Intermediate Levels Of Resistance Research Articles

Isolation and identification of Pseudomonas aeruginosa obtained from dogs and cats in Great Cairo regarding status of phenotypic antimicrobial resistance pattern

BackgroundCompanion animals; dog and cat are closely associated with the daily life of humans and may be implemented in the transmission of many microorganisms to their adopters.Pseudomonas aeruginosa(P. aeruginosa) is a suited opportunistic and harsh to treat pathogen due to its rife environmental distribution, unique intrinsic and acquired resistance to numerous antimicrobials’ categories.ObjectiveThe current study targeted to survey the existence ofP. aeruginosain laboratory samples obtained from diseased dogs and cats. The study also investigated the susceptibility and resistance of recovered isolates against antimicrobials.Materials and methodsA total of 315 samples gathered from veterinary laboratories in Great Cairo governorates; fecal, ear, eye, respiratory, wounds and urine samples were previously collected from diseased dogs and cats. The samples were examined bacteriologically and biochemically to isolateP. aeruginosa. The isolates were assayed for their sensitivity and resistance versus 25 antimicrobials belonging to various categories.Results and conclusionFifty- eightP. aeruginosaisolates (18.41%) were obtained from 315 dogs (44/233, 18.88%) and cats’ (14/82, 17.07%) clinical swabs. The isolates were confirmed biochemically and via VITEK 2 compact system. All isolates showed alpha-type of hemolysis and pigment production. The obtainedP. aeruginosaisolates revealed a multidrug resistance pattern by 70.45% in dog isolates while cat isolates demonstrated a higher ratio 78.57%.P. aeruginosaisolates were highly resistant to cephalosporins, trimethoprim/sulfamethoxazole, and intermediate resistant to erythromycin fosfomycin. On the other hand imipenem, amikacin, azithromycin then gentamycin and ciprofloxacin were the most efficient onP. aeruginosaisolates. The study included thatP. aeruginosaisolates obtained from canine and feline clinical samples collected from Great Cairo laboratories were characterized by high and intermediate levels of antimicrobial resistance. However, this pattern was directed to some classes of antibiotics, which are not authorized for veterinary use, which could expose an early warning mark and give the need for ongoing monitoring.

A highly diversified NLR cluster in melon contains homologs that confer powdery mildew and aphid resistance.

Podosphaera xanthii is the main causal agent of powdery mildew (PM) on Cucurbitaceae. In Cucumis melo, the Pm-w resistance gene, which confers resistance to P. xanthii, is located on chromosome 5 in a cluster of nucleotide-binding leucine-rich repeat receptors (NLRs). We used positional cloning and transgenesis, to isolate the Pm-wWMR 29 gene encoding a coiled-coil NLR (CC-NLR). Pm-wWMR 29 conferred high level of resistance to race 1 of PM and intermediate level of resistance to race 3 of PM. Pm-wWMR 29 turned out to be a homolog of the Aphis gossypii resistance gene Vat-1PI 161375. We confirmed that Pm-wWMR 29 did not confer resistance to aphids, while Vat-1PI 161375 did not confer resistance to PM. We showed that both homologs were included in a highly diversified cluster of NLRs, the Vat cluster. Specific Vat-1PI 161375 and Pm-wWMR 29 markers were present in 10% to 13% of 678 accessions representative of wild and cultivated melon types worldwide. Phylogenic reconstruction of 34 protein homologs of Vat-1PI 161375 and Pm-wWMR 29 identified in 24 melon accessions revealed an ancestor with four R65aa-a specific motif in the LRR domain, evolved towards aphid and virus resistance, while an ancestor with five R65aa evolved towards PM resistance. The complexity of the cluster comprising the Vat/Pm-w genes and its diversity in melon suggest that Vat homologs may contribute to the recognition of a broad range of yet to be identified pests and pathogens.

