Electron micrographs of pathogenic bacterial biofilms from a variety of bacterial infections. (a) Transmission Electron Micrograph (TEM) of a section of lung tissue taken (postmortem) from a CF patient. The matrix-enclosed micro-colony of P. aeruginosa cells is surrounded by a prominent electron-dense “crust” of material that reacted very strongly with antibodies directed against IgG. Image published with permission from Infection and Immunity (59). (b) TEM of a section from the affected bone of a patient with very long-term osteomyelitis that had been treated with antibiotics (for four decades) and several debridations. Note the large number of Gram-positive cells (S. aureus was cultured) and the dehydrated remnants of the fibrous matrix of this massive biofilm. (c) Scanning electron micrograph (SEM) of a struvite crystal from the hilus of the kidney of a patient with acute pyleonephritis, who was affected by “staghorn” calculi. Cells of the infecting agent (P. vulgaris) have formed a biofilm whose matrix has become infused with struvite to produce a “petrified” biofilm. (d) TEM of a section from a vegetation formed on the endocardium of a rabbit in an animal model of native-valve endocarditis. Cells of the infecting agent (viridans group streptococci) are seen to have formed this macroscopic biofilm and to have produced very large amounts of fibrous matrix material. (e) SEM of tissue from a culture-negative prostatitis, showing the presence of rod-shaped bacterial cells. (f) SEM of tissue from the prostatitis patient in e, which had been reacted with the patient’s serum, so that the matrix material of this well-developed biofilm was protected from dehydration, and is shown at its full extent.