Nonlinear spectral compression in high-power narrow-linewidth polarization maintaining fiber amplifiers for SBS suppression.

In this paper, we propose a method for narrowing the spectrum in high-power narrow-linewidth polarization-maintaining (PM) fiber amplifiers and investigate its potential for suppressing the stimulated Brillouin scattering (SBS). In this method, in addition to common phase modulation to suppress SBS, precisely designed amplitude modulation is induced to generate self-phase modulation in a high-power PM fiber amplifier. In this co-modulation way, the spectrum can be gradually compressed along the fiber. Compared to phase modulation alone or fiber-Bragg-gratings (FBGs) based narrow-linewidth fiber oscillator schemes, in which the spectrum remains the same or broadens, this scheme can achieve a higher SBS threshold for the same output spectral linewidth. Experiments on a ∼ 3 kW peak power quasi-continuous wave (QCW) fiber amplifier show that the co-modulation scheme can compress the spectrum from 0.25 nm to 0.084 nm as output peak power increases from 13 W to 3.2 kW and enhances the SBS threshold by ∼1.7 times compared to traditional FBGs-based fiber oscillator schemes, and by ∼1.4 times compared to common phase modulation schemes. This co-modulation scheme has the potential for mitigating SBS in high-power fiber amplifiers.

Clinical impact of the type VI secretion system on clinical characteristics, virulence and prognosis of Acinetobacter baumannii during bloodstream infection.

The type VI secretion system (T6SS) has been regarded as a late-model virulence factor widely distributed in Acinetobacter baumannii (A. baumannii). This study aimed to elucidate the clinical manifestations, the genetic background and microbiological characteristics of A. baumannii isolates causing bloodstream infection (BSI), and assessed the impact of T6SS carrying state on the clinical course. In this study, Clinical samples of A. baumannii causing BSI were collected from a teaching hospital in China from 2016 to 2020 and a retrospective cohort was conducted. Experimental strains were categorized into T6SS positive and negative groups through PCR targeting on hcp gene. The antimicrobials sensitivity test, virulence genes, biofilm formation ability, serum resistance of A. baumannii strains and Galleria mellonella infection model were investigated. Independent risk factors for T6SS+ A. baumannii BSI and Kaplan-Meier curve through follow-up survey were analyzed. A total of 182 A. baumannii strains were isolated from patients with BSI during 5 years and the medical records of all patients were retrospectively reviewed. The proportion of T6SS+ isolates was 62.64% (114/182), which exhibited significantly higher resistance rates of commonly used antibacterial drugs compared to T6SS- group. We found that T6SS+ A. baumannii strains had significantly weaker biofilm formation ability compared to T6SS- A. baumannii. Despite no difference in the positivity rate of tested virulence genes in two groups, T6SS+ strains exhibited higher resistance to the serum and increased virulence in vivo compared to T6SS- strains, indicating that T6SS is likely to enhance the survival and invasive capabilities of A. baumannii in vivo. Indwelling catheter, respiratory diseases, ICU history, white blood cell count and percentage of neutrophils increasing were independent risk factors for T6SS+ A. baumannii BSI. At last, the Kaplan-Meier curve confirmed a higher mortality rate associated with T6SS+ A. baumannii BSI, suggesting that the presence of T6SS may serve as a prognostic factor for mortality. In conclusion, our study revealed that T6SS+ A. baumannii exhibited distinct clinical features, characterized by high antimicrobial resistance and enhanced virulence, providing valuable insights for clinical treatment considerations.

Characterization of resistance mechanisms of Enterobacter cloacae Complex co-resistant to carbapenem and colistin.

BACKGROUND: The emergence of carbapenem-resistant and colistin-resistant ECC pose a huge challenge to infection control. The purpose of this study was to clarify the mechanism of the carbapenems and colistin co-resistance in Enterobacter cloacae Complex (ECC) strains. RESULTS: This study showed that the mechanisms of carbapenem resistance in this study are: 1. Generating carbapenemase (7 of 19); 2. The production of AmpC or ESBLs combined with decreased expression of out membrane protein (12 of 19). hsp60 sequence analysis suggested 10 of 19 the strains belong to colistin hetero-resistant clusters and the mechanism of colistin resistance is increasing expression of acrA in the efflux pump AcrAB-TolC alone (18 of 19) or accompanied by a decrease of affinity between colistin and outer membrane caused by the modification of lipid A (14 of 19). Moreover, an ECC strain co-harboring plasmid-mediated mcr-4.3 and blaNDM-1 has been found. CONCLUSIONS: This study suggested that there is no overlap between the resistance mechanism of co-resistant ECC strains to carbapenem and colistin. However, the emergence of strain co-harboring plasmid-mediated resistance genes indicated that ECC is a potential carrier for the horizontal spread of carbapenems and colistin resistance.

