Biomedical subjects

Mark E Shirtliff

Publications and source records attributed to Mark E Shirtliff.

10 recordsLinked to original sources

PubMed2006

Identification of Staphylococcus aureus proteins recognized by the antibody-mediated immune response to a biofilm infection.

Staphylococcus aureus causes persistent, recurrent infections (e.g., osteomyelitis) by forming biofilms. To survey the antibody-mediated immune response and identify those proteins that are immunogenic in an S. aureus biofilm infection, the tibias of rabbits were infected with methicillin-resistant S. aureus to produce chronic osteomyelitis. Sera were collected prior to infection and at 14, 28, and 42 days postinfection. The sera were used to perform Western blot assays on total protein from biofilm grown in vitro and separated by two-dimensional gel electrophoresis. Those proteins recognized by host antibodies in the harvested sera were identified via matrix-assisted laser desorption ionization-time of flight analysis. Using protein from mechanically disrupted total and fractionated biofilm protein samples, we identified 26 and 22 immunogens, respectively. These included a cell surface-associated beta-lactamase, lipoprotein, lipase, autolysin, and an ABC transporter lipoprotein. Studies were also performed using microarray analyses and confirmed the biofilm-specific up-regulation of most of these genes. Therefore, although the biofilm antigens are recognized by the immune system, the biofilm infection can persist. However, these proteins, when delivered as vaccines, may be important in directing the immune system toward an early and effective antibody-mediated response to prevent chronic S. aureus infections. Previous works have identified S. aureus proteins that are immunogenic during acute infections, such as sepsis. However, this is the first work to identify these immunogens during chronic S. aureus biofilm infections and to simultaneously show the global relationship between the antigens expressed during an in vivo infection and the corresponding in vitro transcriptomic and proteomic gene expression levels.

Animals↗

PubMed2005

The exopolysaccharide alginate protects Pseudomonas aeruginosa biofilm bacteria from IFN-gamma-mediated macrophage killing.

The ability of Pseudomonas aeruginosa to form biofilms and cause chronic infections in the lungs of cystic fibrosis patients is well documented. Numerous studies have revealed that P. aeruginosa biofilms are highly refractory to antibiotics. However, dramatically fewer studies have addressed P. aeruginosa biofilm resistance to the host's immune system. In planktonic, unattached (nonbiofilm) P. aeruginosa, the exopolysaccharide alginate provides protection against a variety of host factors yet the role of alginate in protection of biofilm bacteria is unclear. To address this issue, we tested wild-type strains PAO1, PA14, the mucoid cystic fibrosis isolate, FRD1 (mucA22+), and the respective isogenic mutants which lacked the ability to produce alginate, for their susceptibility to human leukocytes in the presence and absence of IFN-gamma. Human leukocytes, in the presence of recombinant human IFN-gamma, killed biofilm bacteria lacking alginate after a 4-h challenge at 37 degrees C. Bacterial killing was dependent on the presence of IFN-gamma. Killing of the alginate-negative biofilm bacteria was mediated through mononuclear cell phagocytosis since treatment with cytochalasin B, which prevents actin polymerization, inhibited leukocyte-specific bacterial killing. By direct microscopic observation, phagocytosis of alginate-negative biofilm bacteria was significantly increased in the presence of IFN-gamma vs all other treatments. Addition of exogenous, purified alginate to the alginate-negative biofilms restored resistance to human leukocyte killing. Our results suggest that although alginate may not play a significant role in bacterial attachment, biofilm development, and formation, it may play an important role in protecting mucoid P. aeruginosa biofilm bacteria from the human immune system.

Alginates↗

PubMed2005

Assessment of the ability of the bioelectric effect to eliminate mixed-species biofilms.

Microbes have been able to persist in water distribution systems through the development of multicellular communities known as biofilms. This study evaluated the usefulness of the bioelectric effect for the elimination of water distribution system biofilms from annular reactors. The bioelectric effect did not have any bactericidal action either alone or when coupled with free chlorine.

Bioelectric Energy Sources↗

PubMed2003

Detection of Staphylococcus aureus biofilm on tampons and menses components.

Culturing has detected vaginal Staphylococcus aureus in 10%-20% of women. Because growth mode can affect virulence expression, this study examined S. aureus-biofilm occurrence in 44 paired-tampon and vaginal-wash-specimens from 18 prescreened women, using fluorescent in situ hybridization (FISH). All 44 specimens were also analyzed for S. aureus by standard culturing on mannitol salt agar, which produced positive results for 15 of the 44 specimens. FISH detected S. aureus cells in all 44 specimens, and S. aureus biofilm was observed in 37 of the 44 specimens. Independent confirmation of the presence of S. aureus in specimens from all 18 women was also obtained by amplification, via polymerase chain reaction, of an S. aureus-specific nuclease gene. The results of this study demonstrate that S. aureus biofilm can form on tampons and menses components in vivo. Additionally, the prevalence of vaginal S. aureus carriage may be more prevalent than what is currently demonstrated by standard culturing techniques.

Adolescent↗

PubMed2002

Molecular interactions in biofilms.

