Monocyte to High-density Lipoprotein Cholesterol Ratio as a Predictor of Nonalcoholic Fatty Liver Disease in Childhood Obesity.

OBJECTIVE: Inflammation is involved in the development and progression of nonalcoholic fatty liver disease (NAFLD). The monocyte to high-density lipoprotein cholesterol ratio (MHR) has emerged as a marker for various inflammation-related diseases. The aim of the present study was to investigate the association between the MHR and NAFLD in a population with childhood obesity. METHODS: Based on hepatic ultrasound, a total of 504 children with obesity (357 with NAFLD and 147 without NAFLD) were included in the study. The correlation between the MHR and NAFLD risk factors was assessed by Pearson's and Spearman's analyses. Multivariate stepwise logistic regression analyses were conducted to explore the association between the MHR and the risk of NAFLD. RESULTS: The MHR in patients with NAFLD was significantly greater than that in patients without NAFLD [0.52 (0.44-0.67) versus 0.44 (0.34-0.57), P<0.001]. Multivariate stepwise logistic regression analysis demonstrated that the MHR [odds ratio (OR): 1.033, 95% confidence interval (CI): 1.015-1.051; P<0.001] was an independent predictor of NAFLD in childhood obesity patients, as were age (OR: 1.205, 95% CI: 1.059-1.371; P=0.005], waist circumference [OR: 1.037, 95% CI: 1.008-1.067; P=0.012], and alanine transaminase [OR: 1.067, 95% CI: 1.045-1.089; P<0.001]. Additionally, MHR quartiles showed a significant positive association with the incidence of NAFLD after adjusting for potential confounding factors. CONCLUSION: The present study showed that the MHR may serve as an available and useful indicator of NAFLD in individuals with childhood obesity.

Multiattention Mechanism 3D Object Detection Algorithm Based on RGB and LiDAR Fusion for Intelligent Driving.

This paper proposes a multimodal fusion 3D target detection algorithm based on the attention mechanism to improve the performance of 3D target detection. The algorithm utilizes point cloud data and information from the camera. For image feature extraction, the ResNet50 + FPN architecture extracts features at four levels. Point cloud feature extraction employs the voxel method and FCN to extract point and voxel features. The fusion of image and point cloud features is achieved through regional point fusion and voxel fusion methods. After information fusion, the Coordinate and SimAM attention mechanisms extract fusion features at a deep level. The algorithm's performance is evaluated using the DAIR-V2X dataset. The results show that compared to the Part-A2 algorithm; the proposed algorithm improves the mAP value by 7.9% in the BEV view and 7.8% in the 3D view at IOU = 0.5 (cars) and IOU = 0.25 (pedestrians and cyclists). At IOU = 0.7 (cars) and IOU = 0.5 (pedestrians and cyclists), the mAP value of the SECOND algorithm is improved by 5.4% in the BEV view and 4.3% in the 3D view, compared to other comparison algorithms.

Carbapenemase- and Colistin Resistant Escherichia coli Strains from Children in China: High Genetic Diversity and First Report of bla NDM-5, bla CTX-M-65, bla OXA-10, bla TEM-1, and mcr-1.1 Genes Co-Occurrence in E. coli ST156.

Background: The emergence of carbapenem and colistin co-resistant Escherichia coli poses a huge challenge to infection control. The purpose of this study was to clarify the mechanism of the carbapenems and colistin co-resistance in E. coli strains. Methods: Antimicrobial susceptibility test was carried out by agar dilution methods and colistin resistance was confirmed by broth microdilution methods. Whole genome sequencing was carried out, and resistance genes, sequence types and virulence genes of carbapenems and colistin co-resistance E. coli isolates were analyzed. Results: The results showed that among the 176 carbapenem-resistant Enterobacteriaceae strains, 5 multidrug resistant E. coli strains exhibiting coresistance to carbapenem and colistin. The main mechanism of 5 E. coli strains in this study was generating carbapenem. Four E. coli strains were mcr-positive, while one mcr-negative strain had a new MgrB mutation. The blaNDM-5, blaCTX-M-65, blaOXA-10, blaTEM-1 and mcr-1.1 genes were simultaneously detected in E. coli 20IR1127 strain belonging to ST156 lineage. Other antimicrobial resistance genes encoding aminoglycosides-, sulfonamide-, chloramphenicol-, tetracyclines- and macrolides resistance were also detected. Conclusion: The main mechanisms of carbapenem and colistin resistance were encoded by bla NDM and mcr1.1, meanwhile mgrB mutations also contribute to colistin resistance. To our knowledge, this study is the first to report of E. coli ST156 strain in which the bla NDM-5, bla CTX-M-65, bla OXA-10, bla TEM-1 and mcr1.1 genes coexist. In addition, there is also an E. coli ST457 strain, which carries bla TEM-1, bla NDM-9, bla CTX-M-199 and is positive for mcr1.1 gene.

