Fosfomycin: what was old is new again

Preventable serious drug-disease interactions of reserve antibiotics

INTRODUCTION

Antibiotics that are used exclusively in hospital settings and reserved for treating infections caused by multidrug-resistant or extended-resistant bacterial pathogens are referred to as 'reserved' antibiotics. The purpose of this review article is to provide a better understanding of the risks associated with serious interactions between reserved antibiotics and various diseases, as well as to present key strategies for their prevention.

AREAS COVERED

The literature search was conducted in the MEDLINE, SCOPUS, EBSCO, and GOOGLE SCHOLAR databases without any restrictions on time or language. Only clinical studies, observational human studies, case reports, and case series that reported serious drug-disease interactions were considered.

EXPERT OPINION

Knowledge of the interactions between reserve antibiotics and diseases, that have actually occurred and then been described in the medical literature, is crucial to the safe treatment of critically ill patients with infections caused by multidrug-resistant bacterial strains. Introducing into routine practice the checking of possible interactions with diseases that a patient suffers from, strict monitoring of changes in the function of the excretory organs (kidneys and liver), and measuring the concentration of drugs in the plasma will reduce the possibility of adverse drug-disease interactions.

Evaluation of fosfomycin susceptibility testing methods: A focus on multidrug-resistant Klebsiella pneumoniae using ECOFF values

INTRODUCTION

We aimed to evaluate the performance of two methods; disc diffusion and gradient test with the gold standard agar dilution method in determining the susceptibility of fosfomycin, in multidrug-resistant (MDR) K. pneumoniae isolates causing urinary tract infections.

METHODS

K. pneumoniae producing carbapenemase and extended-spectrum beta-lactamase (ESBL) isolated from urine samples submitted to the clinical microbiology laboratory were included in the study. The isolates were tested using gradient test (MTS, Liofilchem, Italy) and disc diffusion (Oxoid, UK). Agar dilution was employed as the reference method. Since there is no MIC value for K. pneumoniae in EUCAST, epidemiological cut-off values (ECOFFs) were determined and susceptibility and error rates were calculated.

RESULTS

In this study, among the 251 ESBL-positive K. pneumoniae isolates, 20(8 %) were also positive for carbapenemase. The ECOFF was determined as 128 mg/L for K. pneumoniae. When all study isolates (n:251) were considered, 87.6%(220/251) were wild-type (WT) for fosfomycin (MIC≤128 mg/L). Among ESBL-positive but carbapenemase-negative isolates (n:231), 87.8%(203/231) were WT for fosfomycin, and among ESBL and carbapenemase-positive isolates (n:20), 85.0%(17/20) were WT. The MIC50/90 values were determined to be 8/256 mg/L. When compared to agar dilution, the categorical agreement was 96.8% for the gradient test and 94.8 % for disc diffusion. While the gradient test showed a 16.1% very major error (VME) rate with no major errors (ME), disk diffusion revealed 35.4 % VME rate and 5.8 % ME rate.

CONCLUSION

A significant proportion of ESBL-positive K. pneumoniae isolates were WT for fosfomycin. The gradient test with 96.8% categorical agreement appears to be a good alternative, but agar dilution remains the gold Standard for reference laboratories.

Intravenous Fosfomycin as Adjunctive Therapy for Gram-Negative Bacteria Bloodstream Infections: A Propensity Score Adjusted Retrospective Cohort Study

BACKGROUND

The role of intravenous fosfomycin (iv-FOS) as a part of combination therapy for Gram-negative bacteria bloodstream infections (GNB-BSI) needs to be evaluated in clinical practice, as in vitro data show potential efficacy.

METHODS

All consecutive patients with a GNB-BSI from 01 January 2021 to 01 April 2023 were included. Primary outcome was 30-day mortality. A Cox regression analysis was used to identify predictors of mortality; an inverse-probability of treatment-weighting (IPTW) analysis was also performed.