Effect of solvent environment on excited state intramolecular proton transfer in 2-(4-(dimethylamino)phenyl)-3-hydroxy-6,7-dimethoxy-4h-chromen-4-one.

The new ratiometric fluorescent probe 2-(4-(dimethylamino)phenyl)-3-hydroxy-6,7-dimethoxy-4h-chromen-4-one (HOF) monitoring of methanol in biodiesel was discovered experimentally (T. Y. Qin et al., Sens. Actuators, B, 2018, 277, 484-491). But the experimental study did not report the reaction mechanism in detail. In this study, density functional theory (DFT) and time-density functional theory (TDDFT) methods were used to theoretically study the excited-state intramolecular proton transfer (ESIPT) process of the HOF molecule. The molecular structure in the ground state and the excited state was optimized, and the infrared vibrational spectra, the frontier molecular orbitals, the charge transfer, the potential energy curves and the transition-state structures were calculated. The calculated results prove that the solvent polarity has a great influence on the ESIPT reaction of the HOF molecule. As the solvent polarity increased, the intensity of the intramolecular hydrogen bond decreased, and ESIPT was more difficult to occur. This work has studied the mechanism of the ESIPT reaction in more detail, and paved the way for future research on HOF molecules.

Circular RNA circSEMA5A facilitates colorectal cancer development by regulating microRNA-195-5p to target CCNE1 axis.

Colorectal cancer (CRC) is one of the most prevalent malignancies with a high mortality rate worldwide. Circular RNAs (circRNAs) have lately emerged as key molecules involved in cancer development and metastasis. CircSEMA5 is reported to be oncogenic in some cancers, yet its role in the pathogenesis of CRC remains unknown. Herein, we attempted to investigate the functional role and molecular mechanism of circSEMA5A underlying CRC progression. RT-qPCR and RNase R digestion assays were used to evaluate circSEMA5A expression characteristics in CRC cells. Loss-of-function assays were performed to clarify circSEMA5A role in CRC biological processes. Bioinformatics and mechanism experiments were conducted to assess the association of circSEMA5A or CCNE1 with miR-195-5p in CRC cells. Rescue assays were conducted to explore the regulatory function of circSEMA5A-miR-195-5p-CCNE1 in CRC cellular processes. Through bioinformatics and functional screening, we found that circSEMA5A was highly expressed in CRC cells and was mainly localized in the nucleus. CircSEMA5A promoted CRC proliferative, migratory, and invasive capabilities in cultured cells and facilitated the tumorigenic process in xenografts; however, circSEMA5A silencing repressed tumor metastasis in CRC cells. Mechanistically, circSEMA5A was competitively bound with miR-195-5p to upregulate CCNE1 expression. Moreover, the impact of circSEMA5A knockdown on CRC cell proliferative, migratory, and invasive capabilities was countervailed by miR-195-5p inhibitor or CCNE1 overexpression. To summarize, circSEMA5A is a novel circRNA that serves as an oncogene in CRC progression. CircSEMA5A facilitates CRC cell malignancy and tumor growth through sponging miR-195-5p to upregulate CCNE1, thus providing a new direction for CRC diagnosis and targeted therapy.

Glabridin Functions as a Quorum Sensing Inhibitor to Inhibit Biofilm Formation and Swarming Motility of Multidrug-Resistant Acinetobacter baumannii.