Predicted resistance to broadly neutralizing antibodies (bnAbs) and associated HIV-1 envelope characteristics among seroconverting adults in Botswana

We used HIV-1C sequences to predict (in silico) resistance to 33 known broadly neutralizing antibodies (bnAbs) and evaluate the different HIV-1 Env characteristics that may affect virus neutralization. We analyzed proviral sequences from adults with documented HIV-1 seroconversion (N = 140) in Botswana (2013–2018). HIV-1 env sequences were used to predict bnAb resistance using bNAb-ReP, to determine the number of potential N-linked glycosylation sites (PNGS) and evaluate Env variable region characteristics (VC). We also assessed the presence of signature mutations that may affect bnAb sensitivity in vitro. We observe varied results for predicted bnAb resistance among our cohort. 3BNC117 showed high predicted resistance (72%) compared to intermediate levels of resistance to VRC01 (57%). We predict low resistance to PGDM100 and 10-1074 and no resistance to 4E10. No difference was observed in the frequency of PNGS by bNAb susceptibility patterns except for higher number of PNGs in V3 bnAb resistant strains. Associations of VC were observed for V1, V4 and V5 loop length and net charge. We also observed few mutations that have been reported to confer bnAb resistance in vitro. Our results support use of sequence data and machine learning tools to predict the best bnAbs to use within populations.

Negative Effects of Phthorimaea absoluta-Resistant Tomato Genotypes on the Zoophytophagous Biocontrol Agent, Orius laevigatus (Fieber) (Hemiptera: Anthocoridae).

Complex interactions between host plant resistance (HPR) and biological control agents, particularly omnivorous predators, can shape the outcome of an integrated pest management (IPM) program. However, such interactions are seldom explored during plant breeding programs. Therefore, in the present study, we compared the performance of the omnivorous biological control agent Orius laevigatus on six tomato genotypes with different levels of resistance to the tomato leaf miner Phthorimaea absoluta. We found that the O. laevigatus fitness components (i.e., egg deposition, egg hatching rate, and duration of egg, early nymphal, late nymphal stages, and their survival) were inferior on the wild resistant genotypes (LA 716 and LA 1777) in comparison to the resistant domesticated genotype EC 620343 and the susceptible genotypes (EC 705464 and EC 519819). It appears that the adverse effects of tomato genotypes on O. laevigatus are determined mainly by glandular and non-glandular trichome densities on the leaves. Comparison of O. laevigatus response to the tested tomato cultivars to that of P. absoluta revealed significant positive correlations in duration of the egg stages, development time of early and late larval stages, and overall immature mortality in both species. It appears, therefore, that defensive plant traits operate in a similar way on the pest and its predator in the system. Overall, the present study of the tomato-P. absoluta-O. laevigatus system provides experimental evidence for the need to optimize pest management by employing intermediate levels of crop resistance together with biological control agents.

Eight-year field performance of backcross American chestnut (Castanea dentata) seedlings planted in the southern Appalachians, USA

The American chestnut (Castanea dentata) is imperiled due primarily to two diseases caused by nonnative pathogens, notably chestnut blight and Phytophthora root rot (PRR) caused by Cryphonectria parasitica and Phytophthora cinnamomi, respectively. Field reintroduction trials are important to test trees bred for blight resistance under forest conditions to quantify survival and field performance in managed stands that represent future restoration sites. We planted 513 pedigreed bare-root (1–0) nursery seedlings into an even-aged regeneration harvest in the Blue Ridge Mountains of eastern Tennessee, USA to test effects of breeding, genetics, and seedling size class on field performance, including survival, total growth, incremental growth (a measure of growth efficiency), and height growth patterns. Mortality was highest in the first two years after planting, and PRR symptoms coupled with soil and root assays that tested positive for P. cinnamomi suggested this disease was a significant contributor to mortality. Chinese chestnut (C. mollissima), known to be resistant to P. cinnamomi and C. parasitica, had the highest survival (96 percent) compared to American chestnut (34 percent) and hybrid generations, including the BC3F3 generation (41 percent). Less advanced hybrid generations, such as the BC1F3 and BC2F3, had the greatest total height and ground-line diameter (GLD) and height growth efficiencies. BC3F3 generation seedlings were associated with higher-than-expected rates of nominal height growth patterns (i.e., flat growth rates over time or early mortality) compared to Chinese chestnut seedlings. Results, however, indicated the breeding program was successfully integrating desired American chestnut growth traits into the hybrid genome while transferring an intermediate level of resistance from the Chinese chestnut. We identified superior and inferior BC3F3 families that can help inform breeding and restoration efforts. Visually grading seedlings before planting affected survival and growth of generations and genetic families differently, indicating that refinement of nursery production and restoration plantings should consider genetic effects. Across generations, seedling size grading improved total height and GLD growth that would save resources necessary for competition control and animal browsing protection, but large-size seedlings also exhibited lower C. parasitica resistance rankings over time, probably owing to earlier bark fissuring. PRR probably affected outcomes, particularly for hybrid and American chestnut seedlings that have very low levels of P. cinnamomi resistance. Managers could expect advanced breeding generations to perform similarly to American chestnut in growth through the critical stage of early stand development. More durable resistance to C. parasitica and mitigation of PRR through better site selection and/or resistance screening will improve future restoration efforts.

