Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

Abstract

Although biofilms represent a common bacterial lifestyle in clinically and environmentally important habitats, there is scant information on the extent of gene transfer in these spatially structured populations. The objective of this study was to gain insight into factors that affect transfer of the promiscuous multidrug resistance plasmid pB10 in Escherichia coli biofilms. Biofilms were grown in different experimental settings, and plasmid transfer was monitored using laser scanning confocal microscopy and plate counting. In closed flow cells, plasmid transfer in surface-attached submerged biofilms was negligible. In contrast, a high plasmid transfer efficiency was observed in a biofilm floating at the air-liquid interface in an open flow cell with low flow rates. A vertical flow cell and a batch culture biofilm reactor were then used to detect plasmid transfer at different depths away from the air-liquid interface. Extensive plasmid transfer occurred only in a narrow zone near that interface. The much lower transfer frequencies in the lower zones coincided with rapidly decreasing oxygen concentrations. However, when an E. coli csrA mutant was used as the recipient, a thick biofilm was obtained at all depths, and plasmid transfer occurred at similar frequencies throughout. These results and data from separate aerobic and anaerobic matings suggest that oxygen can affect IncP-1 plasmid transfer efficiency, not only directly but also indirectly, through influencing population densities and therefore colocalization of donors and recipients. In conclusion, the air-liquid interface can be a hot spot for plasmid-mediated gene transfer due to high densities of juxtaposed donor and recipient cells.

Dissemination of IncFIIK-type plasmids in multiresistant CTX-M-15-producing Enterobacteriaceae isolates from children in hospital paediatric oncology wards

“…Plasmids of incompatibility group F are among the most prevalent antibiotic resistance plasmids in Enterobacteriaceae species [10]. Plasmids of the incompatibility group FII were identified as the main vehicles of bla CTX-M-15 in E. coli and K. pneumoniae, as well as for other antibiotic genes conferring resistance to tetracyclines, aminoglycosides and fluoroquinolones present on IncFII plasmids along with ESBL genes [4,11,22]. Most of the K. pneumoniae isolates as well as other Enterobacteriaceae isolates, including multiresistant epidemiological clone E. coli B2-O25b-ST131, in this study harboured large IncFII K plasmids with multiple antibiotic resistance genes and showed conjugative ability to E. coli as well as Salmonella.…”

Combinatorial discovery of polymers resistant to bacterial attachment

“…Biofilms are surface-associated bacterial communities within which bacteria have up to 1,000 times higher resistance to antimicrobials and host defenses compared with their planktonic counterparts 2,3 . Biofilms present on the surface of medical devices provide the bacterial inocula for disease and can also serve as reservoirs of plasmids carrying antibioticresistance genes 4,5 . Most strategies for reducing biofilm-associated infections focus on the modification of existing materials that are used to manufacture in-dwelling medical devices by the incorporation of antibiotics 6,7 or other antimicrobials, such as silver salts, nitrofurazone, chlorhexidine, polymerized quaternary ammonium surfactants, antibacterial peptides and anionic nanoporous hydrogels [8][9][10][11][12][13][14][15] .…”

Plasmid transfer in biofilms: a perspective on limitations and opportunities

“…23,25,26 Licht et al 27 showed that plasmid invasion was proficient in a biofilm during the initial contact phase, after which no further transfer was detected. In contrast, the efficiency of invasion was initially slower in mixed liquids but constant, and eventually allowed plasmid spread through the entire population.…”