Aims: Polymyxins are an important last-line treatment for infections caused by multidrug-resistant Gram-negative bacteria. Nonetheless, the emergence of polymyxin-resistance and the limiting of polymyxin monotherapy urgently demands its optimisation. Aquilaria malaccensis (Agarwood) has been widely used as traditional medicine. Many parts of the plant including leaves exhibit a considerable in vitro antibacterial activity against microbial pathogens. Exploiting A. malaccensis in combination with polymyxins provides a novel strategy in fighting antimicrobial resistance. The objective of this study was to evaluate the combination effects of A. malaccensis extract with polymyxins against Acinetobacter baumannii and Klebsiella pneumoniae. Methodology and results: In vitro time-kill studies and GC-MS analysis were performed to evaluate the bacterial killing of polymyxin B and extract combination and analyse chemical compounds of the extract, respectively. The combination of polymyxin B (1 mg/L) and A. malaccensis extract (32 mg/mL and 64 mg/mL) treatments exhibited enhanced bacterial killing compared to polymyxin B alone at 4 h and 24 h. Combination treatments also inhibited the bacterial growth of both A. baumannii and K. pneumoniae observed throughout the 24 h. More than sixty compounds including phytol, 9,12-octadecadienal, fatty acid, alkanes and terpenoids were putatively identified as the compounds that likely contributed to the antibacterial activity. Conclusion, significance and impact of study This study was the first to report the potential application of A. malaccensis extract in combination with polymyxin B in treatment against A. baumannii and K. pneumoniae and can be further investigated and optimized for the treatment of bacterial infectious diseases.
Thymelaeaceae ; Polymyxins ; Acinetobacter baumannii--immunology ; Klebsiella pneumoniae--immunology

The emergence of multidrug-resistant Klebsiella pneumoniae highlights the need to develop preventive measures to ameliorate Klebsiella infections. Bacteria-derived extracellular vesicles (EVs) are spherical nanometer-sized proteolipids enriched with outer membrane proteins. Gram-negative bacteria-derived EVs have gained interest for use as nonliving complex vaccines. In the present study, we evaluated whether K. pneumoniae-derived EVs confer protection against bacteria-induced lethality. K. pneumoniae-derived EVs isolated from in vitro bacterial culture supernatants induced innate immunity, including the upregulation of co-stimulatory molecule expression and proinflammatory mediator production. EV vaccination via the intraperitoneal route elicited EV-reactive antibodies and interferon-gamma-producing T-cell responses. Three vaccinations with the EVs prevented bacteria-induced lethality. As verified by sera and splenocytes adoptive transfer, the protective effect of EV vaccination was dependent on both humoral and cellular immunity. Taken together, these findings suggest that K. pneumoniae-derived EVs are a novel vaccine candidate against K. pneumoniae infections.
Animals ; Bacterial Vaccines/immunology/*microbiology/*therapeutic use ; Extracellular Vesicles/immunology/*microbiology ; Female ; Humans ; Immunity, Cellular ; Immunity, Innate ; Interferon-gamma/immunology ; Klebsiella Infections/immunology/*prevention &control ; Klebsiella pneumoniae/*immunology ; Mice, Inbred C57BL ; Vaccination

Klebsiella pneumoniae was cultured followed by the preparation and immunoactivity elucidating of its polysaccharide (CPS). The lysis of cell is the first key step in the preparation, under the co-action of trypsin, lysozyme and NP-40, the cell lysed within 2h, then the lysate was concentrated by ultrafiltration which serves as concentrating and partial purifying action simultaneously. Crude CPS was got by ethanol precipitation, then purified through the Ion-exchange and gel filtration, the purity of CPS was judged by the gel filtration and agarose gel electrophoresis. The effect of CPS on the cell immunoactivity was studied in detail, the results show that CPS possesses bidirectional immunoregulation on the spleen cells of mice, that is, low concentration of CPS can stimulate the immune response while the high concentration manifests the inhibition significantly. The investigation results will benefit on the exploitation of the CPS.
Animals ; Bacterial Capsules ; chemistry ; Culture Media ; Klebsiella pneumoniae ; chemistry ; immunology ; Lymphocyte Activation ; drug effects ; immunology ; Lymphocytes ; immunology ; Mice ; Mice, Inbred BALB C ; Polysaccharides, Bacterial ; immunology ; isolation & purification ; Spleen ; cytology

BACKGROUND/AIMS: The purpose of this study was to evaluate the value of initial C-reactive protein (CRP) as a predictor of clinical outcome and to investigate whether follow-up CRP measurement is useful for the prediction of the clinical outcome of bloodstream infections in patients with liver cirrhosis (LC), whose CRP production in response to infection may be attenuated. METHODS: A retrospective, observational study including 202 LC patients with Escherichia coli or Klebsiella pneumoniae bacteremia was conducted to assess the usefulness of serial CRP measurements in predicting clinical outcome in LC patients. The CRP ratio was defined as the ratio of the follow-up CRP level to the initial CRP level. RESULTS: The overall 30-day mortality rate of the study population was 23.8% (48/202). In the multivariate analysis, advanced age (> or = 70 years), healthcare-associated or nosocomial infections, model for end-stage liver disease (MELD) score of > or = 30, and initial body temperature of < 37degrees C were significant factors associated with mortality (all p < 0.05). No association between initial CRP level and mortality was found. In a further analysis including 87 evaluable cases who had repeated CRP measurements at day 4 and/or 5, a CRP ratio of > or = 0.7 was found to be a significant factor associated with mortality (odds ratio, 19.12; 95% confidence interval, 1.32 to 276.86; p = 0.043) after adjusting for other confounding variables. CONCLUSIONS: Initial CRP level did not predict mortality of sepsis in LC patients. However, serial CRP measurements during the first week of antimicrobial therapy may be useful as a prognostic factor for mortality in LC patients.
Adult ; Age Factors ; Aged ; Aged, 80 and over ; Anti-Infective Agents/therapeutic use ; Bacteremia/drug therapy/*immunology/microbiology/mortality ; Biological Markers/blood ; C-Reactive Protein/*metabolism ; Chi-Square Distribution ; Escherichia coli Infections/drug therapy/*immunology/microbiology/mortality ; Female ; Humans ; Klebsiella Infections/drug therapy/*immunology/microbiology/mortality ; Klebsiella pneumoniae/*isolation & purification ; Liver Cirrhosis/complications/*immunology/mortality ; Logistic Models ; Male ; Middle Aged ; Odds Ratio ; Predictive Value of Tests ; Republic of Korea ; Retrospective Studies ; Risk Assessment ; Risk Factors ; Time Factors ; Treatment Outcome