of the current dosing regimen.

Methods

A dynamic in vitro bladder infection model was developed, replicating urinary fosfomycin concentrations after gastrointestinal absorption, systemic distribution and urinary elimination. Concentrations were measured by LC-MS/MS. Twenty-four Enterobacteriaceae strains (Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae; MIC range 0.25-64 mg/L) were examined. Pathogen kill and emergence of resistance was assessed over 72 h.

Results

Observed in vitro fosfomycin concentrations accurately simulated urinary fosfomycin exposures (Tmax 3.8 ± 0.5 h; Cmax 2630.1 ± 245.7 mg/L; AUC0-24 33 932.5 ± 1964.2 mg·h/L). Fifteen of 24 isolates regrew, with significant rises in fosfomycin MIC (total population MIC50 4 to 64 mg/L, MIC90 64 to > 1024 mg/L, P = 0.0039; resistant subpopulation MIC50 128 to > 1024 mg/L, MIC90 >1024 mg/L, P = 0.0020). E. coli and E. cloacae isolates were killed with pharmacokinetic/pharmacodynamic EI50 of fAUC0-24/MIC = 1922, fCmax/MIC = 149 and fTime>4×MIC = 44 h. In contrast, K. pneumoniae isolates were not reliably killed.

Conclusions

Using dynamic in vitro simulations of urinary fosfomycin exposures, E. coli and E. cloacae isolates with MIC >16 mg/L, and all K. pneumoniae isolates, were not reliably killed. Emergence of resistance was significant. This challenges fosfomycin dosing and clinical breakpoints, and questions the utility of fosfomycin against K. pneumoniae. Further work on in vitro dose optimization is required.

Fosfomycin trometamol vs ciprofloxacin for antibiotic prophylaxis before transrectal ultrasonography-guided prostate biopsy: A meta-analysis of clinical studies

Objectives: To perform a systematic review and meta-analysis of clinical studies to assess the comparative prophylactic effectiveness of fosfomycin trometamol (FMT) vs ciprofloxacin (CIP) in men who underwent transrectal ultrasonography-guided prostate needle biopsy (TRUS-PNB), as infectious complications are a major concern after TRUS-PNB and although fluoroquinolones are currently the first choice, an increase in resistance has raised the question about its recommendation and FMT is a broad-spectrum oral antibiotic with low bacterial resistance.

Methods: A systematic review was performed between January 1970 and June 2017 using the Web of Science, Scopus and PubMed databases to identify relevant studies. Preferred Reporting Items for Systematic Reviews and Meta-analysis criteria were used for article selection. Outcomes of interest were febrile and afebrile urinary tract infections (UTIs) and the presence of fluoroquinolone-resisitant (FQR)- or extended-spectrum β-lactamase (ESBL)-producing uropathogens in urinary cultures.

Results: Four studies including 2331 men were analysed; 1088 had FMT and 1243 CIP as antibiotic prophylaxis before TRUS-PNB. FMT prophylaxis resulted in significantly less afebrile (odds ratio [OR] 0.21, 95% confidence interval [CI] 0.12–0.38; P < 0.001) and febrile (OR 0.15, 95% CI 0.07–0.31; P < 0.001) UTIs than CIP. Amongst all urine cultures, patients in the FMT arm also had a significantly lower prevalence of FQR and ESBL (E. coli or K. pneumoniae) microorganisms when compared to the CIP group (OR 0.25, 95% CI 0.12–0.21, P = 0.001; and OR 0.24, 95% CI 0.10–0.58, P = 0.001, respectively).

Conclusions: Antibiotic prophylaxis with FMT before TRUS-PNB was associated with lower rates of infectious complications when compared to CIP.