Registration of UPR‐Mp‐34 and UPR‐Mp‐42 common bean germplasm with enhanced resistance to ashy stem blight

AbstractCommon bean (Phaseolus vulgaris L.) breeding lines (BL) UPR‐Mp‐34 (Reg no. CV‐313, PI 701379) and UPR‐Mp‐42 (Reg no. CV‐314, PI 701380) were developed at the University of Puerto Rico. UPR‐Mp‐34 was derived from A 195/‘PC 50’//SEA 5, and UPR‐Mp‐42 was developed from BAT 477/NY6020‐4//PRA154 common bean populations. Both BL have intermediate levels of resistance (mean scores, 4–6) to two inoculations of the PRI21 Macrophomina phaseolina (Tassi) Goidanich isolate (the causal agent of ashy stem blight) compared with BAT 477, SEA 5, TARS‐MST1, and XAN 176, which mostly had susceptible scores (7–9) in the greenhouse and field evaluations. UPR‐Mp‐34 has an indeterminate growth habit Type III, has a cream seed (average weight, 26.5 g per 100 seeds), initiates flowering at 32 d after planting, and reaches harvesting maturity at 86 d. Mean seed yield was 730 and 340 kg ha−1 in Isabela and Lajas, respectively. UPR‐Mp‐42 possesses black seed (23.8 g per 100 seeds), has a determinate growth habit Type I, initiates flowering at 30 d, and matures at 76 d. Mean seed yield was 750 kg ha−1 in both locations. The intermediate levels of ashy stem blight resistance from both BL could be combined with other sources of resistance and introgressed into common bean cultivars from different market classes.

Bacterial profile and extended spectrum beta lactamase screening of urinary tract infection among asymptomatic and symptomatic pregnant women attending antenatal care in ALERT Hospital, Addis Ababa, Ethiopia.

The occurrence of extended spectrum beta lactamase-producing uropathogens, especially in pregnant women can result in life-threatening condition and morbidity for both the mother and the newborn due to very limited drug options for treatment of these pathogens. The aim of this study was to determine the bacterial profile, associated factors, and their antimicrobial susceptibility patterns and to identify extended spectrum beta lactamase-producing bacterial uropathogens. A hospital-based cross-sectional study was conducted from July to September 2018 on a total of 177 pregnant women with and without symptoms of urinary tract infection at ALERT Hospital, Addis Ababa, Ethiopia. From these study participants, 72 have symptoms, whereas 105 have no symptoms. All urine samples were inoculated onto cysteine lactose electrolyte deficient medium and MacConkey agar. Colonies were counted to check the presence of significant bacteriuria. Pure isolates of bacterial pathogen were characterized and identified at species level by colony morphology, gram stain, and standard biochemical procedures. All Gram-negative isolates were put into Muller-Hinton agar plates for antibiotic susceptibility test by Kirby-Bauer disc diffusion technique. Extended spectrum beta lactamase was detected using double-disk synergy methods on Muller-Hinton agar. The data were double entered into epidemiological Information system and analyzed using Statistical Package for Social Science version 26. The overall proportion of urinary tract infection among pregnant women was 14.7% (n = 26/177). Klebsiella pneumoniae was the predominant bacterial etiologic agent of urinary tract infection 26.9% (n = 7/26). The proportion of extended spectrum beta lactamase among Gram-negative isolates was 50% (n = 6/12). Among extended spectrum beta lactamase-producing isolates (100%), all are resistance to amikacin and gentamicin while intermediate level resistance rate of 66.7% was observed among trimethoprim-sulphamethoxazole. They were susceptible for some limited drugs, and these were Nitrofurantoin (83.3%) and Chloramphenicol (83.3%). Majority of extended spectrum beta lactamase-producing isolates exhibited co-resistance to other commonly prescribed antibiotics. This indicates that the option of treatment for these pathogens rapidly decreased from time to time which results serious life-threatening conditions, especially in mother and newborn unless the appropriate measure is taken.

