Oral fosfomycin for the treatment of lower urinary tract infections among kidney transplant recipients-Results of a Spanish multicenter cohort

Acidic Urine pH and Clinical Outcome of Lower Urinary Tract Infection in Kidney Transplant Recipients Treated with Ciprofloxacin and Fosfomycin

Different factors, including antimicrobial resistance, may diminish the effectiveness of antibiotic therapy, challenging the management of post-transplant urinary tract infection (UTI). The association of acidic urine pH with microbiological and clinical outcomes was evaluated after fosfomycin or ciprofloxacin therapy in 184 kidney transplant recipients (KTRs) with UTI episodes by Escherichia coli (N = 115) and Klebsiella pneumoniae (N = 69). Initial urine pH, antimicrobial therapy, and clinical and microbiological outcomes, and one- and six-month follow-up were assessed. Fosfomycin was prescribed in 88 (76.5%) E. coli and 46 (66.7%) K. pneumoniae UTI episodes in the total cohort. When the urine pH ≤ 6, fosfomycin was prescribed in 60 (52.2%) E. coli and 29 (42.0%) K. pneumoniae. Initial urine pH ≤ 6 in E. coli UTI was associated with symptomatic episodes (8/60 vs. 0/55, p = 0.04) at one-month follow-up, with a similar trend in those patients receiving fosfomycin (7/47 vs. 0/41, p = 0.09). Acidic urine pH was not associated with microbiological or clinical cure in K. pneumoniae UTI. At pH 5, the ciprofloxacin MIC90 increased from 8 to >8 mg/L in E. coli and from 4 to >8 mg/L in K. pneumoniae. At pH 5, the fosfomycin MIC90 decreased from 8 to 4 mg/L in E. coli and from 512 to 128 mg/L in K. pneumoniae. Acidic urine is not associated with the microbiological efficacy of fosfomycin and ciprofloxacin in KTRs with UTI, but it is associated with symptomatic UTI episodes at one-month follow-up in E. coli episodes.

A joint program of antimicrobial stewardship and hospital-acquired infection control to reduce healthcare-associated infections after kidney transplantation: The Hipomenes study

Infection is a common complication in kidney transplant recipients (KTRs). The usefulness of antimicrobial stewardship programs (ASP) and hospital-acquired infection control (HAIC) initiatives in the general inpatient population is well established. We performed a quasi-experimental study to evaluate a joint ASP/HAIC initiative focused on KTRs. A dedicated ASP team optimized antimicrobial prescriptions in consecutive KTRs during the intervention period (June 2015-March 2016). A multifaceted, evidence-based HAIC program was concurrently implemented. Results were compared with the preceding period (June 2014-March 2015). We included 96 and 100 KTRs in the intervention and preintervention periods, respectively. There was a reduction in the consumption of meropenem (rate ratio [RR]: 0.63; 95% confidence interval [CI]: 0.53-0.75; P <.0001), ceftazidime (RR: 0.31; 95% CI: 0.21-0.45; P <.0001), vancomycin (RR: 0.65; 95% CI: 0.53-0.8; P <.0001), and ciprofloxacin (RR: 0.66; 95% CI: 0.55-0.81; P <.0001) and an increase of fosfomycin (RR: 1.80; 95% CI: 1.17-2.76; P =.008) during the intervention period. The incidence of cystitis (RR: 0.30; 95% CI: 0.28-0.33; P <.001) and upper urinary tract infection (RR: 0.56; 95% CI: 0.33-0.95; P =.04) decreased. A specific ASP/HAIC initiative was effective in optimizing antimicrobial use and reducing the incidence of common bacterial infections among KTRs.

Aptitude of Uropathogenic Escherichia coli in Renal Transplant Recipients: A Comprehensive Review on Characteristic Features, and Production of Extended Spectrum β-Lactamase

Urinary tract infection is the most common infection in almost half of the renal transplant patients. The development of UTI in these patients may progress to bacteremia, acute T cell-mediated rejection, impaired allograft function, or allograft loss, along with the increased risk of hospitalization and death. Among various pathogens implicated, Uropathogenic E. coli (UPEC), especially sequence type 131 (ST131), is the most virulent and multidrug-resistant pathogen. High antimicrobial resistance to most β-lactam antibiotics, mediated by extended spectrum β-lactamases (ESBLs) produced by UPEC, is a challenge in the clinical management of UTIs in kidney transplant recipients. Indeed, multidrug resistance to β-lactam antibiotics is a direct consequence of ESBL production. Resistance to other antibiotics such as aminoglycosides, fluoroquinolones, and trimethoprim-sulphamethoxazole has also been reported in ESBLs-producing UPEC, which reduces the therapeutic options, rising healthcare-associated costs and subsequently leads to renal failure or even graft loss. In this review, we aimed to discuss the post-transplant risk factors of UTI, UPEC virulence factors (VF), and the related factors including quorum sensing, and stress resistance genes. Furthermore, we searched for the current treatment strategies and some of the alternate approaches proposed as therapeutic options that may affirm the treatment of ESBL-producing UPEC.

