Mei Luo

Influence of cAMP receptor protein (CRP) on bacterial virulence and transcriptional regulation of allS by CRP in Klebsiella pneumoniae

cAMP receptor protein (CRP) is one of the most important transcriptional regulators, which can regulate large quantities of operons in different bacteria. The gene allS was well-known as allantoin-utilizing capability and involving in bacterial virulence in Klebsiella pneumoniae (K. pneumoniae). The specific DNA recognition motif of transcription regulator CRP was found in allS promoter region. Therefore, this study is aimed to investigate the function of CRP on virulence and its transcriptional regulation mechanism to gene allS in K. pneumoniae. The wild-type (WT) K. pneumoniae NTUH-2044, crp knockout (Kp-Δcrp) and the complemented knockout (KpC-Δcrp) strains were used to determine the function of crp gene. The lacZ fusion, qRT-PCR, electrophoretic mobility shift and DNase I footprinting assays were performed to study the transcriptional regulation of CRP on allS. The result showed a decreased virulence in crp knockout strain. Complement through supplementing crp fragment in expression plasmid partially restore virulence of knockout bacteria. The CRP could bind to the allS promoter-proximal region and the binding site was further refined to be located from 60bp to 94bp upstream of the allS promoter. Based on these results, we proposed that CRP is an essential virulence regulator and knock out of crp gene will result in reduced virulence in K. pneumoniae. In the meantime, the transcription of gene allS is positively regulated by CRP via directly binding to upstream of allS promoter.

Risk factors for infection and/or colonisation with extended-spectrum β-lactamase-producing bacteria in the neonatal intensive care unit: a meta-analysis

Extended-spectrum β-lactamase (ESBL)-producing bacteria are an important cause of healthcare-associated infections in the neonatal intensive care unit (NICU). The aim of this meta-analysis was to identify risk factors associated with infection and/or colonisation with ESBL-producing bacteria in the NICU. Electronic databases were searched for relevant studies published from 1 January 2000 to 1 July 2016. The literature was screened and data were extracted according to the inclusion and exclusion criteria. The Z-test was used to calculate the pooled odds ratio (OR) of the risk factors. ORs and their 95% confidence intervals were used to determine the significance of the risk. A total of 14 studies, including 746 cases and 1257 controls, were identified. Thirteen risk factors were determined to be related to infection and/or colonisation with ESBL-producing bacteria in the NICU: birthweight [standardised mean difference (SMD) = 1.17]; gestational age (SMD = 1.36); Caesarean delivery (OR = 1.76); parenteral nutrition (OR = 7.51); length of stay in the NICU (SMD = 0.72); mechanical ventilation (OR = 4.8); central venous catheter use (OR = 2.85); continuous positive airway pressure (OR = 5.0); endotracheal intubation (OR = 2.82); malformations (OR = 2.89); previous antibiotic use (OR = 6.72); ampicillin/gentamicin (OR = 2.31); and cephalosporins (OR = 6.0). This study identified risk factors for infection and/or colonisation with ESBL-producing bacteria in the NICU, which may provide a theoretical basis for preventive measures and targeted interventions.

Risk factors of lower respiratory tract infection in patients after tracheal intubation under general anesthesia in the Chinese health care system: A meta-analysis.

BACKGROUND Lower respiratory tract infection (LRTI) after tracheal intubation under general anesthesia poses a serious threat to worldwide health care systems, especially those in developing countries. However, a significant number of studies have found inconsistent results in their investigation of the corresponding risk factors. METHODS Relevant articles published up to September 2015 were retrieved from PubMed, Ovid, Embase, China National Knowledge Infrastructure, Chinese Biological Medical Database, China Science and Technology Journal Database, and Wanfang Data. The z test was used to determine the significance of the pooled odds ratio (OR). ORs and 95% confidence intervals were used to compare the risk factors of LRTI after intubation under general anesthesia. RESULTS Fifteen case-control studies that included 27,304 participants were identified. We identified the following variables as independent risk factors: duration of general anesthesia >3 hours (OR, 2.45), age >60 years (OR, 2.35), normal endotracheal tube (OR, 1.63), deep intubation (OR, 2.66), unpracticed intubation (OR, 2.61), postoperative extubation time >2 hours (OR, 3.76), smoking history (OR, 3.02), chronic respiratory disease history (OR, 2.30), incomplete extubation indication (OR, 3.54), thoracic or craniocerebral surgery (OR, 1.90), and emergent surgery (OR, 2.54). CONCLUSIONS Eleven risk factors, including surgery, anesthesia, and health condition, were related to LRTI after intubation under general anesthesia. Given the limitations of this study, well-designed epidemiologic studies with a large sample size should be performed in the future.

