Mucosal Biofilm Formation on Middle‐Ear Mucosa in a Nonhuman Primate Model of Chronic Suppurative Otitis Media

Dohar, Joseph E.; Hebda, Patricia A.; Veeh, Richard Harold; Awad, Marie; Costerton, J. W.; Hayes, Jason T.; Ehrlich, Garth D.

doi:10.1097/01.mlg.0000172036.82897.d4

Cited by 85 publications

(75 citation statements)

References 14 publications

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“…Infections in the middle ear are thought to occur when pathogens enter the middle ear through the external ear canal or Eustachian tube. Other theories to explain the persistent nature of this disease and repeated infection include toxin production by P. aeruginosa (24), microbes embedding within the dead/ damaged tissue (cholesteatoma) (16,18), formation of biofilms (25,26), recurrent bacterial infection from the nasopharynx not covered by the antibiotics prescribed (21), or development of antibiotic resistance (20,27). Fluorescence in situ hybridization (FISH) has previously shown S. aureus biofilms to be present within the tissue of CSOM patients (28).…”

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Molecular Microbiological Profile of Chronic Suppurative Otitis Media

et al. 2016

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bChronic suppurative otitis media (CSOM) presents with purulent otorrhea (ear discharge), is characterized by chronic inflammation of the middle ear and mastoid cavity, and contributes to a significant disease burden worldwide. Current antibiotic therapy is guided by swab culture results. In the absence of detailed molecular microbiology studies of CSOM patients, our current understanding of the microbiota of CSOM (and indeed of the healthy ear) remains incomplete. In this prospective study, 24 patients with CSOM were recruited, along with 22 healthy controls. Culture-based techniques and 16S rRNA gene amplicon sequencing were used to profile the bacterial community for each patient. Comparisons between patients with and without cholesteatoma in the middle ear and mastoid cavity were also made. A major finding was that the middle ear of many healthy controls was not sterile, which is contradictory to the results of previous studies. However, sequencing data showed that Staphylococcus aureus, along with a range of other Gram-positive and Gram-negative organisms, were present in all subgroups of CSOM and healthy controls. Large interpatient variability in the microbiota was observed within each subgroup of CSOM and controls, and there was no bacterial community "signature" which was characteristic of either health or disease. Comparisons of the culture results with the molecular data show that culture-based techniques underestimate the diversity of bacteria found within the ear. This study reports the first detailed examination of bacterial profiles of the ear in healthy controls and patients with CSOM.

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Molecular Microbiological Profile of Chronic Suppurative Otitis Media

et al. 2016

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“…The Gram-negative pathogen Pseudomonas aeruginosa is a model organism for biofilm studies and causes both acute and chronic infections by exploiting deficiencies in host immunity. P. aeruginosa is thought to exist as a biofilm during infections of the cystic fibrosis (CF) airway (5,48), in acute burn wounds (45), and in chronic suppurative otitis media (13). Biofilm formation in P. aeruginosa is regulated by a complex network of signals that includes small molecules, two-component systems, small RNAs, and nutritional cues (27).…”

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Direct Evaluation of Pseudomonas aeruginosa Biofilm Mediators in a Chronic Infection Model

et al. 2011

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Biofilms contribute to Pseudomonas aeruginosa persistence in a variety of diseases, including cystic fibrosis, burn wounds, and chronic suppurative otitis media. However, few studies have directly addressed P. aeruginosa biofilms in vivo. We used a chinchilla model of otitis media, which has previously been used to study persistent Streptococcus pneumoniae and Haemophilus influenzae infections, to show that structures formed in vivo are biofilms of bacterial and host origin within a matrix that includes Psl, a P. aeruginosa biofilm polysaccharide. We evaluated three biofilm and/or virulence mediators of P. aeruginosa known to affect biofilm formation in vitro and pathogenesis in vivobis-(3,5)-cyclic dimeric GMP (c-di-GMP), flagella, and quorum sensing-in a chinchilla model. We show that c-di-GMP overproduction has a positive impact on bacterial persistence, while quorum sensing increases virulence. We found no difference in persistence attributed to flagella. We conclude from these studies that a chinchilla otitis media model provides a means to evaluate pathogenic mediators of P. aeruginosa and that in vitro phenotypes should be examined in multiple infection systems to fully understand their role in disease.The formation of biofilms facilitates chronic bacterial infections and reduces the efficacy of antimicrobial therapy (20, 39). The Gram-negative pathogen Pseudomonas aeruginosa is a model organism for biofilm studies and causes both acute and chronic infections by exploiting deficiencies in host immunity. P. aeruginosa is thought to exist as a biofilm during infections of the cystic fibrosis (CF) airway (5, 48), in acute burn wounds (45), and in chronic suppurative otitis media (13). Biofilm formation in P. aeruginosa is regulated by a complex network of signals that includes small molecules, two-component systems, small RNAs, and nutritional cues (27). As a result of these signals, a matrix that consists predominately of polysaccharides and extracellular DNA is formed (1,17,25,33,35,52). While P. aeruginosa biofilms have been studied extensively in vitro, there have been few studies characterizing biofilm formation in vivo (31,45,48,53).The chinchilla model has been widely used to study Haemophilus influenzae and Streptococcus pneumoniae otitis media infections, establishing that these pathogens form biofilms in vivo (3,15,19,24,26,42). Addressing biofilms in the context of an intact immune system and the complex environmental and structural features present in a mammalian host is necessary to determine if in vitro phenotypes are relevant to clinical infections. We used a chinchilla otitis media model to characterize P. aeruginosa biofilm formation and then focused on three systems involved in pathogenesis and/or biofilm formationbis-(3Ј,5Ј)-cyclic dimeric GMP (c-di-GMP), flagella, and quorum sensing-in order to understand their contribution to P. aeruginosa infection.The intracellular second messenger c-di-GMP positively regulates aggregation and biofilm formation in P. aeruginosa (22,30,51) and mediates ...

