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1. Comparative resistomics analysis of multidrug‐resistant Chryseobacteria

   https://doi.org/10.1111/1758-2229.13288  

   Pham, Dung_Ngoc; Li, Mengyan (June 2024, Environmental Microbiology Reports)

   Abstract Chryseobacteriaconsists of important human pathogens that can cause a myriad of nosocomial infections. We isolated four multidrug‐resistantChryseobacteriumbacteria from activated sludge collected at domestic wastewater treatment facilities in the New York Metropolitan area. Their genomes were sequenced with Nanopore technology and used for a comprehensive resistomics comparison with 211Chryseobacteriumgenomes available in the public databases. A majority ofChryseobacteriaharbor 3 or more antibiotic resistance genes (ARGs) with the potential to confer resistance to at least two types of commonly prescribed antimicrobials. The most abundant ARGs, including β‐lactam class A (blaCGA‐1andblaCIA) and class B (blaCGB‐1andblaIND) and aminoglycoside (ranAandranB), are considered potentially intrinsic inChryseobacteria. Notably, we reported a new resistance cluster consisting of a chloramphenicol acetyltransferase genecatB11, a tetracycline resistance genetetX, and two mobile genetic elements (MGEs),IS91family transposase andXerDrecombinase. BothcatB11andtetXare statistically enriched in clinical isolates as compared to those with environmental origins. In addition, two other ARGs encoding aminoglycoside adenylyltransferase (aadS) and the small multidrug resistance pump (abeS), respectively, are found co‐located with MGEs encoding recombinases (e.g.,RecAandXerD) or transposases, suggesting their high transmissibility amongChryseobacteriaand across theBacteroidotaphylum, particularly those with high pathogenicity. High resistance to different classes of β‐lactam, as well as other commonly used antimicrobials (i.e., kanamycin, gentamicin, and chloramphenicol), was confirmed and assessed using our isolates to determine their minimum inhibitory concentrations. Collectively, though the majority of ARGs inChryseobacteriaare intrinsic, the discovery of a new resistance cluster and the co‐existence of several ARGs and MGEs corroborate interspecies and intergenera transfer, which may accelerate their dissemination in clinical environments and complicate efforts to combat bacterial infections. 

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2. The impact of aminoglycoside exposure on soil and plant root-associated microbiota: a meta-analysis

   https://doi.org/10.1186/s13750-025-00365-6  

   Coates, Jessica_L; Lawson, Ashanti_J; Bostick, Kathleen; Ayalew, Mentewab (July 2025, Environmental Evidence)

   Abstract BackgroundExposure to aminoglycosides, a class of potent bactericidal antibiotics naturally produced by soil microorganisms and commonly used in agriculture, has the potential to cause shifts in the population dynamics of microorganisms that impact plant and soil health. In particular, aminoglycoside exposure could result in alterations of the soil and plant root-associated bacterial species diversity and richness due to their potent inhibitory action on microbial growth, the creation of selective conditions for the proliferation of antibiotic-resistant bacteria, or a reduction in the ability to suppress soil pathogens. Previous studies have attempted to understand the relationship between aminoglycoside exposure and the plant-associated microbiota with varying results. Thus, this systematic review aims to survey all relevant published data to answer the question, “What is the impact of aminoglycoside exposure on the soil and plant root-associated microbiota?” MethodsWe searched 5 academic databases and 1 specialist organization database for scientific journal publications written in any language. Articles were included based on the criteria described in Coates et al., 2022. Included studies were subject to critical appraisal using the CEE Critical Appraisal Tool Version 0.2 (Prototype) to evaluate their susceptibility to confounding factors, misclassification bias, selection bias, attrition bias, reporting bias and analysis bias. Studies deemed to be high risk based on critical appraisal results were excluded from further analysis. Descriptive data analysis was performed for studies considered low or unclear for risk of bias. Meta-analyses were conducted for antibiotic resistance and microbial diversity. Review findingsOut of 8370 screened records, 50 articles fulfilled the search criteria, and from these, 13 studies were included in meta-analysis. Most studies investigated the impact of aminoglycoside exposure on soil microbiota (93%) in a laboratory setting (62%), primarily from the United States (32%), China (24%), France, Switzerland and Germany (8%). A limited number of studies investigated the impact of aminoglycoside exposure on disease suppression, so it was excluded from meta-analysis. Therefore, our synthesis primarily details the impact of aminoglycoside exposure on the microbial diversity and antibiotic resistance of the soil microbiota. Overall, exposure to aminoglycosides did not result in a significant change in the microbial diversity. However, soil use, pH, and type of aminoglycoside used could be potential modifiers. Additionally, we observed an average 7% of the microbial population exhibiting resistance to aminoglycosides, with the relationship between the exposure concentration and the selection concentration emerging as a potential modifier. ConclusionsCurrent research is limited by gaps in understanding the relationship between aminoglycoside exposure, microbial community dynamics, and disease suppression, as well as by insufficient data on less-studied aminoglycosides and key confounding factors. Current research also suggests a potential relationship between antibiotic concentrations used for exposure and selection of resistant bacteria. These findings emphasize the need for informed antibiotic management policies and rigorous, targeted research to better understand the relationship between soil factors and antibiotic concentrations used on the impact of aminoglycosides on soil microbiota. 

