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1.
Heliyon ; 10(11): e32425, 2024 Jun 15.
Article in English | MEDLINE | ID: mdl-38961906

ABSTRACT

This paper investigates the enrichment of gold through combustion and ash-leaching techniques utilizing woody biomass as a fuel source. It delves into the formation of gold in ashes derived from the fixed grate combustion of pelletized woody biomass containing noble metals, conducted at a pilot-scale boiler. The biomass sample was gathered from a brownfield land at an abandoned mining area, avoiding induced phytoextraction. The fuel contained <0.05 mg/kg gold, while the bottom ash, after heat exchanger ash, deposited ash, and fly ash contained 1.52 mg/kg, 1.99 mg/kg, 2.64 mg/kg, and 3.52 mg/kg of gold, respectively. Although the amount of fly ash is lower compared to bottom ash, the concentration of gold is the highest in fly ash, which follows the after heat exchanger ash and bottom ash. The concentration of gold was enriched by a three-stage procedure of water leaching, acid leaching (10 % HCl), and alkaline leaching (5 % NaOH), after which 12.1 mg/kg and 12.6 mg/kg gold was found in the residues obtained from leached bottom ash and deposited ash, respectively. SEM was utilized to depict the morphology of gold, which appears in bottom ash as individual neat particles with a purity higher than 98 %. Pure gold particles in the size of 1-2 µm are presented in the after heat exchanger ash; meanwhile, gold in fly ash is primarily associated with potassium, sodium, sulfur, and oxygen. The findings in this study pave the way for reclaiming gold from bio-ores as well as assist in better understanding the formation of this precious metal in these secondary resources.

2.
Heliyon ; 10(3): e23546, 2024 Feb 15.
Article in English | MEDLINE | ID: mdl-38322853

ABSTRACT

The extraction of rare earth elements (REEs) and noble metals (NMs) from unconventional resources is playing a crucial role under the context of industrialization and reserve depletions. Plants used for phytoextraction are promising materials for the recovery of metals, but the biomass needs to be reduced to a manageable amount and volume prior to the extraction process. This paper investigates the combustion process of biomass focusing on NMs and REEs flow. The plants harvested from a brownfield land were pelletized and incinerated in a fixed-grate pilot-scale boiler, meanwhile, solid remains from various points in the combustion and flue gas system were captured and analyzed. The results show that levels of NMs in deposited ash and fly ash are greater than in bottom ash. Meanwhile, the higher REE concentration in bottom ash compared to that in other solid residuals demonstrates the less ability of these compounds to escape from the combustion chamber. Generally, the concentrations of REEs and NMs in the solid residues are significantly higher compared to biomass. SEM-EDS analyses of the contaminated solid remains indicate that gold forms individual particles with purity higher than 95 wt% in the bottom ashes, and this finding adds novel insights into gold phytomining.

3.
Bioresour Technol ; 395: 130363, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38253244

ABSTRACT

Rice husk, rich carbon content, is an agricultural waste produced globally at an amount of 120 million tons annually, and it has high potential as a biorefinery feedstock. Herein, we investigated the feasibility of producing various products as D-psicose, bioethanol and lactic acid from rice husk (RH) through a biorefinery process. Alkali-hydrogen peroxide-acetic acid pretreatment of RH effectively removed lignin and silica, resulting in enzymatic hydrolysis yield of approximately 86.3% under optimal hydrolysis conditions. By using xylose isomerase as well as D-psicose-3-epimerase with borate, glucose present in the RH hydrolysate was converted into D-psicose with a 40.6% conversion yield in the presence of borate. Furthermore, bioethanol (85.4%) and lactic acid (92.5%) were successfully produced from the RH hydrolysate. This study confirmed the high potential of RH as a biorefinery feedstock, and it is expected that various platform chemicals and value-added products can be produced using RH.


