Infectious diseases caused by bacterial pathogens are a worldwide burden. Serious bacterial infection-related complications, such as sepsis, affect over a million people every year with mortality rates ranging from 30% to 50%. Crucial clinical microbiology laboratory responsibilities associated with patient management and treatment include isolating and identifying the causative bacterium and performing antibiotic susceptibility tests (ASTs), which are labor-intensive, complex, imprecise, and slow (taking days, depending on the growth rate of the pathogen). Considering the life-threatening condition of a septic patient and the increasing prevalence of antibiotic-resistant bacteria in hospitals, rapid and automated diagnostic tools are needed. This review summarizes the existing commercial AST methods and discusses some of the promising emerging AST tools that will empower humans to win the evolutionary war between microbial genes and human wits.

Significance: Exosomes are tiny vesicles secreted by cells that play an important role in cell-to-cell communication. The RNA, DNA, and proteins in exosomes are reported to be critical biomarkers for precision diagnostics and therapeutics. Exosome analysis thus offers an approach to learn health conditions without tissue biopsy. Clinical application and fundamental study of exosomes require analytical tools capable of physical and biochemical characterization. The challenge in developing such tools lies in that conventional optical microscopy is not suitable for exosome analysis due to its limited sensitivity. In this paper, we report a plasmonic microscopy capable of imaging single exosomes and quantitative analysis of physical (size) and biochemical (interaction with antibody) information.

We present optical imaging-based methods to measure vital physiological signals, including breathing frequency (BF), exhalation flow rate, heart rate (HR), and pulse transit time (PTT). The breathing pattern tracking was based on the detection of body movement associated with breathing using a differential signal processing approach. A motion-tracking algorithm was implemented to correct random body movements that were unrelated to breathing. The heartbeat pattern was obtained from the color change in selected region of interest (ROI) near the subject's mouth, and the PTT was determined by analyzing pulse patterns at different body parts of the subject. The measured BF, exhaled volume flow rate and HR are consistent with those measured simultaneously with reference technologies ( $r = 0.98$ , $p<0.001$ for HR; $r = 0.93$ , $p<0.001$ for breathing rate), and the measured PTT difference (30–40 ms between mouth and palm) is comparable to the results obtained with other techniques in the literature. The imaging-based methods are suitable for tracking vital physiological parameters under free-living condition and this is the first demonstration of using noncontact method to obtain PTT difference and exhalation flow rate.

We present a noncontact method to monitor blood oxygen saturation (SpO ₂ ). The method uses a CMOS camera with a trigger control to allow recording of photoplethysmography (PPG) signals alternatively at two particular wavelengths, and determines the SpO ₂ from the measured ratios of the pulsatile to the nonpulsatile components of the PPG signals at these wavelengths. The signal-to-noise ratio (SNR) of the SpO ₂ value depends on the choice of the wavelengths. We found that the combination of orange (λ = 611 nm) and near infrared (λ = 880 nm) provides the best SNR for the noncontact video-based detection method. This combination is different from that used in traditional contact-based SpO ₂ measurement since the PPG signal strengths and camera quantum efficiencies at these wavelengths are more amenable to SpO ₂ measurement using a noncontact method. We also conducted a small pilot study to validate the noncontact method over an SpO ₂ range of 83%-98%. This study results are consistent with those measured using a reference contact SpO ₂ device (r = 0.936, p <; 0.001). The presented method is particularly suitable for tracking one's health and wellness at home under free-living conditions, and for those who cannot use traditional contact-based PPG devices.