Molecular Characterization of the Convergent Carbapenem-Resistant and Hypervirulent Klebsiella pneumoniae Strain K1-ST23, Collected in Chile during the COVID-19 Pandemic.

The aim of this study was to investigate the genomic features of a carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) isolate (K-2157) collected in Chile. Antibiotic susceptibility was determined using the disk diffusion and broth microdilution methods. Whole-genome sequencing (WGS) and hybrid assembly were performed, using data generated on the Illumina and Nanopore platforms.

Novel Megaplasmid Driving NDM-1-Mediated Carbapenem Resistance in ST1588 in South America.

Carbapenem-resistant Enterobacterales (CRE) is a critical public health problem in South America, where the prevalence of NDM metallo-betalactamases has increased substantially in recent years. In this study, we used whole genome sequencing to characterize a multidrug-resistant (MDR) (UCO-361 strain) clinical isolate from a teaching hospital in Chile. Using long-read (Nanopore) and short-read (Illumina) sequence data, we identified a novel un-typeable megaplasmid (314,976 kb, pNDM-1_UCO-361) carrying the carbapenem resistance gene within a Tn transposon.

Phenotypic and Genotypic Characterization of Macrolide, Lincosamide and Streptogramin B Resistance among Clinical Methicillin-Resistant Isolates in Chile.

Macrolides, lincosamides, and type B streptogramins (MLSB) are important therapeutic options to treat methicillin-resistant Staphylococcus aureus (MRSA) infections; however, resistance to these antibiotics has been emerging. In Chile, data on the MLSB resistance phenotypes are scarce in both community-(CA) and hospital-acquired (HA) MRSA isolates. Antimicrobial susceptibility to MLSB was determined for sixty-eight non-repetitive isolates of each HA-(32) and CA-MRSA (36).

In vitro antibacterial activity of endodontic bioceramic materials against dual and multispecies aerobic-anaerobic biofilm models.

The aim of this in vitro study was to evaluate the antibacterial activity of calcium silicate repair cements and sealers against a dual-species planktonic aerobic model with different aging times and the ability to inhibit the formation of a mature 21-day-old multispecies anaerobic biofilm. The antibacterial activity of ProRoot MTA, MTA Angelus, Biodentine, BioRoot RCS and TotalFill BC sealer against a dual-species aerobic planktonic model, as well as measuring how materials were affected by aging, was evaluated using the Modified Direct Contact Test. Subsequently, the ability to inhibit the formation of a mature multispecies anaerobic biofilm was evaluated using scanning electron microscopy complemented with confocal laser scanning microscopy.

Antibacterial Activity of Copper Nanoparticles (CuNPs) against a Resistant Calcium Hydroxide Multispecies Endodontic Biofilm.

Endodontic treatment reduces the amount of bacteria by using antimicrobial agents to favor healing. However, disinfecting all of the canal system is difficult due to its anatomical complexity and may result in endodontic failure. Copper nanoparticles have antimicrobial activity against diverse microorganisms, especially to resistant strains, and offer a potential alternative for disinfection during endodontic therapy.

[Microbiological air quality in a Community Family Health Center of Talcahuano, Biobío Region, Chile].

Background: Indoor air quality in health centers is essential to protect the health of people. In Chile, the Community Family Health Centers (CECOSF) are places with large attendance of people, favoring the dissemination of microorganisms, and there are no reports of the microbial air loading these health centers.

Aim: To evaluate the microbiological indoor air quality in CECOSF-Centinela in Talcahuano, Biobío Region.

Molecular characterization and antibacterial activity of oral antibiotics and copper nanoparticles against endodontic pathogens commonly related to health care-associated infections.

Objective: To carry out molecular characterization and determine the antibacterial activity of oral antibiotics and copper nanoparticles (Cu-NPs) against endodontic strains isolated from persistent infections.

Materials And Methods: Root canal samples from 24 teeth in different patients with persistent endodontic infections were obtained. The isolated strains were identified by biochemical tests and 16S rDNA sequencing.

[Carbapenemases produced by Carbapenem-resistant Pseudomonas aeruginosa isolated from hospitals in Chile].

Background: Carbapenem resistance mediated by carbapenemases in Pseudomonas aeruginosa is an important mechanism; however, loss of porin OprD remains as the most frequent.

Aim: To determine the proportion of P. aeruginosa isolates, resistant to imipenem and/or meropenem, producing carbapenemases, the type of enzyme produced and the genetic relationship between the isolates.

Antibacterial and cytotoxic evaluation of copper and zinc oxide nanoparticles as a potential disinfectant material of connections in implant provisional abutments: An in-vitro study.

Objective: This study evaluates the antibacterial activity against mono and multispecies bacterial models and the cytotoxic effects of zinc oxide and copper nanoparticles(ZnO-NPs/Cu-NPs) in cell cultures of human gingival fibroblasts(HGFs).

Design: The antibacterial activities of ZnO-NPs and Cu-NPs against 4 bacteria species were tested according to their minimum inhibitory concentrations(MICs) and against mature multispecies anaerobic model by spectral confocal laser scanning microscopy. The viabilities and cytotoxic effects of ZnO-NPs and Cu-NPs to HGFs cell cultures were tested by MTT, LDH assays, production of ROS, and the activation of caspase-3.