RESULTS

Overall, 363 patients were enrolled: 211 (58%) males, with a median (q1-q3) age of 68 (57-78) years, and a median Charlson comorbidity index of 5 (3-7). At GNB-BSI onset, the median SOFA score was 5 (2-7) and 122 patients (34%) presented with septic shock. Pathogens were principally Klebsiella pneumoniae (42%), Escherichia coli (28%) and Pseudomonas aeruginosa (17%); of them, 36% were carbapenem-resistant. The therapy included carbapenems (40%), cephalosporins (37%) and beta-lactams/beta-lactamases-inhibitors (19%); a combination with iv-FOS was used in 98 (27%) cases at a median dosage of 16 (16-18) g/daily. The use of iv-FOS was not associated with reduced crude mortality (21% vs 29%, P = 0.147). However, on multivariable Cox-regression, combination therapy with iv-FOS resulted in protection for mortality (aHR 0.51, 95% CI 0.28-0.92), but not other combo-therapies (HR 0.69, 95% CI 0.44-1.16). This result was also confirmed with the IPTW-adjusted Cox model (aHR 0.52, 95% CI 0.31-0.91). Subgroup analysis suggested a benefit in severe infections (SOFA > 6, PITT ≥ 4) and when iv-FOS was initiated within 24 hours of GNB-BSI onset.

CONCLUSIONS

Fosfomycin in combination therapy for GNB-BSI may have a role in improving survival. These results justify the development of further clinical trials.

Tackling the outer membrane: facilitating compound entry into Gram-negative bacterial pathogens

Emerging resistance to all available antibiotics highlights the need to develop new antibiotics with novel mechanisms of action. Most of the currently used antibiotics target Gram-positive bacteria while Gram-negative bacteria easily bypass the action of most drug molecules because of their unique outer membrane. This additional layer acts as a potent barrier restricting the entry of compounds into the cell. In this scenario, several approaches have been elucidated to increase the accumulation of compounds into Gram-negative bacteria. This review includes a brief description of the physicochemical properties that can aid compounds to enter and accumulate in Gram-negative bacteria and covers different strategies to target or bypass the outer membrane-mediated barrier in Gram-negative bacterial pathogens.

Current and future perspectives in the treatment of multidrug-resistant Gram-negative infections

Microbial resistance is a serious threat to human health worldwide. Among the World Health Organisation's list of priority resistant bacteria, three are listed as critical-the highest level of concern-and all three are Gram-negative. Gram-negative resistance has spread worldwide via a variety of mechanisms, the most problematic being via AmpC enzymes, extended-spectrum β-lactamases, and carbapenemases. A combination of older drugs, many with high levels of toxicity, and newer agents are being used to combat multidrug resistance, with varying degrees of success. This review discusses the current treatments for multidrug-resistant Gram-negative bacteria, including new agents, older compounds, and new combinations of both, and some new treatment targets that are currently under investigation.

Transrectal versus transperineal prostate biopsy under intravenous anaesthesia: a clinical, microbiological and cost analysis of 2048 cases over 11 years at a tertiary institution

BACKGROUND

Transrectal (TR) and transperineal (TP) approaches for prostate biopsy have different morbidity profiles. Our institution transitioned to a preference for multiparametric MRI-based triage and TP biopsy since 2014. The aim of this study was to compare clinical, microbiological and health economic outcomes between TR and TP prostate biopsy.

METHODS

A consecutive cohort study considered prostate biopsies over an 11 year period. Hospital presentations across the region within 30 days of biopsy were analysed for details and subsequent outcomes according to biopsy approach. Cost for each encounter (routine and unplanned) were analysed and generalised linear models applied, as well as cost implications for inclusion of mpMRI-based triage and TP biopsy preference.

RESULTS

In total, 2048 prostate biopsies were performed. Similar re-presentation rates per occurred for each biopsy approach (90 patients, TR 4.8%, TP 3.8%, p = 0.29), with 23 patients presenting more than once (119 total presentations). Presentations after TR biopsy were more likely to be of infectious aetiology (TR 2.92%, TP 0.26% de novo, p < 0.001) and result in hospital admission (TR 43/49, 93.4%; TP 14/24, 58.3%; p = 0.007) for similar rates of urinary retention (TR 2.76% vs TP 3.63%, p = 1). The mean overall cost (biopsy and re-presentations) was higher for the TP group (p < 0.001), adjusted for year and age, but reduced over time and was similar for patients who re-presented (p = 0.98). Incorporation of mpMRI (with subsequently avoided biopsies), TP biopsy and re-presentations resulted in AU$783.27 saving per biopsy.

CONCLUSIONS

TR biopsy resulted in more infectious complications and hospital admissions than TP biopsy for similar rates of re-presentation and urinary retention. TP biopsy costs reduced over time and use in conjunction with mpMRI provides an overall cost saving. Routine TP biopsy is safe and feasible, with further cost savings expected with other approaches (local anaesthetic) under investigation.