Abbreviations: CIP: ciprofloxacin; ESBL: extended-spectrum β-lactamase; FMT: fosfomycin trometamol; FQR: fluoroquinolone-resisitant; OR: odds ratio; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses; TRUS-PNB: TRUS-guided prostate needle biopsy

Fosfomycin tromethamine activity on biofilm and intracellular bacterial communities produced by uropathogenic Escherichia coli isolated from patients with urinary tract infection

Fosfomycin tromethamine (FT), an old antibiotic revived as a new strategy to overcome antibiotic resistance, is an excellent option for the treatment of lower urinary tract infection (UTI). During UTI, Escherichia coli produces biofilms and could invade the bladder epithelial cells, developing intracellular bacterial communities (IBC). The present work aimed to evaluate the activity of FT on biofilms and IBC from clinical isolates of E. coli. A total of 38 E. coli clinical UTI isolates previously characterized as biofilm and IBC producers were studied. FT susceptibility was evaluated and its activity on 48 h biofilm was determined by microtiter plate-based biofilm assay comparing three different antibiotic concentrations. Two UPEC strains were selected to evaluate FT activity on IBC in vitro using T24 bladder cells. The survival percentage of intracellular bacteria after 24 h exposure to FT was calculated and compared to the percentage of intracellular bacteria without antibiotic. All the strains were susceptible to FT. FT produced a significant reduction of biofilms at the three concentrations tested, compared to the control. However, no statistically effect on IBC was observed after 24 h of fosfomycin exposure in cell culture. FT is a good option for bacterial biofilm reduction within UTI. However, it does not affect IBC.

High Rates of Fosfomycin Resistance in Gram-Negative Urinary Isolates from Israel

BACKGROUND

Increasing antimicrobial resistance is a major problem worldwide. Many urinary tract infection (UTI) isolates are resistant to all oral antimicrobial agents, necessitating intravenous treatment even for cystitis. Fosfomycin is a broad-spectrum antibiotic that achieves high and prolonged urinary drug concentration and is considered first-line treatment for uncomplicated cystitis. Our aim was to investigate fosfomycin susceptibility among urinary isolates and search for demographic or bacterial characteristics associated with fosfomycin nonsusceptibility.

MATERIALS AND METHODS

This is a retrospective study of all Gram-negative urinary isolates at Padeh-Poriya Medical Center in northern Israel. A total of 1503 isolates were tested for fosfomycin susceptibility, as well as susceptibility to other antimicrobial agents, by VITEK2 system and disk diffusion testing. Demographic and clinical data were obtained from patient electronic files.

RESULTS

A total of 1,503 isolates from patients' urine were included. Mean patient age was 64.6 years, 937 (62.3%) were female, 913 (60.7%) were Jews, and in 1,058 (70.4%) cases, the infection was community acquired; 28.1% were extended-spectrum beta lactamase (ESBL)-positive. A total of 1099 (73.1%) isolates were susceptible to fosfomycin. Fosfomycin nonsusceptibility was significantly correlated to year: 124 (20.7%) in 2015 versus 280 (30.9%) in 2016; patient age: 17.6% in patients ≤50 years versus 30% in patients >50 years; hospital-acquired UTI: 34.2% versus 23.8%; and presence of ESBL positivity: 31.1% in ESBL-positive versus 20.9% in ESBL-negative isolates (p for all <0.001).

CONCLUSIONS

Fosfomycin nonsusceptibility among urine culture isolates is a worrisome phenomenon that is on the rise and is more often found in elderly patients, patients with nosocomial UTI, and isolates that are ESBL positive.

