Fosfomycin

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 (MIC 90 ≤ 16 μg/ml) but not against Klebsiella spp. (MIC 90 > 512 μg/ml). Acidification of the e...

KPC-producingKlebsiella pneumoniaecauses serious infections associated with high death rates worldwide. Combination therapy consisting of fosfomycin and a carbapenem is better than monotherapy to combat multidrug-resistant microorganisms, but no dosages for the combination have been defined. The MICs of meropenem and fosfomycin were evaluated against 18 clinical isolates of KPC-2-producingK. pneumoniae. The activities of combination antimicrobials were also determined by the checkerboard method. The MIC50and MIC90of each agent alone and in combination were challenged against short (1.5-h) or prolonged (3-h) infusion regimens of meropenem (1 g every 8 h [q8h], 1.5 g q6h, 2 g q8h) and fosfomycin (4 g q8h, 6 g q6h, 8 g q8h) by Monte Carlo simulation to evaluate the time above the MIC of the free drug concentration as a percentage of the dosing interval (fT>MIC). The monotherapy MIC50s and MIC90s were 32 and 256 mg/liter for meropenem and 64 and 512 mg/liter for fosfomycin, respectiv...

FosB is a divalent-metal-dependent thiol-S-transferase implicated in fosfomycin resistance among many pathogenic Gram-positive bacteria. In the present paper, we describe detailed kinetic studies of FosB from Staphylococcus aureus (SaFosB) that confirm that bacillithiol (BSH) is its preferred physiological thiol substrate. SaFosB is the first to be characterized among a new class of enzyme (bacillithiol-S-transferases), which, unlike glutathione transferases, are distributed among many low-G+C Gram-positive bacteria that use BSH instead of glutathione as their major low-molecular-mass thiol. The Km values for BSH and fosfomycin are 4.2 and 17.8 mM respectively. Substrate specificity assays revealed that the thiol and amino groups of BSH are essential for activity, whereas malate is important for SaFosB recognition and catalytic efficiency. Metal activity assays indicated that Mn2+ and Mg2+ are likely to be the relevant cofactors under physiological conditions. The serine analogue of...

Fosfomycin is widely used for the treatment of uncomplicated urinary tract infection (UTI) and recently have been recommended for treating multidrug-resistant (MDR) gram-negative bacilli. Whether urine acidification can improve bacterial susceptibility to fosfomycin oral dosing regimen has not been analyzed. Minimal inhibitory concentration (MIC) was determined using agar dilution in pH 6.0 and 7.0 for 245 Gram negative bacterial isolates, consisting of 158 E. coli and 87 Klebsiella spp. which were collected from patients with UTI. Monte Carlo simulation of urinary fosfomycin area under the concentration-time curve (AUC) after a single oral dose of 3000 mg fosfomycin and 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 pH environment increased bacterial susceptibility in 71% of the isolates and resulted in a statistic...

This is a retrospective study of 15 difficult-to-treat (i.e., exhibiting previous failure, patient side effects, or resistance to ciprofloxacin and co-trimoxazole) chronic bacterial prostatitis infections (5 patients with multidrug-resistantEnterobacteriaceae[MDRE]) receiving fosfomycin-tromethamine at a dose of 3 g per 48 to 72 h for 6 weeks. After a median follow-up of 20 months, 7 patients (47%) had a clinical response, and 8 patients (53%) had persistent microbiological eradication; 4/5 patients with MDRE isolates achieved eradication. There were no side effects. Fosfomycin-tromethamine is a possible alternative therapy for chronic bacterial prostatitis.

ABSTRACTThe combination of fosmidomycin and clindamycin (F/C) is effective in adults and older children for the treatment of malaria and could be an important alternative to existing artemisinin-based combinations (ACTs) if proven to work in younger children. We conducted an open-label clinical trial to assess the efficacy, safety, and tolerability of F/C for the treatment of uncomplicatedP. falciparummalaria in Mozambican children <3 years of age. Aqueous solutions of the drugs were given for 3 days, and the children were followed up for 28 days. The primary outcome was the PCR-corrected adequate clinical and parasitological response at day 28. Secondary outcomes included day 7 and 28 uncorrected cure rates and fever (FCT) and parasite (PCT) clearance times. Fifty-two children were recruited, but only 37 patients were evaluable for the primary outcome. Day 7 cure rates were high (94.6%; 35/37), but the day 28 PCR-corrected cure rate was 45.9% (17/37). The FCT was short (median, ...

