Colistin resistance beyond carbapenems: molecular epidemiology of multi-drug resistant Klebsiella pneumoniae from an Italian hospital

Purpose: Multidrug resistant (MDR) Klebsiella pneumoniae (Kp) is a worldwide concern worsened by colistin resistance emergence. In this study, molecular epidemiology of clinical MDR Kp strains is described, assessing clonal relationships and resistance genes profiles. Prevalence of Extended-Spectrum Beta-Lactamase (ESBL) blaCTX-M, blaTEM and blaSHV genes was evaluated, as well as that associated to carbapenems (blaKPC, blaGES, blaVIM, blaIMP, blaNDM, blaOXA-48) and colistin resistance (mcr-1,2,3,4 and mgrB). Methods & Materials: Twenty-six Kp cultures were collected from âŁœA.Cardarelli⣞ hospital in Molise Region (Central Italy), 57.7% from Intensive Care Unit (ICU). The Minimum Inhibitory Concentration (MIC) was assessed by BD Phoenixâ„¢. Genotyping was achieved through Pulsed-Field Gel Electrophoresis (PFGE) withXbaI and MultiLocus Sequence Typing (MLST). PCRs for resistance genes detection and mgrB sequencing were performed. Results: Most (n = 20, 77%) strains were carbapenems resistant (imipenem, meropenem, ertapenem), and 53% (n = 14) to colistin. A higher prevalence of blaKPC (100%) and blaSHV (96.2%) was found compared with blaTEM (88.5%), blaVIM (69.0%) and blaCTX-M (7.7%). While none colistin-resistant (col-R) strain carried mcr-1,2,3,4 variants, 42.8% (n = 6) had an Insertion Sequence (IS) in mgrB, identified as IS5-like (5/14, 36%) and ISKpn14 (1/14, 7%). The prevalent Sequence Type was ST512 (50%), followed by ST101 (38.5%) and ST307 (11.5%). PFGE detected 12 clusters and 18 pulsotypes (95% similarity), and was more discriminating than MLST (Simpson’s Index 95%vs 61%). An ICU outbreak, during November 2014-January 2015, included five ST512 strains, blaTEM/blaSHV/blaVIM/blaKPC positive, and col-R due to mgrB IS5-like. Conclusion: Molecular epidemiology study identified an outbreak caused by poor compliance with hygienic standards because of reduced personnel during Christmas holidays. Although ST258 is the most prevalent in Italy, half strains were typed as ST512 that represents its monoallelic variant. Our results confirm the endemic blaKPC distribution and blaTEM/blaSHV as the prevalent ESBLs in Kp hospital outbreaks. According to epidemiological data, plasmid mcr variants were not found in col-R strains. Conversely, IS elements prevalence in mgrB explain resistance in about half col-R strains, and was in line with Italian data. Further investigations are needed to identify mgrB mutations in IS negative col-R strains

Recent advances in variable metric first-order methods

Minimization problems often occur in modeling phenomena dealing with real-life applications that nowadays handle large-scale data and require real-time solutions. For these reasons, among all possible iterative schemes, first-order algorithms represent a powerful tool in solving such optimization problems since they admit a relatively simple implementation and avoid onerous computations during the iterations. On the other hand, a well known drawback of these methods is a possible poor convergence rate, especially showed when an high accurate solution is required. Consequently, the acceleration of first-order approaches is a very discussed field which has experienced several efforts from many researchers in the last decades. The possibility of considering a variable underlying metric changing at each iteration and aimed to catch local properties of the starting problem has been proved to be effective in speeding up first-order methods. In this work we deeply analyze a possible way to include a variable metric in first-order methods for the minimization of a functional which can be expressed as the sum of a differentiable term and a nondifferentiable one. Particularly, the strategy discussed can be realized by means of a suitable sequence of symmetric and positive definite matrices belonging to a compact set, together with an Armijo-like linesearch procedure to select the steplength along the descent direction ensuring a sufficient decrease of the objective function

Comparison of NF-κB from the protists Capsaspora owczarzaki and Acanthoeca spectabilis reveals extensive evolutionary diversification of this transcription factor

AbstractWe provide a functional characterization of transcription factor NF-κB in protists and provide information about the evolution and diversification of this biologically important protein. We characterized NF-κB in two protists using phylogenetic, cellular, and biochemical techniques. NF-κB of the holozoan Capsaspora owczarzaki (Co) has an N-terminal DNA-binding domain and a C-terminal Ankyrin repeat (ANK) domain, and its DNA-binding specificity is more similar to metazoan NF-κB proteins than to Rel proteins. Removal of the ANK domain allows Co-NF-κB to enter the nucleus, bind DNA, and activate transcription. However, C-terminal processing of Co-NF-κB is not induced by IκB kinases in human cells. Overexpressed Co-NF-κB localizes to the cytoplasm in Co cells. Co-NF-κB mRNA and DNA-binding levels differ across three Capsaspora life stages. RNA-sequencing and GO analyses identify possible gene targets of Co-NF-κB. Three NF-κB-like proteins from the choanoflagellate Acanthoeca spectabilis (As) contain conserved Rel Homology domain sequences, but lack C-terminal ANK repeats. All three As-NF-κB proteins constitutively enter the nucleus of cells, but differ in their DNA-binding abilities, transcriptional activation activities, and dimerization properties. These results provide a basis for understanding the evolutionary origins of this key transcription factor and could have implications for the origins of regulated immunity in higher taxa.</jats:p