STUDY OF IN-VITRO PROBIOTIC PROPERTIES AND ANTIBIOTIC RESISTANCE IN LACTOBACILLI ISOLATED FROM COMMERCIAL PROBIOTIC PRODUCTS IN PAKISTAN

The aim of the study was analysis of in-vitro probiotic properties and antibiotic resistance in lactobacilli isolated from commercial probiotic products from Pakistan. Lactobacilli were identified by biochemical testing and genus specific polymerase chain reaction. Probiotic properties including tolerance to low pH and bile salts, auto-aggregation, co-aggregation and antimicrobialactivity, and antibiotic resistance pattern of all isolates was determined. A total of 14 lactobacilli isolates were recovered from nine products while three products had no lactobacilli. All isolates except AB6 were tolerant to acidic condition (pH: 2). All isolates except AB13 showed growth in presence of bile salts (0.5%). Lactobacilli showed variable auto-aggregation (01-97%) and co-aggregation with E. coli and S. enteritidis (37.5±7.7-92.4±7.3 and 31.6±6.4-95.8±4.0, respectively). Nine isolates showed activity against S. enteritidis while six isolates had activity against E. coli. Lactobacilli showed higher level of resistance to meropenem (100%), imipenem (92.85%), polymyxin B (92.85%), kanamycin (92.85%) and aztreonam (78.75%), intermediate level of resistance to vancomycin (64.2%), gentamycin (57.14%) and ciprofloxacin (42.85%), low level of resistance to ampicillin (35.71%), bacitracin (35.71%), penicillin (28.5%) and tetracycline (28.50%), and no resistance to erythromycin and chloramphenicol. It was concluded that transferable antibiotic resistance is present in commercial probiotics which may pose a threat to public safety.

Screening a newly developed common bean germplasm with improved resistance to ashy stem blight in multiple environments.

Ashy stem blight (ASB) caused by the necrotrophic fungus Macrophomina phaseolina (Tassi) Goidanich is an important disease in common bean (Phaseolus vulgaris L.) in the Americas and worldwide. Low to intermediate levels of ASB resistance exist in cultivated and landrace genotypes of the common bean and the tertiary gene pool. However, cultivars with higher levels of resistance are not yet available. Our objectives were to 1) pyramid higher levels of resistance from multiple parent populations within the primary gene pool and 2) compare the response of the newly developed breeding lines (BL) with known sources of resistance. The BL UPR-Mp-22, UPR-Mp-34, UPR-Mp-42, and UPR-Mp-48, known sources of resistance, and susceptible checks were inoculated twice per plant with the PRI21 M. phaseolina isolate in the greenhouse and field trials conducted in Isabela and Lajas, Puerto Rico. None of the genotypes tested were resistant (mean scores 1-3). However, the new black UPR-Mp-42 and white UPR-Mp-48 BL had an intermediate response (mean scores 4-6) compared to white common bean genotypes 'Bella,' NY6020-4, and 'Verano' and black bean TARS-MST1 that were susceptible (scores ≥7) in all environments. Andean genotypes A 195, PRA154, PRA155, and UPR-Mp-22 were intermediate in the greenhouse. In contrast, UPR-Mp-34 had significantly lower scores than BAT 477 that had a susceptible reaction in the greenhouse in Isabela and in the field in Lajas and SEA 5 that was susceptible in all environments. These new BL possess an enhanced ASB resistance and may be used to improve common bean cultivars or germplasms of different market classes.