Objective: Acinetobacter baumannii is a hazardous bacterium that causes hospital-acquired nosocomial infections, and the advent of multidrug-resistant A. baumannii (MDR-AB) strains is concerning. Novel antibacterial therapeutic strategies must be developed. The biological effects of glabridin on MDR-AB were investigated in this study. Methods: The minimum inhibitory concentrations (MICs) of glabridin against eight clinical MDR-AB strains were determined using the broth microdilution technique. Crystal violet staining was used to assess biofilm development, which has significant contribution to bacterial resistance. Swarming motility was measured according to surface growth zone of MDR-AB on LB agar medium. qRT-PCR was used to evaluate the expression of quorum sensing genes abaI and abaR. Glabridin and routinely used therapeutic antimicrobial agents were tested for synergistic action using the checkerboard method. Results: According to our findings, glabridin suppressed MDR-AB growth at high doses (512-1024 µg/mL). The 1/4 MIC of glabridin significantly decreased MDR-AB biofilm formation by 19.98% (P < 0.05), inhibited MDR-AB motility by 44.27% (P < 0.05), whereas the 1/2 MIC of glabridin dramatically reduced MDR-AB biofilm development by 27.43% (P < 0.01), suppressed MDR-AB motility by 50.64% (P < 0.05). Mechanistically, glabridin substantially downregulated the expression of quorum sensing-related genes abaI and abaR by up to 39.12% (P < 0.001) and 25.19% (P < 0.01), respectively. However, no synergistic effect between glabridin and antibacterial drugs was found. Conclusion: Glabridin might be a quorum sensing inhibitor that inhibits MDR-AB biofilm development and swarming motility.

Acquisition of Daptomycin Resistance by Enterococcus faecium Confers Collateral Sensitivity to Glycopeptides.

Daptomycin is a last-line antibiotic used in the treatment of multidrug-resistant Enterococcus faecium infections. Alarmingly, daptomycin-resistant E. faecium isolates have emerged. In this study, we investigated the evolution and mechanisms of daptomycin resistance in clinical E. faecium isolates and the corresponding acquisition of collateral sensitivity (CS) as an evolutionary trade-off. We evolved daptomycin resistance in six daptomycin-susceptible E. faecium isolates to obtain daptomycin-resistant mutants. The six E. faecium strains successfully acquired high-level resistance to daptomycin in vitro, but this led to fitness costs in terms of growth, in vitro competition, and virulence. Mutations in liaFSR, yycFG, and cls; increased surface positive charge; thicker cell walls; and elevated expression of dltABCD and tagGH were observed in daptomycin-resistant mutants. Surprisingly, we observed the emergence of CS in SC1762 isolates after the induction of daptomycin resistance. Compared with parental strains, the SC1174-D strain (i.e., daptomycin-resistant mutant of SC1174; non-CS) showed significantly upregulated expression of the vanA gene cluster. However, in SC1762-D (i.e., daptomycin-resistant mutant of SC1762), all vanA cluster genes except the vanX gene were obviously downregulated. Further in silico analyses revealed that an IS1216E-based composite transposon was generated in SC1762-D, and it disrupted the vanH gene, likely affecting the structure and expression of the vanA gene cluster and resulting in resensitization to glycopeptides. Overall, this study reports a novel form of CS between daptomycin and glycopeptides in E. faecium. Further, it provides a valuable foundation for developing effective regimens and sequential combinations of daptomycin and glycopeptides against E. faecium.

Cluster Differences in Antibiotic Resistance, Biofilm Formation, Mobility, and Virulence of Clinical Enterobacter cloacae Complex.

Due to the lack of research on the characteristics of different clusters of Enterobacter cloacae complex (ECC), this study aimed to characterize and explore the differences among species of the ECC. An analysis based on hsp60 showed that Enterobacter hormaechei was predominant in ECC. Interestingly, the antibiotic resistance rates of clusters were different, among which E. hormaechei subsp. steigerwaltii (cluster VIII) and Enterobacter cloacae IX (cluster IX) possessed high resistant rates to ciprofloxacin and levofloxacin, but cluster II (Enterobacter kobei) had low resistant rates. Cluster II exhibited a strong biofilm formation ability. Different motility and protease production ability were shown for distinct clusters. A PCR analysis showed that clusters I, III, VI, VIII, and IX carried more virulence genes, while cluster II had fewer. Clusters I, VIII, and IX with high pathogenicity were evaluated using the Galleria mellonella infection model. Thus, the characteristics of resistance, biofilm-forming ability, mobility, and virulence differed among the clusters. The strains were divided into 12 subgroups based on hsp60. The main clusters of ECC clinical strains were I, II, III, VI, VIII, and IX, among which IX, VIII, and I were predominant with high resistance and pathogenicity, and cluster II (E. kobei) was a special taxon with a strong biofilm formation ability under nutrient deficiency, but was associated with low resistance, virulence, and pathogenicity. Hence, clinical classification methods to identify ECC subgroups are an urgent requirement to guide the treatment of clinical infections.