Subject(s)
Oryza , Oryza/chemistry , Borates , Lactic Acid , Fructose , Hydrolysis
4.
Biotechnol J ; 19(1): e2300309, 2024 Jan.
Article in English | MEDLINE | ID: mdl-38180273

ABSTRACT

Corynebacterium glutamicum is a useful microbe that can be used for producing succinic acid under anaerobic conditions. In this study, we generated a knock-out mutant of the lactate dehydrogenase 1 gene (ΔldhA-6) and co-expressed the succinic acid transporter (Psod:SucE- ΔldhA) using the CRISPR-Cpf1 genome editing system. The highly efficient HPAC (hydrogen peroxide and acetic acid) pretreatment method was employed for the enzymatic hydrolysis of softwood (Pinus densiflora) and subsequently utilized for production of succinic acid. Upon evaluating a 1%-5% hydrolysate concentration range, optimal succinic acid production with the ΔldhA mutant was achieved at a 4% hydrolysate concentration. This resulted in 14.82 g L-1 succinic acid production over 6 h. No production of acetic acid and lactic acid was detected during the fermentation. The co-expression transformant, [Psod:SucE-ΔldhA] produced 17.70 g L-1 succinic acid in 6 h. In the fed-batch system, 39.67 g L-1 succinic acid was produced over 48 h. During the fermentation, the strain consumed 100% and 73% of glucose and xylose, respectively. The yield of succinic acid from the sugars consumed was approximately 0.77 g succinic acid/g sugars. These results indicate that the production of succinic acid from softwood holds potential applications in alternative biochemical processes.


Subject(s)
Corynebacterium glutamicum , Corynebacterium glutamicum/genetics , Succinic Acid , Clustered Regularly Interspaced Short Palindromic Repeats , Fermentation , Glucose , Acetates
5.
Molecules ; 28(8)2023 Apr 18.
Article in English | MEDLINE | ID: mdl-37110796

ABSTRACT

Coffee waste is often viewed as a problem, but it can be converted into value-added products if managed with clean technologies and long-term waste management strategies. Several compounds, including lipids, lignin, cellulose and hemicelluloses, tannins, antioxidants, caffeine, polyphenols, carotenoids, flavonoids, and biofuel can be extracted or produced through recycling, recovery, or energy valorization. In this review, we will discuss the potential uses of by-products generated from the waste derived from coffee production, including coffee leaves and flowers from cultivation; coffee pulps, husks, and silverskin from coffee processing; and spent coffee grounds (SCGs) from post-consumption. The full utilization of these coffee by-products can be achieved by establishing suitable infrastructure and building networks between scientists, business organizations, and policymakers, thus reducing the economic and environmental burdens of coffee processing in a sustainable manner.


Subject(s)
Antioxidants , Polyphenols , Lignin , Flavonoids , Caffeine , Waste Products/analysis
6.
Heliyon ; 9(3): e13945, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36851954

ABSTRACT

Coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has become one of the most serious public health crises worldwide. Most infected people are asymptomatic but are still able to spread the virus. People with mild or moderate illnesses are likely to recover without hospitalization, while critically ill patients face a higher risk of organ injury or even death. In this study, we aimed to identify a novel biomarker that can predict the severity of COVID-19 patients. Clinical information and RNA-seq data of leukocytes from whole blood samples with and without a COVID-19 diagnosis (n = 100 and 26, respectively) were retrieved from the National Center for Biotechnology Information Gene Expression Omnibus database. Raw data were processed using the Transcripts Per Million (TPM) method and then transformed using log2 (TPM+1) for normalization. The CD24-CSF1R index was established. Violin plots, Kaplan-Meier curves, ROC curves, and multivariate Cox proportional hazards regression analyses were performed to evaluate the prognostic value of the established index. The CD24-CSF1R index was significantly associated with ICU admission (n = 50 ICU, 50 non-ICU) and ventilatory status (n = 42 ventilation, 58 non-ventilation) with p = 4.186e-11 and p = 1.278e-07, respectively. The ROC curve produced a relatively accurate prediction of ICU admission with an AUC of 0.8524. Additionally, patients with a high index had significantly fewer mechanical ventilation-free days than patients with a low index (p = 6.07e-07). Furthermore, the established index showed a strong prognostic ability for the risk of using a ventilator in the multivariate Cox regression model (p < 0.001). The CD24-CSF1R index was significantly associated with COVID-19 severity. The established index could have potential implications for prognosis, disease severity stratification, and clinical management.

