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The worldwide resurgence of bed bugs [both Cimex lectularius L. and Cimex hemipterus (F.)] over the past two decades is believed in large part to be due to the development of insecticide resistance. The transcriptomic and genomic studies since 2010, as well as morphological, biochemical and behavioral studies, have helped insecticide resistance research on bed bugs. Multiple resistance mechanisms, including penetration resistance through thickening or remodelling of the cuticle, metabolic resistance by increased activities of detoxification enzymes (e.g. cytochrome P450 monooxygenases and esterases), and knockdown resistance by kdr mutations, have been experimentally identified as conferring insecticide resistance in bed bugs. Other candidate resistance mechanisms, including behavioral resistance, some types of physiological resistance (e.g. increasing activities of esterases by point mutations, glutathione S-transferase, target site insensitivity including altered AChEs, GABA receptor insensitivity and altered nAChRs), symbiont-mediated resistance and other potential, yet undiscovered mechanisms may exist. This article reviews recent studies of resistance mechanisms and the genes governing insecticide resistance, potential candidate resistance mechanisms, and methods of monitoring insecticide resistance in bed bugs. This article provides an insight into the knowledge essential for the development of both insecticide resistance management (IRM) and integrated pest management (IPM) strategies for successful bed bug management.

As part of an insect resistance management plan to preserve Bt transgenic technology, annual monitoring of target pests is mandated to detect susceptibility changes to Bt toxins. Currently Helicoverpa zea (Boddie) monitoring involves investigating unexpected injury in Bt crop fields and collecting larvae from non-Bt host plants for laboratory diet bioassays to determine mortality responses to diagnostic concentrations of Bt toxins. To date, this monitoring approach has not detected any significant change from the known range of baseline susceptibility to Bt toxins, yet practical field-evolved resistance in H. zea populations and numerous occurrences of unexpected injury occur in Bt crops. In this study, we implemented a network of 73 sentinel sweet corn trials, spanning 16 U.S. states and 4 Canadian provinces, for monitoring changes in H. zea susceptibility to Cry and Vip3A toxins by measuring differences in ear damage and larval infestations between isogenic pairs of non-Bt and Bt hybrids over three years. This approach can monitor susceptibility changes and regional differences in other ear-feeding lepidopteran pests. Temporal changes in the field efficacy of each toxin were evidenced by comparing our current results with earlier published studies, including baseline data for each Bt trait when first commercialized. Changes in amount of ear damage showed significant increases in H. zea resistance to Cry toxins and possibly lower susceptibility to Vip3a. Our findings demonstrate that the sentinel plot approach as an in-field screen can effectively monitor phenotypic resistance and document field-evolved resistance in target pest populations, improving resistance monitoring for Bt crops.

Little is known about the prevalence of antimicrobial-resistant (AMR) bacteria in veal meat in the United States. We estimated the prevalence of bacterial contamination and AMR in various veal meats collected during the 2018 U.S. National Antimicrobial Resistance Monitoring System (NARMS) survey of retail outlets in nine states and compared the prevalence with the frequency of AMR bacteria from other cattle sources sampled for NARMS. In addition, we identified genes associated with resistance to medically important antimicrobials and gleaned other genetic details about the resistant organisms. The prevalence of Campylobacter, Salmonella, Escherichia coli, and Enterococcus in veal meats collected from grocery stores in nine states was 0% (0 of 358), 0.6% (2 of 358), 21.1% (49 of 232), and 53.5% (121 of 226), respectively, with ground veal posing the highest risk for contamination. Both Salmonella isolates were resistant to at least one antimicrobial agent as were 65.3% (32 of 49) of E. coli and 73.6% (89 of 121) of Enterococcus isolates. Individual drug and multiple drug resistance levels were significantly higher (P < 0.05) in E. coli and Enterococcus from retail veal than in dairy cattle ceca and retail ground beef samples from 2018 NARMS data. Whole genome sequencing was conducted on select E. coli and Salmonella from veal. Cephalosporin resistance (blaCMY and blaCTX-M), macrolide resistance (mph), and plasmid-mediated quinolone resistance (qnr) genes and gyrA mutations were found. We also identified heavy metal resistance genes ter, ars, mer, fieF, and gol and disinfectant resistance genes qac and emrE. An stx1a-containing E. coli was also found. Sequence types were highly varied among the nine E. coli isolates that were sequenced. Several plasmid types were identified in E. coli and Salmonella, with the majority (9 of 11) of isolates containing IncF. This study illustrates that veal meat is a carrier of AMR bacteria.