Effects of aerobactin-encoding gene iucB and regulator of mucoid phenotype rmpA on the virulence of Klebsiella pneumoniae causing liver abscess.

This study aimed to analyze the influence of the main aerobactin-encoding gene iucB and the regulator of mucoid phenotype rmpA on the virulence of Klebsiella pneumoniae causing liver abscess. In addition, the possible regulatory effects of the main encoding gene iucB on the regulator of mucoid phenotype rmpA were explored, thus providing novel strategies for the prevention and control of hypervirulent K. pneumoniae (hvKp) causing liver abscess. The virulence-related genes iucB and rmpA of K. pneumoniae were detected by PCR. iucB and rmpA were cloned into K. pneumoniae strain by using plasmid pET28b as vector. Quantitative real-time PCR (RT-qPCR) was employed to detect the relative expression of rmpA gene in K. pneumoniae. We investigated the potential effects of aerobactin coding gene iucB and regulator of mucoid phenotype rmpA on the virulence of K. pneumoniae by establishing the Galleria mellonella infection model. Capsule quantitative experiment was conducted to investigate the impact of aerobactin-encoding gene iucB on the modulation of regulator of mucoid phenotype rmpA. The results of the G. mellonella infection model indicated that iucB gene could significantly enhance the virulence of K. pneumoniae, but the presence of rmpA gene did not markedly affect the virulence of K. pneumoniae. RT-qPCR showed that iucB inhibited the expression of rmpA gene. Quantitative capsulation experiments showed that the presence of rmpA gene could not increase the capsulation production of K. pneumoniae. The main encoding gene of aerobactin, namely iucB, could substantially enhance the virulence of K. pneumoniae. The gene iucB might be involved in the biosynthesis of the capsular polysaccharide through an unknown mechanism instead of the gene rmpA. Overall, these findings provide important theoretical support for the treatment of infections caused by hvKp.

Clinical characteristics, tolerance mechanisms, and molecular epidemiology of reduced susceptibility to chlorhexidine among Pseudomonas aeruginosa isolated from a teaching hospital in China.

Chlorhexidine is used widely to prevent the spread of bacteria in the hospital environment. However, bacteria are increasingly becoming tolerant to chlorhexidine. Here we investigated clinical characteristics, tolerance mechanisms, and molecular epidemiology of chlorhexidine-tolerant Pseudomonas aeruginosa. According to the proposed epidemiological cut-off value to determine chlorhexidine tolerance (50 µg/mL) in P. aeruginosa, 32 chlorhexidine-tolerant isolates were detected from 294 P. aeruginosa isolates, which accounted for 10.9%. Our results indicated MICs of chlorhexidine-tolerant strains were 64 µg/mL. Patient's data showed chlorhexidine tolerance was associated with following factors: hospital length of stay, ICU admission, length of stay in ICU, invasive procedure, duration of mechanical ventilation, chlorhexidine usage, and occurrence of nosocomial pneumonia. Tolerance mechanisms were analyzed by efflux pump inhibition test, qRT-PCR, and serial passage experiment. Increased expression of efflux pump genes mexA, mexC, mexE and mexX, and decreased expression of oprD were observed in chlorhexidine-tolerant and chlorhexidine-induced strains, which suggested that hyperexpression of Mex-Opr efflux pump was the main mechanism. Moreover, serial passage experiment found chlorhexidine-induced strains showed decreased susceptibility to tested antibiotics, which illustrated that long-term exposure of P. aeruginosa to chlorhexidine could result in multidrug-resistant (MDR) or cross-resistance phenotypes. MLST and PFGE analysis demonstrated the homology of 32 chlorhexidine-tolerant strains was low and no obvious clonal transmission was observed. We comprehensively investigated the development and molecular mechanisms of chlorhexidine-tolerant P. aeruginosa, which revealed that the control and surveillance of chlorhexidine tolerance should be more strict. Moreover, it seems to make sense to avoid the continuous or unreasonable application of chlorhexidine in hospital settings.

Hypervirulent carbapenem-resistant Klebsiella pneumoniae causing highly fatal meningitis in southeastern China.

