Increased Levels Of Resistance Research Articles

Pro-197-Ser mutation combinations in acetolactate synthase (ALS) homoeologous genes affect ALS inhibitor herbicide resistance levels in Monochoria korsakowii.

Monochoria korsakowii is a common broadleaf weed found in rice (Oryza sativa) fields. Acetolactate synthase (ALS) inhibitor herbicides are commonly used to control broadleaf weeds in rice fields. However, prolonged herbicide use has exacerbated resistance issues. In this study, we evaluated the resistance to ALS inhibitors in populations where the same mutation occurred separately and simultaneously in the two ALS homoeologous genes (ALS1 and ALS2) and investigated the resistance mechanisms in M. korsakowii. Monochoria korsakowii exhibited high resistance to bensulfuron-methyl, low resistance to penoxsulam, and sensitivity to imazethapyr. Three resistant populations were identified: M-1 and M-2, which independently evolved the Pro-197-Ser mutation in ALS1 and ALS2, respectively, and M-3, which harbored this mutation in both ALS1 and ALS2. The sensitivity of ALS isolated from these populations to herbicide inhibition corresponded to the whole-plant resistance levels. Subsequently, we cloned and transformed Pro-197-Ser-mutated ALS1 and ALS2 into Arabidopsis thaliana. The resistance of homozygous A. thaliana to bensulfuron-methyl and penoxsulam aligned with bioassay trends. Furthermore, we measured the ploidy, relative expression, and copy number of ALS1 and ALS2, and found no significant differences, suggesting that the evolution of resistance was primarily attributed to the Pro-197-Ser mutation. Finally, we developed a derived cleaved amplified polymorphic sequence marker for detecting Pro-197-Ser mutation in ALS. The same mutation occurring separately in homoeologous genes resulted in similar resistance levels, whereas simultaneous mutations in homoeologous genes led to increased resistance levels. © 2024 Society of Chemical Industry.

The V410L kdr allele in the VGSC confers higher levels of field resistance to permethrin in urban mosquito populations of Aedes aegypti (L.).

Females of Aedes aegypti transmit emerging arboviruses including Zika, dengue, yellow fever, and chikungunya. Control of these adult mosquitoes heavily relies on synthetic insecticides, including pyrethroids. However, insecticide resistance development in populations poses a significant challenge to vector control, particularly from knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC), the target of pyrethroids. This study investigated the field efficacy of Permanone, a pyrethroid-based insecticide, against Ae. aegypti by assessing the impact of three common kdr mutations (V410L, V1016I, F1534C) on mosquito survival under a real operational mosquito control scenario, by quantifying the pesticide delivered in the field. Field cage tests (FCTs) were conducted while conducting a realistic mosquito control application. Female mosquitoes from six operational areas from Harris County, TX, USA were exposed to Permanone delivered with a handheld sprayer. Permanone deposited near the cages was estimated from aluminum boats placed in the field during FCTs using gas chromatography-mass spectrometry (GC-MS). Mortality rates were recorded, and individual mosquitoes were genotyped for kdr mutations. A probit regression model was used to analyze the factors influencing mosquito survivorship. As the distance from the application source route increased, the amount of Permanone deposited decreased, resulting in higher survivorship frequency of Ae. aegypti females with the triple-resistant kdr genotype (LL/II/CC). The L allele at the 410-site significantly contributed to an increased resistance level when co-occurring with other kdr mutations. This study linked the survival probabilities of mosquitoes with different kdr genotypes, and the amount of pesticide they received in the field. Pesticide quantification, control efficacy results and genotyping allowed us to empirically determine the impact of genotypic resistance on vector control in the field. © 2024 Society of Chemical Industry.

