title: Phenotypes of non-attached Pseudomonas aeruginosa aggregates resemble surface attached biofilm.
abstract: For a chronic infection to be established, bacteria must be able to cope with hostile conditions such as low iron levels, oxidative stress, and clearance by the host defense, as well as antibiotic treatment. It is generally accepted that biofilm formation facilitates tolerance to these adverse conditions. However, microscopic investigations of samples isolated from sites of chronic infections seem to suggest that some bacteria do not need to be attached to surfaces in order to establish chronic infections. In this study we employed scanning electron microscopy, confocal laser scanning microscopy, RT-PCR as well as traditional culturing techniques to study the properties of Pseudomonas aeruginosa aggregates. We found that non-attached aggregates from stationary-phase cultures have comparable growth rates to surface attached biofilms. The growth rate estimations indicated that, independently of age, both aggregates and flow-cell biofilm had the same slow growth rate as a stationary phase shaking cultures. Internal structures of the aggregates matrix components and their capacity to survive otherwise lethal treatments with antibiotics (referred to as tolerance) and resistance to phagocytes were also found to be strikingly similar to flow-cell biofilms. Our data indicate that the tolerance of both biofilms and non-attached aggregates towards antibiotics is reversible by physical disruption. We provide evidence that the antibiotic tolerance is likely to be dependent on both the physiological states of the aggregates and particular matrix components. Bacterial surface-attachment and subsequent biofilm formation are considered hallmarks of the capacity of microbes to cause persistent infections. We have observed non-attached aggregates in the lungs of cystic fibrosis patients; otitis media; soft tissue fillers and non-healing wounds, and we propose that aggregated cells exhibit enhanced survival in the hostile host environment, compared with non-aggregated bacterial populations.
authors: Institute for International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.
authors: Morten
authors: M
authors: Alhede
authors: Kasper Nørskov
authors: KN
authors: Kragh
authors: Klaus
authors: K
authors: Qvortrup
authors: Marie
authors: M
authors: Allesen-Holm
authors: Maria
authors: M
authors: van Gennip
authors: Louise D
authors: LD
authors: Christensen
authors: Peter Østrup
authors: PØ
authors: Jensen
authors: Anne K
authors: AK
authors: Nielsen
authors: Matt
authors: M
authors: Parsek
authors: Dan
authors: D
authors: Wozniak
authors: Søren
authors: S
authors: Molin
authors: Tim
authors: T
authors: Tolker-Nielsen
authors: Niels
authors: N
authors: Høiby
authors: Michael
authors: M
authors: Givskov
authors: Thomas
authors: T
authors: Bjarnsholt
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001422:Bacterial Adhesion / Q000187:drug effects / Q000502:physiology*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D003091:Colistin / Q000494:pharmacology; D004269:DNA, Bacterial / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005453:Fluorescence; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics; D010586:Phagocytes / Q000166:cytology / Q000187:drug effects; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D013499:Surface Properties / Q000187:drug effects; D013997:Time Factors; D014031:Tobramycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D003851:Deoxyribonucleases; D014031:Tobramycin; D003091:Colistin