Browsing by Author "Hu, Fen Z."

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Intelligent implants to battle biofilms
(2004) Ehrlich, Garth D.; Hu, Fen Z.; Lin, Qiao; Costerton, J. William; Post, J. C.
Mucosal biofilm formation on middle-ear mucosa in the chinchilla model of otitis media
(2002-04) Ehrlich, Garth D.; Veeh, Richard Harold; Wang, Xue; Costerton, J. William; Hayes, Jay D.; Hu, Fen Z.; Daigle, Bernie J.; Ehrlich, Miles D.; Post, J. C.
CONTEXT Chronic otitis media with effusion (OME) has long been considered to be a sterile inflammatory process. The previous application of molecular diagnostic technologies to OME suggests that viable bacteria are present in complex communities known as mucosal biofilms; however, direct imaging evidence of mucosal biofilms associated with OM is lacking. OBJECTIVE. To determine whether biofilm formation occurs in middle-ear mucosa in an experimental model of otitis media. DESIGN and MATERIALS. A total of 48 research-grade, young adult chinchillas weighing 500g were used for 2 series of animal experiments: one to obtain specimens for scanning electron microscopy and the other to obtain specimens for confocal laser scanning microscopy using vital dyes. In each series, 21 animals were bilaterally injected with viable Haemophilus influenzae bacteria and 1 was inoculated to account for expected mortality. Three served as negative controls. Effusions and mucosal specimens were collected from 2 infected animals that were euthanized at 3, 6, 12, and 24 hours and at days 2, 4, 5, 10, 16, and 22 after inoculation. MAIN OUTCOME MEASURES. Images were analyzed for biofilm morphology, including presence of microcolony formation and for presence of bacteria on tissue surfaces. RESULTS. Scanning electron microscopy demonstrated that biofilm formation was evident in all specimens from animals beginning 1 day after infection and was present through 21 days. Confocal laser scanning microscopy indicated that bacteria within the biofilms was viable. CONCLUSION. These preliminary findings provide evidence that mucosal biofilms form in an experimental model of otitis media and suggest that biofilm formation may be an important factor in the pathogenesis of chronic otitis media with effusion.
Nanoscale Structural and Mechanical Properties of Nontypeable Haemophilus influenzae Biofilms
(2009-02) Arce, Fernando Teran; Carlson, Ross P.; Monds, James; Veeh, Richard Harold; Hu, Fen Z.; Stewart, Philip S.; Lal, Ratnesh; Ehrlich, Garth D.; Avci, Recep
Nontypeable Haemophilus influenzae (NTHI) bacteria are commensals in the human nasopharynx, as well as pathogens associated with a spectrum of acute and chronic infections. Two important factors that influence NTHI pathogenicity are their ability to adhere to human tissue and their ability to form biofilms. Extracellular polymeric substances (EPS) and bacterial appendages such as pili critically influence cell adhesion and intercellular cohesion during biofilm formation. Structural components in the outer cell membrane, such as lipopolysaccharides, also play a fundamental role in infection of the host organism. In spite of their importance, these pathogenic factors are not yet well characterized at the nanoscale. Here, atomic force microscopy (AFM) was used in aqueous environments to visualize structural details, including probable Hif-type pili, of live NTHI bacteria at the early stages of biofilm formation. Using single-molecule AFM-based spectroscopy, the molecular elasticities of lipooligosaccharides present on NTHI cell surfaces were analyzed and compared between two strains (PittEE and PittGG) with very different pathogenicity profiles. Furthermore, the stiffness of single cells of both strains was measured and subsequently their turgor pressure was estimated.
New methods for the detection of orthopedic and other biofilm infections
(2011-03) Costerton, J. William; Post, J. C.; Ehrlich, Garth D.; Hu, Fen Z.; Kreft, R.; Nistico, L.; Kathju, S.; Stoodley, Paul; Hall-Stoodley, Luanne; Maale, G.; James, Garth A.; Sotereanos, N.; DeMeo, P.
The detection and identification of bacteria present in natural and industrial ecosystems is now entirely based on molecular systems that detect microbial RNA or DNA. Culture methods were abandoned in the 1980s because direct observations showed that <1% of the bacteria in these systems grew on laboratory media. Culture methods comprise the backbone of the Food and Drug Administration-approved diagnostic systems used in hospital laboratories, with some molecular methods being approved for the detection of specific pathogens that are difficult to grow in vitro. In several medical specialties, the reaction to negative cultures in cases in which overt signs of infection clearly exist has produced a spreading skepticism concerning the sensitivity and accuracy of traditional culture methods.We summarize evidence from the field of orthopedic surgery, and from other medical specialties, that support the contention that culture techniques are especially insensitive and inaccurate in the detection of chronic biofilm infections. We examine the plethora of molecular techniques that could replace cultures in the diagnosis of bacterial diseases, and we identify the new Ibis technique that is based on base ratios (not base sequences), as the molecular system most likely to fulfill the requirements of routine diagnosis in orthopedic surgery.
Role of biofilms in neurosurgical device-related infections
(2005-10) Baxton Jr, Ernest E.; Ehrlich, Garth D.; Hall-Stoodley, Luanne; Stoodley, Paul; Veeh, Rick; Fux, C. A.; Hu, Fen Z.; Quigley, Matthew; Post, J. C.
Bacterial biofilms have recently been shown to be important in neurosurgical device-related infections. Because the concept of biofilms is novel to most practitioners, it is important to understand that both traditional pharmaceutical therapies and host defense mechanisms that are aimed at treating or overcoming free-swimming bacteria are largely ineffective against the sessile bacteria in a biofilm. Bacterial biofilms are complex surface-attached structures that are composed of an extruded extracellular matrix in which the individual bacteria are embedded. Superimposed on this physical architecture is a complex system of intercellular signaling, termed quorum sensing. These complex organizational features endow biofilms with numerous microenvironments and a concomitant number of distinct bacterial phenotypes. Each of the bacterial phenotypes within the biofilm displays a unique gene expression pattern tied to nutrient availability and waste transport. Such diversity provides the biofilm as a whole with an enormous survival advantage when compared to the individual component bacterial cells. Thus, it is appropriate to view the biofilm as a multicellular organism, akin to metazoan eukaryotic life. Bacterial biofilms are much hardier than free floating or planktonic bacteria and are primarily responsible for device-related infections. Now that basic research has demonstrated that the vast majority of bacteria exist in biofilms, the paradigm of biofilm-associated chronic infections is spreading to the clinical world. Understanding how these biofilm infections affect patients with neurosurgical devices is a prerequisite to developing strategies for their treatment and prevention.