Comparison of genotypic features between two groups of antibiotic resistant Klebsiella pneumoniae clinical isolates obtained before and after the COVID-19 pandemic from Egypt

Klebsiella pneumoniae is a common pathogen capable of causing a wide range of infections. Antibiotic resistance complicates treatment of these infections significantly. We are comparing resistance levels and genotypes among two collections of K. pneumoniae clinical isolates from Alexandria Main University Hospital (AMUH). We used disc diffusion and Minimum Inhibitory Concentration (MIC) by microbroth dilution to assess resistance levels and performed whole genome sequencing (WGS) to describe multilocus sequence types (MLST) and resistance gene presence. Among a collection of 56 K. pneumoniae clinical isolates (19 from 2019 to 37 from 2021), multidrug resistance (MDR) was 33% and 10%, extended drug resistance (XDR) was 24% and 46% and pan-drug resistance (PDR) was 43% and 43%, respectively. We identified 15 MLST STs including two novel types (ST-6118 and ST-6119 ). ST-101 and ST-383 were common between the two collections; ST-101 was the most common genotype in 2019 (28.6%) and ST-147 was most common in 2021 (25%). Ampicillin/sulbactam, amikacin, cefepime, ceftriaxone and ertapenem MICs were significantly higher in 2021. Prevalence of aph(3’) – Ia, aph(3’)-VI, mphA was significantly higher in 2021. The increasing resistance levels and the persistence of some MDR/XDR genotypes is concerning. Understanding mechanisms of resistance will inform infection control and antimicrobial stewardship plans to prevent evolution and spread of XDR and PDR strains.

Physiological characteristics of microbial transformation during chronic exposure to triclosan as a hydrophobic antibacterial agent and post-antibacterial cessation

ABSTRACT The use of triclosan (TCS) in hygiene products and other materials raises concerns about increased antimicrobial resistance. Research has shown that bacteria can develop resistance to TCS, but there is limited understanding of how bacterial behavior changes after TCS is removed. This study focuses on how bacteria adapt to prolonged TCS exposure and recover after its removal. It aims to improve practices for using antimicrobial agents in sanitation products and emphasize the importance of understanding exposure and recovery times to prevent resistance development. The study evaluated the bacterial behavior, determining the minimum inhibition concentration of TCS that 90% of Escherichia coli was inhibited (MIC90), predicting bacterial growth kinetics using the Modified Gompertz model and membrane permeability recovery. Bacteria showed a significant increase in resistance levels during exposure, with the MIC90 steadily increasing over 30 days and peaking at 16 mg/L. Upon removal, there was a notable 2-fold decrease in resistance after 10 days of reculturing in a non-chemical medium, likely due to restructuring changes in cell membranes. Therefore, in addition to reducing the occurrence of antibacterial agents in the environment, advanced treatments for eliminating antibacterial resistance should be performed on wastewater before being discharged into the environment.

Barley yellow dwarf virus in winter barley: Control in light of resistance issues and loss of neonicotinoid insecticides

AbstractBarley yellow dwarf virus (BYDV) is the most widespread viral disease of cereal crops vectored by aphids, causing stunting of the crop and significant yield loss. Management recommendations for autumn sown cereals has centred on the timely control of aphid vectors, particularly their management before the crop has reached Growth Stage 31 (stem elongation). In recent years two separate but related issues have emerged, (i) the detection of pyrethroid resistance in a single Sitobion avenae SA3 clone and (ii) the withdrawal of neonicotinoid insecticide seed dressing; widely used to manage aphids in the early development of cereal crops. A series of replicated field studies were conducted from 2016 to 2019 to ascertain if the pyrethroid insecticide is still effective in light of the SA3 clones' presence in aphid populations and if withdrawal of neonicotinoid seed dressings has negatively affected aphid management. Both disease levels and yields confirmed that the neonicotinoid, clothianidin, applied as a seed treatment significantly contributed to the management of BYDV in the different trials investigated. Results of this study demonstrate application of a foliar (lambda‐cyhalothrin or a sulfoxaflor) insecticide has a significant positive impact on yield. Foliar pyrethroid insecticides were as effective in protecting yield from BYDV as the neonicotinoid seed treatments. In the absence of neonicotinoid seed dressing, alternative insecticides still offer protection for winter barley crops against the aphid vectors of BYDV and associated yield loss. Furthermore, the presence of a pyrethroid resistant Sitobion avenae SA3 clone had no observable impact on field efficacy of the pyrethroid insecticide, lambda‐cyhalothrin in these trials. However, this needs continuous monitoring because of potential further increases in resistance levels or emergence of additional resistance mechanisms, which could render pyrethroid insecticides ineffective.