Nitrofurantoin and fosfomycin for resistant urinary tract infections: old drugs for emerging problems

Uncomplicated urinary tract infection is one of the most common indications for antibiotic use in the community However the Gram-negative organisms that can cause the infection are becoming more resistant to antibiotics

Many multidrug resistant organisms retain susceptibility to two old antibiotics nitrofurantoin and fosfomycin Advantages over newer drugs include their high urinary concentrations and minimal toxicity

Fosfomycin is a potential treatment option for patients with uncomplicated urinary tract infection due to resistant organisms Nitrofurantoin may be more effective and can be used for urinary infections in pregnant women

Fosfomycin Permeation through the Outer Membrane Porin OmpF

Fosfomycin is a frequently prescribed drug in the treatment of acute urinary tract infections. It enters the bacterial cytoplasm and inhibits the biosynthesis of peptidoglycans by targeting the MurA enzyme. Despite extensive pharmacological studies and clinical use, the permeability of fosfomycin across the bacterial outer membrane is largely unexplored. Here, we investigate the fosfomycin permeability across the outer membrane of Gram-negative bacteria by electrophysiology experiments as well as by all-atom molecular dynamics simulations including free-energy and applied-field techniques. Notably, in an electrophysiological zero-current assay as well as in the molecular simulations, we found that fosfomycin can rapidly permeate the abundant Escherichia coli porin OmpF. Furthermore, two triple mutants in the constriction region of the porin have been investigated. The permeation rates through these mutants are slightly lower than that of the wild type but fosfomycin can still permeate. Altogether, this work unravels molecular details of fosfomycin permeation through the outer membrane porin OmpF of E. coli and moreover provides hints for understanding the translocation of phosphonic acid antibiotics through other outer membrane pores.

Antimicrobial resistance and treatment: an unmet clinical safety need

INTRODUCTION

Infections due to multidrug-resistant (MDR) bacteria are burdened by high mortality rates. The development of new compounds to face the global threat of resistance is urgently needed. Combination regimens including "old" high-dose antimicrobials are currently limited by the risk of toxicity, resistance selection, and reduced efficacy. Following the Infectious Diseases Society of America call to develop 10 new antibacterials by 2020, new molecules are currently under development or have become available for use in clinical practice.

AREAS COVERED

We have reviewed safety characteristics and tolerability of old antimicrobials that are currently employed in combination regimens as well as new antimicrobials, including beta-lactams/beta-lactamase inhibitors, new cephalosporins, quinolones, and aminoglycosides.

EXPERT OPINION

The availability of new compounds that show in vitro efficacy against MDR represents a unique opportunity to face the threat of resistance and to optimize the current use of antimicrobials, potentially reducing toxicity. Agents that are potentially active against MDR Gram-negatives are ceftozolane/tazobactam, new carbapenems and cephalosporins, the combination of avibactam with ceftazidime, and plazomicin. Further data from clinical trials and post-marketing studies for drugs targeting MDR pathogens are crucial to confirm their efficacy and safety.

Genomic insights into nitrofurantoin resistance mechanisms and epidemiology in clinical Enterobacteriaceae

Aim:

Multidrug-resistant enterobacteria are highly associated with invasive devices and intensive care units. Increasing resistance to carbapenems is leading to the use of older and neglected antibiotics such as nitrofurantoin (NFT). The genomics of NFT resistance was investigated.

Results & conclusion:

High-level resistance to NFT (minimum inhibitory concentration ≥128–512 mg/l) was recorded in 31/36 isolates (89.6%), many of which were from intensive care units (n = 20), urine (n = 17) or invasive procedures (n = 10). Efflux pump inhibitors had little effect on NFT's minimum inhibitory concentrations albeit oqxAB was prevalent in most isolates (n = 32). Various species- and clone-specific mutations mediating high-level NFT resistance were detected in nfsA, nfsB and ribE proteins through comparative genomics. Global phylogenomics showed local and independent emergence of NFT resistance in Enterobacteriaceae. NFT stewardship is advised.

Nitrofurantoin (NFT) is an important antibiotic indicated for uncomplicated urinary tract infections. Resistance to NFT is slow and uncommon, making it an important drug for treating urinary tract infections resistant to common and last-resort antibiotics such as cephalosporins, fluoroquinolones, aminoglycosides and carbapenems. Increasing resistance to most antibiotics among uropathogens makes NFT a key choice for clinicians. Thus, the high-level NFT resistance in extradrug- and pandrug-resistant uropathogens found in this study is exceptionally worrying as treatment options will be extremely limited. Mutations in nfsA, nfsB and ribE genes in the same and different strains emerged locally and independently to confer NFT resistance.