A biofilm may be defined as a microbially derived, sessile community characterized by cells that attach to an interface, embed in a matrix of exopolysaccharide, and demonstrate an altered phenotype. This review covers the current understanding of the nature of biofilms and the impact that molecular interactions may have on biofilm development and phenotype using the motile gram-negative rod Pseudomonas aeruginosa and the nonmotile gram-positive cocci Staphylococcus aureus as examples.

Biofilms↗

PubMed2002

Experimental osteomyelitis treatment with antibiotic-impregnated hydroxyapatite.

A calcium hydroxyapatite antibiotic implant was evaluated to determine its efficacy as an antibiotic delivery system in a localized osteomyelitis rabbit model. Localized rabbit tibial osteomyelitis was developed with an intramedullary injection of methicillin resistant Staphylococcus aureus. Infected rabbits were randomized and divided into eight groups depending on treatment with or without debridement, systemic antibiotics, antibiotic-impregnated polymethylmethacrylate beads, or calcium hydroxyapatite implants with and without antibiotic impregnation. All treatments began 2 weeks after infection. After 4 weeks of therapy, the involved bones were cultured for concentrations of Staphylococcus aureus per gram of bone. Rabbits (n = 11) that had calcium hydroxyapatite (impregnated with vancomycin) implanted into the dead space after the debridement surgery had an 81.8% infection clearance after treatment. Rabbits (n = 10) that had polymethylmethacrylate beads (impregnated with vancomycin) implanted into the dead space after debridement surgery had a 70% clearance rate. All other treatment modalities resulted in less than 50% clearance rates. Calcium hydroxyapatite may be an effective alternative to polymethylmethacrylate for providing local antibiotic therapy in cases of methicillin resistant Staphylococcus aureus osteomyelitis.

Animals↗

PubMed2002

Gatifloxacin efficacy in treatment of experimental methicillin-sensitive Staphylococcus aureus-induced osteomyelitis in rabbits.

The effectiveness of oral gatifloxacin was compared to that of standard parenteral antibiotic therapy (nafcillin) for the treatment of experimental methicillin-sensitive Staphylococcus aureus-induced osteomyelitis in a rabbit model. Gatifloxacin was as effective as nafcillin in clearing the infection. Therefore, oral gatifloxacin treatment of osteomyelitis may be an effective alternative to intravenous nafcillin treatment.

Administration, Oral↗

PubMed2002

Acute septic arthritis.

Acute septic arthritis may develop as a result of hematogenous seeding, direct introduction, or extension from a contiguous focus of infection. The pathogenesis of acute septic arthritis is multifactorial and depends on the interaction of the host immune response and the adherence factors, toxins, and immunoavoidance strategies of the invading pathogen. Neisseria gonorrhoeae and Staphylococcus aureus are used in discussing the host-pathogen interaction in the pathogenesis of acute septic arthritis. While diagnosis rests on isolation of the bacterial species from synovial fluid samples, patient history, clinical presentation, laboratory findings, and imaging studies are also important. Acute nongonococcal septic arthritis is a medical emergency that can lead to significant morbidity and mortality. Therefore, prompt recognition, rapid and aggressive antimicrobial therapy, and surgical treatment are critical to ensuring a good prognosis. Even with prompt diagnosis and treatment, high mortality and morbidity rates still occur. In contrast, gonococcal arthritis is often successfully treated with antimicrobial therapy alone and demonstrates a very low rate of complications and an excellent prognosis for full return of normal joint function. In the case of prosthetic joint infections, the hardware must be eventually removed by a two-stage revision in order to cure the infection.

Acute Disease↗

PubMed2002

Human leukocytes adhere to, penetrate, and respond to Staphylococcus aureus biofilms.

Staphylococcus aureus is a common pathogen responsible for nosocomial and community infections. It readily colonizes indwelling catheters, forming microbiotic communities termed biofilms. S. aureus bacteria in biofilms are protected from killing by antibiotics and the body's immune system. For years, one mechanism behind biofilm resistance to attack from the immune system's sentinel leukocytes has been conceptualized as a deficiency in the ability of the leukocytes to penetrate the biofilm. We demonstrate here that under conditions mimicking physiological shear, leukocytes attach, penetrate, and produce cytokines in response to maturing and fully matured S. aureus biofilm.

Biofilms↗

PubMedDate not supplied

Immunology of Staphylococcal biofilm infections in the eye: new tools to study biofilm endophthalmitis.

Endophthalmitis is an important disease of the eye that is most frequently caused by postoperative and post-traumatic introduction of bacteria into the posterior segment of the eye. In the case of severe infections, visual acuity is greatly damaged or completely lost. Much work has focused on the ability of planktonic bacteria to cause infection and ocular damage while little work has focused on chronic infections in endophthalmitis mediated by the formation of bacterial biofilms on the surface of the lens. This review focuses on the interaction of Staphylococcus aureus and Staphylococcus epidermidis lens-associated biofilms in endophthalmitis. Additionally, this review highlights some relevant biofilm-immune system interactions and outlines a new in vivo mouse model to explore biofilm-related infections in endophthalmitis.

Animals↗