The citrus red mite, Panonychus citri (McGregor), is an important spider mite pest in citrus producing areas. Owing to long-term acaricide exposure, resistance has evolved rapidly in recent years. To evaluate the extent of resistance, seven field mite populations sampled from various geographical locations in China during 2015–2018 were tested using the leaf-dip bioassay method to determine their susceptibilities to four acaricides. In comparison with the susceptible strain maintained in the laboratory, low or moderate levels of fenpropathrin resistance, while no resistance to abamectin or cyflumetofen, were found among populations sampled from Liangping, Wanzhou, Daying, and Anyue in Southwestern China during the test period. High levels (>1,000-fold, with LC50 values that were greater than the recommended concentration) of resistance to fenpropathrin had evolved in field populations from Southern China, including Guilin, Nanning, and Yuxi, when compared with that of the susceptible strain. Populations from Guilin and Nanning also evolved high resistance levels to abamectin (1,088-fold and 1,401-fold) and cyflumetofen (2,112-fold and 9,093-fold). All the populations sampled in 2018 showed a moderate or high resistance to bifenazate. Generally, field populations of citrus red mites from Southwestern China were more sensitive to the tested acaricides than those of Southern China.The data provide a foundation for developing acaricide resistance management strategies in these regions.

The diamondback moth, Plutella xylostella L., is a worldwide crop pest that is difficult to control because of its ability to develop resistance to many insecticides. To provide a reference for resistance management of P. xylostella in China, the present study used a leaf-dip bioassay to monitor the resistance of P. xylostella to nine insecticides in eight regions of China. The results showed that P. xylostella had developed a high level of resistance to beta-cypermethrin (resistance ratio [RR] > 112), and moderate (RR < 40) to high levels of resistance to indoxacarb, abamectin, and chlorfluazuron. For chlorantraniliprole, RRs > 100 were found in Midu (Yunnan Province) and Jinghai (Tianjin). In most regions, the resistance to spinetoram and chlorfenapyr and Bacillus thuringiensis (Bt) was low. No resistance was detected to diafenthiuron. Overall, P. xylostella resistance to insecticides was higher in Midu than in other regions. The data in this study should help guide the selection of insecticides for management of P. xylostella in China.

Chlorantraniliprole, an anthranilic diamide insecticide, is widely used for controlling lepidopteran pests, because of its high insecticidal activity. However, overuse of chlorantraniliprole has led to the selection of resistance in many insect pests, including Chilo suppressalis (Lepidoptera:Crambidae), one of the most damaging rice pests in China. In this study, resistance levels to chlorantraniliprole for C. suppressalis was surveyed from eight populations of three provinces in China. The levels of resistance were ranged from 34.4-fold to 284.0-fold compared with a susceptible population.Then, a 15402 bp fragment of the full-length cDNA of ryanodine receptor gene (CsRyR) from the XS strain, the highest resistant population, and a 1992 bp fragment of CsRyR cDNA encoding the carboxyl-terminal of CsRyR gene from the other seven populations were sequenced. A common previously identified mutation that was associated with chlorantraniliprole resistance against C. suppressalis, G4910E, was not detected in any of the eight populations in this study. However, another mutation I4758M was found in all seven resistant populations. Furthermore, the relative mRNA expression levels of CsRyR gene in the seven resistant populations were all reduced compared with susceptible strain. Our study provides new insights into the basis of monitoring the development of resistance and the mechanism of resistance to chlorantraniliprole in C. suppressalis.

The beet armyworm Spodoptera exigua (Hübner) is a serious polyphagous pest that infests vegetable crops worldwide and has rapidly developed resistance due to its long-term exposure to insecticides. The current resistance statuses to four insecticides exhibited by three field populations of beet armyworms collected in southern China from 2014 to 2018 were investigated. Monitoring data from five consecutive years demonstrated that all three tested S. exigua populations developed extremely high resistance to chlorantraniliprole in 2018 (220.58- to 2,597.39-fold). Two populations (Baiyun and Fengxian) developed low to moderate resistance to spinosad, whereas the Huangpi population remained susceptible (except in 2014, with RR of 6.11-fold). The RR of the Fengxian and Baiyun populations to indoxacarb steadily increased over the years, whereas that of the Huangpi population increased relatively slowly. The Baiyun and Fengxian populations developed moderate to high resistance to indoxacarb and methoxyfenozide, whereas the Huangpi population exhibited susceptibility to low resistance (1.06- to 6.45-fold) to indoxacarb and susceptibility to moderate resistance (1.53- to 14.22-fold) to methoxyfenozide. These results suggest that chlorantraniliprole should not be employed to control this pest in southern China. Reduced use of indoxacarb and methoxyfenozide or the use of alternating insecticides with low levels of resistance is recommended. Spinosad remains an effective insecticide for the management of S. exigua. To avoid the rapid development of insecticide resistance, rotations of insecticides with low levels of resistance and different modes of action based on the resistance patterns of S. exigua should be performed in southern China.

In this study, the sensitivity of 20 field populations of Chilo suppressalis (Walker) from five provinces in China to seven insecticides was evaluated during 2016–2018. The results indicated that 20 field populations of C. suppressalis had evolved moderate to high levels of resistance to triazophos (RR 64.5–461.3) and chlorpyrifos (RR 10.1–125.0). Furthermore, C. suppressalis exhibited low to moderate levels of resistance to abamectin (RR 6.5–76.5) and decreased susceptibility to cyantraniliprole (RR 1.0–34.0). The population collected from Nanchang in Jiangxi Province (JXNC) showed high resistance to chlorantraniliprole (RR 148.3–294.3), and other geographical populations remained susceptible to moderate levels of resistance (RR 1.0–37.5). In contrast, C. suppressalis remained susceptible to low levels of resistance to spinetoram (RR 1.0–6.7) and spinosad (RR 1.0–4.6). Significant correlations were found between the Log LC50 values of chlorantraniliprole and cyantraniliprole, chlorpyrifos and triazophos, as well as cyantraniliprole and chlorpyrifos and triazophos. Similarly, significant correlations were found among abamectin, chlorpyrifos, and triazophos. In addition, a significant correlation was also observed between the activity of the detoxification enzymes and the log LC50 values of chlorantraniliprole, cyantraniliprole, abamectin, chlorpyrifos, and triazophos. The findings provide an important reference for implementing effective resistance management strategies and the development of new insecticides in insect pest control.