The efficacy of Tai Chi for depression: A protocol for systematic review and meta-analysis.

BACKGROUND: Depression is a commonly occurring and recurrent mental disorder cross the world. Tai Chi is a traditional Chinese mind-body exercise which could be used to treat mental disorders including depression. This study aimed to conduct a systematic review and meta-analysis to assess the efficiency of Tai Chi for patients with depression. METHODS: This protocol follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol statement. Literature will be searched at PubMed, EMBASE, Web of Science, Cochrane Library, China Biology Medicine Database, China National Knowledge Infrastructure, Technology Journal Database, and Wan Fang database from the start date to September 2021. The Review Manager 5.3 software will be used to manage literature. After literature screening, 2 reviewers will extract data from the respects of general information, methodology, and results. The data analysis will be conducted with Review Manager and Stata 16 software, and the publication bias and literature quality will be both evaluated. RESULTS: The results will contain the evaluation of clinical efficacy of Tai Chi practice for depression, as well as the assessment of literature quality and publication bias. CONCLUSION: The current review will provide new evidence on whether and to what extent patients with depression can benefit from Tai Chi practice.Registration number: DOI: 10.17605/OSF.IO/AUDNQ (https://osf.io/audnq).

Effect of chlorogenic acid on the quorum-sensing system of clinically isolated multidrug-resistant Pseudomonas aeruginosa.

AIMS: Quorum sensing (QS) is the intercellular communication used by bacteria to regulate collective behaviour. QS regulates the production of virulence factors in many bacterial species and is considered to be an attractive target for reducing bacterial pathogenicity. Chlorogenic acid (CA) is abundant in vegetables, fruits, and traditional Chinese medicine, and has multiple activities. This study aimed to investigate the QS quenching activity of CA against clinically isolated multidrug-resistant Pseudomonas aeruginosa. METHODS AND RESULTS: The results showed that CA inhibited the mobility of bacteria, reduced the production of pyocyanin, and inhibited the activity of elastase. Furthermore, crystal violet staining and scanning electron microscope experiments showed that CA inhibited the formation of multidrug-resistant P. aeruginosa biofilm. CA at or below the concentration of 2560 µg/mL exerted negligible cytotoxicity to RAW264.7 cells. The study also examined the expression of QS-related genes, including lasI, lasR, rhlI, rhlR, pqsA, and pqsR in P. aeruginosa and found that the expression of these genes was down-regulated under CA treatment. CONCLUSIONS: The study showed that CA could be used as an anti-virulence factor for treating clinical P. aeruginosa infection. SIGNIFICANCE AND IMPACT OF STUDY: For the first time, this study took clinically isolated multidrug-resistant P. aeruginosa as the experimental object, and suggested that CA might be an effective antimicrobial compound targeting QS in treating P. aeruginosa infection, thus providing a new therapeutic direction for treating bacterial infection and effectively alleviating bacterial resistance.

Advances in laboratory detection methods and technology application of SARS-CoV-2.

At present, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is raging worldwide, and the coronavirus disease 2019 outbreak caused by SARS-CoV-2 seriously threatens the life and health of all humankind. There is no specific medicine for novel coronavirus yet. So, laboratory diagnoses of novel coronavirus as soon as possible and isolation of the source of infection play a vital role in preventing and controlling the epidemic. Therefore, selecting appropriate detection techniques and methods is particularly important to improve the efficiency of disease diagnosis and treatment and to curb the outbreak of infectious diseases. In this paper, virus nucleic acid, protein, and serum immunology were reviewed to provide a reference for further developing virus detection technology to provide better prevention and treatment strategies and research ideas for clinicians and researchers.