Molecular Characterization of Carbapenem and Colistin Resistance in Klebsiella pneumoniae Isolates Obtained from Clinical Samples at a University Hospital Center in Algeria.

The current study aimed to determine the molecular mechanisms of carbapenem and colistin resistance among the clinical isolates of Klebsiella pneumoniae from hospitalized patients admitted to a university hospital in Eastern Algeria. In total, 124 non-duplicate isolates of K. pneumoniae were collected from September 2018 to April 2019. Bacterial identification was performed using MALDI-TOF MS. The presence of extended spectrum β-lactamase (ESBL) genes, carbapenemase genes, chromosomal mutation and mcr genes in colistin-resistant K. pneumoniae were evaluated by PCR. ESBLs represented a rate of 49.1% and harbored blaCTX-M, blaTEM and blaSHV genes. Concerning carbapenems, 12 strains (9.6%) were resistant to ertapenem (MIC: 1-32 μg/mL), of which one strain (0.8%) was also resistant to imipenem (MIC: 32 μg/mL). Among these strains, nine (75%) harbored blaOXA-48 gene. Seven strains (5.6%) expressed resistance to colistin (MIC: 2-32 μg/mL), of which two harbored mcr-8 and mgrB genes simultaneously. The existence of a double resistance to colistin in the same strain is new in Algeria, and this could raise concerns about the increase in levels of resistance to this antibiotic (MIC: 32 μg/mL). The mgrB gene alone was observed in five isolates (71.4%), including two strains harboring blaOXA-48. This is the first report revealing the presence of K. pneumoniae strains carrying the blaOXA-48 gene as well as a mutation in the mgrB gene. Large-scale surveillance and effective infection control measures are also urgently needed to prevent the outbreak of various carbapenem- and colistin-resistant isolates.

Impact of different mutations on Kelch13 protein levels, ART resistance, and fitness cost in Plasmodium falciparum parasites.

Parasites with lowered sensitivity to artemisinin-based drugs are becoming widespread. However, even in these "resistant" parasites not all parasites survive treatment. We found that the proportion of surviving parasites correlates with the fitness cost of resistance-inducing mutations which might indicate that the growth disadvantages prevents resistance levels where all parasites survive treatment. We also found that combining two common resistance mutations did not increase resistance levels. However, selection through repeated ART-exposure did, even-though the known resistance genes, including k13, were not further altered, suggesting other causes of increased resistance. We also observed a disproportionally high fitness cost of a resistance mutation in resistance gene ubp1. Such high fitness costs may explain why mutations in ubp1 and other genes functioning in the same pathway as k13 are rare. This highlights that k13 mutations are unique in their ability to cause resistance at a comparably low fitness cost.

Reevaluation of Sensitivity of Monilinia fructicola Isolates to the DMI Fungicide Propiconazole in the Southeastern United States and Investigation of the Genetic Element Mona.

Sterol demethylation inhibitor (DMI) fungicides continue to be essential components for the control of brown rot of peach caused by Monilinia fructicola in the United States and worldwide. In the southeastern United States, resistance to DMIs had been associated with overexpression of the cytochrome P450 14α-demethylase gene MfCYP51 as well as the genetic element Mona, a 65 bp in length nucleotide sequence located upstream of MfCYP51 in resistant isolates. About 20 years after the first survey, we reevaluated sensitivity of M. fructicola from South Carolina and Georgia to propiconazole and also evaluated isolates from Alabama for the first time. A total of 238 M. fructicola isolates were collected from various commercial and two experimental orchards, and sensitivity to propiconazole was determined based on a discriminatory dose of 0.3 μg/ml. Results indicated 16.2, 89.2, and 72.4% of isolates from Alabama, Georgia, and South Carolina, respectively, were resistant to propiconazole. The detection of resistance in Alabama is the first report for the state. All resistant isolates contained Mona, but it was absent from most sensitive isolates. It was unclear if the resistance frequency had increased in South Carolina and Georgia. However, the resistance levels (as assessed by the isolate frequency in discriminatory dose-based relative growth categories) did not change notably, and no evidence of other resistance genotypes was found. Analysis of the upstream MfCYP51 gene region in the resistant isolate CF010 revealed an insertion sequence described for the first time in this report. Our study suggests that current fungicide spray programs have been effective against increasing resistance levels in populations of M. fructicola and suppressing development of new resistant genotypes of the pathogen.