Serum Leptin Levels in Patients with Hepatitis B: A Meta-analysis

Background and Aims: Hepatitis B virus (HBV) infection is a widespread disease affecting people worldwide. With more and more research on the deepening of the leptin, which suggested a close relationship between serum leptin levels and HBV. In this study, we explored the correlation between serum leptin levels and HBV through meta-analysis. Methods: Potentially relevant studies between 2007 and 2017 were retrieved from PubMed, Ovid, Embase, Web of Science, Weipu Journal, Chinese Biomedical, China National Knowledge Infrastructure, and Wan Fang Data. Z-test was used to determine the significance of the pooled standardized mean difference (SMD). Results: We analyzed 16 studies, which involved 884 HBV patients and 618 healthy controls. And then pooled the SMD and calculated the 95% confidence interval (CI) by using a random-effects model from heterogeneity analysis. High serum leptin levels were observed in HBV patients (SMD: 1.16, 95%CI: 0.72-1.59, P<0.00001). Stratification analysis on the ethnicity, study design, and detection method revealed significant increases in the serum leptin levels among the Asian population of the ethnicity subgroup, case-control study of the study design subgroup, and ELISA or RIA of the detection method subgroup. Conclusion: This meta-analysis suggests a significant difference between HBV patients and healthy controls. Therefore, serum leptin levels may serve as a prognostic marker for hepatitis B disease.

Transcriptional regulation of galF by RcsAB affects capsular polysaccharide formation in Klebsiella pneumoniae NTUH-K2044

RcsAB is an atypical two-component regulatory system that can regulate exopolysaccharide biosynthesis and is involved in the virulence of K. pneumoniae. The gene galF is well known as a gene involved in the biosynthesis of capsular polysaccharide (CPS). The specific DNA identification sequence for transcriptional regulation of RcsAB was found to be present in the promoter region of galF. This study aimed to detect the function of RcsAB in virulence and in biofilm and CPS formation. In addition, the transcriptional regulation of the galF gene in K. pneumoniae was studied. To determine the function of rcsAB gene, the wild-type K. pneumoniae strain NTUH-K2044 and the rcsAB knockout and complemented strains were used. The results showed decreased virulence, biofilm formation, and CPS levels in the rcsAB knockout strain. Complementation of the knockout by introducing an rcsAB fragment on an expression plasmid partially restored the virulence, biofilm, and CPS functions of the knockout strain. It indicated that the rcsAB genes might affect CPS formation and virulence of K. pneumonia. RT-qPCR, EMSA and DNase I footprinting assays were conducted to identify the transcriptional regulation of galF by RcsAB. RcsAB was seen to bind to the galF promoter-proximal region, and the binding site was further identified to be located from -177 bp to -152 bp upstream of the galF promoter. In conclusion, RcsAB could regulate the transcription of the galF gene positively by binding to the galF promoter DNA directly, and then affects the CPS formation of K. pneumonia.

