The aim of this study was to optimize the extraction of free and bound phenolic acids from Chilean Cristalino corn by response surface methodology based on the total phenolic contents (TPCs) and the ...2,2-diphenyl-1-picrylhydrazyl scavenging-linked antioxidant capacity (AC) as response variables. Central Composite 2
2
+ axial points experimental designs were applied. The best extraction conditions for the free and bound phenolic fraction were acetone 69% in water for 63 min and a hydrolysis with 3 M NaOH for 90 min, respectively. Under these conditions, TPCs in free and bound forms were 59.9 ± 0.7 and 172.9 ± 1.1 mg gallic acid equivalents/100 g, respectively. Further, AC found in free and bound fractions was 186 ± 3 and 694.5 ± 3.3 µmol Trolox equivalents/100 g, respectively. The experimental and predicted values of TPC and AC were similar in case of free phenolic fraction indicating that the model was adequate and reproducible. Major phenolic acids were found in the bound fraction and were ferulic and p-coumaric acids.
Abstract
Background
Carbapenem-resistant Enterobacterales (CRE) are a major public health threat, largely due to the presence of carbapenemases, which are globally disseminated in mobile genetic ...elements. The emergence of CRE carrying multiple carbapenemases has been reported in several countries, particularly after the COVID-19 pandemic. In this study, we report the emergence of dual-producing CRE (DP-CRE) in Chile and provide a phenotipic and genomic characterization using whole-genome sequencing (WGS).
Methods
We evaluated the presence of carbapenemase in a total of 1367 CRE isolates recovered from invasive infections in 11 healthcare centers since 2018. Among them, 9 DP-CRE were detected and included in this report. Antimicrobial susceptibility was tested by broth microdilution and disk diffusion methods (CLSI, 2023), while blaKPC, blaVIM, blaIMP and blaNDM genes were detected by PCR. WGS was carried out using short and long reads (Illumina and Oxford Nanopore) and hybrid assemblies were performed.
Results
All 9 DP-CRE identified were recovered between November 2021 and June 2022 from 3 healthcare centers of a single city. In terms of species, 6 were identified as E. coli, one isolate of K. pneumoniae, one K. oxytoca and one C. freundii. All DP-CRE identified carried the combination of blaKPC and blaNDM. Genomic analyses confirmed all but one isolate carried blaKPC-2 and blaNDM-7. The remaining genome belonged to a K. pneumoniae that harboured blaKPC-3 and blaNDM-7. All 9 isolates exhibited resistance to all β-lactams, including carbapenems, aztreonam (ATM), cephalosporins and β-lactam/β-lactamase inhibators. Cefiderocol (FDC) was the only compound active against all the isolates. Also, all the DP-CRE became susceptible to ATM when combined with ceftazidime/avibactam (CZA). Hybrid assemblies revealed that blaKPC and blaNDM were harboured on independent plasmids (∼58,900 bp and ∼41,100 bp, respectively) as shown in Figure 1.
Conclusion
To the best of our knowledge, this is the first report of the emergence of DP-CRE in Chile after COVID-19 pandemic. Our results highlight the relevance of active surveillance of multidrug-resistance pathogens. FDC and CZA/ATM were the only compounds that remained active in vitro against these pathogens.
Disclosures
All Authors: No reported disclosures
Abstract
Background
Carbapenem resistance (CR) in Klebsiella pneumoniae is most frequently mediated by the production of carbapenemases. However, non-carbapenemase-producing K. pneumoniae ...(non-CP-Kpn) have been well documented. Overexpression of narrow β-lactamases can play an important role in the development of CR in the absence of carbapenemases. Here, we investigated the role of avibactam, a potent β-lactamase inhibitor, in preventing the in vitro development of CR in a non-CP-Kpn.
Methods
We used SCL-1, a non-CP-Kpn strain recovered from the bloodstream of a patient that developed CR in vivo during treatment with imipenem (IMI). SCL-1 was exposed to serial passages of increasing concentrations of IMI alone 0.25-16 μg/mL or in combination with avibactam (IMI-AVI) during 8 days. In the case of IMI-AVI, the concentration of AVI was fixed at 4 μg/mL. Evolution assays were performed in triplicate and considered 3 independent evolutionary lines (ELs). MICs at each time-point were measured to IMI and IMI-AVI by broth microdilution as per CLSI. Growth curves of SCL-1 and evolved strains were performed to assess fitness. The expression levels of narrow spectrum β-lactamases blaOXA-1,blaOXA-10, and of the ESBL blaCTX-M-15 were measured by RT-qPCR.
Results
In vitro exposure to IMI led to CR, with the MICs increasing from 0.5 μg/mL to 8 μg/mL in all 3 ELs. In contrast, all ELs exposed to IMI-AVI remained fully susceptible to IMI after 8 days, with a final MIC of 1 μg/mL. In addition, the MIC to IMI of the evolved, IMI-resistant strains, in the presence of AVI (4 μg/mL) dropped from 8 to 1 μg/mL. Growth curves revealed that IMI-resistant strains evolved in IMI alone exhibited a growth defect as compared to both SCL-1 and the susceptible strains evolved in IMI-AVI. Finally, compared to the SCL-1, the expression level of blaOXA-1 was significantly increased (p< 0.05) in all evolved isolates that developed IMI resistance (MIC=8 μg/mL). No significant changes were observed in the expression of blaOXA-10 and blaCTX-M-15 (Figure 1).Figure 1.RT-qPCR analysis of β-lactamase gene transcript levels for SCL-1 and evolutive lines (A and B). Data shown are individual data points with mean±SD superimposed.