Klebsiella pneumoniae (K. pneumoniae) is one of the most common causes of bacterial meningitis worldwide. The purpose of this study was to investigate the clinical and microbiological characteristics of K. pneumoniae meningitis, as well as the association of antimicrobial resistance, virulence, and patient prognosis. The clinical data of patients with K. pneumoniae meningitis from 2014 to 2020 in a tertiary teaching hospital were retrospectively evaluated. Antimicrobial susceptibility profiles were performed by the agar dilution method and broth microdilution method. The isolates were detected for virulence-related genes, resistance genes, capsular serotypes, and molecular subtypes. A total of 36 individuals with K. pneumoniae meningitis were included in the study, accounting for 11.3% (36/318) of all cases of bacterial meningitis. Of the 36 available isolates, K1, K47, and K64 were tied for the most frequent serotype (7/36, 19.4%). MLST analysis classified the isolates into 14 distinct STs, with ST11 being the most common (14/36, 38.9%). Carbapenem resistance was found in 44.4% (16/36) of the isolates, while hypervirulent K. pneumoniae (HvKP) was found in 66.7% (24/36) of the isolates. The isolates of hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP) were then confirmed to be 36.1% (13/36). Importantly, individuals with meningitis caused by Hv-CRKP had a statistically significant higher mortality than the other patients (92.3%, 12/13 vs. 56.5%, 13/23; P < 0.05). The high percentage and fatality of K. pneumoniae-caused meningitis, particularly in Hv-CRKP strains, should be of significant concern. More effective surveillance and treatment solutions will be required in future to avoid the spread of these life-threatening infections over the world.

[A cloud detection algorithm for MODIS images combining Kmeans clustering and multi-spectral threshold method].

An improved method for detecting cloud combining Kmeans clustering and the multi-spectral threshold approach is described. On the basis of landmark spectrum analysis, MODIS data is categorized into two major types initially by Kmeans method. The first class includes clouds, smoke and snow, and the second class includes vegetation, water and land. Then a multi-spectral threshold detection is applied to eliminate interference such as smoke and snow for the first class. The method is tested with MODIS data at different time under different underlying surface conditions. By visual method to test the performance of the algorithm, it was found that the algorithm can effectively detect smaller area of cloud pixels and exclude the interference of underlying surface, which provides a good foundation for the next fire detection approach.

Quercetin Rejuvenates Sensitization of Colistin-Resistant Escherichia coli and Klebsiella Pneumoniae Clinical Isolates to Colistin.

Colistin is being considered as "the last ditch" treatment in many infections caused by Gram-negative stains. However, colistin is becoming increasingly invalid in treating patients who are infected with colistin-resistant Escherichia coli (E. coli) and Klebsiella Pneumoniae (K. pneumoniae). To cope with the continuous emergence of colistin resistance, the development of new drugs and therapies is highly imminent. Herein, in this work, we surprisingly found that the combination of quercetin with colistin could efficiently and synergistically eradicate the colistin-resistant E. coli and K. pneumoniae, as confirmed by the synergy checkboard and time-kill assay. Mechanismly, the treatment of quercetin combined with colistin could significantly downregulate the expression of mcr-1 and mgrB that are responsible for colistin-resistance, synergistically enhancing the bacterial cell membrane damage efficacy of colistin. The colistin/quercetin combination was notably efficient in eradicating the colistin-resistant E. coli and K. pneumoniae both in vitro and in vivo. Therefore, our results may provide an efficient alternative pathway against colistin-resistant E. coli and K. pneumoniae infections.

Comparison of Anti-Microbic and Anti-Biofilm Activity Among Tedizolid and Radezolid Against Linezolid-Resistant Enterococcus faecalis Isolates.