7.
Bioresour Technol ; 372: 128694, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36731613

ABSTRACT

Herein, we investigated the possibility of co-producing xylo-oligosaccharides (XOSs) from bamboo, as value-added products, along with succinic and lactic acids, as platform chemicals. Xylan was extracted from bamboo using the alkali method under mild conditions. From xylan, XOSs were produced by partial enzymatic hydrolysis at a conversion rate of 83.9%, and all reaction conditions resulted in similar degrees of polymerization. Hydrogen peroxide-acetic acid (HPAC) pretreatment effectively removed lignin from NaOH-treated bamboo, and the enzymatic hydrolytic yield of NaOH and HPAC-treated bamboo was 84.3% of the theoretical yield. The production of succinic and lactic acids from the hydrolysate resulted in conversion rates of approximately 63.2% and 91.3% of the theoretical yield using Corynebacterium glutamicum Δldh and Actinobacillus succinogenes, respectively, under facultative anaerobic conditions. This study demonstrates that bamboo has a high potential to produce value-added products using a biorefinery process and is an alternative resource for compounds typically derived from petroleum.


Subject(s)
Lactic Acid , Succinic Acid , Fermentation , Succinic Acid/chemistry , Sodium Hydroxide , Xylans , Oligosaccharides , Hydrolysis , Hydrogen Peroxide
8.
Environ Sci Ecotechnol ; 15: 100238, 2023 Jul.
Article in English | MEDLINE | ID: mdl-36785801

ABSTRACT

The rate of textile waste generation worldwide has increased dramatically due to a rise in clothing consumption and production. Here, conversion of cotton-based, colored cotton-based, and blended cotton-polyethylene terephthalate (PET) textile waste materials into value-added chemicals (bioethanol, sorbitol, lactic acid, terephthalic acid (TPA), and ethylene glycol (EG)) via enzymatic hydrolysis and fermentation was investigated. In order to enhance the efficiency of enzymatic saccharification, effective pretreatment methods for each type of textile waste were developed, respectively. A high glucose yield of 99.1% was obtained from white cotton-based textile waste after NaOH pretreatment. Furthermore, the digestibility of the cellulose in colored cotton-based textile wastes was increased 1.38-1.75 times because of the removal of dye materials by HPAC-NaOH pretreatment. The blended cotton-PET samples showed good hydrolysis efficiency following PET removal via NaOH-ethanol pretreatment, with a glucose yield of 92.49%. The sugar content produced via enzymatic hydrolysis was then converted into key platform chemicals (bioethanol, sorbitol, and lactic acid) via fermentation or hydrogenation. The maximum ethanol yield was achieved with the white T-shirt sample (537 mL/kg substrate), which was 3.2, 2.1, and 2.6 times higher than those obtained with rice straw, pine wood, and oak wood, respectively. Glucose was selectively converted into sorbitol and LA at a yield of 70% and 83.67%, respectively. TPA and EG were produced from blended cotton-PET via NaOH-ethanol pretreatment. The integrated biorefinery process proposed here demonstrates significant potential for valorization of textile waste.

9.
Chemosphere ; 297: 134259, 2022 Jun.
Article in English | MEDLINE | ID: mdl-35271907

ABSTRACT

The increasing demand for rare earth elements (REEs) for modern industry has led to a surge in mining activities and consequently has released these metals into the environment. Intensifying REEs in a habitat has impacts on its ecosystem, but on the other side, it also provides the opportunity to recover REEs from low-grade minerals. Phytomining has emerged as an ecologically sound technique to extract these valuable elements from contaminated soils where traditional mining is not competitive. This paper presents and reviews the concept of REE phytomining from three scientific areas. The accumulation of rare earth metals in plants is the first stage, referred to as the phytoextraction process. This is followed by elevating REE concentrations into bio-ores via the enrichment phase. Ultimately, extraction is the final step to complete the phytomining pathway for reclaiming REEs in brownfield land.


Subject(s)
Ecosystem , Metals, Rare Earth , Metals , Metals, Rare Earth/analysis , Mining , Plants
10.
Chemosphere ; 286(Pt 3): 131805, 2022 Jan.
Article in English | MEDLINE | ID: mdl-34391113

ABSTRACT

Phytomining of noble metals (NMs) offers a promising possibility of metal extraction at sites where traditional mining activities or recovering NMs from low-grade minerals are not competitive. In addition to conventional mining, producing NMs from secondary resources strengthening the circular economy has been paid worldwide attention. The review presented in this paper links three scientific areas as the essential elements to form the phytomining chain of NMs. The accumulation of NMs in plants is the first step, referred as the phytoextraction process. This is followed by heightening the concentration of NMs via the enrichment stage. Eventually, although less well understood, extraction methods of NMs from biomass solid remains as well as from diverse secondary sources particularly incineration ashes are discussed that assist to visualize the potential pathways in phytomining.


