RESUMO
This study was aimed at understanding the distributions of the MICs (minimum inhibitory concentrations) of aztreonam-avibactam, ceftazidime-avibactam and meropenem with respect to Klebsiella pneumoniae isolates producing different types of carbapenemases and their combinations. K. pneumoniae isolates were collected between 2019 and 2022 from 37 hospitals. PCR was used to screen for blaKPC-, blaNDM- and blaOXA-48-like genes. MICs were determined by the broth microdilution method for meropenem, aztreonam-avibactam and ceftazidime-avibactam at a constant avibactam concentration of 4 mg l-1. MIC distributions were analyzed for groups of isolates based on the identified carbapenemases including their combinations. The AZT/AVI MIC50 and MIC90 for all NDM-positive isolates were 0.25 and 0.5, respectively, and for serine-carbapenemase-only producers, they were 0.25 and 1 mg l-1, respectively. The CZD/AVI MIC50 and MIC90 values for serine-carbapenemase-only producers were 1 and 4 mg l-1, respectively. The AZT/AVI MIC50 and MIC90 values for co-producers and single carbapenemase producers were the same (i.e., 0.25 and 1 mg l-1, respectively). The total proportion of meropenem-susceptible isolates (≤8 mg l-1) among all the carbapenemase producers was 25.1% (31.1% among single-carbapenemase producers and 9.2% among co-producers). The results support the use of aztreonam-avibactam for the empirical treatment of infections caused by any carbapenemase producers.
RESUMO
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.
Assuntos
Antibacterianos , Infecções por Klebsiella , Humanos , Meropeném/farmacologia , Antibacterianos/farmacologia , Klebsiella pneumoniae , Proteínas de Bactérias/genética , Proteínas de Bactérias/farmacologia , beta-Lactamases/genética , beta-Lactamases/farmacologia , Carbapenêmicos/farmacologia , Testes de Sensibilidade Microbiana , Infecções por Klebsiella/tratamento farmacológico , Infecções por Klebsiella/microbiologiaRESUMO
The minimal inhibitory concentration (MIC) is conventionally used to define in vitro levels of susceptibility or resistance of a specific bacterial strain to an antibiotic and to predict its clinical efficacy. Along with MIC, other measures of bacteria resistance exist: the MIC determined at high bacterial inocula (MICHI) that allow the estimation of the occurrence of inoculum effect (IE) and the mutant prevention concentration, MPC. Together, MIC, MICHI and MPC represent the bacterial "resistance profile". In this paper, we provide a comprehensive analysis of such profiles of K. pneumoniae strains that differ by meropenem susceptibility, ability to produce carbapenemases and specific carbapenemase types. In addition, we have analyzed inter-relations between the MIC, MICHI and MPC for each tested K. pneumoniae strain. Low IE probability was detected with carbapenemase-non-producing K. pneumoniae, and high IE probability was detected with those that were carbapenemase-producing. MICs did not correlate with the MPCs; significant correlation was observed between the MICHIs and the MPCs, indicating that these bacteria/antibiotic characteristics display similar resistance properties of a given bacterial strain. To determine the possible resistance-related risk due to a given K. pneumoniae strain, we propose determining the MICHI. This can more or less predict the MPC value of the particular strain.
RESUMO
The inoculum effect (IE) is a well-known phenomenon with beta-lactams. At the same time, the IE has not been extensively studied with carbapenem/carbapenemase inhibitor combinations. The antibiotic-to-inhibitor concentration ratio used in susceptibility testing can influence the in vitro activity of the combination. To explore the role of these factors, imipenem/relebactam and doripenem/relebactam MICs were estimated against six Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae strains at standard inocula (SI) and high inocula (HI) by two methods: with a fixed relebactam concentration and with a fixed, pharmacokinetic-based carbapenem-to-relebactam concentration ratio. The combination MICs at HI, compared to SI, increased with most of the tested strains. However, the IE occurred with only two K. pneumoniae strains regardless of the MIC testing method. The relationship between the MICs at SI and the respective inoculum-induced MIC changes was observed when the MICs were estimated at pharmacokinetic-based carbapenem-to-relebactam concentration ratios. Thus, (1) IE was observed with both carbapenem/relebactam combinations regardless of the MIC testing method; however, IE was not observed frequently among tested K. pneumoniae strains. (2) At HI, carbapenem/relebactam combination MICs increased to levels associated with carbapenem resistance. (3) Combination MICs determined at pharmacokinetic-based carbapenem-to-inhibitor concentration ratios predict susceptibility elevations at HI in KPC-producing K. pneumoniae.
RESUMO
The emergence of carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) is a new threat to healthcare. In this study, we analyzed nine CR-hvKp isolates of different sequence-types (ST) recovered from patients with nosocomial infections in two hospitals in Saint Petersburg. Whole-genome sequencing showed that eight of them harbored large mosaic plasmids carrying resistance to carbapenems and hypervirulence simultaneously, and four different types of hybrid plasmids were identified. BLAST analysis showed a high identity with two hybrid plasmids originating in the UK and Czech Republic. We demonstrated that hybrid plasmids emerged due to the acquisition of resistance genes by virulent plasmids. Moreover, one of the hybrid plasmids carried a novel New Delhi metallo-beta-lactamase (NDM) variant, differing from NDM-1 by one amino acid substitution (D130N), which did not provide significant evolutionary advantages compared to NDM-1. The discovery of structurally similar plasmids in geographically distant regions suggests that the actual distribution of hybrid plasmids carrying virulence and resistance genes is much wider than expected.