BACKGROUND: The emergence and spread of linezolid-resistant Enterococcus faecalis (E. faecalis) have emerged as a serious threat to human health globally. Therefore, this study aims to compare the anti-microbic as well as the anti-biofilm activity of linezolid, tedizolid, and radezolid against linezolid-resistant E. faecalis. METHODS: A total of 2128 E. faecalis isolates were assessed from the First Affiliated Hospital of Wenzhou Medical University from 2011 to 2019. Antibiotic sensitivity was evaluated using the micro broth dilution method. Oxazolidinone-resistant chromosomal and plasmid-borne genes such as cfr, cfr(A), cfr(B), cfr(C), cfr(D), optrA, and poxtA were detected by PCR and then sequenced to detect the presence of mutations in the domain V of the 23S rRNA and the ribosomal proteins L3, L4, and L22. Conjugation experiments were conducted using the broth method. The inhibition and eradication of biofilm were evaluated through crystal violet staining, whereas the efflux pump activities were detected by agar dilution. RESULTS: Out of 2128 isolated E. faecalis, 71 (3.34%) were linezolid-resistant isolates in which the MICs of tedizolid and radezolid ranged from 1 to 4 µg/mL and 0.5-1 µg/mL, respectively. The MIC50/MIC90 of tedizolid and radezolid were 4 and 8-fold lower than the linezolid, respectively. Out of 71 resistant isolates, 57 (80.28%) carried optrA, 1 (1.41%) carried cfr, 4 (5.63%) carried optrA and cfr, and 6 (8.45%) carried optrA and cfr(D), with no mutations of 23S rRNA gene and ribosomal proteins L3, L4, and L22. Besides, the transfer rate of the optrA, cfr, and cfr(D) was 17.91%, 0% and 0%, respectively. Radezolid showed more effectiveness in eradicating biofilm (8 × MIC). However, tedizolid was more effective than radezolid and linezolid in inhibiting the biofilm formation (1/4 MIC, 1/8MIC, and 1/16MIC). Additionally, in combination with CCCP, the MICs of radezolid in all linezolid-resistant isolates decreased ≥4-fold. CONCLUSION: Radezolid showed greater antimicrobial activity than tedizolid and linezolid against linezolid-resistant E. faecalis. However, both tedizolid and radezolid showed differential activity on biofilm inhibition, eradication, and efflux pump compared to linezolid. Thus, our study might bring important clinical value in the application of these drugs for resistant pathogenic strains.

Evaluation of NitroSpeed-Carba NP test for rapid identification among different classes of carbapenemases in Enterobacterales and Pseudomonas aeruginosa.

OBJECTIVES: This study aimed to evaluate the performance of the NitroSpeed-Carba NP test for detecting carbapenemases in the clinical strains of Enterobacterales and Pseudomonas aeruginosa (P. aeruginosa), and analyze its advantages and limitations. METHODS: The antimicrobial susceptibility tests were performed according to the agar dilution method. Using the modified carbapenemase inactivation method (mCIM), polymerase chain reaction (PCR), and sequencing, the production of carbapenemase and the prevalence of genes were studied. The NitroSpeed-Carba NP test was performed to detect different types of carbapenemases in Enterobacterales and P. aeruginosa. The results of PCR and sequencing were used as the gold standard. RESULTS: Among 144 carbapenemase-producing and 54 carbapenemase-negative strains of Enterobacterales and P. aeruginosa, the NitroSpeed-Carba NP test correctly detected 143 of 144 carbapenemase producers and 51 of 54 non-carbapenemase producers. Moreover, the sensitivity and specificity of all tested isolates were 99.31% and 94.44%, respectively (99.28% and 92.86% for Enterobacterales; 100% and 100% for P. aeruginosa). The sensitivity was 100% for class A (56 of 56), 100% for class B (60 of 60), and 100% for class D (27 of 27). CONCLUSIONS: The results suggest that NitroSpeed-Carba NP test is a simple and valuable assay that could be used as a rapid and stable detection method to identify the carbapenemases in Enterobacterales and P. aeruginosa strains.

Unraveling Mechanisms and Epidemic Characteristics of Nitrofurantoin Resistance in Uropathogenic Enterococcus faecium Clinical Isolates.

PURPOSE: Multidrug-resistant (MDR) Enterococcus faecium is an important nosocomial pathogen causing urinary tract infection, and the reapplication of nitrofurantoin (NIT) in the clinic has attracted great attention. This study aims to explore the NIT resistance mechanisms and epidemiological characteristics of E. faecium clinical isolates. PATIENTS AND METHODS: A total of 633 E. faecium clinical isolates was obtained from urine samples in a clinical teaching hospital during 2017-2018. Among them, 40 NIT-resistant strains, and a similar number of -intermediate and -susceptible strains were isolated. The minimum inhibitory concentrations (MICs) of NIT were detected by agar dilution method. The prevalence and mutations of nitroreductase-encoding genes ef0404 and ef0648 were explored by polymerase chain reaction (PCR), followed by efflux pump inhibition test and quantitative real-time PCR (qRT-PCR) to investigate the resistance mechanisms of NIT. Furthermore, the epidemiological characteristics were detected by multilocus sequence typing (MLST). RESULTS: The carrying rates of nitroreductase in NIT-susceptible, -intermediate, and -resistant isolates were 100%, 50%, and 20%, respectively. After exposure to the efflux pump inhibitor, the MIC of 12 E. faecium decreased by ≥4-fold. However, the efflux pump genes efrAB, emeA, and oqxAB were not overexpressed in NIT-resistant E. faecium isolates. Moreover, MLST analysis revealed that all the NIT-resistant isolates belonged to CC17, of which 30 (75%) were associated with ST78. CONCLUSION: This study has established for the first time that the absence of EF0404 and EF0648 is the main mechanism of NIT resistance in E. faecium. Our findings are likely to fill the knowledge gap pertaining to the NIT resistance mechanism in E. faecium and provide important insights for molecular epidemiological characteristics analysis.