Bacterial Etiology and Antibiotic Susceptibility Profile in Neonatal Sepsis

Background: Sepsis is a leading cause of morbidity and mortality in neonates. Objectives: This study aimed to investigate the bacterial profile and antibiotic sensitivity in infants with sepsis. Methods: This cross-sectional study was conducted on 90 neonates with sepsis admitted to the neonatal intensive care unit of Namazi Hospital, a tertiary-level hospital, in Shiraz, Iran, from 2020 to 2021. Demographic and clinical data including gestational age, previous diseases, maternal infectious, underlying diseases, history and duration of premature rupture of the membrane and delivery, clinical symptoms (fever, reduced breastfeeding, and lethargy), laboratory results (complete blood cell and C-reactive protein), and results of blood and urine cultures were recorded and analyzed. Results: Among 90 neonates with sepsis, the average age was 6.7 ± 7.6 days; 54 were male (60.0%), and 36 were female (40.0%). Fifty (55.5%) neonates had early sepsis. Gram-negative organisms were grown in 61% of positive blood cultures; the most common was Klebsiella. Among Gram-positive organisms, Staphylococcus epidermidis was the most common. Most organisms were sensitive to colistin, and most were resistant to cefotaxime. There was a significant relationship between the age of onset of sepsis symptoms and birth weight in infants with positive blood cultures (P = 0.004) (r = 0.3). Conclusions: Gram-negative bacteria are the most common causes of sepsis, mainly resistant to aminoglycosides and cefotaxime. Therefore, increasing awareness about the optimal use of antibiotics is necessary to curb the increase in resistance levels.

The potential for development of clinically relevant microbial resistance to rifaximin-α: a narrative review.

Rifaximin-α is a gut-targeted antibiotic indicated for numerous gastrointestinal and liver diseases. Its multifaceted mechanism of action goes beyond direct antimicrobial effects, including alterations in bacterial virulence, cytoprotective effects on host epithelial cells, improvement of impaired intestinal permeability, and reduction of proinflammatory cytokine expression via activation of the pregnane X receptor. Rifaximin-α is virtually non-absorbed, with low systemic drug levels contributing to its excellent safety profile. While there are high concentrations of drug in the colon, low water solubility leads to low colonic drug bioavailability, protecting the gut microbiome. Rifaximin-α appears to be more active in the bile-rich small bowel. Its important biologic effects are largely at sub-inhibitory concentration. Although in vitro testing of clinical isolates from rifaximin recipients has revealed rifaximin-resistant strains in some studies, the risk of emergent rifaximin-α resistance appears to be lower than for many other antibiotics. Rifaximin-α has been used for many years for traveler's diarrhea with no apparent increase in resistance levels in causative pathogens. Further, rifaximin-α retains its efficacy after long-term and recurrent usage in chronic gastrointestinal disorders. There are numerous reasons why the risk of microbial resistance to rifaximin-α may be lower than that for other agents, including low intestinal bioavailability in the aqueous colon, the mechanisms of action of rifaximin-α not requiring inhibitory concentrations of drug, and the low risk of cross transmission of rifaximin-α resistance between bacterial species. Reported emergence of vancomycin-resistant Enterococcus in liver-disease patients maintained on rifaximin needs to be actively studied. Further studies are required to assess the possible correlation between in vitro resistance and rifaximin-α efficacy.

