Insight into the impacts and mechanisms of ketone stress on the antibiotic resistance in Escherichia coli

Prevalence and molecular characterization of multi-drug and extreme drug resistant Escherichia coli in companion animals in Bangladesh

The study aimed to investigate multi-drug resistant (MDR) Escherichia coli (E. coli) in companion animals in Bangladesh, with a focus on the resistance profiles of isolates from non-food-producing animals. In 2023, the studied samples were from cats, dogs, and environmental sources linked with companion animal hospitals in Dhaka city, Bangladesh. E. coli was isolated using standard techniques and its antimicrobial resistance (AMR) was assessed against 23 antibiotics following the CLSI protocols. Metallo-beta-lactamase genes (blaNDM-1 and blaNDM-5) and mobile genetic elements (class 1 integron) were detected by multiplex PCR. The overall prevalence of E. coli was 70%, 76% in cats, 65.71% in dogs, and 65.71% in the environmental samples. Cefuroxime exhibited the highest resistance at 25%, while imipenem and nitrofurantoin showed the highest sensitivity at 100%, followed by ceftazidime at 95%. MDR strains made up 38.10%, while 11.90% were extremely drug-resistant (XDR). Additionally, 29% of E. coli were extended-spectrum beta-lactamase (ESBL) producers. The prevalence and association among class 1 integron and the resistant genes including blaNDM-1 and blaNDM-5 were also notable. This highlights the complex AMR challenges in these settings, including the presence of class 1 integron-a key element involved in capturing and transferring antimicrobial resistance genes.

Antibiotics and antibiotic resistance change bacterial community compositions in marine sediments

Emerging contaminants, including antibiotics, antibiotic-resistant bacteria (ARB), and extracellular antibiotic resistance genes (eARGs), have been detected in large numbers in the aquatic environment. The effects of emerging contaminants on bacterial communities in marine sediments are not well studied. In this study, the effects of emerging contaminants (antibiotics, ARB, and eARGs) on the variations of bacterial populations in marine sediments of the Bohai Sea, Yellow Sea, East China Sea, and South China Sea were investigated. The results showed that the abundance of the host bacterial phylum Probacteria in the marine sediments of the Bohai Sea was the lowest among the four seas after exposure to different antibiotics, ARB, and eARGs. The inputs of exogenous antibiotics and resistance genes significantly affected the community function, resulting in significant differences in community abundance at the genus level. The abundance of Halomonas, Sulfitobacter, and Alcanivorax in the four sea areas displayed noteworthy differences in response to the addition of exogenous antibiotics and eARGs. These findings contribute to a more comprehensive understanding of the intricate interplay between emerging contaminants and the dynamics of bacterial communities in natural ecosystems.

Selective degradation of antibiotic in a novel Cu7S4/peroxydisulfate system via heterogeneous Cu(III) formation: Performance, mechanism and toxicity evaluation

Efficient degradation of antibiotic by peroxydisulfate (PDS)-based advanced oxidation processes in complex water environment is challenging due to the interference of impurities and the low activation efficiency of PDS caused by its symmetric structure. Herein, a novel Cu₇S₄/PDS system was developed, which can selectively remove tetracycline hydrochloride (TC) without interference of inorganic ions (e.g., Cl^- and HCO₃^-) and natural organic matter (e.g., humic acid). The results of quenching and probe experiments demonstrated that surface high-valent copper species (Cu(III)), rather than radicals and ¹O₂, are main active species for TC degradation. Cu(III) can be generated via Cu(I)/O₂ and Cu(II)/Cu(I)/PDS systems and the S species on the surface of Cu₇S₄ promotes the cycle of Cu(II)/Cu(I) and Cu(III)/Cu(II), resulting in continuous generation of Cu(III). In addition, the degradation pathways of TC were proposed based on product analysis and DFT theory calculations. The acute toxicity, developmental toxicity and mutagenicity of treated TC were significantly reduced according to the results of toxicity estimation software tool. This study shows a promising Cu₇S₄/PDS system for the degradation and detoxication of antibiotic in complex water environment, while also providing a comprehensive understanding of PDS activation by Cu₇S₄ to generate active Cu(III) species.

Augmented dissemination of antibiotic resistance elicited by non-antibiotic factors

The emergence and rapid spread of antibiotic resistance seriously compromise the clinical efficacy of current antibiotic therapies, representing a serious public health threat worldwide. Generally, drug-susceptible bacteria can acquire antibiotic resistance through genetic mutation or gene transfer, among which horizontal gene transfer (HGT) plays a dominant role. It is widely acknowledged that the sub-inhibitory concentrations of antibiotics are the key drivers in promoting the transmission of antibiotic resistance. However, accumulating evidence in recent years has shown that in addition to antibiotics, non-antibiotics can also accelerate the horizontal transfer of antibiotic resistance genes (ARGs). Nevertheless, the roles and potential mechanisms of non-antibiotic factors in the transmission of ARGs remain largely underestimated. In this review, we depict the four pathways of HGT and their differences, including conjugation, transformation, transduction and vesiduction. We summarize non-antibiotic factors accounting for the enhanced horizontal transfer of ARGs and their underlying molecular mechanisms. Finally, we discuss the limitations and implications of current studies.