Browsing by Subject "Staphylococcus aureus"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
Item Blood Serum Affects Polysaccharide Production and Surface Protein Expression in S. Aureus(Juniper, 2017) Islam, Nazrul; Hossain, Khwaja G.; Ross, Julia M.; Marten, Mark R.Background: S. aureus biofilm serves a major role in pathogenesis. Two of the major components of bacterial biofilm are Polysaccharides intercellular adhesions (PIA) and surface proteins. It is not known how PIA and surface proteins expressions are affected in presence of blood serum. Analyses of surface proteins expressions will provide more effective biomarker discovery that might lead to development of antimicrobial therapeutics to meet the challenges of biofilm-related infections. Method: Secondary cultures of S. aureus Philips, a biofilm-forming bacterium, were generated by inoculating 1 ml of overnight culture into 50 ml of TSB. Bacteria were cultured at several concentrations of blood serum and found that 12.5% supplemented blood serum provide s similar growth curve as normal TSB (100%). One and 2 D SASPAGE were used to separate proteins and the differentially expressed proteins were identified by nano-LC/MS. Results: Polysaccharide intercellular adhesions production was significantly increased due to the addition of blood serum in the media. We also identified two serum proteins, apolipoprotein and globulin (Fc and Fab), that remained attached with the membrane fraction of bacterial proteins. Conclusion: These results have strongly demonstrated that blood serum influences the exopolysaccharide expression in S. aureus.Item A comparison of Lyse-It to other cellular sample preparation, bacterial lysing, and DNA fragmentation technologies(PLOS, 2019-07-23) Santaus, Tonya M.; Li, Shan; Saha, Lahari; Chen, Wilbur H.; Bhagat, Siya; Stine, O. Colin; Geddes, Chris D.The ability for safe and rapid pathogenic sample transportation and subsequent detection is an increasing challenge throughout the world. Herein, we describe and use bead-beating, vortex, sonication, 903 protein saver cards, and Lyse-It methods, aiming to inactivate Grampositive and -negative bacteria with subsequent genome DNA (quantitative Polymerase Chain Reaction) qPCR detection. The basic concepts behind the four chosen technologies is their versatility, cost, and ease of use in developed and underdeveloped countries. The four methods target the testing of bacterial resilience, cellular extraction from general and complex media and subsequent DNA extraction for qPCR detection and amplification. These results demonstrate that conventional high temperature heating, 903 protein saver cards, and Lyse-It are all viable options for inactivating bacterial growth for safe shipping. Additionally, Lyse-It was found to be particularly useful as this technology can inactivate bacteria, extract cells from 903 protein saver cards, lyse bacterial cells, and additionally keep genomic DNA viable for qPCR detection.Item Fluorescent silica particles for monitoring oxygen levels in three‐dimensional heterogeneous cellular structures(Wiley Periodicals, 2012-04-17) Acosta, Miguel A.; Velasquez, Melissa; Williams, Katelyn; Ross, Julia M.; Leach, Jennie B.Bacterial biofilms are a major obstacle challenging the development of more effective therapies to treat implant infections. Oxygen availability to bacterial cells has been implicated in biofilm formation and planktonic cell detachment; however, there are insufficient tools available to measure oxygen concentrations within complex three-dimensional structures with ~1 μm resolution. Such measurements may complement measures of biofilm structure and cell activity to provide a more comprehensive understanding of biofilm biology. Thus, we developed oxygensensing microparticles specifically designed to characterize oxygen transport through the volume of bacterial biofilms. The Stöber method was used to synthesize monodisperse silica microparticles of approximately the same size as a bacterium (~1 μm). Two fluorophores, oxygensensitive Ru(Ph₂phen₃)Cl₂, and the reference fluorophore Nile blue chloride were immobilized on the surface of the particles. We demonstrate application of the microparticles toward measuring the oxygen concentration profiles within a live Staphylococcus aureus biofilm.Item Identification and characterization of the pckA gene from Staphylococcus aureus(American Society for Microbiology, 1996-06) Scovill, William H.; Schreier, Harold J.; Bayles, Kenneth W.The Staphylococcus aureus pckA gene was identified and characterized. A pckA mutant lacked detectable phosphoenolpyruvate carboxykinase activity and grew poorly in the absence of glucose. Both enzymatic activity and pckA promoter activity in wild-type cells grown in the absence of glucose were at least 22-fold greater than activities in cells grown in the presence of glucose.Item Impact of cell substratum adhesion pattern and cluster spatial distribution on the development of Staphylococcus aureus biofilm under physiologically-relevant shear rates.