Chronic bacterial prostatitis (CBP, NIH category II) is a difficult- to-eradicate, recurring, chronic infection of the prostate, often characterized by disabling symptoms, significantly reducing the quality of life of patients. Fluoroquinolones have been for many years first-line agents for treatment of this condition. However, mounting pathogen resistance trends (especially in Mediterranean countries like Greece and Italy) are progressively restricting the usage of fluoroquinolones for treating many Gram-positive or Gram-negative infections in the urological field, and clinicians are increasingly treating bacterial prostatitis by empirically administering agents which have not been adequately tested in the frame of clinical trials. In recent years, reports on the efficacy of the bactericidal antibiotic fosfomycin on CBP have been published. Most articles published so far are case reports, and only few case series or cohort studies are available. The aim of this article is to review...

BACKGROUND The incidence of urinary tract infections (UTIs) caused by extended-spectrum-beta-lactamase (ESBL) producing Escherichia coli (ESBL-EC) and Klebsiella pneumoniae (ESBL-KP) has been on the rise limiting oral treatment options. Fosfomycin was reported to be highly efficacious against these organisms, however, data is lacking in Lebanon and the Middle East. OBJECTIVE To determine the in vitro activity of fosfomycin against ESBL and non-ESBL-producing E. coli and K. pneumoniae uropathogens in Lebanon. METHODS A total of 542 consecutive non-duplicate isolates of ESBL-producing E. coli (n = 374) and K. pneumoniae (n = 168), and 291 isolates of non-ESBL-producing E. coli (n = 236) and K. pneumoniae (n = 55) were recovered from urine specimens of patients tested at the American University of Beirut Medical Center (AUBMC) during 2010. Each isolate was tested against a battery of 13 antimicrobials by disk diffusion according to the guidelines of CLSI testing and result interpretati...

S-Carvone has been described as a negative regulator of mevalonic acid (MVA) production by interfering with 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMGR) activity, a key player in isoprenoid biosynthesis. The impact of this monoterpene on the production of capsidiol in Nicotiana tabacum, an assumed MVA-derived sesquiterpenoid phytoalexin produced in response to elicitation by cellulase, was investigated. As expected, capsidiol production, as well as early stages of elicitation such as hydrogen peroxide production or stimulation of 5-epi-aristolochene synthase activity, were repressed. Despite the lack of capsidiol synthesis, apparent HMGR activity was boosted. Feeding experiments using (1-13C)Glc followed by analysis of labeling patterns by 13C-NMR, confirmed an MVA-dependent biosynthesis; however, treatments with fosmidomycin, an inhibitor of the MVA-independent 2-C-methyl-d-erythritol 4-phosphate (MEP) isoprenoid pathway, unexpectedly down-regulated the biosynthesis of t...

Isoprenoid biosynthesis via the methylerythritol phosphate pathway is a target against pathogenic bacteria and the malaria parasite Plasmodium falciparum. 4-(Hydroxyamino)-4-oxobutylphosphonic acid and 4-[hydroxy(methyl)amino]-4-oxobutyl phosphonic acid, two novel inhibitors of DXR (1-deoxy-D-xylulose 5-phosphate reducto-isomerase), the second enzyme of the pathway, have been synthesized and compared with fosmidomycin, the best known inhibitor of this enzyme. The latter phosphonohydroxamic acid showed a high inhibitory activity towards DXR, much like fosmidomycin, as well as significant antibacterial activity against Escherichia coli in tests on Petri dishes.

ABSTRACTLimited antimicrobial agents are available for the treatment of implant-associated infections caused by fluoroquinolone-resistant Gram-negative bacilli. We compared the activities of fosfomycin, tigecycline, colistin, and gentamicin (alone and in combination) against a CTX-M15-producing strain ofEscherichia coli(Bj HDE-1)in vitroand in a foreign-body infection model. The MIC and the minimal bactericidal concentration in logarithmic phase (MBClog) and stationary phase (MBCstat) were 0.12, 0.12, and 8 μg/ml for fosfomycin, 0.25, 32, and 32 μg/ml for tigecycline, 0.25, 0.5, and 2 μg/ml for colistin, and 2, 8, and 16 μg/ml for gentamicin, respectively. In time-kill studies, colistin showed concentration-dependent activity, but regrowth occurred after 24 h. Fosfomycin demonstrated rapid bactericidal activity at the MIC, and no regrowth occurred. Synergistic activity between fosfomycin and colistinin vitrowas observed, with no detectable bacterial counts after 6 h. In animal studi...