Skin and soft tissue infection caused by Cysteiniphilum litorale in an immunocompetent patient: A case report.

Cysteiniphilum litorale is a Gram-negative coccobacillus first isolated from the seawater of Wailingding Island near the estuary of Pearl River in southern China. This organism was previously not considered to cause disease in animals or humans. We report a case of a 19-year-old female patient infected with abscess caused by C. litorale in the middle digit of her right hand after minor trauma during the handling of estuarine shrimps at home. C. litorale was cultured from the wound exudate of the patient and identified by 16S rRNA gene sequencing. Whether C. litorale may be transmitted to humans via other channels requires further exploration.

Salmonella enterica subsp. diarizonae Harboring ST233, ST1263, and ST1845 in Children.

Objective: This study aims to analyze the molecular epidemiology, resistance, and pathogenicity of Salmonella enterica subsp. diarizonae isolated from children. Methods: Whole genome sequencing was carried out, and molecular serotypes, sequence types, resistance genes, and virulence genes of S. enterica subsp. diarizonae isolates were analyzed. Antimicrobial susceptibility test was determined by commercialized microdilution method. Results: A total of three isolates of S. enterica subsp. diarizonae were isolated during 2015 to 2020. The molecular serotypes of the three strains were 61:c:z35, 61:l,v:1,5,7:[z57], and 65:k:z, respectively, and the sequence types were ST1845, ST233, and ST1263. All the three isolates were susceptible to ceftriaxone, ceftazidime, cefepime, amoxycillin/clavulanic acid, piperacillin/tazobactam, ertapenem, imipenem, levofloxacin, and trimethoprim/sulfamethoxazole. No other resistant gene was detected except aac(6')-Iaa. There were no resistant plasmids detected in all the three isolates. A total of 76 genes were present in all isolates, containing 49 genes of Type III Secretion System (T3SS) mediated by SPI-1and SPI-2, 13 genes of adherence (type 1 fimbriae, Agf, and MisL-related genes), 11 genes of iron uptake (Yersiniabactin), two genes of magnesium uptake, and one gene of typhoid toxin(cdtB). Conclusion: The serotypes and sequence types of S. enterica subsp. diarizonae isolates were rarely reported in children; all the S. enterica subsp. diarizonae isolates were susceptible to detected antibiotics; T3SS, adherence, iron uptake, magnesium uptake, and typhoid toxin were responsible for pathogenicity of the S. enterica subsp. diarizonae isolates in children.

Difference in biofilm formation between carbapenem-resistant and carbapenem-sensitive Klebsiella pneumoniae based on analysis of mrkH distribution.

OBJECT: To analyze the difference in biofilm formation between carbapenem-resistant and carbapenem-sensitive Klebsiella pneumoniae based on analysis of mrkH distribution and to further explore the function of mrkH for biofilm formation from the perspective of gene regulation. METHODS: 40 imipenem-resistant strains and 40 imipenem-sensitive strains were selected to conduct experiments. Carbapenem (imipenem) susceptibility test was performed by the agar-dilution method. blaKPC resistance gene, type 3 fimbriae-related coding genes (mrkA and mrkD) and regulation gene (mrkH) were screened by PCR. Biofilm formation assay was performed using crystal violet staining method in MHB. The relative expression of genes that critically involved in biofilm formation (mrkA, luxS, pgaA) and carbapenem resistance (ompk35, ompk36, acrB) were measured by quantitative real-time PCR (qRT-PCR). Furthermore, the mrkH cassette was cloned into pGEM-T Easy plasmid to yield pGEM:pmrkH and expressed in Escherichia coli DH5α and K. pneumoniae FK1911, and the biofilm formation assay after transformation was further tested. RESULTS: The MICs of imipenem were all more than 16 µg/mL in 40 imipenem-resistant strains and ranged from 0.125 µg/mL to 0.5 µg/mL in 40 imipenem-sensitive strains. Moreover, the blaKPC was identified in the 40 imipenem-resistant K. pneumoniae strains. All 80 K. pneumoniae strains were found to carry mrkA and mrkD genes. Interestingly, the mrkH gene was detected in 43 strains, of which 32 were carbapenem-sensitive strains. The biofilm formation capacity of strains carried mrkH cassette was significantly higher than other 37 strains in MHB media. The relative expression of mrkA in K. pneumoniae carrying mrkH gene was significantly up-regulated. Importantly, the biofilm formation ability of FK1911-pGEM:pmrkH strain was more higher than the strain of FK1911 in MHB medium. CONCLUSIONS: Our data demonstrated that MrkH played a crucial role in the regulation of biofilm formation by K. pneumoniae. In contrast to carbapenem-sensitive K. pneumoniae, carbapenem-resistant K. pneumoniae was less likely to have strong biofilm-forming capacity because it does not carry the mrkH gene.

