OXA-48 carbapenemases are frequently expressed by Klebsiella pneumoniae clinical isolates; they decrease the effectiveness of carbapenem therapy, particularly with meropenem. Among these isolates, meropenem-susceptible carbapenemase-producers may show decreased meropenem effectiveness. However, the probability of the emergence of resistance in susceptible carbapenemase-producing isolates and its dependence on specific K. pneumoniae meropenem MICs is not completely known. It is also not completely clear what resistance patterns will be exhibited by these bacteria exposed to meropenem, if they would follow the patterns of non-beta-lactamase-producing bacteria and other than beta-lactams antibiotics. These issues might be clarified if patterns of meropenem resistance related to the mutant selection window (MSW) hypothesis. To test the applicability of the MSW hypothesis to meropenem, OXA-48-carbapenemase-producing K. pneumoniae clinical isolates with MICs in a 64-fold range (from susceptible to resistant) were exposed to meropenem in a hollow-fiber infection model; epithelial lining fluid meropenem pharmacokinetics were simulated following administration of 2 grams every 8 hours in a 3-hour infusion. Strong bell-shaped relationships between the meropenem daily dose infused to the model as related to the specific isolate MIC and both the antimicrobial effect and the emergence of resistance were observed. The applicability of the MSW hypothesis to meropenem and carbapenemase producing K. pneumoniae was confirmed. Low meropenem efficacy indicates very careful prescribing of meropenem to treat K. pneumoniae infections when the causative isolate is confirmed as an OXA-48-carbapenemase producer.
The rapid spread of gram-negative bacteria resistance to carbapenems due to the production of carbapenemases requires new treatment options. The activity of carbapenem antibiotic biapenem, recently registered in Russia, against producers of various carbapenemases was studied in comparison with other antibiotics of this group. Among NDM-type carbapenemase producers, 77.8% demonstrated clinical susceptibility to biapenem; 50.3% and 21.1% of isolates were susceptible to meropenem and imipenem, respectively. Among the producers of OXA-48-type carbapenemases, 82,6%, 60,9%, and 65,2% of isolates demonstrated susceptibility to biapenem, imipenem, and meropenem, respectively.Producers of KPC-type carbapenemases were 100% resistant to all carbapenems. The introduction of biapenem will significantly expand the possibilities of treating severe infections caused by carbapenemase producers.
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