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3. Environmental alkalization suppresses deployment of virulence strategies in Pseudomonas syringae pv. tomato DC3000

   https://doi.org/10.1128/jb.00086-24  

   Yang, Zichu; Wang, Haibi; Keebler, Robert; Lovelace, Amelia; Chen, Hsiao-Chun; Kvitko, Brian; Swingle, Bryan (November 2024, Journal of Bacteriology)

   Becker, Anke (Ed.)

   ABSTRACT Plant pathogenic bacteria encounter a drastic increase in apoplastic pH during the early stages of plant immunity. The effects of alkalization on pathogen-host interactions have not been comprehensively characterized. Here, we used a global transcriptomic approach to assess the impact of environmental alkalization onPseudomonas syringaepv.tomatoDC3000in vitro. In addition to the Type 3 Secretion System, we found expression of genes encoding other virulence factors such as iron uptake and coronatine biosynthesis to be strongly affected by environmental alkalization. We also found that the activity of AlgU, an important regulator of virulence gene expression, was induced at pH 5.5 and suppressed at pH 7.8, which are pH levels that this pathogen would likely experience before and during pattern-triggered immunity, respectively. This pH-dependent control requires the presence of periplasmic proteases, AlgW and MucP, that function as part of the environmental sensing system that activates AlgU in specific conditions. This is the first example of pH-dependency of AlgU activity, suggesting a regulatory pathway model where pH affects the proteolysis-dependent activation of AlgU. These results contribute to deeper understanding of the role apoplastic pH has on host-pathogen interactions.IMPORTANCEPlant pathogenic bacteria, likePseudomonas syringae, encounter many environmental changes including oxidative stress and alkalization during plant immunity, but the ecological effects of the individual responses are not well understood. In this study, we found that transcription of many previously characterized virulence factors inP. syringaepv.tomatoDC3000 is downregulated by the level of environmental alkalization these bacteria encounter during the early stages of plant immune activation. We also report for the first time the sigma factor AlgU is post-translationally activated by low environmental pH through its natural activation pathway, which partially accounts for the expression Type 3 Secretion System virulence genes at acidic pH. The results of this study demonstrate the importance of extracellular pH on global regulation of virulence-related gene transcription in plant pathogenic bacteria. 

