Background: The emergence and spread of carbapenem-resistant Escherichia coli (E. coli) pose a serious threat to human health worldwide. This study aimed to investigate the molecular mechanisms underlying carbapenem resistance and their prevalence among E. coli in China. Methods: A collection of 5796 E. coli clinical isolates were collected from the First Affiliated Hospital of Wenzhou Medical University from 2002 to 2017. Sensitivity to antibiotics was determined using the agar dilution method. The detection of carbapenemases production and the prevalence of resistance-associated genes were investigated through modified carbapenem inactivation method (mCIM), PCR and sequencing. The mutations in outer membrane porins genes (ompC and ompF) were also analyzed by PCR and sequencing assays. The effect of efflux pump mechanism on carbapenem resistance was also tested. E. coli were typed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Results: A total of 58 strains (1.0%) of carbapenem-resistant E. coli were identified. The strains carrying bla KPC-2 and bla NDM accounted for 22.4% (13/58) and 51.7% (30/58), respectively. Among bla NDM -positive strains, 27 bla NDM genes were assigned to bla NDM-5 , while the remaining three strains were bla NDM-1 , whereas bla VIM , bla IMP , bla OXA-48 , and bla SHV were not found. The CTX-M-type β-lactamase genes accounted for 96.6% (56/58). In addition, bla TEM-1 genes were identified in 58.6% of tested strains. In carbapenem-resistant isolates, mutations in OmpC (the majority of mutated sites were D192G and Q104_F141del, accounting for 54.5%) and OmpF (large deletions S75_V127del, W83_D135del and Q88_D135del) were detected. Of note, the antibiotic resistance was not associated with overexpression of efflux pump. Moreover, MLST categorized the 58 carbapenem-resistant isolates into 19 different sequence types. PFGE analysis revealed that homology among the carbapenem-resistant isolates was low and sporadic. Conclusion: The bla NDM was the principal resistance mechanism of carbapenem-resistant E. coli in the hospital. bla NDM-5 is becoming a new threat to public health and the alteration of outer membrane porins might help further increase the MIC of carbapenem.

Background: Colistin resistance is considered a serious problem due to a lack of alternative antibiotics. The Rapid ResaPolymyxin Acinetobacter/Pseudomonas NP test is a resazurin reduction-based technique that relies on the visual detection of bacterial growth in the presence of a defined concentration of colistin. The aim of this study was to evaluate the performance of the Rapid ResaPolymyxin Acinetobacter/Pseudomonas NP test in the detection of colistin susceptibility in common clinical Gram-negative bacteria. Results: A total of 253 clinical isolates from a teaching hospital, including Acinetobacter baumanii (n = 58, 8 colistinresistant), Pseudomonas aeruginosa (n = 61, 11 colistin-resistant), Klebsiella pneumoniae (n = 70, 20 colistin-resistant) and Escherichia coli (n = 64, 14 colistin-resistant) were tested in this study. The sensitivity and specificity of the Rapid ResaPolymyxin Acinetobacter/Pseudomonas NP test compared to Broth microdilution method was 100 and 99%, respectively. Conclusions: Our results suggest that Rapid ResaPolymyxin Acinetobacter/Pseudomonas NP test could be used as an accurate detection method for colistin resistance.

Background We aimed to determine the evolutionary pathways of rifampicin resistance in Staphylococcus aureus, and the impact of resistance mutations in the rpoB gene on fitness. Methods Three clinical strains and one reference strain were used to select for rifampicin-resistant S. aureus variants. The mutations responsible for rifampicin resistance in all of the selected isolates in vitro were investigated by polymerase chain reaction (PCR) and DNA sequencing. To compare the fitness cost of rpoB mutations against their corresponding original isolates, we performed bacterial growth curve assays, static biofilm assays, in vitro competition experiments and an infection model of Galleria mellonella larvae. Results We obtained four rifampicin-resistant S. aureus isolates that showed high levels of resistance to rifampicin with a minimal inhibitory concentration (MIC) of 128 mg/L, and all isolates had a mutation at position 481 (H481F/Y) in RpoB. A broth microdilution assay indicated that mutation of H481F/Y did not affect susceptibility to common antibacterial drugs but slightly increased the vancomycin MIC. To identify the pathways involved in the development of rifampicin resistance, 32 variants (eight mutants for each strain) and four original isolates were selected for gene sequencing. Different generations of isolates were found to harbor various mutations sites. Compared with the corresponding original isolates, an in vitro fitness assay of the variant isolates showed that growth and virulence were reduced, with a statistically significantly decreased fitness, whereas the capacity for biofilm formation was elevated. Conclusions Our findings suggested that the acquisition of rifampicin resistance in S. aureus was dynamic and was associated with a significant fitness cost.

BackgroundSince the first HIV/AIDS case appeared in 1980s, HIV/AIDS has been the focus of international attention. As a major public health problem, there are epidemiological uncertainties about the future of HIV/AIDS. It is important to monitor the global statistics of HIV/AIDS prevalence, deaths, disability adjusted life years (DALYs), and risk factors for adequate prevention and control.MethodsThe Global Burden of Disease Study 2019 database was used to analyze the burden of HIV/AIDS in 1990–2019. By extracting global, regional, and national data on HIV/AIDS prevalence, deaths, and DALYs, we described the distribution by age and sex, explored the risk factors, and analyzed the trends in HIV/AIDS.ResultsIn 2019, there were 36.85 million HIV/AIDS cases (95% UI: 35.15–38.86 million), 863.84 thousand deaths (95% UI: 78.61–99.60 thousand), and 47.63 million (95% UI: 42.63–55.65 million) DALYs. The global age-standardized HIV/AIDS prevalence, death, and DALY rates were 454.32 (95% UI: 433.76–478.59), 10.72 (95% UI: 9.70–12.39), and 601.49 (95% UI: 536.16–703.92) per 100,000 cases, respectively. In 2019, the global age-standardized HIV/AIDS prevalence, death, and DALY rates increased by 307.26 (95% UI: 304.45–312.63), 4.34 (95% UI: 3.78–4.90), and 221.91 (95% UI: 204.36–239.47) per 100,000 cases, respectively, compared to 1990. Age-standardized prevalence, death, and DALY rates decreased in high sociodemographic index (SDI) areas. High age-standardized rates were observed in low sociodemographic index areas, while low age-standardized rates were observed in high sociodemographic index areas. In 2019, the high age-standardized prevalence, death, and DALY rates were predominant in Southern Sub-Saharan Africa, and global DALYs peaked in 2004 and subsequently decreased. The highest global HIV/AIDS DALYs were in the 40–44 age group. The main risk factors affecting HIV/AIDS DALY rates included behavioral risks, drug use, partner violence, and unsafe sex.ConclusionsHIV/AIDS disease burden and risk factors vary by region, sex, and age. As access to health care increases across countries and treatment for HIV/AIDS infection improves, the HIV/AIDS disease burden is concentrated in areas with low SDIs, particularly in South Africa. Regional differences should be fully considered to target optimal prevention strategies and treatment options based on risk factors.