The Pseudomonas aeruginosa Resistome: Permanent and Transient Antibiotic Resistance, an Overview.

One of the most concerning characteristics of Pseudomonas aeruginosa is its low susceptibility to several antibiotics of common use in clinics, as well as its facility to acquire increased resistance levels. Consequently, the study of the antibiotic resistance mechanisms of this bacterium is of relevance for human health. For such a study, different types of resistance should be distinguished. The intrinsic resistome is composed of a set of genes, present in the core genome of P. aeruginosa, which contributes to its characteristic, species-specific, phenotype of susceptibility to antibiotics. Acquired resistance refers to those genetic events, such as the acquisition of mutations or antibiotic resistance genes that reduce antibiotic susceptibility. Finally, antibiotic resistance can be transiently acquired in the presence of specific compounds or under some growing conditions. The current article provides information on methods currently used to analyze intrinsic, mutation-driven, and transient antibiotic resistance in P. aeruginosa.

Advanced backcross QTL analysis and comparative mapping with RIL QTL studies and GWAS provide an overview of QTL and marker haplotype diversity for resistance to Aphanomyces root rot in pea (Pisum sativum).

Aphanomyces euteiches is the most damaging soilborne pea pathogen in France. Breeding of pea resistant varieties combining a diversity of quantitative trait loci (QTL) is a promising strategy considering previous research achievements in dissecting polygenic resistance to A. euteiches. The objective of this study was to provide an overview of the diversity of QTL and marker haplotypes for resistance to A. euteiches, by integrating a novel QTL mapping study in advanced backcross (AB) populations with previous QTL analyses and genome-wide association study (GWAS) using common markers. QTL analysis was performed in two AB populations derived from the cross between the susceptible spring pea variety "Eden" and the two new sources of partial resistance "E11" and "LISA". The two AB populations were genotyped using 993 and 478 single nucleotide polymorphism (SNP) markers, respectively, and phenotyped for resistance to A. euteiches in controlled conditions and in infested fields at two locations. GWAS and QTL mapping previously reported in the pea-Aphanomyces collection and from four recombinant inbred line (RIL) populations, respectively, were updated using a total of 1,850 additional markers, including the markers used in the Eden x E11 and Eden x LISA populations analysis. A total of 29 resistance-associated SNPs and 171 resistance QTL were identified by GWAS and RIL or AB QTL analyses, respectively, which highlighted 10 consistent genetic regions confirming the previously reported QTL. No new consistent resistance QTL was detected from both Eden x E11 and Eden x LISA AB populations. However, a high diversity of resistance haplotypes was identified at 11 linkage disequilibrium (LD) blocks underlying consistent genetic regions, especially in 14 new sources of resistance from the pea-Aphanomyces collection. An accumulation of favorable haplotypes at these 11 blocks was confirmed in the most resistant pea lines of the collection. This study provides new SNP markers and rare haplotypes associated with the diversity of Aphanomyces root rot resistance QTL investigated, which will be useful for QTL pyramiding strategies to increase resistance levels in future pea varieties.

Gene amplifications cause high-level resistance against albicidin in gram-negative bacteria.

Antibiotic resistance is a continuously increasing concern for public healthcare. Understanding resistance mechanisms and their emergence is crucial for the development of new antibiotics and their effective use. The peptide antibiotic albicidin is such a promising candidate that, as a gyrase poison, shows bactericidal activity against a wide range of gram-positive and gram-negative bacteria. Here, we report the discovery of a gene amplification-based mechanism that imparts an up to 1000-fold increase in resistance levels against albicidin. RNA sequencing and proteomics data show that this novel mechanism protects Salmonella Typhimurium and Escherichia coli by increasing the copy number of STM3175 (YgiV), a transcription regulator with a GyrI-like small molecule binding domain that traps albicidin with high affinity. X-ray crystallography and molecular docking reveal a new conserved motif in the binding groove of the GyrI-like domain that can interact with aromatic building blocks of albicidin. Phylogenetic studies suggest that this resistance mechanism is ubiquitous in gram-negative bacteria, and our experiments confirm that STM3175 homologs can confer resistance in pathogens such as Vibrio vulnificus and Pseudomonas aeruginosa.