1-Deoxy-D-xylulose 5-phosphate reductoisomerase (Dxr) is a key enzyme in a biosynthetic pathway for isoprenoids that is unique to eubacteria and plants. Dxr catalyzes the rearrangement and NADPH-dependent reduction of 1-deoxy-D-xylulose 5-phosphate to 2-C-methyl-D-erythritol 4-phosphate. The authors have purified Escherichia coli Dxr and devised a high-throughput screen (HTS) for compounds that bind to this enzyme at a functional site. Evidence is presented that the surrogate ligand directly binds or allosterically affects both the D-1-deoxyxylulose 5-phosphate (DXP) and NADPH binding sites. Compounds that bind at either or both sites that compete for binding with the surrogate ligand register as hits. The time-resolved fluorescence-based assay represents an improvement over the Dxr enzyme assay that relies on relatively insensitive measurements of NADPH oxidation. Screening 32,000 compounds from a diverse historical library, the authors obtained 89 potent inhibitors in the surrogat...

Plants synthesize an astonishing diversity of isoprenoids, some of which play essential roles in photosynthesis, respiration, and the regulation of growth and development. Two independent pathways for the biosynthesis of isoprenoid precursors coexist within the plant cell: the ...

ABSTRACTOur objective was to evaluate the antimicrobial susceptibility ofEnterobacteriaceaecausing urinary tract infections (UTIs) in adults in Africa. The PubMed database was systematically searched to identify relevant studies published after 2000. Google, World Health Organization, and African Field Epidemiology networks were also searched. Twenty-eight studies, accounting for 381,899 urine isolates from 14 African countries, met the inclusion criteria.Escherichia coli,Klebsiellaspp., andProteusspp. were the most commonly encountered uropathogens. Cefotaxime, imipenem, fosfomycin, and ciprofloxacin were the antibiotics with the highest activity againstE. coliisolates from outpatients, with susceptibility being 92 to 99, 100, 100, and 68 to 91%, respectively. The susceptibility amongKlebsiellaspp. isolates from outpatients varied from 80 to 100% for amikacin and from 53 to 100% for ciprofloxacin, while susceptibility was 74 to 78, 97, and 77% for ciprofloxacin, amikacin, and fosfo...

The use of fosfomycin for treatment of systemic infections due to MDR Pseudomonas aeruginosa is increasing. However, pharmacodynamic data for fosfomycin are limited. Sixty-four clinical isolates of P. aeruginosa (MDR and non-MDR) from two Australian hospitals were collected; 59 isolates were from patients with cystic fibrosis and 5 isolates were from critically ill patients. The in vitro pharmacodynamic properties of fosfomycin (disodium) were investigated via MICs (all isolates) and, for selected isolates, via time-kill kinetics (static and dynamic models; concentration range, 1-1024 mg/L), population analysis profiles (PAPs) and post-antibiotic effect (PAE). Two inocula (∼10(6) and ∼10(8) cfu/mL) were included in static time-kill studies to examine the effect of inocula on bacterial killing. MICs ranged from 1 to >512 mg/L, with 61% of isolates considered fosfomycin susceptible (MIC ≤64 mg/L). The MIC distributions for MDR and non-MDR isolates were similar. Baseline PAPs indica...

Phage-mediated lysis has been an essential laboratory tool for rapidly identifying Bacillus anthracis for more than 40 years, relying on the γ phage derivative of a Bacillus cereus prophage called W. The complete genomic sequences of the temperate W phage, referred to as Wβ, and its lytic variant γ were determined and found to encode 53 open reading frames each, spanning 40,864 bp and 37,373 bp, respectively. Direct comparison of the genomes showed that γ evolved through mutations at key loci controlling host recognition, lysogenic growth, and possibly host phenotypic modification. Included are a cluster of point mutations at the gp14 tail fiber locus of γ, encoding a protein that, when fused to green fluorescent protein, binds specifically to B. anthracis. A large 2,003-bp deletion was also identified at the γ lysogeny module, explaining its shift from a temperate to a lytic lifestyle. Finally, evidence of recombination was observed at a dicistronic Wβ locus, encoding putative bact...

