RESUMEN
The simultaneous development of antibiotic resistance in bacteria due to metal exposure poses a significant threat to the environment and human health. This study explored how exposure to both arsenic and antibiotics affects the ability of an arsenite oxidizer, Achromobacter xylosoxidans CAW4, to transform arsenite and its antibiotic resistance patterns. The bacterium was isolated from arsenic-contaminated groundwater in the Chandpur district of Bangladesh. We determined the minimum inhibitory concentration (MIC) of arsenite, cefotaxime, and tetracycline for A. xylosoxidans CAW4, demonstrating a multidrug resistance (MDR) trait. Following this determination, we aimed to mimic an environment where A. xylosoxidans CAW4 was exposed to both arsenite and antibiotics. We enabled the strain to grow in sub-MIC concentrations of 1 mM arsenite, 40 µg/mL cefotaxime, and 20 µg/mL tetracycline. The expression dynamics of the arsenite oxidase (aioA) gene in the presence or absence of antibiotics were analyzed. The findings indicated that simultaneous exposure to arsenite and antibiotics adversely affected the bacteria's capacity to metabolize arsenic. However, when arsenite was present in antibiotics-containing media, it promoted bacterial growth. The study observed a global downregulation of the aioA gene in arsenic-antibiotic conditions, indicating the possibility of increased susceptibility through co-resistance across the entire bacterial population of the environment. This study interprets that bacterial arsenic-metabolizing ability can rescue the bacteria from antibiotic stress, further disseminating environmental cross-resistance. Therefore, the co-selection of metal-driven antibiotic resistance in bacteria highlights the need for effective measures to address this emerging threat to human health and the environment.
Asunto(s)
Arsénico , Arsenitos , Humanos , Arsénico/farmacología , Arsénico/metabolismo , Arsenitos/farmacología , Arsenitos/metabolismo , Antibacterianos/farmacología , Antibacterianos/metabolismo , Bacterias , Metales/farmacología , Metales/metabolismo , Farmacorresistencia Microbiana , Cefotaxima/metabolismo , Cefotaxima/farmacología , Tetraciclinas/metabolismo , Tetraciclinas/farmacologíaRESUMEN
Mine tailings sites are considered as a continuous source of discharged metal(loid)s and residual organic flotation reagents. They are extremely toxic environments representing unique ecological niches for microbial communities. Mine tailings as a source of multi-resistance genes have been poorly investigated. Metagenomic analysis for four active nonferrous metal(loid) tailings sites with different environmental parameters was conducted. The abundance of Thiobacillus, able to tolerate acidity and showing iron- and sulfur/sulfide oxidation capacities, was significantly different (p < 0.05) between acid and neutral tailings sites. Correlation analyses showed that Zn, Pb, TP, Cd, and Cu were the main drivers influencing the bacterial compositions. Multi-metal resistance genes (MRGs) and antibiotic resistance genes (ARGs), such as baca and copA, were found to be co-selected by high concentrations of metal(loid)s tailings. The main contributors to different distributions of MRGs were Thiobacillus and Nocardioides genus, while genera with low abundance (<0.1%) were the main contributors for ARGs. Functional metabolic pathways related to Fe-S metabolism, polycyclic aromatic hydrocarbons (PAHs) degradation and acid stress were largely from Altererythrobacter, Lysobacter, and Thiobacillus, respectively. Such information provides new insights on active tailings with highly toxic contaminants. Short-term metal(loid) exposure of microorganism in active nonferrous metal(loid) tailings contribute to the co-occurrence of ARGs and MRGs, and aggravation of tailings acidification. Our results recommend that the management of microorganisms involved in acid tolerance and metal/antibiotic resistance is of key importance for in-suit treatment of the continuous discharge of tailings with multiple metal(loid) contaminants into impoundments.
RESUMEN
Duck/fish polyculture farming is a typical farming model in the Pearl River delta in southern China. We examined soil, water, and sediment samples from three duck-fish farms in Guangdong Province in September and December 2014. We determined the abundance of three metal resistance genes, 16S rDNA, and 23 antibiotic resistance genes encoding resistance to tetracycline, sulfonamides, quinolones, chloramphenicol, and ß-lactamases. Microbial community structure was quantified by Illumina high-throughput sequencing of 16S rDNA genes. We found a prevalence of antibiotic resistance genes and the sul1, sul2, tetA, tetM, aac(6')-Ib, and floR genes were the most abundant. Levels of Cu and Zn were significantly correlated with numerous ARG types and sul2, floR, and tetM were identified as potential antibiotic resistance gene indicators. Cu levels were significantly and positively correlated with the relative abundance of sul3, tetT, tetW, qnrB, qnrS, fexB, sul1, sul2, tetM, and qnrA. Zn was significantly correlated to relative abundance of sul2, sul3, tetM, tetA, tetT, tetW, qnrA, qnrB, qnrS, aac(6')-Ib, qepA, blaSHV, cmlA, floR, fexA, cfr, and fexB. The levels of Acinetobacter, Brevibacillus, and Wautersiella showed significant positive correlations with metal resistance genes as well as qnrB, oqxA, oqxB, and blaSHV (p > 0.8). Sphingobacterium, Flavobacterium, Acidothermus, and Corynebacterium had significant correlations with abundance of tetracycline resistance genes, sulfonamide resistance genes, blaTEM, blaCTX, and cfr (p > 0.8). Sphingobacterium, Flavobacterium, Acidothermus, and Corynebacterium were most abundant in soil samples while Acinetobacter, Brevibacillus, and Wautersiella were most abundant in water samples. Dissemination of antibiotic resistance genes in aquaculture environments is extensive and tracing their origins is necessary to establish risk assessment methods required for aquatic environmental protection.