Toxicity and resistance levels of phosphine against Tribolium castaneum (Herbst) and Sitophilus oryzae (L.) populations

The most destructive stored grain pests in India are the rust red flour beetle and the rice weevil. The most common method for controlling these two pests in storage is phosphine fumigation. However, frequent and acute or chronic doses of exposure than the recommended doses lead to the development of genetic and morphological resistance by changing their traits towards phosphine.Our recent study aimed to detect phosphine resistance degreesin T. castaneum and S. oryzae populations from twelve locations in Odisha. According to bioassay analysis, for S. oryzae after 24 hrs exposure period forphosphine gas to all the assessed populations, the LC50 value varied from 0.004 mg/l to 0.038 mg/l and the population of one location i.e., Chhata (Kendrapara) was found to have strong resistance to phosphine with 9.50 fold more resistant in comparison with the laboratory population. The phosphine toxicity levels for T. castaneum ranged from the LC50 values of 0.130 mg/l (Kendupali, Barghar) to 0.011 mg/l (Durgapali, Sambalpur), i.e., they were 13.00 and 1.10 times more resistant than the laboratory-susceptible population. It is possible that increasing resistance levels is due to storage structures are not tightly sealed during fumigation leading to sub-lethal phosphine concentration and lack of knowledge about fumigation procedures.

Achieving pre-eminence of antimicrobial resistance among non-fermenting Gram-negative bacilli causing septicemia in intensive care units: A single center study of a tertiary care hospital.

Bloodstream infections in the intensive care unit have always been a global healthcare challenge. The present study was conducted with the aim to evaluate the yearly trend of antibiotic resistance in non-fermenting Gram-negative bacilli (NFGNB) causing septicemia in intensive care units. Blood samples were collected from the patients admitted in various intensive care units and processed for isolation and identification of non-fermenting Gram-negative bacilli. The isolated bacterial strains were subjected to antibiotic susceptibility testing as per standard operating procedures. Out of 3632 blood samples, 977 (26.9%) samples showed microbial growth, of which 10.1% were Gram positive cocci, 8.7% were Gram negative bacilli (Enterobacterales), 7% were NFGNB and 1% were Candida spp. Increasing resistance among Acinetobacter baumannii complex was observed to ceftazidime, cefepime, amikacin, ciprofloxacin, levofloxacin, meropenem and trimethoprim-sulfamethoxazole. Moreover, Pseudomonas aeruginosa strains were found to be associated with increased resistance to ciprofloxacin, levofloxacin, ceftazidime and meropenem. A substantial increase in resistance levels was observed among Stenotrophomonas maltophilia and Sphingomonas paucimobilis as well. An increasing trend of antimicrobial resistance in NFGNB envisages the worst consequences in ICUs in the coming years. Therefore, reviewing and strict implementation of the antimicrobial policies including 'rational use of antibiotics' is recommended.

Characterization of tomato yellow leaf curl virus resistance genes and genetic variability in commercial tomato F1 hybrids