The Effect of Pretreatment Potential Resistance to NNRTIs on Antiviral Therapy in Patients With HIV/AIDS

With the increasing coverage of antiretroviral therapy, concerns for the emergence and transmission of HIV drug resistance (HIVDR) are arising. HIVDR was divided into 5 levels: sensitive, potentially resistant, low resistant, intermediate resistant, and high resistant. Most of the articles on HIVDR involved low-level, intermediate-level, and high-level drug resistance to antiretroviral drug, and few articles deal with potential drug resistance. Treatment failure associated with the level of low-level, intermediate-level, and high-level resistance to antiretroviral drug has been reported. However, whether virological failure (VF) is related to potential resistance remains unclear. In this study, we aimed to describe the situation of potential resistance to antiretroviral drug and whether it is related to VF. We analyzed the demographic, behavioral information, medical history, and drug resistance-associated mutation data from subjects. Drug resistance mutations at baseline and time of failure in patients suffering VF were detected by using the Vela automated next-generation sequencing platform. The χ2 test or Fisher exact test and logistic regression were used to assess the risk factors that contribute to VF in the potential drug-resistant people. The prevalence of overall pretreatment drug resistance was 7.06% (233/3300), and the prevalence of pretreatment potential resistance was 8.79% (290/3300). All these patients with pretreatment potential first-line drugs resistance showed potential resistance to nonnucleoside reverse transcriptase inhibitors (NNRTIs), and some of them had potential drug resistance to NNRTIs and NRTIs or NNRTIs and PIs; among these patients, 94.71% (179/189) had V179 D/E mutations. The VF rate of first-line treatment for potentially resistant people is 17.99%. CD4+ T-cell count ≤200 cells/L at antiretroviral therapy initiation are risk factors for the failure of first-line treatment. The prevalence of potential drug resistance among individuals with HIV and the VF rate of first-line treatment for potential drug-resistant people were high. To better optimize clinical management, prevention, and control of HIV, attention should be devoted to the potential resistance of nonnucleoside drugs.

Variation of Salvia officinalis L. Essential Oil and Hydrolate Composition and Their Antimicrobial Activity

This study aimed to investigate the chemical composition of steam distillate essential oil and corresponding hydrolate obtained from S. officinalis grown in Serbia, as well as the influence of weather conditions (temperature and precipitations) on their chemical profiles. Furthermore, their antimicrobial activity was investigated in vitro. The main compounds in essential oil were cis-thujone, followed by camphor, trans-thujone, and 1,8-cineole, while hydrolate was slightly different from the essential oil, with camphor, cis-thujone, and 1,8-cineole as the main compounds. Among the eight respiratory-associated microorganisms, Klebsiella oxytoca was the most sensitive to the tested EOs (minimum inhibitory concentration (MIC)/minimal bactericidal/fungicidal concentration (MBC/MFC) were 14.20 and 28.4 μL mL−1, respectively). MIC and MBC values of other tested bacteria ranged between 28.40 and 227.25 μL mL−1 while for Candida albicans MIC/MFC ranged from 28.40/56.81 to 56.81–113.63 μL mL−1. Antibiotic susceptibility patterns for the analyzed eight respiratory-associated microorganisms showed an intermediate level of resistance to commonly used antibiotics such as ampicillin, levofloxacin, and ciprofloxacin. As a preliminary approach to the antimicrobial profiling of the tested EO, the obtained results revealed that the tested samples possess remarkable antibacterial activities and could be used to develop pharmaceutical formulations as an alternative to conventional antibiotic therapy.

Antibiotic Exposure Leads to Reduced Phage Susceptibility in Vancomycin Intermediate Staphylococcus aureus (VISA).