Pharmacokinetic/Pharmacodynamic Analysis of Oral Calcium Fosfomycin: Are Urine Levels Sufficient to Ensure Efficacy for Urinary Tract Infections?

Urinary tract infections (UTIs) are extremely common and a major driver for the use of antimicrobials. Calcium fosfomycin is an old antibiotic indicated for the treatment of UTIs; however, data about its urine pharmacokinetic profile are scarce. In this work, we have evaluated the pharmacokinetics of fosfomycin from urine concentrations after oral administration of calcium fosfomycin to healthy women. Moreover, we have assessed, by pharmacokinetic/pharmacodynamic (PK/PD) analysis and Monte Carlo simulations, its effectiveness considering the susceptibility profile of Escherichia coli, the main pathogen involved in UTIs. The accumulated fraction of fosfomycin excreted in urine was around 18%, consistent with its low oral bioavailability and its almost exclusively renal clearance by glomerular filtration as unchanged drug. PK/PD breakpoints resulted to be 8, 16, and 32 mg/L for a single dose of 500 mg, a single dose of 1000 mg, and 1000 mg q8h for 3 days, respectively. For empiric treatment, the estimated probability of treatment success was very high (>95%) with the three dose regimens, considering the susceptibility profile of E. coli reported by EUCAST. Our results show that oral calcium fosfomycin at a dose level of 1000 mg every 8 h provides urine concentrations sufficient to ensure efficacy for the treatment of UTIs in women.

Extended-spectrum β-lactamase-producing and carbapenem-resistant Enterobacterales bloodstream infection after solid organ transplantation: Recent trends in epidemiology and therapeutic approaches

Background

Infections caused by multidrug‐resistant gram‐negative bacilli (MDR GNB), in particular extended‐spectrum β‐lactamase‐producing (ESBL‐E) and carbapenem‐resistant Enterobacterales (CRE), pose a major threat in solid organ transplantation (SOT). Outcome prediction and therapy are challenging due to the scarcity of randomized clinical trials (RCTs) or well‐designed observational studies focused on this population.

Methods

Narrative review with a focus on the contributions provided by the ongoing multinational INCREMENT‐SOT consortium (ClinicalTrials identifier NCT02852902) in the fields of epidemiology and clinical management.

Results

The Spanish Society of Transplantation (SET), the Group for Study of Infection in Transplantation of the Spanish Society of Infectious Diseases and Clinical Microbiology (GESITRA‐SEIMC), and the Spanish Network for Research in Infectious Diseases (REIPI) recently published their recommendations for the management of MDR GNB infections in SOT recipients. We revisit the SET/GESITRA‐SEIMC/REIPI document taking into consideration new evidence that emerged on the molecular epidemiology, prognostic stratification, and treatment of post‐transplant ESBL‐E and CRE infections. Results derived from the INCREMENT‐SOT consortium may support the therapeutic approach to post‐transplant bloodstream infection (BSI). The initiatives devoted to sparing the use of carbapenems in low‐risk ESBL‐E BSI or to repurposing existing non‐β‐lactam antibiotics for CRE in both non‐transplant and transplant patients are reviewed, as well as the eventual positioning in the specific SOT setting of recently approved antibiotics.

Conclusion

Due to the clinical complexity and relative rarity of ESBL‐E and CRE infections in SOT recipients, multinational cooperative efforts such as the INCREMENT‐SOT Project should be encouraged. In addition, RCTs focused on post‐transplant serious infection remain urgently needed.

Urinary Tract Infections in Kidney Transplant Recipients-Is There a Need for Antibiotic Stewardship?

