The tigecycline resistance gene tetX has an expensive fitness cost based on increased outer membrane permeability and metabolic burden in Escherichia coli.

Livestock-derived tetX-positive Escherichia coli with tigecycline resistance poses a serious risk to public health. Fitness costs, antibiotic residues, and other tetracycline resistance genes (TRGs) are fundamental in determining the spread of tetX in the environment, but there is a lack of relevant studies. The results of this study showed that both tetO and tetX resulted in reduction in growth and an increased in the metabolic burden of E. coli, but the presence of doxycycline reversed this phenomenon. Moreover, the protection of E. coli growth and metabolism by tetO was superior to that of tetX in the presence of doxycycline, resulting in a much lower competitiveness of tetX-carrying E. coli than tetO-carrying E. coli. The results of RNA-seq showed that the increase in outer membrane proteins (ompC, ompF and ompT) of tetX-carrying E. coli resulted in increased membrane permeability and biofilm formation, which is an important reason for fitness costs. Overall, the increased membrane permeability and metabolic burden of E. coli is the mechanistic basis for the high fitness cost of tetX, and the spread of tetO may limit the spread of tetX. This study provides new insights into the rational use of tetracycline antibiotics to control the spread of tetX.

Bioconversion of cyanobacteria by black soldier fly larvae (Hermetia illucens L.): Enhancement by antioxidants.

Cyanobacterial blooms have been a global environmental problem for decades. Bioconversion by black soldier fly larvae (BSFL) has been widely reported to be a clean and efficient method to remove organic pollutants. In this study, BSFL bioconversion was used to treat cyanobacterial blooms. Antioxidants (a mixture of l-ascorbic acid [180 mg/kg fresh feed] and α-tocopherol [360 mg/kg fresh feed]) were added to compare bioconversion performance against a non-supplemented group. With increasing proportions of cyanobacteria (0%-25% dry mass), the bioconversion efficiency of the antioxidant group improved significantly compared to the control group, and the survival rate of larvae rose from 96.50-45.50% to 98.00-55.83% with antioxidant addition. The toxic effects of exogenous anti-nutrients could be reduced by the antioxidants through inactivation of trypsin inhibitor and enhancement of the microcystin-LR degradation rate. Overall, the BSFL bioremediation capacity was improved with addition of exogenous antioxidants, verifying both the effects and mechanism of antioxidant addition in promoting the bioconversion of cyanobacteria by BSFL and providing a basis for future application and study.

Clinical value of the emergency department in screening and diagnosis of COVID-19 in China.

Since the global outbreak of severe acute respiratory syndrome (SARS) in 2003, China has gradually built a robust prevention and control system for sudden infectious diseases. All large hospitals have a fever clinic that isolates patients with all kinds of acute communicable diseases as the first line of medical defense. The emergency department, as the second line of medical defense in hospitals, is constantly shouldering the heavy responsibility of screening communicable diseases while also treating all kinds of other non-communicable acute and critical diseases (Zhang et al., 2012; Zhu et al., 2015; Wang et al., 2017; Feng et al., 2018; Lu, 2018; Xu and Lu, 2019). An outbreak of pneumonia of unknown etiology that began in Wuhan city (China) has spread rapidly in China since December 2019 (Huang et al., 2020; WHO, 2020; Zhu et al., 2020). In February 2020, the National Health Commission of China named the disease a novel coronavirus pneumonia (NCP); then, it was formally named the coronavirus disease 2019 (COVID-19) by the World Health Organization (WHO) on Feb. 11, 2020. The Coronavirus Study Group of the International Committee on Taxonomy of Viruses designated this causative virus as SARS coronavirus 2 (SARS-CoV-2). SARS-CoV-2 belongs to the ß coronavirus genus, and its pathogenic mechanism has not been clarified, which requires further study. To better understand the clinical characteristics of COVID-19 and more effectively prevent and control this disease, we retrospectively analyzed four representative cases of COVID-19 that had recently been screened and diagnosed in our emergency department.