Copper-Polyurethane Composite Materials: Particle Size Effect on the Physical-Chemical and Antibacterial Properties.

In this work, thermoplastic polyurethane (TPU) composites incorporated with 1.0 wt% Cu particles were synthesized by the melt blending method. The effect of the incorporated copper particle size on the antibacterial, thermal, rheological, and mechanical properties of TPU was investigated.

Colistin Heteroresistance among Extended Spectrum β-lactamases-Producing .

Colistin-heteroresistant (CST-HR) Enterobacterales isolates have been identified recently, challenging the clinical laboratories since routine susceptibility tests fail to detect this phenotype. In this work we describe the first CST-HR phenotype in extended-spectrum β-lactamase (ESBL)-producing isolates in South America. Additionally, we determine the genomic mechanisms of colistin heteroresistance in these strains.

Phenotypic and Genotypic Antimicrobial Resistance in Non-O157 Shiga Toxin-Producing Isolated From Cattle and Swine in Chile.

Non-O157 Shiga toxin-producing (STEC) is a zoonotic pathogen that causes bloody diarrhea and hemolytic-uremic syndrome in humans, and a major cause of foodborne disease. Despite antibiotic treatment of STEC infections in humans is not recommended, the presence of antimicrobial-resistant bacteria in animals and food constitutes a risk to public health, as the pool of genes from which pathogenic bacteria can acquire antibiotic resistance has increased. Additionally, in Chile there is no information on the antimicrobial resistance of this pathogen in livestock.

Antibiotic resistance in bacterial isolates from freshwater samples in Fildes Peninsula, King George Island, Antarctica.

Anthropic activity in Antarctica has been increasing considerably in recent years, which could have an important impact on the local microbiota affecting multiple features, including the bacterial resistome. As such, our study focused on determining the antibiotic-resistance patterns and antibiotic-resistance genes of bacteria recovered from freshwater samples collected in areas of Antarctica under different degrees of human influence. Aerobic heterotrophic bacteria were subjected to antibiotic susceptibility testing and PCR.

Draft genome sequence of a multidrug-resistant KPC-2 and SRT-2 co-producing Serratia marcescens strain isolated from a hospitalised patient in Chile.

Objectives: Serratia marcescens is a neglected opportunistic pathogen of public-health concern, especially due to its antimicrobial resistance features. Here we report the draft genome sequence of the first KPC-2 and SRT-2 co-producing S. marcescens strain (UCO-366) recovered from a catheter tip culture of a hospitalised patient in Santiago, Chile, in 2014.

On-Farm Surfaces in Contact with Milk: The Role of -Containing Biofilms for Udder Health and Milk Quality.

is a Gram-positive bacterium that causes intramammary infections and bulk tank milk (BTM) contamination in dairy operations around the world in spite of on-farm application of preventive measures. The study was conducted on a 30-cow dairy farm in the Ñuble Region of Chile. For BTM culture and somatic cell count (SCC) analysis, three consecutive BTM samples were collected.

Occurrence of Transferable Integrons and and Genes Among Sulfonamide-and/or Trimethoprim-Resistant Bacteria Isolated From Chilean Salmonid Farms.

Salmon farming industry in Chile currently uses a significant quantity of antimicrobials to control bacterial pathologies. The main aims of this study were to investigate the presence of transferable sulfonamide- and trimethoprim-resistance genes, and , and their association with integrons among bacteria associated to Chilean salmon farming. For this purpose, 91 Gram-negative strains resistant to sulfisoxazole and/or trimethoprim recovered from various sources of seven Chilean salmonid farms and mainly identified as belonging to the genus (81.

Evolutionary dynamics of carbapenem-resistant Acinetobacter baumannii circulating in Chilean hospitals.

We analyze the evolutionary dynamics of ninety carbapenem-resistant Acinetobacter baumannii (CRAB) isolates collected between 1990 and 2015 in Chile. CRAB were identified at first in an isolate collected in 2005, which harbored the ISAba1-bla arrangement. Later, OXA-58- and OXA-23-producing A.

Introduction of NDM-1 and OXA-370 from Brazil into Chile in strains of Klebsiella pneumoniae isolated from a single patient.

Carbapenemase-producing Enterobacteriaceae have rapidly disseminated worldwide and can colonize patients in healthcare centers. As in Chile the first isolations of NDM-1 and OXA-370 carbapenemases were related with a patient arriving from Brazil, the genetic relatedness of Klebsiella pneumoniae strains producers of these enzymes and isolated in both countries was assessed. PFGE analyses revealed that the isolates were clonally related, illustrating how travel contributes to the spread of multidrug-resistant microorganisms.

Genomic Diversity of Isolated from Clinical and Non-Clinical Samples in Chile.

is the causative agent of listeriosis, which is an uncommon but severe infection associated with high mortality rates in humans especially in high-risk groups. This bacterium survives a variety of stress conditions (e.g.

[Molecular basis of methicillin-resistance in Staphylococcus aureus].

Staphylococcus aureus isolates resistant to several antimicrobials have been gradually emerged since the beginning of the antibiotic era. Consequently, the first isolation of methicillin-resistant S. aureus occurred in 1960, which was described a few years later in Chile.