(1) Background: Urinary tract infections (UTI) are the most common infections after kidney transplantation. Given the risk of urosepsis and the potential threat to the graft, the threshold for treating UTI and asymptomatic bacteriuria with broad spectrum antibiotics is low. Historically fluoroquinolones were prescription favorites for patients that underwent kidney transplantation (KT). After the recent recommendation to avoid them in these patients, however, alternative treatment strategies need to be investigated (2) Methods: We retrospectively analyzed the charts of 207 consecutive adult kidney transplantations that were performed at the department of General, Visceral and Transplantation Surgery of the University Hospital of Tuebingen between January 2015 and August 2020. All charts were screened for the diagnosis and treatment of asymptomatic bacteriuria (ASB) and urinary tract infections (UTI) and the patients' clinical characteristics and outcomes were evaluated. (3) Results: Of the 207 patients, 68 patients suffered from urinary tract infections. Patients who developed UTI had worse graft function at discharge (p = 0.024) and at the 12 months follow-up (p < 0.001). The most commonly prescribed antibiotics were Ciprofloxacin and Piperacillin/Tazobactam. To both, bacterial resistance was more common in the study cohort than in the control group. (4) Conclusions: Urinary tract infections appear to be linked to worse graft functions. Thus, prevention and treatment should be accompanied by antibiotic stewardship teams.

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.

Asymptomatic bacteriuria and urinary tract infections in kidney transplant recipients

PURPOSE OF REVIEW

Urinary tract infection (UTI) is the most common infection in kidney transplant recipients (KTRs). Several elements increase the risk of UTI and/or modify its clinical presentation among KTRs (e.g. immunosuppressive therapy, kidney allograft denervation, and use of urinary catheters). Also, KTRs may have UTIs because of difficult-to-identify and/or difficult-to-treat organisms. We provide an overview of the current knowledge regarding bacterial UTIs in KTRs, with a focus on recent findings.

RECENT FINDINGS

There is accumulating evidence from clinical trials that screening for and treating asymptomatic bacteriuria is not beneficial in most KTRs (i.e. those who are ≥1-2 months posttransplant and do not have a urinary catheter). These patients have a point-prevalence of asymptomatic bacteriuria of only 3% and treating asymptomatic bacteriuria probably does not improve their outcomes. There is no clinical trial evidence to guide the management of symptomatic UTI in KTRs. Several important clinical questions remain unanswered, especially regarding the management of posttransplant pyelonephritis and the prevention of UTI in KTRs.

SUMMARY

Despite its frequency and associated morbidity, UTI after kidney transplantation is an understudied infection. In an era of increasing antimicrobial resistance and limited resources, further research is needed to ensure optimal use of antimicrobials in KTRs with UTI.

Carbapenemase-producing Enterobacteriaceae in transplant patients

Carbapenemase-producing Enterobacteriaceae (CPE) are a serious public health concern and represent a major threat to immunocompromised hosts, including solid organ (SOT) and stem cell transplant (HSCT) recipients. Transplant patients are at particular risk of developing CPE colonization and/or infection due to their frequent exposure to prolonged courses of broad-spectrum antibiotics, altered immunocompetence and exposure to invasive procedures and immunosuppressive drugs. Gut colonization with CPE, in particular carbapenem-resistant Klebsiella pneumoniae, may occur before or after SOT in 2%-27% of patients and among 2%-9% of HSCT and has been associated with increased risk of developing CPE infections. In endemic areas, CPE infections occur in up to 18% of SOT, and HSCT patients can account for 5%-18% of all patients with CPE bacteraemia. Mortality rates up to 70% have been associated with CPE infections in both patient populations. The rapid initiation of an active therapy against CPE is advocated in these infections. Therapeutic options, however, are limited by the paucity of novel compounds that are currently available and by potential antibiotic-associated toxicities. Therefore, a multidisciplinary approach involving infection control and antimicrobial stewardship programmes still represents the mainstay for the management of CPE infections among transplant patients. The evidence for the use of prevention strategies such as CPE-targeted perioperative prophylaxis or gut decolonization is still scarce. Large, multicentre trials are required to better define prevention strategies and to guide the management of CPE infections in the transplant setting.