ABSTRACTIn the time of antimicrobial resistance, phage therapy is frequently suggested as a possible solution for such difficult-to-treat infections. Vancomycin-intermediate Staphylococcus aureus (VISA) remains a relatively rare yet increasing occurrence in the clinic for which phage therapy may be an option. However, the data presented herein suggest a potential cross-resistance mechanism to phage following vancomycin exposure in VISA strains. When comparing genetically similar strains differing in their susceptibility to vancomycin, those with intermediate levels of vancomycin resistance displayed decreased sensitivity to phage in solid and liquid assays. Serial passaging with vancomycin induced both reduced vancomycin susceptibility and phage sensitivity. As a consequence, the process of phage infection was shown to be interrupted after DNA ejection from adsorbed phage but prior to phage DNA replication, as demonstrated through adsorption assays, lysostaphin sensitivity assays, electron microscopy, and quantitative PCR (qPCR). At a time when phage products are being used for experimental treatments and tested in clinical trials, it is important to understand possible interference between mechanisms underlying antibiotic and phage resistance in order to design effective therapeutic regimens.

Winter Wheat Variety Response to Timing and Number of Fungicide Applications During the 2020–2021 Growing Season in Kansas

The objective of this project was to evaluate the yield response of different winter wheat varieties to different fungicide management treatments during the 2020–2021 growing season in Kansas. Fourteen varieties were evaluated under four fungicide treatments (no fungicide, application either at jointing, heading, or at both stages) in four locations across Kansas in a split-plot design. Disease incidence was assessed approximately 20 d after each fungicide application. Septoria blotch and tan spot were the most prevalent early-season diseases at the studied fields, while stripe rust, leaf rust, and tan spot prevailed later in the season. While varieties responded differently to fungicide management and there was a range in yield response across locations, there was an overall yield increase of 4.2 bushels per acre resulting from the jointing fungicide application; 10.3 bu/a from the heading fungicide; and 9.9 bu/a from the combination of both applications. Although there were some similarities, the ranking of the highest yielding varieties was not uniform across locations. While different reactions occurred regarding the response of the varieties to fungicide management, overall susceptible varieties had a greater response to fungicide management compared to varieties with intermediate or high levels of genetic resistance. Our preliminary data suggest that the application of fungicide to winter wheat in Kansas might be advantageous, but the degree of this benefit will depend upon the environment, variety, and level of disease incidence.

AAC Awesome special purpose spring wheat

AAC Awesome is a high yielding spring wheat (Triticum aestivum L.) cultivar eligible for the Canada Western Special Purpose (CWSP) wheat class. Based on 29 site-years of testing over 3 years in the General Purpose Wheat Registration trial (2013–2015), AAC Awesome yielded 14% more grain than AC Andrew, and surpassed yields of Sadash, 5702PR, and Pasteur by 12%, 22%, and 9%, respectively. AAC Awesome had similar maturity, was slightly taller, had higher test weight and larger kernels as compared to AC Andrew. AAC Awesome had excellent levels of resistance to the prevalent races of leaf, stem and stripe rust. It expressed an intermediate level of resistance to Fusarium head blight (FHB), common bunt and loose smut. It also expressed tolerance to the orange wheat blossom midge. AAC Awesome is eligible for grades of Canada Western Special Purpose Wheat class.

Performance of Solanum phureja-derived bacterial-wilt resistant potato clones in a field naturally infested with Ralstonia solanacearum in Central Brazil

ABSTRACT Bacterial wilt (BW), or brown rot, caused by the soil and seed borne bacterium Ralstonia solanacearum, is one of the most devastating diseases of potatoes cultivated in warmer regions of the world. There are no potato cultivars with a desirable level of BW resistance, although it has been recognized that resistance can be an outstanding component for disease management. However, the sources of resistance available lack agronomic traits required by potato growers, therefore being of little interest to breeders. The objective of this work was to evaluate the performance of 11 clones selected for BW resistance and improved for tuber traits upon selection in the last two decades. The clones under test were compared with susceptible and resistant clones and cultivars, in a completely randomized blocks design with three replications of single lines of 10 plants, in a field naturally infested with race 1, biovar 1, phylotype II of R. solanacearum. BW incidence was assessed 60-70 days after planting and total tuber yield in each plot was recorded 110 days after planting. All the evaluated clones presented higher levels of resistance to BW compared with the commercial varieties, not differing from the resistant, not commercial, controls. In a next step, these clones will be characterized for other desirable traits and those which combine high level of resistance and commercial characteristics will be recommended for breeders for enriching the genotypic background in the search for commercial varieties. We also confirmed that the cultivar BRSIPR Bel displays an intermediate level of resistance, what makes it an interesting genitor for its good agronomic characteristics. The findings of this work demonstrate that the improved potato clones selected under tropical conditions in the Embrapa’s pre-breeding project possess high and stable levels of resistance to bacterial wilt, being a valuable resource for breeders.