Fosmidomycin is effective against malaria, but it needs to be given for ≥4 days when used alone. We conducted a study of 50 children with Plasmodium falciparum malaria to evaluate the safety and efficacy of consecutively shortened regimens of artesunate-fosmidomycin (1 to 2 mg/kg of body weight and 30 mg/kg of body weight, respectively; doses given every 12 hours). All dosing regimens were well tolerated. Artesunate-fosmidomycin acted rapidly, resulting in consolidated geometric mean parasite and fever clearance times of 24 h and 15 h, respectively. Treatment regimens of ≥2 days led to cure ratios of 100% by day 14 (39/39; 95% confidence interval [95% CI], 91% to 100%). Most importantly, the 3-day regimen achieved 100% cure on day 28 (10/10; 95% CI, 69% to 100%). Treatment with artesunate-fosmidomycin was associated with transient grade I or II neutropenia (absolute neutrophil counts of 750 to 1,200/μl and 400 to 749/μl, respectively) in six or two patients, respectively. Artesunate...

Results A total of 231 ESBL-EC (42.4% CTX-M-15, 34.2% SHV-12 and 23.4% CTX-M-14) were collected. The overall rate of fosfomycin resistance was 9.1%, but varied according to ESBL type (5.6% of CTX-M-14 isolates, 5.1% of SHV-12 and 15.3% of CTX-M-15). Of 67 O25b/B2 ...

S-Carvone has been described as a negative regulator of mevalonic acid (MVA) production by interfering with 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMGR) activity, a key player in isoprenoid biosynthesis. The impact of this monoterpene on the production of capsidiol in Nicotiana tabacum, an assumed MVA-derived sesquiterpenoid phytoalexin produced in response to elicitation by cellulase, was investigated. As expected, capsidiol production, as well as early stages of elicitation such as hydrogen peroxide production or stimulation of 5-epi-aristolochene synthase activity, were repressed. Despite the lack of capsidiol synthesis, apparent HMGR activity was boosted. Feeding experiments using (1-13C)Glc followed by analysis of labeling patterns by 13C-NMR, confirmed an MVA-dependent biosynthesis; however, treatments with fosmidomycin, an inhibitor of the MVA-independent 2-C-methyl-d-erythritol 4-phosphate (MEP) isoprenoid pathway, unexpectedly down-regulated the biosynthesis of t...

Isoprenoid biosynthesis via the methylerythritol phosphate pathway is a target against pathogenic bacteria and the malaria parasite Plasmodium falciparum. 4-(Hydroxyamino)-4-oxobutylphosphonic acid and 4-[hydroxy(methyl)amino]-4-oxobutyl phosphonic acid, two novel inhibitors of DXR (1-deoxy-D-xylulose 5-phosphate reducto-isomerase), the second enzyme of the pathway, have been synthesized and compared with fosmidomycin, the best known inhibitor of this enzyme. The latter phosphonohydroxamic acid showed a high inhibitory activity towards DXR, much like fosmidomycin, as well as significant antibacterial activity against Escherichia coli in tests on Petri dishes.

Apicomplexa are important pathogens that include the causative agents of malaria, toxoplasmosis, and cryptosporidiosis. Apicomplexan parasites contain a relict chloroplast, the apicoplast. The apicoplast is indispensable and an attractive drug target. The apicoplast is home to a 1-deoxy-D-xylulose-5-phosphate (DOXP) pathway for the synthesis of isoprenoid precursors. This pathway is believed to be the most conserved function of the apicoplast, and fosmidomycin, a specific inhibitor of the pathway, is an effective antimalarial. Surprisingly, fosmidomycin has no effect on most other apicomplexans. Using Toxoplasma gondii, we establish that the pathway is essential in parasites that are highly fosmidomycin resistant. We define the molecular basis of resistance and susceptibility, experimentally testing various host and parasite contributions in T. gondii and Plasmodium. We demonstrate that in T. gondii the parasite plasma membrane is a critical barrier to drug uptake. In strong support...