In Vitro and In Vivo Synergism of Fosfomycin in Combination with Meropenem or Polymyxin B against KPC-2-Producing Klebsiella pneumoniae Clinical Isolates

Abstract

Fosfomycin disodium is a potential therapeutic option to manage difficult-to-treat infections, especially when combined with other antimicrobials. In this study, we evaluated the activity of fosfomycin in combination with meropenem or polymyxin B against contemporaneous KPC-2-producing K. pneumoniae clinical isolates (KPC-KPN). Synergistic activity was assessed by checkerboard (CKA) and time–kill (TKA) assays. TKA was performed using serum peak and trough concentrations. The activity of these combinations was also assessed in the Galleria mellonella model. Biofilm disruption was assessed by the microtiter plate technique. CKA resulted in an 8- to 2048-fold decrease in meropenem MIC, restoring meropenem activity for 82.4% of the isolates when combined with fosfomycin. For the fosfomycin + polymyxin B combination, a 2- to 128-fold reduction in polymyxin B MIC was achieved, restoring polymyxin B activity for 47% of the isolates. TKA resulted in the synergism of fosfomycin + meropenem (3.0–6.7 log10 CFU/mL decrease) and fosfomycin + polymyxin B (6.0–6.2 log10 CFU/mL decrease) at peak concentrations. All larvae treated with fosfomycin + meropenem survived. Larvae survival rate was higher with fosfomycin monotherapy (95%) than that observed for fosfomycin + polymyxin B (75%) (p-value < 0.0001). Finally, a higher biofilm disruption was observed under exposure to fosfomycin + polymyxin B (2.4–3.4-fold reduction). In summary, we observed a synergistic effect of fosfomycin + meropenem and fosfomycin + polymyxin B combinations, in vitro and in vivo, against KPC-KPN, as well as biofilm disruption.

Animal models of Klebsiella pneumoniae mucosal infections

“…In the G. mellonella case in particular, the larvae has an innate immune system somewhat similar to ours, but it lacks an adaptative response (Ménard et al, 2021). In K. pneumoniae infection models, G. mellonella has been used with vastly different goals, such as to evaluate phage-mediated survival (Feng et al, 2023), synergistic activity of antimicrobials (Ribeiro et al, 2023) and pathogenicity (Liu et al, 2023). However, when used to compare hypervirulent and common K. pneumoniae strains, the model did not reproduce the same differences observed in outbred mice (Russo and MacDonald, 2020).…”

Relationship between biofilm formation and antibiotic resistance of Klebsiella pneumoniae and updates on antibiofilm therapeutic strategies

“…Fosfomycin in combination with polymyxin B resulted in a 2.4-3.4 fold reduction in biofilm formation; whereas fosfomycin alone and polymyxin B alone reduced formation by 2.231-3.470 and 2.378-3.423 fold, respectively. For the combination of fosfomycin and meropenem, as well as meropenem alone, biofilm formation decreased by 1.481-2.724 fold and 1.335-2.385-fold, respectively, with two isolates reducing to a non-adherent state (Ribeiro et al, 2023). Higher biofilm disruption was observed for fosfomycin in combination with polymyxin B, followed by polymyxin B and fosfomycin alone (p < 0.001).…”

“…Synergistic activity of fosfomycin/ colistin combined against biofilms of Gram-negative strains including K. pneumoniae were also reported where the synergistic effects were not species-related or dependent on their MICs, resistance mechanisms, or clonal lineage (Boncompagni et al, 2022). The synergistic antibiofilm activity of fosfomycin in combination with polymyxin B or meropenem against KPC-2producing K. pneumoniae clinical isolates (KPC-KPN) were reported (Ribeiro et al, 2023). Biofilm disruption was observed when exposed to antimicrobials alone and in combination.…”

Emergence of KPC-113 and KPC-114 variants in ceftazidime-avibactam-resistant Klebsiella pneumoniae belonging to high-risk clones ST11 and ST16 in South America

“…pneumoniae 331. After 1 h, larvae were treated with 10 µL of 0.5 mg/mL meropenem or 10 µL of 1.0 mg/mL meropenem, in order to achieve clinical human doses of 1 g and 2 g meropenem, respectively, as standardized by the EUCAST for intravenous regimens ( 22 , 23 ). The inoculum was delivered in the last right proleg, and the treatments were injected in the last left proleg by using a sterile insulin syringe.…”