Subject(s)
Metals, Heavy , Soil Pollutants , Biodegradation, Environmental , Incineration , Metals , Metals, Heavy/analysis , Mining , Soil Pollutants/analysis
11.
Bioresour Technol ; 346: 126618, 2022 Feb.
Article in English | MEDLINE | ID: mdl-34954357

ABSTRACT

Spent coffee grounds (SCG) are inexpensive materials with a complex composition that makes them promising feedstocks for a biorefinery.Here, conversion of SCG into a wide range of high value-added products (coffee oil, bio-ethanol, D-mannose, manno-oligosaccharide (MOS), cafestol and kahweol) using a novel integrated system was evaluated. The process involves oil extraction, MOS production by mannanase obtained from Penicillium purpurogenum, NaOH (Na) and hydrogen peroxide (HP) pretreatment for the degradation of lignin and phenolic compounds, diterpenes extraction, enzymatic hydrolysis, and fermentation, which can be performed using environmentally friendly technologies. Approximately 97 mL of coffee oil, 164 g of D-mannose, 102 g of MOS, 99 g of bioethanol and a dash of cafestol/kahweol were produced from 1 kg of dry SCG. Producing high-value co-products from SCG using an integrated approach as demonstrated here may be an efficient strategy to reduce waste generation, while improving the economics of the biorefinery production process.


Subject(s)
Coffee , Ethanol , Fermentation , Hydrolysis , beta-Mannosidase
12.
Radiol Case Rep ; 16(9): 2658-2662, 2021 Sep.
Article in English | MEDLINE | ID: mdl-34345326

ABSTRACT

Ischiopagus conjoined twinning is a rare congenital defect. The surgical separation of conjoined twins is difficult because of the complex anatomy and physiology. Careful preoperative assessment, planning, and effective surgical teams are critically important for achieving a good outcome. We describe the successful separation of ischiopagus tetrapus conjoined twins as a representative case demonstrating the growth of pediatric surgery in southern Vietnam.

13.
Radiol Case Rep ; 16(8): 2311-2314, 2021 Aug.
Article in English | MEDLINE | ID: mdl-34194596

ABSTRACT

Acute renal failure due to primary renal Burkitt lymphoma in children is extremely rare. We report a case with acute secondary renal failure in a 4-year-old boy who presented with abdominal pain, anorexia, and vomiting. Abdominal computed tomography scans showed bilateral nephromegaly with multiple hypoenhancing regions. Renal biopsy confirmed Burkitt lymphoma. There was no lymphadenopathy or evidence of other solid organ involvement. The patient was responsive to treatment using the EPOCH-R protocol (etoposide, prednisone, vincristine, cyclophosphamide , doxorubicin, and rituximab). Here, we describe the clinical and imaging features associated with this rare entity.

14.
Radiol Case Rep ; 16(8): 1931-1933, 2021 Aug.
Article in English | MEDLINE | ID: mdl-34149977

ABSTRACT

Spontaneous cerebrospinal fluid (CSF) rhinorrhea is rare and may develop secondary to inner ear malformation. A possible diagnosis of CSF leak should be considered in any pediatric patient who presents with hearing impairment, rhinorrhea, or otorrhea. Temporal bone computed tomography should be performed in children with hearing impairments. We describe a case of congenital inner ear anomaly in a 12-month-old girl who presented with intermittent rhinorrhea after birth and detected hearing problems when she was 6 months. After diagnosis, the CSF leak was surgically repaired without complications.

15.
Radiol Case Rep ; 16(8): 2139-2141, 2021 Aug.
Article in English | MEDLINE | ID: mdl-34158907

ABSTRACT

Hepatic mesenchymal hamartoma is an uncommon tumor composed of myxoid mesenchymal tissue with fluid accumulation. Here, we report a case of hepatic mesenchymal hamartoma in a 3-year-old patient who was referred to the hospital with abdominal pain and a slight fever. An abdominal ultrasound suggested a liver abscess; however, computed tomography revealed a mass with both cystic and solid components. Liver biopsy confirmed hepatic mesenchymal hamartoma, and this patient underwent the complete removal of this tumor.