Tomato (Solanum lycopersicum L.) resistance to Tomato Yellow Leaf Curl Virus (TYLCV) is a major objective of breeding programs. Tomato breeders are now interested in the subsequent introgression of many resistance genes to increase resistance levels, expand resistance spectrum, and prolong the longevity of resistant cultivars. Many F1 hybrids are now multigene resistant. To select the best breeding materials, 15 commercial F1 tomato TYLCV-tolerant hybrids were evaluated for TYLCV resistance and productivity during the 2018 and 2019 fall seasons. Resistance genes were identified using gene-based molecular markers. Most hybrids have multiple heterozygous resistance genes. ‘Brivio’, ‘Dania’, ‘SV8320’, and ‘Tyrmes’ comprised resistance genes Ty-1/Ty-3, Ty-2, Ty-4, and ty-5. Thus, F1 hybrids exhibited moderate to mild symptoms, and viral replication was detected in their symptomless plants by PCR and qt-PCR. Genetic variability among hybrids, hybrid relationships, and inter-trait correlations were estimated based on phenotypes of TYLCV-tolerance, productivity, and fruit quality. Most traits had high estimates of genetic variance, genotypical coefficient of variance, and heritability. Genetic variability sufficed in selecting the best genotype. Based on multivariate analyses of principal components and hierarchical clusters, hybrids were highly diversified and divided into three clusters. Clusters 1 and 3 were better at TYLCV tolerance, yield, and fruit quality. Positive genotypical correlations were found between tolerance, total yield, and fruit quality (firmness, equatorial diameter, and TSS content). The use of ‘Brivio’, ‘Dania’, ‘SV8320’, and ‘Tyrmes’ will be very useful in TYLCV resistance breeding programs to pyramiding resistance genes by marker-assisted selection technique.

Differences in Physiological Metabolism and Antioxidant System of Different Ecotypes of Miscanthus floridulus under Cu Stress

To reveal the similarities and differences in the resistance mechanisms of different ecotypes to Cu stress, a pot experiment was used to systematically compare the physiological responses of non-mining ecotype Miscanthus floridulus (collected from Boluo County, Huizhou City) and mining ecotype Miscanthus floridulus (collected from Dabaoshan mining area) under different Cu concentrations. The results showed that chlorophyll a, chlorophyll b and total chlorophyll in the leaves of the two ecotypes of M. floridulus were negatively correlated with Cu stress concentration (p < 0.01), but the extent of decrease for the ecotypes in the mining area was lower than that for the ecotypes in the non-mining area. The values of chlorophyll a/b for both ecotypes increased with increasing Cu treatment concentration, indicating that Cu is more harmful to chlorophyll b than to chlorophyll a for M. floridulus. Cu stress can lead to the accumulation of malondialdehyde (MDA) in the leaves of M. floridulus with the amount of MDA accumulation observed being greater in the non-mining ecotype than in the mining ecotype (p < 0.05). The content of antioxidant substances (ascorbic acid and reduced glutathione) in the mining ecotype M. floridulus was significantly higher than that in the non-mining ecotype. The activity of SOD in the leaves of non-mining ecotypes was inhibited by Cu stress and the activity of POD was increased by Cu stress. However, the increase in POD in the mining ecotypes was greater than that in the non-mining ecotypes and the activities of the two enzymes in the mining ecotypes were significantly higher than those in the non-mining ecotypes at the highest concentration of Cu. Cu had different effects on PPO activity in the leaves of the two ecotypes of M. floridulus. The plant leaves of the non-mining ecotype at 400 and 800 mg·kg−1 were significantly fewer than those of the control group (p < 0.05), which were 87.1% and 65.2% of the control group, respectively. The PPO activity in the plant leaves of the mining ecotype was higher than that in the leaves of the non-mining ecotype and was significantly higher at 400 and 800 mg·kg−1 than that of the control group (p < 0.05), at 226.5% and 268.1% of the control group, respectively. These results indicate that the mining ecotype M. floridulus is more resistant to copper stress, that resistant ecotypes have been formed, and that small-molecule antioxidant substances play an important role in increasing resistance levels.

Prevalence of efflux pump and heavy metal tolerance encoding genes among Salmonella enterica serovar Infantis strains from diverse sources in Brazil.