Combining Colistin with Furanone C-30 Rescues Colistin Resistance of Gram-Negative Bacteria in Vitro and in Vivo.

The spread of multidrug-resistant (MDR) Gram-negative bacteria (GNB) has led to serious public health problems worldwide. Colistin, as a "last resort" for the treatment of MDR bacterial infections, has been used significantly in recent years and has led to the continuous emergence of colistin-resistant strains. In this study, we aimed to investigate the synergistic effect on the antimicrobial and antibiofilm activities of a colistin/furanone C-30 combination against colistin-resistant GNB in vitro and in vivo. According to antimicrobial resistance profiles, most of the colistin-resistant strains we collected showed MDR phenotypes. The checkerboard method and time-kill curve showed that the combination with furanone C-30 increases the antibacterial activity of colistin significantly. In addition, the furanone C-30/colistin combination can not only inhibit the formation of bacterial biofilm but also has a better eradication effect on preformed mature biofilms. The result of scanning electron microscopy (SEM) demonstrated that the furanone C-30/colistin combination led to a significant reduction in the number of cells in biofilms. Furthermore, furanone C-30 at 50 µg/ml did not cause any additional toxicity to RAW264.7 cells according to a cytotoxicity assay. In in vivo infection experiments, the furanone C-30/colistin combination increased the survival rate of infected Galleria mellonella larvae as well as decreased the microbial load in a mouse thigh infection model. The synergistic effect of the furanone C-30/colistin combination against colistin-resistant GNB is encouraging, and this work may shed light on a new therapeutic approach to combat colistin-resistant pathogens. IMPORTANCE Colistin is among the few antibiotics effective against multidrug-resistant Gram-negative bacteria (GNB) clinical isolates. However, colistin-resistant GNB strains have emerged in recent years. Therefore, the combination of colistin and nonantibacterial drugs has attracted much attention. In this study, the furanone C-30/colistin combination showed good antibacterial and antibiofilm activity in vitro and in vivo. In addition, increased membrane permeability leads to the synergistic effect of the furanone C-30/colistin combination. Because of the low cytotoxicity of furanone C-30, this combination has good application prospects in clinical anti-infective therapy. This finding might shed light on the discovery of combination therapy for infections caused by colistin-resistant GNB pathogens.

Molecular Mechanisms and Epidemiology of Carbapenem-Resistant Enterobacter cloacae Complex Isolated from Chinese Patients During 2004-2018.

BACKGROUND: The emergence and spread of carbapenem-resistant Enterobacter cloacae complex (ECC) have posed a serious threat to human health worldwide. This study aimed to investigate the molecular mechanism of carbapenem resistance and its prevalence among ECC in China. METHODS: A total of 1314 ECC clinical isolates were collected from the First Affiliated Hospital of Wenzhou Medical University from 2004 to 2018. Sensitivity to antibiotics was determined using the agar dilution method. The production of carbapenemases and the prevalence of resistance-associated genes were investigated using PCR. The expression of outer membrane porin (OMP) genes (ompC/ompF) and cephalosporinase gene ampC was analyzed by quantitative real-time PCR. The effect of efflux pump mechanism on carbapenem resistance was tested. ECC was typed by multilocus sequence typing (MLST). RESULTS: In this study, 113 carbapenem-nonsusceptible ECC strains were identified. The prevalence rates of carbapenemase genes bla KPC-2 and bla NDM were 12.4% (14/113) and 17.7% (20/113), and that of the extended-spectrum ß-lactamase (ESBL) genes bla CTX-M, bla TEM, and bla SHV were 28.3% (32/113), 27.4% (31/113), and 14.2% (16/113), respectively. Among 67 carbapenem-nonsusceptible ECC isolates producing non-carbapenemase, low expression of ompC/ompF and overexpression of ampC were found in 46 and 40 strains, respectively. In addition, the carbapenem resistance was related to the overexpression of the efflux pump in the study. Finally, the 113 carbapenem-nonsusceptible ECC strains were categorized into 39 different sequence types using MLST. CONCLUSION: Carbapenem-nonsusceptible ECC strains producing non-carbapenemase were predominant. The low expression of OMP with the overexpression of cephalosporinase or production of ESBLs and overexpression of efflux pump might contribute to the resistance to carbapenem for carbapenem-nonsusceptible ECC strains producing non-carbapenemase. The bla NDM and bla KPC comprised the principal resistance mechanism of carbapenemase-producing ECC in the hospital, causing a threat to public health. Therefore, monitoring programs to prevent the emergence and further spread of antibiotic resistance are urgently needed.