Genome-wide identification of genes regulated by RcsA, RcsB, and RcsAB phosphorelay regulators in Klebsiella pneumoniae NTUH-K2044

Rcs phosphorelay system is a two-component signal transduction system, which can regulate the transcription of capsule polysaccharide and biofilm related genes in Enterobacteriaceae. In this study, microarray technology was used to investigate the overall genes regulated by RcsA, RcsB, and RcsAB and the regulation mechanism in Klebsiella pneumoniae, then COG analysis was performed to explore the functions of the differentially expressed genes. According to the microarray data result, a total of 45, 223 and 217 genes regulated by RcsA, RcsB, and RcsAB were screened. The result of COG analysis suggested that inorganic ion transport and metabolism related genes have a majority in RcsA regulating genes. Most of RcsB regulated genes were showed involved in energy production and conversion process. Besides Carbohydrate transport and metabolism genes were identified as the major components of the RcsAB regulated genes. 15 differentially expressed genes were confirmed by quantitative real-time PCR (RT-qPCR). The RT-qPCR results indicated that 13 genes consistent with microarray data. The results of this study provided important evidence for further research to investigate the influence of RcsA, RcsB, RcsAB regulators and further efforts to address the diseased caused by K.pneumoniae, such as pneumonia, bacteremia, and urinary tract infection.

Epidemiology of pathogens and antimicrobial resistanceof catheter-associated urinary tract infections in intensivecare units: A systematic review and meta-analysis

Background: In the intensive care unit (ICU), catheter‐associated urinary tract infection (CAUTI) is the most common urinary tract infection. Nevertheless, there is no systematic review to investigate the epidemiology of pathogens and antimicrobial resistance of CAUTIs in ICUs. Methods: Eight electronic databases were searched for eligible studies. A meta‐analysis was performed to calculate the CAUTI incidence per 1,000 catheter days, the proportion of pathogen distribution, and the resistance rate with R3.3.2 software. Results: Seventy‐five studies were included. The total weighted CAUTI incidence per 1,000 catheter days was 7.78. Gram‐negative bacteria (47.46%), fungi (27.81%), and gram‐positive bacteria (19.06%) were isolated. Candida spp (27.4%), Escherichia spp (23.41%), and Enterococcus spp (15.0%) were the most frequent pathogens. Candida albicans, Candida tropicalis, and Candida glabrata were generally resistant to itraconazole, with resistance rates of 42.5%, 53.0%, and 59.7%, respectively. Escherichia spp displayed high rates of resistance to ampicillin (87.3%), ciprofloxacin (71.7%), and norfloxacin (71.2%). Enterococcus spp showed high rates of resistance to erythromycin (83.9%), penicillin (76.7%), and levofloxacin (73.8%). Conclusions: In ICUs, the CAUTI incidence per 1,000 catheter days is high. CAUTIs were mainly caused by gram‐negative bacteria that were resistant to common antibiotics. There is a pressing demand for future research into CAUTI, including effective prevention, an understanding of antimicrobial resistance mechanisms, and development of new antibiotics for patient safety.

The KP1_4563 gene is regulated by the cAMP receptor protein and controls type 3 fimbrial function in Klebsiella pneumoniae NTUH-K2044

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic pathogen that can adhere to host cells or extracellular matrix via type 1 and type 3 fimbriae. KP1_4563 is a gene encoding a hypothetical protein in K. pneumoniae NTUH-K2044. KP1_4563 is located between the type 1 and type 3 fimbrial gene clusters and is likely associated with fimbrial function given its putative conserved domains of unknown function (DUF1471). Cyclic AMP receptor protein (CRP) regulates virulence-related gene expression and is a crucial transcriptional regulator in many bacteria. The predicted DNA recognition motif of CRP is present in the KP1_4563 promoter region. This study aimed to investigate the function of KP1_4563 in fimbriae and its transcriptional regulation mechanism by CRP. We generated Kp-Δ4563 mutant and complementation strains. We utilized phenotype and adhesion assays to evaluate the role of KP1_4563 in fimbriae. We conducted quantitative RT-PCR (qRT-PCR), LacZ fusion, electrophoretic mobility shift, and DNase I footprinting assays to study the transcriptional regulation of KP1_4563 gene by CRP. We found that KP1_4563 negatively regulates the function of type 3 fimbriae. Compared with NTUH-K2044, the absence of KP1_4563 enhanced the ability of Kp-Δ4563 to adhere to A549 cells. CRP negatively regulates KP1_4563 by directly binding to its promoter region. KP1_4563 plays an important role in type 3 fimbrial function. This novel insight will assist in the development of strategies for preventing K. pneumoniae infection.