Multiple mutations in the predicted transmembrane domains of the cellulose synthase 3 (CesA3) of Phytophthora capsici can confer semi-dominant resistance to carboxylic acid amide fungicides

The current study established a clearer understanding of the molecular basis for resistance to carboxylic acid amide (CAA) fungicides. Although four cellulose synthase (CesA) genes were investigated, only F1073L, G1105A, V1109L in CesA3 were found to link to CAA-resistance in Phytophthora capsici. Back-transformation experiments confirmed the role of the three mutations in CAA-resistance. Inheritance studies also confirmed the link and indicated the resistance was semi-dominant with the heterozygous F1 and F2 progeny exhibiting intermediate resistance levels compared to the homozygous parents, which was validated by the pyrosequencing results. The semi-dominant nature of CAA-resistance implies that it could be easy for resistance to spread once resistance emerged, being facilitated by both sexual and asexual reproduction. Bioinformatic analysis indicated all mutations occurred in either the first or second of the predicted transmembrane domains at C-terminus of CesA3. Resistant isolates bearing different combinations of mutations were found to exhibit different resistance levels to different CAAs, indicating that each mutation could make different contributions to resistance phenotype depending on structural differences in different CAAs. The current results highlight the complex combinations of mutations and resistance phenotype, and further reinforces the research necessity to completely characterize CAA-resistance to develop appropriate strategies to manage resistance development.

The poultry pathogen Riemerella anatipestifer appears as a reservoir for Tet(X) tigecycline resistance.

The transferability of bacterial resistance to tigecycline, the 'last-resort' antibiotic, is an emerging challenge of global health concern. The plasmid-borne tet(X) that encodes a flavin-dependent monooxygenase represents a new mechanism for tigecycline resistance. Natural source for an ongoing family of Tet(X) resistance determinants is poorly understood. Here, we report the discovery of 26 new variants [tet(X18) to tet(X44)] from the poultry pathogen Riemerella anatipestifer, which expands extensively the current Tet(X) family. R. anatipestifer appears as a natural reservoir for tet(X), of which the chromosome harbours varied copies of tet(X) progenitors. Despite that an inactive ancestor rarely occurs, the action and mechanism of Tet(X2/4)-P, a putative Tet(X) progenitor, was comprehensively characterized, giving an intermediate level of tigecycline resistance. The potential pattern of Tet(X) dissemination from ducks to other animals and humans was raised, in the viewpoint of ecological niches. Therefore, this finding defines a large pool of natural sources for Tet(X) tigecycline resistance, heightening the need of efficient approaches to manage the inter-species transmission of tet(X) resistance determinants.

Isolation and Characterization of Gram-Negative Bacterial Species from Pasteurized Dairy Products: Potential Risk to Consumer Health

Pathogenic bacterial contaminants of dairy products cause economic and human life losses if not destroyed by pasteurization. Gram-negative bacteria are among such major contaminants. Contamination persists because of faulty pasteurization or occurs during postpasteurization processing. Many factors, including presence of asymptomatic healthy carriers, existence of broad-range host pathogens, and resistance of pathogens to ordinary disinfectants, hamper the control of such pathogens. Here, samples of pasteurized dairy products were subjected to enrichment/selective cultures to test for possible Salmonella contamination, followed by growth on/in various media to test for phenotypic properties and some virulence characteristics of isolates (catalase, urease, oxidase, gelatinase, etc.). Isolates were characterized by phenotypic and genotypic tests for identification and resistance to clinically relevant antibiotics, including disk diffusion and for β-lactamase production. All milk samples harbored Gram-negative bacilli, which constitute a public health hazard. All of the isolates exhibited intermediate-level or higher resistance to ≥2 clinically relevant antibiotics, while some were susceptible. None tested positive for phenotypic gelatin hydrolysis but exhibited alpha- or beta-hemolysis. Sequence alignments of 16S rRNA gene partial sequences suggested up to 99% sequence similarities to subspecies of Salmonella enterica. Most isolates were also β-lactamase producers, especially blaTEM. In conclusion, high contamination rates were found in all Ethiopian pasteurized milk samples. The reasons for this burden of contamination need to be elucidated for meaningful and targeted control. Larger studies are needed, specifically to reveal points of entry of potential pathogens into dairy products. Information from this work will help to address and control previously unrecognized health hazards associated with consumption of pasteurized dairy products.