16.
BMC Gastroenterol ; 21(1): 216, 2021 May 12.
Article in English | MEDLINE | ID: mdl-33980171

ABSTRACT

BACKGROUND: This retrospective analysis was undertaken to evaluate the efficiency of SIRT with Y-90 microspheres and determined prognostic factors affecting patients with unresectable HCC. METHODS: A total of 97 patients diagnosed with unresectable HCC who underwent SIRT with Y-90 microspheres. Patient survival was assessed using the Kaplan-Meier method, and prognostic factors affecting survival were assessed using log-rank tests and Cox proportional hazards regression. RESULTS: Among the 97 patients (90 males, mean age 60.4 ± 12.3 years) who underwent SIRT, the median clinical follow-up was 16.4 (1.8-62) months. The median overall survival (OS) was 23.9 ± 2.4 months. Tumor response according to the Modified RECIST in patients followed up beyond 6 months included a complete response (CR) to treatment in 12 patients (18.8%), partial response (PR) in 23 (35.8%), stable disease (SD) in 8 (12.5%), and progressive disease (PD) in 21 (32.8%). Factors associated with longer OS included age > 65 years, BCLC stage B, tumor size < 5 cm, tumor burden < 25%, and tumor response (CR/PR). In multivariate analysis, unilobar disease and objective tumor response (CR/PR) were predictors of longer OS. CONCLUSION: SIRT was an effective treatment for unresectable HCC. Unilobar disease before SIRT and tumor response (CR/PR) were positive prognostic factors.


Subject(s)
Carcinoma, Hepatocellular , Liver Neoplasms , Aged , Carcinoma, Hepatocellular/radiotherapy , Humans , Liver Neoplasms/radiotherapy , Male , Middle Aged , Retrospective Studies , Treatment Outcome , Yttrium Radioisotopes/adverse effects
17.
Int J Cancer ; 148(11): 2848-2856, 2021 06 01.
Article in English | MEDLINE | ID: mdl-33586202

ABSTRACT

Acetylserotonin O-methyltransferase (ASMT) is a key enzyme in the synthesis of melatonin. Although melatonin has been shown to exhibit anticancer activity and prevents endocrine resistance in breast cancer, the role of ASMT in breast cancer progression remains unclear. In this retrospective study, we analyzed gene expression profiles in 27 data sets on 7244 patients from 11 countries. We found that ASMT expression was significantly reduced in breast cancer tumors relative to healthy tissue. Among breast cancer patients, those with higher levels of ASMT expression had better relapse-free survival outcomes and longer metastasis-free survival times. Following treatment with tamoxifen, patients with greater ASMT expression experienced longer periods before relapse or distance recurrence. Motivated by these results, we devised an ASMT gene signature that can correctly identify low-risk cases with a sensitivity and specificity of 0.997 and 0.916, respectively. This signature was robustly validated using 23 independent breast cancer mRNA array data sets from different platforms (consisting of 5800 patients) and an RNAseq data set from TCGA (comprising 1096 patients). Intriguingly, patients who are classified as high-risk by the signature benefit from adjuvant chemotherapy, and those with grade II tumors who are classified as low-risk exhibit improved overall survival and distance relapse-free outcomes following endocrine therapy. Together, our findings more clearly elucidate the roles of ASMT, provide strategies for improving the efficacy of tamoxifen treatment and help to identify those patients who may maximally benefit from adjuvant or endocrine therapies.


Subject(s)
Acetylserotonin O-Methyltransferase/genetics , Breast Neoplasms/drug therapy , Sequence Analysis, RNA/methods , Tamoxifen/therapeutic use , Up-Regulation , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Databases, Genetic , Female , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , Humans , Neoplasm Grading , Oligonucleotide Array Sequence Analysis , Retrospective Studies , Survival Analysis , Treatment Outcome
18.
Sci Rep ; 11(1): 3207, 2021 02 05.
Article in English | MEDLINE | ID: mdl-33547398

ABSTRACT

99mTc-macroaggregated albumin (MAA) imaging is performed before transarterial radioembolization (TARE), in which SPECT/CT is presumed more precise than planar image. However, additive role of SPECT/CT has not been well established. Thirty-four consecutive hepatocellular carcinoma patients of intermediate and advanced stages who underwent 90Y-microsphere TARE were recruited. On pre-treatment planning scan using 99mTc-MAA, image characteristics and absorbed dose for target tumors calculated by partition model methods were estimated on planar image and SPECT/CT, respectively. The measurements were repeated on post-treatment 90Y PET/CT, as the reference standard. Treatment response was assessed and predictive values of image parameters were analyzed. The image characteristics including heterogeneity, necrosis and thrombosis uptake were better delineated on SPECT/CT than planar scan. The agreement and correlation of TNr between SPECT/CT and PET/CT were stronger than those between planar scan and PET/CT. Tumor dose estimated on 99mTc-MAA SPECT/CT was more effective than planar image for prediction of treatment response, with cutoff value 125 Gy (sensitivity of 86% and specificity of 75%). In conclusion, 99mTc-MAA SPECT/CT is more closely correlated with post-treatment 90Y PET/CT, and is more effective for predicting treatment response than planar scan. SPECT/CT is superior to planar image in simulation before 90Y TARE.