Conclusion
Our findings suggest that the addition of AVI can prevent the in vitro development of IMI resistance in non-CP-Kpn. Our results have important implications for the clinical use of AVI as a strategy to combat CR in non-CP-Kpn infections.
Disclosures
All Authors: No reported disclosures
Abstract
Background
Vancomycin-resistant enterococci has increased globally in recent decades, with Enterococcus faecium (VREfm) being the most prevalent species. Although the prevalence of VREfm in ...Chile is high (∼70%), its molecular epidemiology is not well-described. Here, we used whole genome sequencing (WGS) to characterize the circulating lineages of VREfm in Chile.
VRE= Vancomycin resistant Enterococcus faecium, SD=Standard deviation, IQR=in˝ter-quartile range; ¥ comorbidities included diagnoses apart from the primary cause for admission such as hypertension, chronic kidney disease and coronary artery disease; *Chi-square or Fisher´s exact were used for categorial variables; T-test for continues variables; P value<0.05 was considered significant.•
Methods
A total of 96 invasive clinical VREfm isolates causing invasive infections were collected from 96 patients admitted to 3 hospitals in Chile as part of an ongoing surveillance program (2018 – 2022). Clinical data including demographics, source of infection, and hospital outcomes were collected. All isolates were subjected to WGS on an Illumina platform. After assembly, in silico MLST and resistome were determined. Further, 5 representative strains were sequenced with Oxford Nanopore Technology (ONT) to further characterize the location of the van gene cluster.
Results
The mean age of the cohort was 62 years, with 61% of males and a mean Charlson Comorbidity Score of 3. All isolates were resistant to vancomycin, ampicillin and ciprofloxacin and remained susceptible to linezolid. Resistance to teicoplanin (16%), high-level resistance to gentamicin (48%) and streptomycin (20%) was also observed. A total of 75 VREfm harbored vanB, with the most common STs being ST17 (23%) and ST656 (25%). Only 7 VREfm isolates carried vanA, 43% of which corresponded to ST17. Surprisingly, 14 VREfm simultaneously carried vanA and vanB (vanA/vanB), most of them belonging to ST233 (50%) or ST2137 (36%). For the VREfm vanA/vanB isolates, the vanB cluster was located on the chromosome, while the vanA gene cluster was harbored on a plasmid (ca. 45Mb) which also contained ermB. A summary of the clinical characteristics of the cohort is shown in Table 1.
Conclusion
vanB was the most frequently observed genotype in Chile, with ST17 and ST656 accounting for most isolates. Importantly, a substantial proportion of VREfm carried both vanA and vanB clusters in Chile, which was mainly observed in two different genomic lineages (ST233 and ST2137). Active surveillance of VREfm is essential to monitor the epidemiology of this critical pathogen in South America.
Disclosures
William R. Miller, M.D., Merck: Grant/Research Support|UpToDate: Honoraria
The global dissemination of methicillin-resistant Staphylococcus aureus (MRSA) is associated with the emergence and establishment of clones in specific geographic areas. The Chilean-Cordobes clone ...(ChC) (ST5-SCC
I) has been the predominant MRSA clone in Chile since its first description in 1998, despite the report of other emerging MRSA clones in recent years. Here, we characterize the evolutionary history of MRSA from 2000 to 2016 in a Chilean tertiary health care center using phylogenomic analyses. We sequenced 469 MRSA isolates collected between 2000 and 2016. We evaluated the temporal trends of the circulating clones and performed a phylogenomic reconstruction to characterize the clonal dynamics. We found a significant increase in the diversity and richness of sequence types (STs; Spearman
= 0.8748,
< 0.0001) with a Shannon diversity index increasing from 0.221 in the year 2000 to 1.33 in 2016, and an effective diversity (Hill number; q = 2) increasing from 1.12 to 2.71. The temporal trend analysis revealed that in the period 2000 to 2003 most of the isolates (94.2%;
= 98) belonged to the ChC clone. However, since then, the frequency of the ChC clone has decreased over time, accounting for 52% of the collection in the 2013 to 2016 period. This decline was accompanied by the rise of two emerging MRSA lineages, ST105-SCC
II and ST72-SCC
VI. In conclusion, the ChC clone remains the most frequent MRSA lineage, but this lineage is gradually being replaced by several emerging clones, the most important of which is clone ST105-SCC
II. To the best of our knowledge, this is the largest study of MRSA clonal dynamics performed in South America.
Methicillin-resistant Staphylococcus aureus (MRSA) is a major public health pathogen that disseminates through the emergence of successful dominant clones in specific geographic regions. Knowledge of the dissemination and molecular epidemiology of MRSA in Latin America is scarce and is largely based on small studies or more limited typing techniques that lack the resolution to represent an accurate description of the genomic landscape. We used whole-genome sequencing to study 469 MRSA isolates collected between 2000 and 2016 in Chile providing the largest and most detailed study of clonal dynamics of MRSA in South America to date. We found a significant increase in the diversity of MRSA clones circulating over the 17-year study period. Additionally, we describe the emergence of two novel clones (ST105-SCC
II and ST72-SCC
VI), which have been gradually increasing in frequency over time. Our results drastically improve our understanding of the dissemination and update our knowledge about MRSA in Latin America.
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