Photonic crystals and microcavities act as on-chip nano-optical tweezers for identification and manipulation of biological objects. Until now, optical trapping of virus and bacteria has been achieved and their presence in the vicinity of the optical resonator is deduced by the shift in the resonant wavelength. Here, we show trapping and identification of bacteria through a properly tuned silicon on insulator microcavity. Through the spatial and temporal observations of bacteria–cavity interaction, the optical identification of three different kinds of bacteria is demonstrated.

Fast and label-free techniques to analyze viruses and bacteria are of crucial interest in biological and bio-medical applications. For this purpose, optofluidic systems based on the integration of photonic structures with microfluidic layers were shown to be promising tools for biological analysis, thanks to their small footprint and to their ability to manipulate objects using low powers. In this letter, we report on the optical trapping of living bacteria in a 2D silicon hollow photonic crystal cavity. This structure allows for the Gram-type differentiation of bacteria at the single cell scale, in a fast, label-free, and non-destructive way.

The growing number of drug-resistant bacterial infections worldwide is driving renewed interest in phage therapy. Based on the use of a personalized cocktail composed of highly specific bacterial viruses, this therapy relies on a range of tests on agar media to determine the most active phage on a given bacterial target (phage susceptibility testing), or to isolate new lytic phages from an environmental sample (enrichment of phage banks). However, these culture-based techniques are still solely interpreted through direct visual detection of plaques. The main objective of this work is to investigate computer-assisted methods in order to ease and accelerate diagnosis in phage therapy but also to study phage plaque growth kinetics. For this purpose, we designed a custom wide-field lensless imaging device, which allows continuous monitoring over a very large area sensor (3.3 cm²). Here we report bacterial susceptibility toStaphylococcus aureusphage in 3 hr and estimation of infectious titer in 8 hr 20 min. These are much shorter time-to-results than the 12 to 24 hours traditionally needed, since naked eye observation and counting of phage plaques is still the most widely used technique for susceptibility testing prior to phage therapy. Moreover, the continuous monitoring of the samples enables the study of plaque growth kinetics, which enables a deeper understanding of the interaction between phage and bacteria. Finally, thanks to the 4.3 μm resolution, we detect phage-resistant bacterial microcolonies ofKlebsiella pneumoniaeinside the boundaries of phage plaques and thus show that our prototype is also a suitable device to track phage resistance. Lensless imaging is therefore an all-in-one method that could easily be implemented in cost-effective and compact devices in phage laboratories to help with phage therapy diagnosis.

A low-cost, innovative and non-invasive colorimetric test, which can be universally used, is proposed to detect pathogenic bacteria via the simple and fast detection of volatile metabolites released by enzymatic hydrolysis. The proof of concept is shown via three sets of experiments studying the release of the p-nitrophenol metabolite in solution in the E. coli cultures containing 4-nitrophenyl-β-D-glucuronide, the trapping efficiency of the gaseous metabolite by various tailored and functionalized xerogels, and the trapping and detection of gaseous p-nitrophenol released by E. coli bacteria.

In the context of bacteriophage (phage) therapy, there is an urgent need for a method permitting multiplexed, parallel phage susceptibility testing (PST) prior to the formulation of personalized phage cocktails for administration to patients suffering from antimicrobial-resistant bacterial infections. Methods based on surface plasmon resonance imaging (SPRi) and phase imaging were demonstrated as candidates for very rapid (<2 h) PST in the broth phase. Biosensing layers composed of arrays of phages 44AHJD, P68, and gh-1 were covalently immobilized on the surface of an SPRi prism and exposed to liquid culture of either Pseudomonas putida or methicillin-resistant Staphylococcus aureus (i.e., either the phages’ host or non-host bacteria). Monitoring of reflectivity reveals susceptibility of the challenge bacteria to the immobilized phage strains. Investigation of phase imaging of lytic replication of gh-1 demonstrates PST at the single-cell scale, without requiring phage immobilization. SPRi sensorgrams show that on-target regions increase in reflectivity more slowly, stabilizing later and to a lower level compared to off-target regions. Phage susceptibility can be revealed in as little as 30 min in both the SPRi and phase imaging methods.