Subject(s)
Carcinoma, Hepatocellular/diagnosis , Liver Neoplasms/diagnosis , Single Photon Emission Computed Tomography Computed Tomography/methods , Technetium Tc 99m Aggregated Albumin/analysis , Aged , Albumins/analysis , Carcinoma, Hepatocellular/diagnostic imaging , Carcinoma, Hepatocellular/therapy , Embolization, Therapeutic , Female , Humans , Liver Neoplasms/diagnostic imaging , Liver Neoplasms/therapy , Male , Middle Aged , Prognosis
19.
Biosci Biotechnol Biochem ; 84(11): 2293-2302, 2020 Nov.
Article in English | MEDLINE | ID: mdl-32741269

ABSTRACT

High collagenolytic activity has been detected in pathogenic bacteria. Collagenase plays an essential role in the invasion step in animals and humans. In this study, we characterized collagenase found in the nonpathogenic bacterium Lysinibacillus sphaericus VN3, which was isolated from soil in Vietnam. The collagenase activity of the purified enzyme was strongly inhibited by Cu2+, but it was significantly increased by Zn2+. The purified enzyme with a molecular mass of approximately 110 kDa exhibited collagenolytic, gelatinolytic, and caseinolytic activity. The kinetic studies showed that this enzyme had greater hydrolyzing activity toward collagen and gelatin compared with casein. Based on the ratio V max/K m, collagen is likely to be the best substrate among three proteins. We found that this collagenase could digest small pieces of bovine skin and tendon into a collagen solution. Interestingly, at pH 6.0-8.0, the soluble collagen could form a collagen membrane, which is useful as a wound-healing biomaterial.


Subject(s)
Bacillaceae/enzymology , Collagenases/metabolism , Hydrolysis , Temperature
20.
Front Vet Sci ; 6: 174, 2019.
Article in English | MEDLINE | ID: mdl-31294033

ABSTRACT

Chicken is, among farmed species, the target of the highest levels of antimicrobial use (AMU). There are considerable knowledge gaps on how and when antimicrobials are used in commercial small-scale chicken farms. These shortcomings arise from cross-sectional study designs and poor record keeping practiced by many such farmers. Furthermore, there is a large diversity of AMU metrics, and it is not clear how these metrics relate to each other. We performed a longitudinal study on a cohort of small-scale chicken farms (n = 102) in the Mekong Delta (Vietnam), an area regarded as a hotspot of AMU, from October 2016 to May 2018. We collected data on all medicine products administered to 203 flocks with the following aims: (1) to describe types and quantities of antimicrobial active ingredients (AAIs) used; (2) to describe critical time points of AMU; and (3) to compare AMU using three quantitative metrics: (a) weight of AAIs related to bird weight at the time of treatment (mg/kg at treatment); (b) weight of AAIs related to weight of birds sold (mg/kg sold); and (c) "treatment incidence" (TI), or the number of daily doses per kilogram of live chicken [Vietnamese animal daily dose (ADDvetVN)] per 1,000 days. Antimicrobials contained in commercial feed, administered by injection (n = N = 6), or antimicrobials for human medicine (n = N = 16) were excluded. A total of 236 products were identified, containing 42 different AAIs. A total of 76.2% products contained AAIs of "critical importance" according to the World Health Organization (WHO). On average, chickens consumed 791.8 (SEM ±16.7) mg/kg at treatment, 323.4 (SEM ±11.3) mg/kg sold, and the TI was 382.6 (SEM ±5.5) per 1,000 days. AMU was more common early in the production cycle and was highly skewed, with the upper 25% quantile of flocks accounting for 60.7% of total AMU. The observed discrepancies between weight- and dose-based metrics were explained by differences in the strength of AAIs, mortality levels, and the timing of administration. Results suggest that in small-scale chicken production, AMU reduction efforts should preferentially target the early (brooding) period, which is when birds are most likely to be exposed to antimicrobials, whilst restricting access to antimicrobials of critical importance for human medicine.

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