Articles by Jun Yan in JoVE
Murine Oropharyngeal Aspiration Model of Ventilator-associated and Hospital-acquired Bacterial Pneumonia Travis B. Nielsen1, Jun Yan1, Brian Luna1, Brad Spellberg1,2 1Department of Molecular Microbiology and Immunology, University of Southern California, 2Division of Infectious Diseases, Department of Medicine, LAC+USC Medical Center Infectious pneumonia is among the most common infections in human. An appropriate in vivo model is critical for understanding disease pathogenesis and testing the efficacy of novel therapeutics. With this murine oropharyngeal aspiration pneumonia model, one can examine the pathogenesis and new treatments against these deadly infections.
Other articles by Jun Yan on PubMed
Selectable Markers for Use in Genetic Manipulation of Extensively Drug-Resistant (XDR) HUMC1 MSphere. Mar-Apr, 2017 | Pubmed ID: 28497114 is one of the most antibiotic-resistant pathogens in clinical medicine, and extensively drug-resistant (XDR) strains are commonly isolated from infected patients. Such XDR strains are already resistant to traditional selectable genetic markers, limiting the ability to conduct pathogenesis research by genetic disruption. Optimization of selectable markers is therefore critical for the advancement of fundamental molecular biology techniques to use in these strains. We screened 23 drugs that constitute a broad array of antibiotics spanning multiple drug classes against HUMC1, a highly virulent and XDR clinical blood and lung isolate. HUMC1 is resistant to all clinically useful antibiotics that are reported by the clinical microbiology laboratory, except for colistin. Ethical concerns about intentionally establishing pan-resistance, including to the last-line agent, colistin, in a clinical isolate made identification of other markers desirable. We screened additional antibiotics that are in clinical use and those that are useful only in a lab setting to identify selectable markers that were effective at selecting for transformants . We show that supraphysiological levels of tetracycline can overcome innate drug resistance displayed by this XDR strain. Last, we demonstrate that transformation of the (tetracycline resistance) and (zeocin resistance), but not (puromycin resistance), resistance cassettes allow for selection of drug-resistant transformants. These results make the genetic manipulation of XDR strains easily achieved. Multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) strains of have frequently been characterized. The ability of to develop resistance to antibiotics is a key reason this organism has been difficult to study using genetic and molecular biology approaches. Here we report selectable markers that are not only useful but necessary for the selection of drug-resistant transformants in the setting of drug-resistant backgrounds. Use of these selectable markers can be applied to a variety of genetic and molecular techniques such as mutagenesis and transformation. These selectable markers will help promote genetic and molecular biology studies of otherwise onerous drug-resistant strains, while avoiding the generation of pathogenic organisms that are resistant to clinically relevant antibiotics.
Diabetes Exacerbates Infection Via Hyperinflammation by Signaling Through TLR4 and RAGE MBio. Aug, 2017 | Pubmed ID: 28830942 For more than a century, diabetic patients have been considered immunosuppressed due to defects in phagocytosis and microbial killing. We confirmed that diabetic mice were hypersusceptible to bacteremia caused by Gram-negative bacteria (GNB), dying at inocula nonlethal to nondiabetic mice. Contrary to the pervasive paradigm that diabetes impedes phagocytic function, the bacterial burden was no greater in diabetic mice despite excess mortality. However, diabetic mice did exhibit dramatically increased levels of proinflammatory cytokines in response to GNB infections, and immunosuppressing these cytokines with dexamethasone restored their resistance to infection, both of which are consistent with excess inflammation. Furthermore, disruption of the receptor for advanced glycation end products (RAGE), which is stimulated by heightened levels of AGEs in diabetic hosts, protected diabetic but not nondiabetic mice from GNB infection. Thus, rather than immunosuppression, diabetes drives lethal hyperinflammation in response to GNB by signaling through RAGE. As such, interventions to improve the outcomes from GNB infections should seek to suppress the immune response in diabetic hosts. Physicians and scientists have subscribed to the dogma that diabetes predisposes the host to worse outcomes from infections because it suppresses the immune system. This understanding was based largely on studies of blood from patients and animals with diabetes. However, we have found that the opposite is true and worse outcomes from infection are caused by overstimulation of the immune system in response to bacteria. This overreaction occurs by simultaneous ligation of two host receptors: TLR4 and RAGE. Both signal via a common downstream messenger, MyD88, triggering hyperinflammation. In summary, contrary to hundred-year-old postulations about immune suppression in diabetic hosts, we find that diabetes instead predisposes to more severe infections because of additional inflammatory output through dual activation of MyD88 by not only TLR4 but also RAGE. It is the activation of RAGE during GNB infections in those with diabetes that accounts for their heightened susceptibility to infection compared to nondiabetic hosts.
Monoclonal Antibody Protects Against Acinetobacter Baumannii Infection by Enhancing Bacterial Clearance and Evading Sepsis The Journal of Infectious Diseases. Aug, 2017 | Pubmed ID: 28931235 Extremely drug-resistant (XDR) Acinetobacter baumannii is one of the most commonly encountered, highly resistant pathogens requiring novel therapeutic interventions.