Development of Real‐Time In Vivo Imaging of Device‐Related Staphylococcus epidermidis Infection in Mice and Influence of Animal Immune Status on Susceptibility to Infection (original) (raw)
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We have developed a rapid, continuous method for real-time monitoring of biofilms, both in vitro and in a mouse infection model, through noninvasive imaging of bioluminescent bacteria colonized on Teflon catheters. Two important biofilm-forming bacterial pathogens, Staphylococcus aureus and Pseudomonas aeruginosa, were made bioluminescent by insertion of a complete lux operon. These bacteria produced significant bioluminescent signals for both in vitro studies and the development of an in vivo model, allowing effective real-time assessment of the physiological state of the biofilms. In vitro viable counts and light output were parallel and highly correlated (S. aureus r ؍ 0.98; P. aeruginosa r ؍ 0.99) and could be maintained for 10 days or longer, provided that growth medium was replenished every 12 h. In the murine model, subcutaneous implantation of the catheters (precolonized or postimplant infected) was well tolerated. An infecting dose of 10 3 to 10 5 CFU/catheter for S. aureus and P. aeruginosa resulted in a reproducible, localized infection surrounding the catheter that persisted until the termination of the experiment on day 20. Recovery of the bacteria from the catheters of infected animals showed that the bioluminescent signal corresponded to the CFU and that the lux constructs were highly stable even after many days in vivo. Since the metabolic activity of viable cells could be detected directly on the support matrix, nondestructively, and noninvasively, this method is especially appealing for the study of chronic biofilm infections and drug efficacy studies in vivo.
FEMS Immunology & Medical Microbiology, 2010
The virulence of Staphylococcus epidermidis is related to its capacity to form biofilms. Such biofilm-related infections are extremely difficult to treat and to detect in early stages by the traditional microbiological analyses. The determination of the chemical composition of the extracellular polymeric substances (EPS) of the biofilm matrix, as well as the elucidation of the sensitivity of biofilms to enzymatic degradation should facilitate the development of new therapies against biofilm-related infections. The chemical analyses of EPS had shown qualitative and quantitative variations of their nature, depending on the strains and culture conditions. The poly-N-acetylglucosamine (PNAG) is considered the main component of staphylococcal biofilms. However, certain strains form biofilms without PNAG. In addition to PNAG and proteins, extracellular teichoic acid was identified as a new component of the staphylococcal biofilms. The sensitivity of staphylococcal biofilms to enzymatic treatments depended on their relative chemical composition, and a PNAG-degrading enzyme, in conjunction with proteases, could be an efficient solution to eliminate the staphylococcal biofilms. A detection of specific 'antibiofilm' antibodies in the blood serum of patients could serve as a convenient noninvasive and inexpensive diagnostic tool for the detection of foreign body-associated staphylococcal infections. Used as a coating antigen in the enzyme-linked immunosorbent assay test, PNAG did not sufficiently discriminate healthy individuals from the infected patients.
Staphylococcus epidermidis in Biomaterial-Associated Infections
Biomaterials Associated Infection, 2012
ABSTRACT Coagulase-negative staphylococci, mainly Staphylococcus epidermidis, are currently the most frequent cause of hospital acquired infections in the USA. Mostly, but not exclusively, S. epidermidis infections are linked to the use of implanted medical devices like central venous catheters, prosthetic joints and heart valves, pacemakers, cardiac assist devices, cerebrospinal fluid shunts, and intraocular lenses. As new molecular techniques reveal that S. epidermidis are by no means the most prominent bacteria of the skin and mucous membrane flora, the implication is that S. epidermidis has specific virulence factors, which transforms this commensal bacterial species into one of the most successful pathogens in modern medicine. A vast array of specific attachment factors for native and host protein-modified device surfaces and the ability to accumulate in adherent multilayered biofilms appear to be vital for the success of S. epidermidis as a pathogen. Biofilm formation contributes to the ability of the organism to withstand the host’s innate and acquired immune defense mechanisms and to resist antimicrobial therapy, so that device removal is a regular feature for the treatment of S. epidermidis biomaterial-associated infection. Recent developments in the understanding of S. epidermidis virulence are reviewed in this chapter.