Molecular Mechanisms and Epidemiology of Fosfomycin Resistance in Staphylococcus aureus Isolated From Patients at a Teaching Hospital in China.

Staphylococcus aureus is a major cause of hospital- and community-acquired infections placing a significant burden on the healthcare system. With the widespread of multidrug-resistant bacteria and the lack of effective antibacterial drugs, fosfomycin has gradually attracted attention as an "old drug." Thus, investigating the resistance mechanisms and epidemiology of fosfomycin-resistant S. aureus is an urgent requirement. In order to investigate the mechanisms of resistance, 11 fosfomycin-resistant S. aureus isolates were analyzed by PCR and sequencing. The genes, including fosA, fosB, fosC, fosD, fosX, and tet38, as well as mutations in murA, glpT, and uhpT were identified. Quantitative real-time PCR (qRT-PCR) was conducted to evaluate the expression of the target enzyme gene murA and the efflux pump gene tet38 under the selection pressure of fosfomycin. Furthermore, multilocus sequence typing (MLST) identified a novel sequence type (ST 5708) of S. aureus strains. However, none of the resistant strains carried fosA, fosB, fosC, fosD, and fosX genes in the current study, and 12 distinct mutations were detected in the uhpT (3), glpT (4), and murA (5) genes. qRT-PCR revealed an elevated expression of the tet38 gene when exposed to increasing concentration of fosfomycin among 8 fosfomycin-resistant S. aureus strains and reference strain ATCC 29213. MLST analysis categorized the 11 strains into 9 STs. Thus, the mutations in the uhpT, glpT, and murA genes might be the primary mechanisms underlying fosfomycin resistance, and the overexpression of efflux pump gene tet38 may play a major role in the fosfomycin resistance in these isolates.

Hypertonic glucose inhibits growth and attenuates virulence factors of multidrug-resistant Pseudomonas aeruginosa.

BACKGROUND: Pseudomonas aeruginosa is the most common Gram-negative pathogen responsible for chronic wound infections, such as diabetic foot infections, and further exacerbates the treatment options and cost of such conditions. Hypertonic glucose, a commonly used prolotherapy solution, can accelerate the proliferation of granulation tissue and improve microcirculation in wounds. However, the action of hypertonic glucose on bacterial pathogens that infect wounds is unclear. In this study, we investigated the inhibitory effects of hypertonic glucose on multidrug-resistant P. aeruginosa strains isolated from diabetic foot infections. Hypertonic glucose represents a novel approach to control chronic wound infections caused by P. aeruginosa. RESULTS: Four multidrug-resistant P. aeruginosa clinical strains isolated from diabetic foot ulcers from a tertiary hospital in China and the reference P. aeruginosa PAO1 strain were studied. Hypertonic glucose significantly inhibited the growth, biofilm formation, and swimming motility of P. aeruginosa clinical strains and PAO1. Furthermore, hypertonic glucose significantly reduced the production of pyocyanin and elastase virulence factors in P. aeruginosa. The expression of major quorum sensing genes (lasI, lasR, rhlI, and rhlR) in P. aeruginosa were all downregulated in response to hypertonic glucose treatment. In a Galleria mellonella larvae infection model, the administration of hypertonic glucose was shown to increase the survival rates of larvae infected by P. aeruginosa strains (3/5). CONCLUSIONS: Hypertonic glucose inhibited the growth, biofilm formation, and swimming motility of P. aeruginosa, as well as reduced the production of virulence factors and quorum sensing gene expression. Further studies that investigate hypertonic glucose therapy should be considered in treating chronic wound infections.

