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.

The detection of KPC-type carbapenemases is necessary for guiding appropriate antibiotic therapy and the implementation of antimicrobial stewardship and infection control measures. Currently, few tests are capable of differentiating carbapenemase types, restricting the lab reports to their presence or not. The aim of this work was to raise antibodies and develop an ELISA test to detect KPC-2 and its D179 mutants. The ELISA-KPC test was designed using rabbit and mouse polyclonal antibodies. Four different protocols were tested to select the bacterial inoculum with the highest sensitivity and specificity rates. The standardisation procedure was performed using 109 previously characterised clinical isolates, showing 100% of sensitivity and 89% of specificity. The ELISA-KPC detected all isolates producing carbapenemases, including KPC variants displaying the ESBL phenotype such as KPC-33 and -66.

Cephalexin is a beta‐lactam antibiotic of the first generation of cephalosporins which is very effective against various bacterial infections. In this work, we investigate the structure and antibacterial activity of cephalexin solutions submitted to forced degradation under heat stress and photolytic irradiation. A combination of analytical techniques gathering LC/ESI‐MS and NMR spectroscopy allowed us to identify different chemical species amongst the byproducts, revealing that photolysis via UVA light leads to significant amounts of oxidized species that conserve the dihydrothiazine ring adjacent to the beta‐lactam ring. In contrast, thermodegradation induces the rupture of the bioactive moiety possibly with the production of cephalosporinic acid and deaminated species, which are inactive to bacteria. Microbiological analyses using E. coli as a model organism indicated that the antimicrobial capacity of samples submitted to thermolysis is suppressed while solutions submitted to irradiation with UVA light preserve their bactericidal power. Atomic force microscopy showed that cells incubated with photodegraded cephalexin are much longer than those incubated with the undegraded antibiotic, indicating that byproducts from photolysis inhibit septum formation and likely affect the action of penicillin‐binding protein 3 in the divisome of E. coli cells.

No abstract