Direct and Fast Assessment of Antimicrobial Surface Activity Using Molecular Dynamics Simulation and Time-Lapse Imaging.

With the alarming rise of antimicrobial resistance, studies on bacteria-surface interactions are both relevant and timely. Scanning electron microscopy and colony forming unit counting are commonly used techniques but require sophisticated sample preparation and long incubation time. Here, we present a direct method based on molecular dynamics simulation of nanostructured surfaces providing in silico predictions, complemented with time-lapse fluorescence imaging to study live interactions of bacteria at the membrane-substrate level. We evaluate its effectiveness in predicting and statistically analyzing the temporal evolution and spatial distribution of prototypical bacteria with costained nucleoids and membranes (E. coli) on surfaces with nanopillars. We observed cell reorientation, clustering, membrane damage, growth inhibition, and in the extreme case of hydrocarbon-coated nanopillars, this was followed by cell disappearance, validating the obtained simulation results. Contrary to commonly used experimental methods, microscopy data are fast processed, in less than 1 h. In particular, the bactericidal effects can be straightforwardly detected and correlated with surface morphology and/or wettability.

Erratum: Surface cytometer for fluorescent detection and growth monitoring of bacteria over a large field-of-view: publisher's note.

[This corrects the article on p. 2101 in vol. 10, PMID: 31061773.].

Surface cytometer for fluorescent detection and growth monitoring of bacteria over a large field-of-view.

Monitoring the early onset of bacterial film formation is critical in many clinical, environmental, and food quality control applications. We built a small inexpensive optical surface cytometer, in contrast with bulk spectroscopic methods, around a light-emitting diode (LED) and a complementary metal-oxide-semiconductor (CMOS) image sensor. It is designed to offer a large field-of-view of 200 mm2 and a large depth-of-field of 2-3 mm to overcome the limitations of routine methods like spectrophotometry and fluorescence microscopy. It provides a direct measurement without the need for complex image post-processing with a limit-of-detection around 104 cells/mm2, which is competitive with other similar yet more complex devices already available.