Mutations in the MepRAB efflux system contribute to the in vitro development of tigecycline resistance in Staphylococcus aureus.

OBJECTIVE: To characterize the evolutionary pathways of tigecycline (TGC) resistance and alterations in the biological characteristics of hospital-derived Staphylococcus aureus isolates under selective pressure. METHODS: Three clinical S. aureus strains and one standard S. aureus strain, ATCC 29213, were used for the in vitro selection of TGC-resistant S. aureus variants with gradient concentrations of TGC. Changes in drug resistance and genetic alterations in resistance-related genes (operon mepRAB and rpsJ) in mutant strains were determined. The efflux inhibitor assay for MepA and the fitness cost, determined by comparing the growth and virulence of parental and mutant strains, were also investigated. RESULTS: Mutants induced in vitro showed a 64- to 128-fold increase in the minimum inhibitory concentration (MIC) of TGC. Substitution mutations were detected in the transcriptional repressor mepR and the efflux pump gene mepA. A K57M amino acid substitution occurred in the ribosomal S10 protein-encoding gene rpsJ. The MICs of TGC in the final mutants were significantly decreased in the presence of efflux pump inhibitors. It was worth noting that growth was unaffected by TGC resistance selection in vitro, with the exception of one strain, and the MICs of other antibiotics and virulence were also unaffected. CONCLUSIONS: The evolution of TGC resistance in S. aureus in vitro is associated with a loss-of-function mutation in the efflux pump transcriptional repressor mepR and a missense mutation in the efflux pump-encoding gene mepA. Our work further validated the resistance mechanisms of S. aureus to TGC and reported previously undiscovered mutations.

Hyper-expression of the efflux pump gene adeB was found in Acinetobacter baumannii with decreased triclosan susceptibility.

OBJECTIVES: Triclosan is usually employed as a disinfectant in a wide range of medical and consumer care products, which may have imposed a selective pressure on bacteria. This study was designed to evaluate the resistance mechanisms of triclosan and molecular epidemiology of triclosan-resistant isolates of Acinetobacter baumannii in Wenzhou, China. METHODS: A collection of 626 A. baumannii were isolated from the First Affiliated Hospital of Wenzhou Medical University during 2016-2017 and antimicrobial susceptibility testing of these isolates were performed via agar dilution method. Molecular mechanisms of triclosan resistance, including the existence of mutations in reductase (FabI) were investigated by PCR and sequencing. Furthermore, quantitative RT-PCR was conducted to evaluate the expression levels of the fabI gene and efflux pump genes (adeB, adeG, adeJ, abeM, amvA and abeS) at normal condition and sub-inhibitory concentration of triclosan, and the epidemiological characteristics were analyzed by PFGE and MLST. RESULTS: 2.7% (17/626) of A. baumannii exhibited resistance to triclosan. The FabI mutation Gly95Ser was found in one triclosan resistant strain. The expression of fabI and adeB gene were significant difference between triclosan-resistant and susceptible strains (P < 0.05). The expression of fabI, adeG, adeJ and abeM were increased after triclosan induction. The clones of these resistant isolates were diverse and sporadic. CONCLUSIONS: The hyper-expression of fabI was probably the main mechanism of triclosan resistance in this study, and the efflux pump AdeB, AdeG, AdeJ and AbeM might also be related to decreased triclosan susceptibility.

Deciphering colistin heteroresistance in Acinetobacter baumannii clinical isolates from Wenzhou, China.