(2018-01-01) Ajayi, Opeyemi O; Ross, Julia M; Leach, Jennie B; Chemical, Biochemical & Environmental Engineering; Engineering, Chemical and BiochemicalBacterial cells, in nature, prefer to exist as a surface-attached coalescent community of slime-encased cells known as biofilms. This biofilm-forming existence offers several advantages to the cells, including evasion of host immune response, resistance to antimicrobials and antibiotics, communal expression of metabolites, and overall increased survivability in unfavorable environmental conditions. Biofilm formation has been observed for several species of bacteria across multiple scientific disciplines and affecting a wide variety of industries including the food industry, waste treatment, and healthcare. In healthcare settings, S. aureus is a major etiological agent of biofilm-based infections in humans. Furthermore, the hydrodynamic environment of the cardiovascular system complicates the eradication of biofilm-based infection due to metastasis of eroded cells to multiple infection sites. Therefore, remediation efforts of staphylococcal infections are aimed at the prevention and disruption of biofilm development. Regardless of infection site, pathogenesis is initiated by adhesion of planktonic cells to host tissue or implanted biomaterials, culminating in the formation of mature biofilm that can subsequently seed planktonic cells. In S. aureus the transition of adhered bacterial cells into biofilm depends on cellular production and detection of a signal peptide molecule called auto-inducer peptide (AIP). Biofilm development and virulence are regulated by the sensing mechanism of the cells to their local AIP concentration. With this in mind, I hypothesized that biofilm development may be inhibited by specifying initial parameters within the biofilm environment that influence local AIP concentrations; these parameters include fluid shear stress as well as the geometric features of initial cell-substrate adhesion, including distance between adhesion sites and the area of the adhesion sites on the substrate. The broad objectives of this study were to characterize and quantify the morphology of S. aureus biofilms under fluid flow that were initiated on substrates with micropatterned cell-adhesion sites of controlled spacing, size, and total area. First, the underlying mechanism of biofilm-dependent growth was predicted via in silico simulation of AIP concentration. Then laboratory experiments demonstrated that: 1) increased spacing between microcolonies correlated with diminished S. aureus biofilm development; and 2) inhibition of biofilm development was greater when exposed to increased fluid shear stress. These findings unveil new strategies to potentially slow down or prevent biofilm-based infections in the human cardiovascular system.Item Incidence of and risk factors for bacteraemia in HIV-infected adults in the era of highly active antiretroviral therapy(Wiley, 2011-03-23) Yehia, BR; Fleishman, JA; Wilson, L; Hicks, PL; Gborkorquellie, TT; Gebo, KABackground HIV-infected patients have an increased risk for bacteraemia compared with HIV-negative patients. Few data exist on the incidence of and risk factors for bacteraemia across time in the current era of highly active antiretroviral therapy (HAART). Methods We assessed the incidence of bacteraemia among patients followed between 2000 and 2008 at 10 HIV Research Network sites. This large multisite, multistate clinical cohort study collected demographic, clinical and therapeutic data longitudinally. International Statistical Classification of Diseases and Related Health Problems (ICD)-9 codes were examined to identify all cases of in-patient bacteraemia. Logistic regression analysis was used to assess risk factors for bacteraemia and trends over time in the odds of bacteraemia. Results A total of 39 318 patients were followed for 146 289 person-years (PY). During the study period, there were 2025 episodes of bacteraemia (incidence 13.8 events/1000 PY). The most common bacteraemia diagnosis was ‘bacteraemia, not otherwise specified (NOS)’ (51%) followed by Staphylococcus aureus (16%) and Streptococcus species (6.5%). In multivariate analysis, the likelihood of bacteraemia was found to have increased in 2005–2008, compared with 2000. Other factors associated with higher odds of bacteraemia included a history of injection drug use (IDU), age ≥50 years, Black race and greater immunosuppression. Conclusions The likelihood of bacteraemia has risen slightly in recent years. Patients who are Black or have a history of IDU are at higher risk. Further research is needed to identify reasons for this increase and to evaluate programmes designed to reduce the bacteraemia risk.Item The incidence of and risk factors for MRSA bacteraemia in an HIV-infected cohort in the HAART era(Wiley, 2008-10-27) Burkey, MD; Wilson, LE; Moore, RD; Lucas, GM; Francis, J; Gebo, KAObjectives To define the incidence and risk factors for methicillin resistant Staphylococcus aureus (MRSA) bacteraemia in an HIV-infected population. Methods From January 1, 2000 to December 31, 2004, we conducted a retrospective cohort study. We identified all cases of Staphylococcus aureus bacteraemia (SAB), including MRSA, among patients enrolled in the Johns Hopkins Hospital out-patient HIV clinic. A conditional logistic regression model was used to identify risk factors for MRSA bacteraemia compared with methicillin-sensitive SAB and no bacteraemia in unmatched (1:1) and matched (1:4) nested case-control analyses, respectively. Results Of 4607 patients followed for a total of 11 020 person-years (PY) of follow-up, 216 episodes of SAB occurred (incidence: 19.6 cases per 1000 PY), including 94 cases (43.5%) which were methicillin-resistant. The incidence of MRSA bacteraemia increased from 5.3 per 1000 PY in 2000–2001 to 11.9 per 1000 PY in 2003–2004 (P=0.001). Multivariate analysis demonstrated that independent predictors of MRSA bacteraemia (vs. no bacteraemia) were injection drug use (IDU), end-stage renal disease (ESRD) and CD4 count <200 cells/μL. Conclusions MRSA bacteraemia was an increasingly common diagnosis in our HIV-infected cohort, especially in patients with history of IDU, low CD4 cell count and ESRD.