Salmonella enterica subspecies enterica serovar Infantis (S. Infantis) is a non-typhoid, zoonotic and foodborne serovar with worldwide distribution, and often associated with increasing antimicrobial resistance. Efflux pumps are antimicrobial resistance mechanisms able to promote and increase resistance levels to multiple distinct drug classes. Heavy metal tolerance genes have been demonstrated to promote resistance against these compounds and act in the co-selection of antimicrobial resistant strains. Despite the relevance of S. Infantis in clinical and non-clinical fields, few studies worldwide have investigated the occurrence of such genes in strains from diverse sources. Therefore, the present study aimed at determining the prevalence of antimicrobial efflux pump and heavy metal tolerance genes and their genomic relatedness through core-genome multi-locus sequence typing (cgMLST) of 80 S. Infantis strains isolated from food, environmental, human and animal sources from 2013 to 2018 in Brazil. Twenty efflux pump encoding genes were detected, with 17 of these (acrA, acrB, baeR, crp, emrB, emrR, hns, kdpE, kpnF, marA, marR, mdtK, msbA, rsmA, sdiA, soxR and soxS) detected in all strains studied, golS in 98.75%, mdfA in 58.75% and tet(A) in 37.5%. Tolerance genes to arsenic (arsR) were detected in 100% of the strains, gold (golS and golT) in 98.75%, silver (silABCDEFPRS) in 36.25% and mercury (merR and merT) in 1.25%. cgMLST demonstrated a closer genetic relationship among strains harboring similar profiles of heavy metal and efflux pump encoding genes, despite their origin. In conclusion, the high prevalence of some efflux pump and heavy metal tolerance encoding genes alert us about the importance of strong surveillance measures to monitor resistance and the transmission of S. Infantis among diverse sources in Brazil.

Lethal and Sublethal Effects of Fluxametamide on Rice-Boring Pest, Rice Stem Borer Chilo suppressalis

(1) Background: Fluxametamide is a novel isoxazoline insecticide. Rice stem borer Chilo suppressalis (Walker) is a destructive Lepidoptera pest of rice in China, and novel effective insecticides are required to be developed for controlling it due to its increasing resistance levels. (2) Results: In the lethal assay, the insecticidal activity of fluxametamide with median lethal dose (LD50) value of 1.308 mg/kg to the fourth-instar larvae of C. suppressalis was higher than that of chlorantraniliprole (LD50, 3.112 mg/kg) and lower than that of emamectin benzoate (LD50, 0.006 mg/kg). In the sublethal (LD10 and LD30) assay, the duration of third to sixth-instar larvae, the pupal duration, pupation rate, and life cycle rate were significantly increased in F0 generation. Both the length and weight of the ovarian tube were decreased with the dose increase of fluxametamide, and were significantly smaller in the LD30 treatment than those of the control group. In F1 generation, only the duration of eggs was significantly increased with LD30 treatment of fluxametamide, whereas other developmental parameters had no significant change. (3) Conclusion: Fluxametamide had relatively strong lethal and sublethal effects on C. suppressalis and probably was able to affect the population growth and progeny of C. suppressalis.

Chalcones with potential antibacterial and antibiofilm activities against periodontopathogenic bacteria

ObjectivesPeriodontitis is a pathology resulting from complex interaction of microorganisms in the dental biofilm with the host's immune system. Increased use of antibiotics associated with their inappropriate use has increased resistance levels in anaerobic bacteria. Therefore, identifying new antimicrobial compounds, such as chalcones, is urgent. This study evaluates the antibacterial activity and the antibiofilm activity of 15 chalcones against the periodontopathogenic bacteria Prevotella nigrescens (ATCC 33563), P. oralis (ATCC 33269), Peptostreptococcus anaerobius (ATCC 27337), Actinomyces viscosus (ATCC 43146), Porphyromonas asaccharolytica (ATCC 25260), and Fusobacterium nucleatum (ATCC 25586). MethodsThe compounds were evaluated by minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC) tests. ResultsCompounds 1–6 showed good antibacterial and antibiofilm activities against most of the evaluated bacteria: MIC was lower than or equal to 6.25 μg/mL, biofilm biomass was reduced by 95%, and the compounds at concentrations between 0.78 and 100 μg/mL totally inhibited cell viability. Among the tested chalcones, 3 stood out: it was effective against all the bacteria, as revealed by the MIC and MBIC results. ConclusionsOur results have consolidated a base for the development of new studies on the effects of the tested chalcones as agents to combat and to prevent periodontitis.