Background Campylobacter spp. is the most frequent cause of bacterial food-borne gastroenteritis and a high priority antibiotic resistant bacterium according to the World Health Organization (WHO). European monitoring of thermotolerant Campylobacter spp. does not reflect the global burden of resistances already circulating within the bacterial population worldwide. Methods We systematically compared whole genome sequencing with comprehensive phenotypic antimicrobial susceptibility, analyzing 494 thermotolerant Campylobacter poultry isolates from Vietnam and Germany. Any discrepancy was checked by repeating the wet lab and improving the dry lab part. Selected isolates were additionally analyzed via long-read Oxford Nanopore technology, leading to closed chromosomes and plasmids. Results Overall, 22 different resistance genes and gene variants (e. g. erm (B), aph(3’)-IIIa , aph(2’’)-If , catA , lnu (C), bla OXA , sat4 ) and point mutations in three distinct genes ( gyrA , 23S rRNA, rpsL ) associated with AMR were present in the Campylobacter isolates. Two AMR genes were missing in the database and one falsely associated with resistance. Bioinformatic analysis based on short-read data partly failed to identify tet (O) and aadE , when the genes were present as duplicate or homologous gene variants. Intriguingly, isolates also contained different determinants, redundantly conferring resistance to chloramphenicol, gentamicin, kanamycin, lincomycin and streptomycin. We found a novel tet (W) in tetracycline sensitive strains, harboring point mutations. Furthermore, analysis based on assemblies from short-read data was impaired to identify full length phase variable aad9 , due to variations of the poly-C tract within the gene. The genetic determinant responsible for gentamicin resistance of one isolate from Germany could not be identified. GyrT86I, presenting the main determinant for (fluoro-)quinolone resistance led to a rare atypical phenotype of ciprofloxacin resistance but nalidixic acid sensitivity. Long-read sequencing predicted AMR genes were mainly located on the chromosome, and rarely on plasmids. Predictions from long- and short-read sequencing, respectively, often differed. AMR genes were often organized in multidrug resistance islands (MDRI) and partially located in proximity to transposase genes, suggesting main mobilization of resistance determinants is via natural transformation and transposition in Campylobacter . Conclusions The results of this study suggest that there is frequent resistance gene duplication, mosaicism, and mutation leading to gene variation and truncation in Campylobacter strains that have not been reported in previous studies and are missing from databases. Furthermore, there is a need for deciphering yet unknown resistance mechanisms and resistance spread in thermotolerant Campylobacter spp. that may pose a challenge to global food safety.

Proposals to update the harmonised monitoring and reporting of antimicrobial resistance (AMR) from a public health perspective in Salmonella, Campylobacter coli, Campylobacter jejuni, Escherichia coli, Enterococcus faecalis, Enterococcus faecium and methicillin‐resistant Staphylococcus aureus (MRSA) from food‐producing animals and derived meat in the EU are presented in this report, accounting for recent trends in AMR, data collection needs and new scientific developments. Phenotypic monitoring of AMR in bacterial isolates, using microdilution methods for testing susceptibility and interpreting resistance using epidemiological cut‐off values is reinforced, including further characterisation of those isolates of E. coli and Salmonella showing resistance to extended‐spectrum cephalosporins and carbapenems, as well as the specific monitoring of ESBL/AmpC/carbapenemase‐producing E. coli. Combinations of bacterial species, food‐producing animals and meat, as well as antimicrobial panels have been reviewed and adapted, where deemed necessary. Considering differing sample sizes, numerical simulations have been performed to evaluate the related statistical power available for assessing occurrence and temporal trends in resistance, with a predetermined accuracy, to support the choice of harmonised sample size. Randomised sampling procedures, based on a generic proportionate stratified sampling process, have been reviewed and reinforced. Proposals to improve the harmonisation of monitoring of prevalence, genetic diversity and AMR in MRSA are presented. It is suggested to complement routine monitoring with specific cross‐sectional surveys on MRSA in pigs and on AMR in bacteria from seafood and the environment. Whole genome sequencing (WGS) of isolates obtained from the specific monitoring of ESBL/AmpC/carbapenemase‐producing E. coli is strongly advocated to be implemented, on a voluntary basis, over the validity period of the next legislation, with possible mandatory implementation by the end of the period; the gene sequences encoding for ESBL/AmpC/carbapenemases being reported to EFSA. Harmonised protocols for WGS analysis/interpretation and external quality assurance programmes are planned to be provided by the EU‐Reference Laboratory on AMR.