In vitro evaluation of dual carbapenem combinations against carbapenemase-producing Enterobacteriaceae

Objectives: This study aimed to analyse the in vitro activity of dual combinations of carbapenems against Klebsiella pneumoniae producing the main carbapenemase types.Methods: MIC values of the carbapenems, imipenem, meropenem, ertapenem and doripenem were determined alone and in dual combinations for 20 clinical K. pneumoniae isolates producing representative carbapenemases, i.e. OXA-48 (n = 6), NDM-1 (n = 4), NDM-1 + OXA-48 (n = 2) and KPC-2 (n = 8). MICs were also determined for Escherichia coli recombinant strains with or without permeability defects producing NDM-1, OXA-48 or KPC-2. In vitro synergy combination testing was performed using the microdilution and chequerboard techniques. Fractional inhibitory concentration indexes were calculated to determine whether the combinations were synergistic, indifferent or antagonistic.Results: All carbapenemase producers were resistant to the tested carbapenems, with most isolates showing MICs of carbapenems >32 mg/L. None of the combinations was antagonistic. For KPC producers, synergistic combinations were observed with imipenem/ertapenem (5/8 isolates), imipenem/doripenem (4/8), imipenem/doripenem (4/8), meropenem/doripenem (3/8) and ertapenem/doripenem (3/8), while no synergy was observed with meropenem/ertapenem. For OXA-48 producers, synergies were observed with imipenem/ertapenem and with imipenem/meropenem for both isolates tested. Notably, combining imipenem with a non-carbapenem β-lactam (cefalotin) did not give any synergistic result. No synergy was observed for all NDM-1 and NDM-1+OXA-48 producers. Time–kill assays confirmed most of the data obtained by chequerboard testing.Conclusions: The data strongly support the hypothesis that dual carbapenem combinations might be effective against serine-β-lactamase producers (KPC, OXA-48). The imipenem-containing combinations appeared to be the most efficient

In-vitro study of ISApl1-mediated mobilization of the colistin resistance gene mcr-1

The plasmid-mediated mcr-1 gene encodes a phosphoethanolamine transferase conferring resistance to polymyxins. The mcr-1 gene is associated with insertion sequence ISApl1 (IS30 family). In-vitro mobilization assays demonstrated the functionality of the composite transposon structure ISApl1-mcr-1-ISApl1. Transposition generated a 2-bp duplication and occurred in AT-rich DNA regions. This is the first report demonstrating the mobility of the mcr-1 gene by transposition

High prevalence of carbapenemase-producing enterobacteriaceae among hospitalized children in luanda, angola

This study aimed to evaluate the prevalence of carbapenemase-producing Enterobacteriaceae in Luanda, Angola. A total of 157 rectal samples were collected from children visiting a pediatric hospital in Luanda in March 2015. Fifty-seven imipenem-nonsusceptible enterobacterial isolates were recovered, most of which were non-clonally related. The blaOXA-181 (50/57) and blaNDM-1 (7/57) carbapenemase genes were identified. Notably, OXA-181-producing Escherichia coli isolates rarely coproduced extended-spectrum β-lactamases and consequently remained susceptible to broad-spectrum cephalosporins. The blaOXA-181 gene was always located on an IncX3 plasmid, while the blaNDM-1 gene was located on either IncFIA or IncA/C plasmids. The study identified a high prevalence of OXA-181 among hospitalized children in Angola

Co-production of MCR-1 and extended-spectrum β-lactamase in Escherichia coli recovered from urinary tract infections in Switzerland

International audienc

Genetic features of MCR-1-producing colistin-resistant Escherichia coli isolates in South Africa

A series of colistin-resistant Escherichia coli clinical isolates was recovered from hospitalized and community patients in South Africa. Seven clonally unrelated isolates harbored the mcr-1 gene located on different plasmid backbones. Two distinct plasmids were fully sequenced, and identical 2,600-bp-long DNA sequences defining a mcr-1 cassette were identified. Promoter sequences responsible for the expression of mcr-1, deduced from the precise identification of the +1 transcription start site for mcr- 1, were characterized

Antimicrobial activity of octenidine against multidrug-resistant Gram-negative pathogens

Multidrug-resistant (MR) Gram-negative (GN) pathogens pose a major and growing threat for healthcare systems, as therapy of infections is often limited due to the lack of available systemic antibiotics. Well-tolerated antiseptics, such as octenidine dihydrochloride (OCT), may be a very useful tool in infection control to reduce the dissemination of MRGN. This study aimed to investigate the bactericidal activity of OCT against international epidemic clones of MRGN. A set of five different species (Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Acinetobacter baumannii, and Pseudomonas aeruginosa) was studied to prove OCT efficacy without organic load, under “clean conditions” (0.3 g/L albumin) and under “dirty conditions” (3 g/L albumin + 3 mL/L defibrinated sheep blood), according to an official test norm (EN13727). We used five clonally unrelated isolates per species, including a susceptible wild-type strain, and four MRGN isolates, corresponding to either the 3MRGN or 4MRGN definition of multidrug resistance. A contact time of 1 min was fully effective for all isolates by using different OCT concentrations (0.01% and 0.05%), with a bacterial reduction factor of >5 log10 systematically observed. Growth kinetics were determined with two different wild-type strains (A. baumannii and K. pneumoniae), proving a time-dependent efficacy of OCT. These results highlight that OCT may be extremely useful to eradicate emerging highly resistant Gram-negative pathogens associated with nosocomial infections