[An improved method for forest fire spot detection based on variance between-class].

An improved method using variance between-class and smoke plume mask is described. The brightness temperature threshold of potential fire pixels was adjusted to be 305 K. Based on the variance between-class of TIR channel brightness temperature and a smoke plume detection algorithm, the improved algorithm can separate the hot fire spots from the background and seek out the cool fire spots, respectively, with suitable thresholds of variance between-class. This algorithm has been used in the forest fires that happened in Fujian province and Heilongjiang province. Study shows that detection results with the algorithm are more satisfactory. It is adapted in different environments and can be more accurately detected the high-temperature fire spot and the smoder at low temperature. It increases the ability and accuracy to detect fire spots.

A Social Group-Based Information-Motivation-Behavior Skill Intervention to Promote Acceptability and Adoption of Wearable Activity Trackers Among Middle-Aged and Older Adults: Cluster Randomized Controlled Trial.

BACKGROUND: Wearable activity trackers offer potential to optimize behavior and support self-management. To assist older adults in benefiting from mobile technologies, theory-driven deployment strategies are needed to overcome personal, technological, and sociocontextual barriers in technology adoption. OBJECTIVE: To test the effectiveness of a social group-based strategy to improve the acceptability and adoption of activity trackers by middle-aged and older adults. METHODS: A cluster randomized controlled trial was conducted among 13 groups of middle-aged and older adults (≥45 years) performing group dancing (ie, square dancing) as a form of exercise in Guangzhou from November 2017 to October 2018. These dancing groups were randomized 1:1 into two arms, and both received wrist-worn activity trackers and instructions at the baseline face-to-face assessment. Based on the Information-Motivation-Behavior Skill framework, the intervention arm was also given a tutorial on the purpose of exercise monitoring (Information), encouraged to participate in exercise and share their exercise records with their dancing peers (Motivation), and were further assisted with the use of the activity tracker (Behavior Skill). We examined two process outcomes: acceptability evaluated by a 14-item questionnaire, and adoption assessed by the uploaded step count data. Intention-to-treat analysis was applied, with the treatment effects estimated by multilevel models. RESULTS: All dancing groups were followed up for the postintervention reassessment, with 61/69 (88%) participants of the intervention arm (7 groups) and 56/80 (70%) participants of the control arm (6 groups). Participants' sociodemographic characteristics (mean age 62 years, retired) and health status were comparable between the two arms, except the intervention arm had fewer female participants and lower cognitive test scores. Our intervention significantly increased the participants' overall acceptability by 6.8 points (95% CI 2.2-11.4), mainly driven by promoted motivation (adjusted group difference 2.0, 95% CI 0.5-3.6), increased usefulness (adjusted group difference 2.5, 95% CI 0.9-4.1), and better perceived ease of use (adjusted group difference 1.2, 95% CI 0.1-2.4), whereas enjoyment and comfort were not increased (adjusted group difference 0.9, 95% CI -0.4-2.3). Higher adoption was also observed among participants in the intervention arm, who were twice as likely to have valid daily step account data than their controlled counterparts (adjusted incidence relative risk [IRR]=2.0, 95% CI 1.2-3.3). The average daily step counts (7803 vs 5653 steps/day for the intervention and control, respectively) were similar between the two arms (adjusted IRR=1.4, 95% CI 0.7-2.5). CONCLUSIONS: Our social group-based deployment strategy incorporating information, motivation, and behavior skill components effectively promoted acceptability and adoption of activity trackers among community-dwelling middle-aged and older adults. Future studies are needed to examine the long-term effectiveness and apply this social engagement strategy in other group settings or meeting places. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR-IOC-17013185; https://tinyurl.com/vedwc7h.