Real time noninvasive monitoring of contaminating bacteria in a soft tissue implant infection model
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2009
Infection is the main cause of biomaterials-related failure. A simple technique to test in-vivo new antimicrobial and/or nonadhesive implant coatings is unavailable. Current in vitro methods for studying bacterial adhesion and growth on biomaterial surfaces lack the influence of the host immune system. Most in vivo methods to study biomaterials-related infections routinely involve implant-removal, preventing comprehensive longitudinal monitoring. In vivo imaging circumvents these drawbacks and is based on the use of noninvasive optical imaging of bioluminescent bacteria. Staphylococcus aureus Xen29 is genetically modified to be stably bioluminescent, by the introduction of a modified full lux operon onto its chromosome. Surgical meshes with adhering S. aureus Xen29 were implanted in mice and bacterial growth and spread into the surrounding tissue was monitored longitudinally from bioluminescence with a highly sensitive CCD camera. Distinct spatiotemporal bioluminescence patterns, extending beyond the mesh area into surrounding tissues were observed. After 10 days, the number of living organisms isolated from explanted meshes was found to correlate with bioluminescence prior to sacrifice of the animals. Therefore, it is concluded that in vivo imaging using bioluminescent bacteria is ideally suited to study antimicrobial coatings taking into account the host immune system. In addition, longitudinal monitoring of infection in one animal will significantly reduce the number of experiments and animals. '
Infection and immunity
Infection of biomedical devices is characterized by biofilm formation and colonization of surrounding tissue by the causative pathogens. To investigate whether bacteria detected microscopically in tissue surrounding infected devices were viable, we used bromodeoxyuridine (BrdU), a nucleotide analogue that is incorporated into bacterial DNA and can be detected with antibodies. Infected human tissue was obtained postmortem from patients with intravascular devices, and mouse biopsy specimens were obtained from mice with experimental biomaterial infection. In vitro experiments showed that Staphylococcus epidermidis incorporated BrdU, as judged from staining of the bacteria with anti-BrdU antibodies. After incubation of bacteria with BrdU and subsequent staining of microscopic sections with anti-BrdU antibodies, bacteria could be clearly visualized in the tissue surrounding intravascular devices of deceased patients. With this staining technique, relapse of infection could be visualized ...
Fems Immunology and Medical Microbiology, 2003
The contribution of in vivo biofilm-forming potential of Staphylococcus aureus and Staphylococcus epidermidis was studied in an experimental model of foreign body infections. Increasing inocula (from 10 2 to 10 7 organisms) of ica-positive strains of S. aureus and S. epidermidis and their ica-negative isogenic mutants (the ica locus codes for a major polysaccharide component of biofilm) were injected into subcutaneously implanted tissue cages in guinea pigs. Surprisingly, bacterial counts and time-course of tissue cage infection by icapositive strains of S. aureus or S. epidermidis were equivalent to those of their respective ica-negative mutants, in the locally infected fluids and on tissue-cage-inserted plastic coverslips.
Pathogenic Mechanisms and Host Interactions in Staphylococcus epidermidis Device-Related Infection
Frontiers in microbiology, 2017
Staphylococcus epidermidis is a permanent member of the normal human microbiota, commonly found on skin and mucous membranes. By adhering to tissue surface moieties of the host via specific adhesins, S. epidermidis is capable of establishing a lifelong commensal relationship with humans that begins early in life. In its role as a commensal organism, S. epidermidis is thought to provide benefits to human host, including out-competing more virulent pathogens. However, largely due to its capacity to form biofilm on implanted foreign bodies, S. epidermidis has emerged as an important opportunistic pathogen in patients receiving medical devices. S. epidermidis causes approximately 20% of all orthopedic device-related infections (ODRIs), increasing up to 50% in late-developing infections. Despite this prevalence, it remains underrepresented in the scientific literature, in particular lagging behind the study of the S. aureus. This review aims to provide an overview of the interactions of ...
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