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1. Quantifying Antibiotic Distribution in Solid and Liquid Fractions of Manure Using a Two-Step, Multi-Residue Antibiotic Extraction

   https://doi.org/10.3390/antibiotics11121735  

   Poindexter, Carlton ; Yarberry, Andrea ; Rice, Clifford ; Lansing, Stephanie ( December 2022 , Antibiotics)

   Antibiotic distribution and analysis within liquid and solid fractions of manure are highly variable due to each compound’s respective physiochemical properties. This study developed and evaluated a uniform method extracting 10 antibiotics from 4 antibiotic classes (tetracycline, sulfonamides, macrolides, and β-lactam) from unprocessed manure, solid–liquid separated manure, and composted solids. Through systematic manipulation of previously published liquid chromatography tandem mass spectrometry methods; this study developed an extraction protocol with optimized recovery efficiencies for varied manure substrates. The method includes a two-step, liquid-solid extraction using 10 mL of 0.1 M EDTA-McIlviane buffer followed by 10 mL of methanol. Antibiotics recoveries from unprocessed manure, separated liquids, separated solids, and heat-treated solids using the two-step extraction method had relative standard deviations < 30% for all but ceftiofur. Total antibiotic recoveries were 67–131% for tetracyclines, 56% for sulfonamide, 49–53% for macrolides, and 1.3–66% for β-lactams. This is the first study to use one protocol to assess four classes of antibiotics in liquid and solid manure fractions. This study allowed for more precise risk assessment of antibiotic transport in manure waste stream applied to fields as a liquid or solid compost. 

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2. Modeling Antibiotic Use Strategies in Intensive Care Units: Comparing De-escalation and Continuation

   https://doi.org/10.1007/s11538-019-00686-x  

   Huo, Xi ( January 2020 , Bulletin of Mathematical Biology)
3. Effects of Nutrient Level and Growth Rate on the Conjugation Process That Transfers Mobile Antibiotic Resistance Genes in Continuous Cultures

   https://doi.org/10.1128/aem.01121-22  

   Shafieifini, Mohammadreza ; Sun, Yuepeng ; Staley, Zachery R. ; Riethoven, Jean-Jack ; Li, Xu ( October 2022 , Applied and Environmental Microbiology)

   Elkins, Christopher A. (Ed.)

   WWTPs have been regarded as an important hot spot of ARGs. The discharge point of WWTP effluent, where ARGs may be horizontally transferred from bacteria of treated wastewater to bacteria of receiving water, is an important interface between the human-dominated ecosystem and the natural environment.

    

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4. Analysis of virulence phenotypes and antibiotic resistance in clinical strains of Acinetobacter baumannii isolated in Nashville, Tennessee

   https://doi.org/10.1186/s12866-020-02082-1  

   Boone, Ranashia L. ; Whitehead, Briana ; Avery, Tyra M. ; Lu, Jacky ; Francis, Jamisha D. ; Guevara, Miriam A. ; Moore, Rebecca E. ; Chambers, Schuyler A. ; Doster, Ryan S. ; Manning, Shannon D. ; et al ( December 2021 , BMC Microbiology)

   null (Ed.)