The challenge of urinary tract infections in renal transplant recipients

Urinary tract infections (UTI) are an important cause of morbidity and mortality in renal transplant patients. These infections are quite common, and the goal of care is to identify and reduce risk factors while providing effective prophylaxis and treatment. Better understanding of long-term outcomes from these infections has led to the distinctions among UTI, recurrent UTI, and asymptomatic bacteriuria (ASB), and that each requires a different therapeutic approach. Specifically, new research has supported the perspective that asymptomatic bacteriuria should not be treated. Symptomatic UTI, on the other hand, requires intervention and remains an ongoing challenge for infectious disease clinicians. Many bacteria species are responsible for UTI in renal transplant patients, and in recent years there has been a global rise in infection caused by bacteria with newly acquired antibacterial resistance genes. Many renal transplant patients who experience UTI will also have multiple recurring episodes, which likely has a distinct pathophysiological mechanism leading to chronic colonization of the urinary tract. In these cases, long-term management includes bacterial suppression, which aims to reduce rather than eliminate bacteria to levels below the threshold for symptomatic infection. This review will address the current understanding of UTI epidemiology, pathogenesis, and risk factors in the renal transplant community, and also focus on current prevention and treatment strategies for patients who face an environment of increasingly antibiotic-resistant bacteria.

Community-acquired Lower Urinary Tract Infections: Etiology, Antimicrobial Resistance, and Treatment Results in Female Patients

Background/Purpose:

Most community-acquired urinary tract infections (UTIs) are usually treated empirically. The knowledge of antibiotic resistance patterns of the microorganisms causing UTI is essential for defining the empirical treatment.

Objective:

The aim of the present study is to determine the distribution of bacterial strains isolated from lower UTIs and their resistance patterns against commonly used antimicrobial agents and treatment results in female patients.

Subjects and Methods:

This is a retrospective analysis of medical case records of 90 female patients with lower UTI for a period of 4 years from January 2013 to December 2016 in a tertiary care hospital in the Trakya region of Turkey.

Results:

The most common causative agent was Escherichia coli (66.6% of cases) followed by Klebsiella pneumoniae (16.6%). Fosfomycin was the most active agent against E. coli (resistant isolates: 5.5%), followed by nitrofurantoin (resistant isolates: 7.4%). Extended-spectrum beta-lactamases (ESBLs) production was observed in 29 (32.2%) isolates (22 in E. coli, 6 in K. pneumoniae, and 1 in Enterobacter spp.). The antimicrobial resistance rates among ESBL-producing E. coli isolates for trimethoprim-sulfamethoxazole, ciprofloxacin, fosfomycin, and nitrofurantoin were 77.7%, 72.7%, 13.6%, and 18.2%, respectively (P < 0.05). The estimated microbiological eradication rates for nitrofurantoin and fosfomycin were 89.7% and 83.8%, respectively.

Conclusions:

The results of the present study indicate that nitrofurantoin and fosfomycin may be considered for empirical therapy of lower UTIs in Trakya region of Turkey.

