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

Adverse events during intravenous fosfomycin therapy in a real-life scenario. Risk factors and the potential role of therapeutic drug monitoring

BACKGROUND

Intravenous fosfomycin (IVFOF) is gaining interest in severe infections. Its use may be limited by adverse events (AEs). Little experience exists on IVFOF therapeutic drug monitoring (TDM) in real-life setting.

PATIENTS AND METHODS

Retrospective study of patients receiving IVFOF for > 48 h at Policlinico Hospital (Milan, Italy) from 01/01/2019 to 01/01/2023. AEs associated to IVFOF graded CTCAE ≥ II were considered. Demographic and clinical risk factors for IVFOF-related AEs were analysed with simple and multivariable regression models. The determination of IVFOF TDM was made by a rapid ultraperformance liquid chromatography mass spectrometry method (LC-MS/MS) on plasma samples. The performance of TDM (trough levels (Cmin) in intermittent infusion, steady state levels (Css) in continuous infusion) in predicting AEs ≤ 5 days after its assessment was evaluated.

RESULTS

Two hundred and twenty-four patients were included. At IVFOF initiation, 81/224 (36.2%) patients were in ICU and 35/224 (15.7%) had septic shock. The most frequent infection site was the low respiratory tract (124/224, 55.4%). Ninety-five patients (42.4%) experienced ≥ 1AEs, with median time of 4.0 (2.0-7.0) days from IVFOF initiation. Hypernatremia was the most frequent AE (53/224, 23.7%). Therapy discontinuation due to AEs occurred in 38/224 (17.0%). ICU setting, low respiratory tract infections and septic shock resulted associated with AEs (RRadjusted 1.59 (95%CI:1.09-2.31), 1.46 (95%CI:1.03-2.07) and 1.73 (95%CI:1.27-2.37), respectively), while IVFOF daily dose did not. Of the 68 patients undergone IVFOF TDM, TDM values predicted overall AEs and hypernatremia with AUROC of 0.65 (95%CI:0.44-0.86) and 0.91 (95%CI:0.79-1.0) respectively for Cmin, 0.67 (95%CI:0.39-0.95) and 0.76 (95%CI:0.52-1.0) respectively for Css.

CONCLUSIONS

We provided real world data on the use of IVFOF-based regimens and associated AEs. IVFOF TDM deserves further research as it may represent a valid tool to predict AEs.

KEY POINTS

Real world data on intravenous fosfomycin for severe bacterial infections. AEs occurred in over 40% (therapy discontinuation in 17%) and were related to baseline clinical severity but not to fosfomycin dose. TDM showed promising results in predicting AEs.

Intravenous Fosfomycin for Systemic Multidrug-Resistant Pseudomonas aeruginosa Infections

Human Pseudomonas infections have high morbidity and mortality rates. Pseudomonas bacteria can cause sepsis or septic shock; they produce biofilm and commonly exhibit a multidrug-resistant phenotype. The choice of antimicrobial therapy in many cases is challenging, and deep knowledge of clinical, microbiological, and pharmacological issues is required. Intravenous fosfomycin is being repurposed in a combination given its favorable pharmacokinetic/pharmacodynamic properties (a small molecule with favorable kinetic both in bloodstream infection and in deep-seated infections), antibiofilm activity, and its interesting synergistic effects with other antimicrobials. Recent literature on epidemiological, microbiological, pharmacological, and clinical data on intravenous fosfomycin therapy against Pseudomonas is herein reviewed and discussed.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Intravenous fosfomycin as salvage therapy for osteomyelitis caused by multidrug-resistant Pseudomonas aeruginosa

PURPOSE

A case of osteomyelitis caused by multidrug-resistant (MDR) Pseudomonas aeruginosa is reported.

SUMMARY

An 84-year-old Caucasian male with an underlying history of type 2 diabetes, peripheral vascular disease, and coronary artery disease had chronic nonhealing wounds on his right foot. Wound care and a course of intravenous (IV) ertapenem with oral ciprofloxacin were ineffective. His initial wound culture grew Staphylococcus aureus, group G streptococcus and P. aeruginosa; the Pseudomonas was susceptible to multiple agents. The patient eventually required midtarsal amputation and angioplasties to his right leg. Twenty days after the operation, 2 openings were discovered at the surgical site, 1 of which was probed to the bone. He was readmitted 5 weeks after the operation. A repeat wound swab grew MDR P. aeruginosa and Finegoldia magna. The Pseudomonas was susceptible to gentamicin and colistin. The patient had revision of the infected amputation site with the goal of salvaging his right lower limb. The patient developed acute renal failure after 26 days of IV gentamicin, IV ceftriaxone, and oral metronidazole. Additional susceptibility testing was performed to identify alternatives. The bacteria were considered susceptible to IV fosfomycin, the last resort, by our microbiology laboratory. This was combined with ceftolozane/tazobactam followed by meropenem to treat the residual infection. After 2 weeks of IV fosfomycin, the patient's wound improved and further amputation was avoided.

CONCLUSION

Our case demonstrates that IV fosfomycin may provide an effective salvage therapy when combined with β-lactams for the treatment of severe diabetic foot infection or osteomyelitis caused by MDR P. aeruginosa.