Physiological effects of tangeretin and heptamethoxyflavone on obese C57BL/6J mice fed a high-fat diet and analyses of the metabolites originating from these two polymethoxylated flavones.

Two compounds from citrus peel, tangeretin (TAN) and 3′,4′,3,5,6,7,8‐heptamethoxyflavone (HMF), were investigated for their abilities to repair metabolic damages caused by an high‐fat diet (HFD) in C57BL/6J mice. In the first 4 weeks, mice were fed either a standard diet (11% kcal from fat) for the control group, or a HFD (45% kcal from fat) to establish obesity in three experimental groups. In the following 4 weeks, two groups receiving the HFD were supplemented with either TAN or HMF at daily doses of 100 mg/kg body weight, while the two remaining groups continued to receive the standard healthy diet or the nonsupplemented HFD. Four weeks of supplementation with TAN and HMF resulted in intermediate levels of blood serum glucose, leptin, resistin, and insulin resistance compared with the healthy control and the nonsupplemented HFD groups. Blood serum peroxidation (TBARS) levels were significantly lower in the TAN and HMF groups compared with the nonsupplemented HFD group. Several differences occurred in the physiological effects of HMF versus TAN. TAN, but not HMF, reduced adipocyte size in the mice with pre‐existent obesity, while HMF, but not TAN, decreased fat accumulation in the liver and also significantly increased the levels of an anti‐inflammatory cytokine, IL‐10. In an analysis of the metabolites of TAN and HMF, several main classes occurred, including a new set of methylglucuronide conjugates. It is suggested that contrasts between the observed physiological effects of TAN and HMF may be attributable to the differences in numbers and chemical structures of TAN and HMF metabolites.

Resistance to Bemisia tabaci (Hemiptera: Aleyrodidae) Mediterranean (Q Biotype) in Landrace and Wild Tomato Populations from Mexico

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Mediterranean (Q biotype) is a major pest of tomato (Solanum lycopersicum L.; Solanaceae) globally. To our knowledge, no whitefly resistant cultivar has been released commercially, and breeding programs are hampered by the lack of resistance sources to this insect which are related closely to the cultivated tomato. Two non-free-choice experiments on B. tabaci with 22 landrace (S. lycopersicum) and wild tomato (S. lycopersicum var. ‘cerasiforme') populations from Mexico were performed to find sources of antibiosis resistance to this insect. Plants were infested with 20 insects per 1 leaflet of each plant using plastic micro-cages. In both assays, the number of adults and eggs were counted at 4 d post infestation, the number of nymphs (12 d post infestation), new adults, and non-glandular trichomes at 28 d post infestation. The highest B. tabaci resistance was detected in the UTC-SV13 population followed by UTC-SV12, UTC-SV1, and UTC-SV3 with a range of 15.0 to 20.0 dead adults, 0.0 to 16.5 eggs, 0.0 to 12.6 nymphs, 0.0 to 9.7 new adults per leaflet, and with a reproduction index of 0.0 to 21.7. Ten populations showed an intermediate level of resistance significantly lower in the number of dead adults, eggs, nymphs, new adults, and reproduction index compared to the commercial cultivar (‘Bonny Best') used as the standard. The remaining 8 genotypes and the commercial cultivar were fully susceptible to B. tabaci. The number of non-glandular trichomes correlated significantly with the number of eggs, nymphs, and new adults emerging from the infested plants, suggesting that the density of non-glandular trichomes is favorable for whitefly reproduction. Those genotypes with moderate to high levels of resistance to B. tabaci are potential candidates for developing commercial tomato cultivars with some resistance levels to this insect.