This study aimed to investigate the characteristics and mechanisms responsible for heteroresistance to colistin in Acinetobactor baumannii clinical isolates from a Chinese teaching hospital. Five hundred and seventy-six nonduplicate A. baumannii clinical isolates isolated from 2014 to 2015 were tested. Colistin heteroresistance was determined using population analysis profiles (PAPs). Susceptibility testing was conducted using the broth microdilution method (BMD). The ability to form biofilm formation was determined using 96-well flat bottom microtiter plates. Time-kill assays were also conducted. PCR and sequencing were used to detect the presence of resistant genes. Expression levels of efflux pump genes were determined by qRT-PCR. LPS analysis was conducted by SDS-PAGE. Lipid A characteristic were determined via MALDI-TOF MS. Nine colistin heteroresistant A. baumannii clinical isolates which were selected by PAPs, exhibited multidrug-resistant phenotypes. The microplate biofilm assay revealed that colistin heteroresistant A. baumannii clinical isolates had weaker biofilm formation capacity than A. baumannii ATCC19606. Colistin-heteroresistant A. baumannii isolates exhibited regrowth after 12 h at 0.5 × MIC, 1 × MIC, and 2 × MIC. The results of PCR and sequencing revealed mutations of lpxACD in some colistin heteroresistant A. baumannii isolates. qRT-PCR also showed that the expressions of efflux pump genes were upregulated in some of the heteroresistant isolates. Our study was the first report of colistin heteroresistant A. baumannii clinical isolates in China. The transition of colistin heteroresistance to resistance should be of concern in future clinical surveillance.

Molecular Mechanisms and Epidemiology of Carbapenem-Resistant Escherichia coli Isolated from Chinese Patients During 2002-2017.

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 ß-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.

Effects of iron on the growth, biofilm formation and virulence of Klebsiella pneumoniae causing liver abscess.

BACKGROUND: Klebsiella pneumoniae is considered the most clinically relevant species of Enterobacteriaceae, known to cause severe infections including liver abscesses. To the best of our knowledge, a large proportion of iron in the human body is accumulated and stored in the liver. We hypothesize that increased iron availability is an important factor driving liver abscess formation and we therefore aim to understand the effects of iron on K. pneumoniae causing liver abscesses. RESULTS: All tested K. pneumoniae clinical isolates, including those isolated from liver abscesses and other abdominal invasive infection sites, grew optimally when cultured in LB broth supplemented with 50 µM iron and exhibited the strongest biofilm formation ability under those conditions. Decreased growth and biofilm formation ability were observed in all tested strains when cultured with an iron chelator (P < 0.05). The infection model of G. mellonella larvae indicated the virulence of liver abscess-causing K. pneumoniae (2/3) cultured in LB broth with additional iron was significantly higher than those under iron-restricted conditions (P < 0.05). The relative expression levels of the four siderophore genes (iucB, iroB, irp1, entB) in K. pneumoniae strains isolated from liver abscesses cultured with additional iron were lower than those under iron-restricted conditions (P < 0.05). CONCLUSIONS: It is suggested by our research that iron in the environment can promote growth, biofilm formation and enhance virulence of K. pneumoniae causing liver abscesses. A lower expression of siderophore genes correlates with increased virulence of liver abscess-causing K. pneumoniae. Further deeper evaluation of these phenomena is warranted.

Molecular mechanisms and epidemiology of fosfomycin resistance in enterococci isolated from patients at a teaching hospital in China, 2013-2016.

OBJECTIVES: The aim of this study was to investigate the mechanisms of fosfomycin resistance and epidemiological characteristics in fosfomycin-resistant enterococci in China. METHODS: A collection of 761 enterococcal clinical isolates from a teaching hospital in Wenzhou, China were studied. The fosfomycin susceptibility of the isolates was investigated by the agar dilution method. The isolates were also analysed for mechanisms of re fosfomycin resistance by PCR and quantitative real-time PCR. Furthermore, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to analyse the molecular epidemiological characteristics of the fosfomycin-resistant isolates. RESULTS: In this study, 0.3% (1/372) of Enterococcus faecalis and 4.9% (19/389) of Enterococcus faecium clinical isolates were found to be resistant to fosfomycin. Among the 20 fosfomycin-resistant isolates, 5 harboured the fosB gene, 10 carried multiple amino acid substitutions in MurA, and 6 showed high-level expression of the fosX gene; of note, 1 isolate simultaneously carried fosB and amino acid mutation in MurA. Furthermore, a high degree of homology in the fosfomycin-resistant enterococci was confirmed using MLST and PFGE. CONCLUSION: These finding demonstrate that the fosB gene, mutations in the fosfomycin target enzyme MurA, and a high expression level of fosX were the resistance mechanisms in these fosfomycin-resistant enterococci.

Zebrafish and Galleria mellonella: Models to Identify the Subsequent Infection and Evaluate the Immunological Differences in Different Klebsiella pneumoniae Intestinal Colonization Strains.