ESBL-producing Escherichia coli and Its Rapid Rise among Healthy People

Since around the 2000s, Escherichia coli (E. coli) resistant to both oxyimino-cephalosporins and fluoroquinolones has remarkably increased worldwide in clinical settings. The kind of E. coli is also identified in patients suffering from community-onset infectious diseases such as urinary tract infections. Moreover, recoveries of multi-drug resistant E. coli from the feces of healthy people have been increasingly documented in recent years, although the actual state remains uncertain. These E. coli isolates usually produce extended-spectrum β-lactamase (ESBL), as well as acquisition of amino acid substitutions in the quinolone-resistance determining regions (QRDRs) of GyrA and/or ParC, together with plasmid-mediated quinolone resistance determinants such as Qnr, AAC(6')-Ib-cr, and QepA. The actual state of ESBL-producing E. coli in hospitalized patients has been carefully investigated in many countries, while that in healthy people still remains uncertain, although high fecal carriage rates of ESBL producers in healthy people have been reported especially in Asian and South American countries. The issues regarding the ESBL producers have become very complicated and chaotic due to rapid increase of both ESBL variants and plasmids mediating ESBL genes, together with the emergence of various "epidemic strains" or "international clones" of E. coli and Klebsiella pneumoniae harboring transferable-plasmids carrying multiple antimicrobial resistance genes. Thus, the current state of ESBL producers outside hospital settings was overviewed together with the relation among those recovered from livestock, foods, pets, environments and wildlife from the viewpoint of molecular epidemiology. This mini review may contribute to better understanding about ESBL producers among people who are not familiar with the antimicrobial resistance (AMR) threatening rising globally.

Pharmacodynamic Evaluation of Fosfomycin against Escherichia coli and Klebsiella spp. from Urinary Tract Infections and the Influence of pH on Fosfomycin Activities

Fosfomycin is widely used for the treatment of uncomplicated urinary tract infection (UTI), and it has recently been recommended that fosfomycin be used to treat infections caused by multidrug-resistant (MDR) Gram-negative bacilli. Whether urine acidification can improve bacterial susceptibility to fosfomycin oral dosing regimens has not been analyzed. The MIC of fosfomycin for 245 Gram-negative bacterial isolates, consisting of 158 Escherichia coli isolates and 87 Klebsiella isolates which were collected from patients with urinary tract infections, were determined at pH 6.0 and 7.0 using the agar dilution method. Monte Carlo simulation of the urinary fosfomycin area under the concentration-time curve (AUC) after a single oral dose of 3,000 mg fosfomycin and the MIC distribution were used to determine the probability of target attainment (PTA). Fosfomycin was effective against E. coli (MIC₉₀ ≤ 16 μg/ml) but not against Klebsiella spp. (MIC₉₀ > 512 μg/ml). Acidification of the environment increased the susceptibility of 71% of the bacterial isolates and resulted in a statistically significant decrease in bacterial survival. The use of a regimen consisting of a single oral dose of fosfomycin against an E. coli isolate with an MIC of ≤64 mg/liter was able to achieve a PTA of ≥90% for a target pharmacodynamic index (AUC/MIC) of 23 in urine; PTA was not achieved when the MIC was higher than 64 mg/liter. The cumulative fractions of the bacterial responses (CFR) were 99% and 55% against E. coli and Klebsiella spp., respectively, based on simulated drug exposure in urine with an acidic pH of 6.0. A decrease of the pH from 7.0 to 6.0 improved the PTA and CFR of the target pharmacodynamic index in both E. coli and Klebsiella isolates.

The Potential Role of Fosfomycin in Neonatal Sepsis Caused by Multidrug-Resistant Bacteria

The broad-spectrum activity of fosfomycin, including against multidrug-resistant (MDR) strains, has led to renewed interest in its use in recent years. Neonatal sepsis remains a substantial cause of morbidity and mortality at a global level, with evidence that MDR bacteria play an increasing role. The evidence for use of fosfomycin in neonatal subjects is limited. We summarise current knowledge of the pharmacokinetics and clinical outcomes for the use of fosfomycin in neonatal sepsis and issues specific to neonatal physiology. While fosfomycin has a broad range of coverage, we evaluate the extent to which it may be effective against MDR bacteria in a neonatal setting, in light of recent evidence suggesting it to be most effective when administered in combination with other antibiotics. Given the urgency of clinical demand for treatment of MDR bacterial sepsis, we outline directions for further work, including the need for future clinical trials in this at-risk population.