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“…The types of infection caused by P. aeruginosa include otitis media (19), infection of burn wounds (37), and lung infection in cystic fibrosis (CF) patients (27). In many instances, infection by P. aeruginosa assumes the form of a biofilm, which is highly resistant to antibiotics and to attack by immune effector cells (20).…”

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Nitrate Sensing and Metabolism Modulate Motility, Biofilm Formation, and Virulence in Pseudomonas aeruginosa

et al. 2007

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Infection by the bacterial opportunist Pseudomonas aeruginosa frequently assumes the form of a biofilm, requiring motility for biofilm formation and dispersal and an ability to grow in nutrient-and oxygen-limited environments. Anaerobic growth by P. aeruginosa is accomplished through the denitrification enzyme pathway that catalyzes the sequential reduction of nitrate to nitrogen gas. Mutants mutated in the two-component nitrate sensor-response regulator and in membrane nitrate reductase displayed altered motility and biofilm formation compared to wild-type P. aeruginosa PAO1. Analysis of additional nitrate dissimilation mutants demonstrated a second level of regulation in P. aeruginosa motility that is independent of nitrate sensor-response regulator function and is associated with nitric oxide production. Because motility and biofilm formation are important for P. aeruginosa pathogenicity, we examined the virulence of selected regulatory and structural gene mutants in the surrogate model host Caenorhabditis elegans. Interestingly, the membrane nitrate reductase mutant was avirulent in C. elegans, while nitrate sensor-response regulator mutants were fully virulent. The data demonstrate that nitrate sensing, response regulation, and metabolism are linked directly to factors important in P. aeruginosa pathogenesis.Pseudomonas aeruginosa is a ubiquitous gram-negative bacterium capable of causing infection in the immunocompromised host. The types of infection caused by P. aeruginosa include otitis media (19), infection of burn wounds (37), and lung infection in cystic fibrosis (CF) patients (27). In many instances, infection by P. aeruginosa assumes the form of a biofilm, which is highly resistant to antibiotics and to attack by immune effector cells (20).P. aeruginosa growth in biofilms is characterized by its ability to grow in nutrient-and oxygen-limited environments. Anaerobic growth by P. aeruginosa is accomplished through a denitrification enzyme pathway that catalyzes a four-step sequential reduction of nitrate to nitrogen gas, with nitrite, nitric oxide, and nitrous oxide, respectively, as intermediates. Two different nitrate reductase complexes mediate nitrate reduction to nitrite in P. aeruginosa (4, 68), a plasma membrane-bound nitrate reductase complex encoded by the narK1K2GHJI operon and a periplasmic nitrate reductase encoded by napEFDABC. Reduction of either nitrate or nitrite substrates provides energy for P. aeruginosa anaerobic growth, with nitrate reduction to nitrite via nitrate reductase contributing more significantly to proton motive force and hence energy production (4, 68). A well-described environment for P. aeruginosa growth under anoxic conditions is as a biofilm within the mucus of the CF lung (66). Nitrate and nitrite levels in CF mucus, generated in part by the host inflammatory response to infection, are sufficient to support anaerobic metabolism of P. aeruginosa (27).Biofilm formation and organism dispersal leading to spread of infection by P. aeruginosa are dependent on motility. ...

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Mucosal Biofilm Formation on Middle‐Ear Mucosa in a Nonhuman Primate Model of Chronic Suppurative Otitis Media

Cited by 85 publications

References 14 publications

Molecular Microbiological Profile of Chronic Suppurative Otitis Media

Molecular Microbiological Profile of Chronic Suppurative Otitis Media

Direct Evaluation of Pseudomonas aeruginosa Biofilm Mediators in a Chronic Infection Model

Nitrate Sensing and Metabolism Modulate Motility, Biofilm Formation, and Virulence in Pseudomonas aeruginosa

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