The intestine is the main reservoir of bacterial pathogens in most organisms. Klebsiella pneumoniae is an important opportunistic pathogen associated with nosocomial bacterial infections. Intestinal colonization with K. pneumoniae has been shown to be associated with an increased risk of subsequent infections. However, not all K. pneumoniae strains in the intestine cause further infection, and the distinction of the difference among strains that cause infection after colonization and the ones causing only asymptomatic colonization is unclear. In this study, we report a case of a hospitalized patient from the ICU. We screened out two intestine colonization strains (FK4111, FK4758) to analyze the subsequent infection conditions. We set up infection models of zebrafish and Galleria mellonella to establish the differences in the potential for causing subsequent infection and the immunological specificities after K. pneumoniae intestine colonization. Sudan Black B and neutral red staining results indicated that FK4758 was more responsive to neutrophil recruitment and phagocytosis of macrophages than FK4111. The results of the assessment of the organ bacterial load revealed that FK4111 and FK4758 both had the highest bacterial loads in the zebrafish intestine compared to those in other organs. However, in the zebrafish spleen, liver, and heart, the FK4758 load was significantly higher than that of FK4111. The ST37 strain FK4111, which does not produce carbapenemase, did not cause infection after colonization, whereas the ST11 strain FK4758, which produces carbapenemase, caused infection after intestinal colonization. Our finding demonstrated that not all intestinal colonization of K. pneumoniae subsequently caused infections, and the infections of K. pneumoniae after colonization are different. Therefore, the infection models we established provided possibility for the estimation of host-microbial interactions.

Clinical, microbiological, and molecular epidemiological characteristics of Klebsiella pneumoniae-induced pyogenic liver abscess in southeastern China.

Background: Klebsiella pneumoniae-induced pyogenic liver abscess (KP-PLA) has emerged as a life-threatening disease worldwide. However, to date, a limited number of scholars have attempted to systematically elucidate the characteristics of KP-PLA. The aim of the present study was to analyze clinical, microbiological, and molecular epidemiological characteristics of KP-PLA patients in Southeastern China. Methods: The KP-PLA cases from a tertiary teaching hospital in China from January 2016 to December 2017 were systemically studied and elucidated comprehensively. The virulence factors, resistant spectrum, and clones of K. pneumoniae isolates were identified with string test, polymerase chain reaction (PCR), antimicrobial susceptibility test, and multilocus sequence typing. Moreover, the characteristics in KP-PLA patients with and without other hepatobiliary diseases (OHD) were also been compared. Results: A total of 163 KP-PLA cases were enrolled, in which the majority of those cases were senior males, and often associated with multiple underlying diseases, including diabetes (49.7%). The remaining cases belonged to healthy individuals (50.3%). The clinical symptoms were common but nonspecific, characterized by increased inflammatory parameters and abnormal liver function parameters. The abscess was often right-sided solitary presentation (58.3%). Cephalosporin or carbapenem plus metronidazole combined with percutaneous puncture or catheter drainage were favorable therapeutics. Although low resistance rates of commonly used antimicrobial drugs (< 10%) were observed, twelve strains were identified as multidrug resistant (MDR) strains, and were mainly isolated from the OHD patients. The hypermucoviscosity, as well as K1 and K2 serotypes accounted for 30.7, 40.5, and 19.0%, respectively. Except for iroN (24.5%) and magA (45.4%), the high prevalence of virulence genes (e.g. aerobactin, rmpA, mrkD, fimH, uge, ureA, entB, ybtA, kfuBC, and wcaG) was identified (68.7-100.0%). Additionally, ST23 was found as a predominant sequence type (ST; 38.7%), and three novel STs (ST3507, ST3508 and ST3509) were noted as well. Conclusions: The present study reported the abundant hvKp strains in KP-PLA, as well as convergence of hypervirulent and MDR K. pneumoniae isolates from the KP-PLA patients, particularly those cases with OHD. Given the various clinical manifestations and destructive pathogenicity, determination of the comprehensive characteristics of such isolates is highly essential to effectively carry out for optimal management and treatment of KP-PLA.

Evolution of resistance mechanisms and biological characteristics of rifampicin-resistant Staphylococcus aureus strains selected in vitro.

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.