   Abstract Background Acinetobacter baumannii is a gram-negative bacterium which causes opportunistic infections in immunocompromised hosts. Genome plasticity has given rise to a wide range of strain variation with respect to antimicrobial resistance profiles and expression of virulence factors which lead to altered phenotypes associated with pathogenesis. The purpose of this study was to analyze clinical strains of A. baumannii for phenotypic variation that might correlate with virulence phenotypes, antimicrobial resistance patterns, or strain isolation source. We hypothesized that individual strain virulence phenotypes might be associated with anatomical site of isolation or alterations in susceptibility to antimicrobial interventions. Methodology A cohort of 17 clinical isolates of A. baumannii isolated from diverse anatomical sites were evaluated to ascertain phenotypic patterns including biofilm formation, hemolysis, motility, and antimicrobial resistance. Antibiotic susceptibility/resistance to ampicillin-sulbactam, amikacin, ceftriaxone, ceftazidime, cefotaxime, ciprofloxacin, cefepime, gentamicin, levofloxacin, meropenem, piperacillin, trimethoprim-sulfamethoxazole, ticarcillin- K clavulanate, tetracyclin, and tobramycin was determined. Results Antibiotic resistance was prevalent in many strains including resistance to ampicillin-sulbactam, amikacin, ceftriaxone, ceftazidime, cefotaxime, ciprofloxacin, cefepime, gentamicin, levofloxacin, meropenem, piperacillin, trimethoprim-sulfamethoxazole, ticarcillin- K clavulanate, tetracyclin, and tobramycin. All strains tested induced hemolysis on agar plate detection assays. Wound-isolated strains of A. baumannii exhibited higher motility than strains isolated from blood, urine or Foley catheter, or sputum/bronchial wash. A. baumannii strains isolated from patient blood samples formed significantly more biofilm than isolates from wounds, sputum or bronchial wash samples. An inverse relationship between motility and biofilm formation was observed in the cohort of 17 clinical isolates of A. baumannii tested in this study. Motility was also inversely correlated with induction of hemolysis. An inverse correlation was observed between hemolysis and resistance to ticarcillin-k clavulanate, meropenem, and piperacillin. An inverse correlation was also observed between motility and resistance to ampicillin-sulbactam, ceftriaxone, ceftoxamine, ceftazidime, ciprofloxacin, or levofloxacin. Conclusions Strain dependent variations in biofilm and motility are associated with anatomical site of isolation. Biofilm and hemolysis production both have an inverse association with motility in the cohort of strains utilized in this study, and motility and hemolysis were inversely correlated with resistance to numerous antibiotics. 

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5. Selective Methylation by an ArsM S -Adenosylmethionine Methyltransferase from Burkholderia gladioli GSRB05 Enhances Antibiotic Production

   https://doi.org/10.1021/acs.est.2c04324  

   Chen, Jian ; Galván, Adriana E. ; Viswanathan, Thiruselvam ; Yoshinaga, Masafumi ; Rosen, Barry P. ( September 2022 , Environmental Science & Technology)

   Arsenic methylation contributes to the formation and diversity of environmental organoarsenicals, an important process in the arsenic biogeochemical cycle. The arsM gene encoding an arsenite (As(III)) S-adenosylmethionine (SAM) methyltransferase is widely distributed in members of every kingdom. A number of ArsM enzymes have been shown to have different patterns of methylation. When incubated with inorganic As(III), Burkholderia gladioli GSRB05 has been shown to synthesize the organoarsenical antibiotic arsinothricin (AST) but does not produce either methylarsenate (MAs(V)) or dimethylarsenate (DMAs(V)). Here, we show that cells of B. gladioli GSRB05 synthesize DMAs(V) when cultured with either MAs(III) or MAs(V). Heterologous expression of the BgarsM gene in Escherichia coli conferred resistance to MAs(III) but not As(III). The cells methylate MAs(III) and the AST precursor, reduced trivalent hydroxyarsinothricin (R-AST-OH) but do not methylate inorganic As(III). Similar results were obtained with purified BgArsM. Compared with ArsM orthologs, BgArsM has an additional 37 amino acid residues in a linker region between domains. Deletion of the additional 37 residues restored As(III) methylation activity. Cells of E. coli co-expressing the BgarsL gene encoding the noncanonical radical SAM enzyme that catalyzes the synthesis of R-AST-OH together with the BgarsM gene produce much more of the antibiotic AST compared with E. coli cells co-expressing BgarsL together with the CrarsM gene from Chlamydomonas reinhardtii, which lacks the sequence for additional 37 residues. We propose that the presence of the insertion reduces the fitness of B. gladioli because it cannot detoxify inorganic arsenic but concomitantly confers an evolutionary advantage by increasing the ability to produce AST. 

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