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4. CRISPR RNA ‐guided integrase enables high‐efficiency targeted genome engineering in Agrobacterium tumefaciens

   https://doi.org/10.1111/pbi.13872  

   Aliu, Ephraim; Lee, Keunsub; Wang, Kan (July 2022, Plant Biotechnology Journal)

   Summary Agrobacterium tumefaciens, the causal agent of plant crown gall disease, has been widely used to genetically transform many plant species. The inter‐kingdom gene transfer capability madeAgrobacteriuman essential tool and model system to study the mechanism of exporting and integrating a segment of bacterial DNA into the plant genome. However, many biological processes such asAgrobacterium‐host recognition and interaction are still elusive. To accelerate the understanding of this important plant pathogen and further improve its capacity in plant genetic engineering, we adopted a CRISPR RNA‐guided integrase system forAgrobacteriumgenome engineering. In this work, we demonstrate thatINsertion ofTransposableElements byGuideRNA–AssistedTargEting (INTEGRATE) can efficiently generate DNA insertions to enable targeted gene knockouts. In addition, in conjunction with Cre‐loxPrecombination system, we achieved precise deletions of large DNA fragments. This work provides new genetic engineering strategies forAgrobacteriumspecies and their gene functional analyses. 

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5. Antibiotic resistance trends among Vibrio vulnificus and Vibrio parahaemolyticus isolated from the Chesapeake Bay, Maryland: a longitudinal study

   https://doi.org/10.1128/aem.00539-24  

   Morgado, Michele E; Brumfield, Kyle D; Chattopadhyay, Suhana; Malayil, Leena; Alawode, Taiwo; Amokeodo, Ibiyinka; He, Xin; Huq, Anwar; Colwell, Rita R; Sapkota, Amy R (June 2024, Applied and Environmental Microbiology)

   Elkins, Christopher A (Ed.)

   ABSTRACT Antibiotics are often used to treat severeVibrioinfections, with third-generation cephalosporins and tetracyclines combined or fluoroquinolones alone being recommended by the US Centers for Disease Control and Prevention. Increases in antibiotic resistance of both environmental and clinical vibrios are of concern; however, limited longitudinal data have been generated among environmental isolates to inform how resistance patterns may be changing over time. Hence, we evaluated long-term trends in antibiotic resistance of vibrios isolated from Chesapeake Bay waters (Maryland) across two 3-year sampling periods (2009–2012 and 2019–2022).Vibrio parahaemolyticus(n= 134) andVibrio vulnificus(n= 94) toxR-confirmed isolates were randomly selected from both sampling periods and tested for antimicrobial susceptibility against eight antibiotics using the Kirby-Bauer disk diffusion method. A high percentage (94%–96%) ofV. parahaemolyticusisolates from both sampling periods were resistant to ampicillin and only 2%–6% of these isolates expressed intermediate resistance or resistance to third-generation cephalosporins, amikacin, tetracycline, and trimethoprim-sulfamethoxazole. Even lower percentages of resistantV. vulnificusisolates were observed and those were mostly recovered from 2009 to 2012, however, the presence of multiple virulence factors was observed. The frequency of multi-drug resistance was relatively low (6%–8%) but included resistance against antibiotics used to treat severe vibriosis in adults and children. All isolates were susceptible to ciprofloxacin, a fluoroquinolone, indicating its sustained efficacy as a first-line agent in the treatment of severe vibriosis. Overall, our data indicate that antibiotic resistance patterns amongV. parahaemolyticusandV. vulnificusrecovered from the lower Chesapeake Bay have remained relatively stable since 2009.IMPORTANCEVibriospp. have historically been susceptible to most clinically relevant antibiotics; however, resistance and intermediate-resistance have been increasingly recorded in both environmental and clinical isolates. Our data showed that while the percentage of multi-drug resistance and resistance to antibiotics was relatively low and stable across time, someVibrioisolates displayed resistance and intermediate resistance to antibiotics typically used to treat severe vibriosis (e.g., third-generation cephalosporins, tetracyclines, sulfamethoxazole-trimethoprim, and aminoglycosides). Also, given the high case fatality rates observed withVibrio vulnificusinfections, the presence of multiple virulence factors in the tested isolates is concerning. Nevertheless, the continued susceptibility of all tested isolates against ciprofloxacin, a fluoroquinolone, is indicative of its use as an effective first-line treatment of severeVibriospp. infections stemming from exposure to Chesapeake Bay waters or contaminated seafood ingestion. 

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