Efficacy and safety of oral fosfomycin for asymptomatic bacteriuria in kidney transplant recipients: Results from a Spanish multicenter cohort

Current guidelines recommend against systematic screening or treating asymptomatic bacteriuria (AB) among kidney transplant (KT) recipients, although the evidence regarding episodes occurring early after transplantation or in the presence of anatomical abnormalities is inconclusive. Oral fosfomycin may constitute a good option for the treatment of post-transplant AB, particularly due to the emergence of multidrug-resistant (MDR) uropathogens. Available clinical evidence supporting its use in this specific setting, however, remains scarce. We performed a retrospective study in 14 Spanish institutions from January 2005 to December 2017. Overall, 137 episodes of AB diagnosed in 133 KT recipients treated with oral fosfomycin (calcium and trometamol salts) with a test-of-cure urine culture within the first 30 days were included. Median time from transplantation to diagnosis was 3.1 months (interquartile range [IQR]: 1.1 - 10.5). Most episodes (96.4% [132/137]) were caused by gram-negative bacteria (GNB), and 56.9% (78/137) were categorized as MDR (extended-spectrum β-lactamase-producing Enterobacterales [20.4%] and carbapenem-resistant GNB [2.9%]). Rate of microbiological failure at month 1 was 40.1% (95% confidence interval [95%CI]: 31.9 - 48.9) for the whole cohort and 42.3% (95%CI: 31.2 - 54.0) for episodes due to MDR pathogens. Previous urinary tract infection (odds ratio [OR]: 2.42; 95%CI: 1.11 - 5.29; P-value = 0.027) and use of fosfomycin as salvage therapy (OR: 8.31; 95%CI: 1.67 - 41.35; P-value = 0.010) were predictors of microbiological failure. No severe treatment-related adverse event were detected. Oral fosfomycin appears to be a suitable and safe alternative for the treatment (if indicated) of AB after KT, including those episodes due to MDR uropathogens.

Effect of Fosfomycin on Cyclosporine Nephrotoxicity

Fosfomycin (Fos) has emerged as a potential treatment against multidrug-resistant organisms, however, there has been little work done on its influence on calcineurin inhibitor nephrotoxicity (CIN). This study was designed to evaluate the effect of Fos in combination with cyclosporine (CsA) on CIN. Two sets of experiments were undertaken. In the first, Wistar rats received different doses of Fos: 0, 62.5, 125, 250, and 500 mg/kg. In the second, rats were divided into four groups: control, CsA 15 mg/kg s.c., CsA + fosfomycin 62.5 mg/kg (CsA + LF), and CsA + Fos 500 mg/kg (CsA + HF). CsA was administrated daily for 14 days, whereas Fos administration started on the ninth day followed by two more doses, delivered 48 h apart. The administration of different Fos doses did not alter renal function. In contrast, CsA induced arteriolopathy, hypoperfusion, a reduction in the glomerular filtration rate, and downregulation of eNOS, angiotensinogen, and AT1R mRNA levels. Lower doses of Fos did not modify CIN. Instead, the CsA + HF group exhibited greater hypoperfusion, arteriolopathy, and oxidative stress, and increased mRNA levels of pro-inflammatory cytokines. This study shows that Fos administered by itself at different doses did not cause renal injury, but when it was given repeatedly at high dosages (500 mg/kg) in combination with CsA, it increased CIN through the promotion of greater oxidative stress and renal inflammation.

Oral Fosfomycin Efficacy with Variable Urinary Exposures following Single and Multiple Doses against Enterobacterales: the Importance of Heteroresistance for Growth Outcome

Oral fosfomycin trometamol is licensed as a single oral dose for the treatment of uncomplicated urinary tract infections, with activity against multidrug-resistant uropathogens. The impact of interindividual variability in urinary concentrations on antimicrobial efficacy, and any benefit of giving multiple doses, is uncertain. We therefore performed pharmacodynamic profiling of oral fosfomycin, using a dynamic bladder infection in vitro model, to assess high and low urinary exposures following a single oral dose and three repeat doses given every 72 h, 48 h, and 24 h against 16 clinical isolates with various MICs of fosfomycin (8 Escherichia coli, 4 Enterobacter cloacae, and 4 Klebsiella pneumoniae isolates). Baseline fosfomycin high-level-resistant (HLR) subpopulations were detected prior to drug exposure in half of the isolates (2 E. coli, 2 E. cloacae, and 4 K. pneumoniae isolates; proportion, 1 × 10^-5 to 5 × 10^-4% of the total population). Fosfomycin exposures were accurately reproduced compared to mathematical modeling (linear regression slope, 1.1; R ², 0.99), with a bias of 3.8% ± 5.7%. All 5/5 isolates with MICs of ≤1 μg/ml had no HLR and were killed, whereas 8/11 isolates with higher MICs regrew regardless of exposure to high or low urinary concentrations. A disk diffusion zone of <24 mm was a better predictor for baseline HLR and regrowth. Administering 3 doses with average exposures provided very limited additional kill. These results suggest that baseline heteroresistance is important for treatment response, while increased drug exposure and administering multiple doses may not be better than standard single-dose fosfomycin therapy.