A method of fluorescence base imaging and monitoring of a target to screen the target for contamination, the method comprising: labelling a selected biomarker at the target with at least one exogenous bacteria-specific fluorescing contrast agent, wherein the labelling comprises topically applying the contrast agent to the target; with a device for fluorescence-based imaging and monitoring of the target comprising: a light source for emitting light for illuminating the target, the emitted light including at least one wavelength or wavelength band causing at least one biomarker associated with the target to fluoresce; an optical filter holder configured to accommodate one or more optical filters; a power supply; a digital image acquisition device having a lens and configured to acquire a fluorescence based image of the target, wherein the digital image acquisition device is a digital camera, video recorder, camcorder, cellular telephone with a built-in digital camera, smart phone with a digital camera, or a personal digital assistant, or a webcam, and comprises a viewing screen; and a housing that houses the all the components of the device in one entity and comprises means of securing the digital image acquisition device within the housing, wherein the housing is configured to be hand-held, compact and portable, illuminating the target with the light source of the device with a wavelength of 400 nm to 450 nm, preferably 405 nm; detecting fluorescence having a wavelength of 500 to 550 nm and greater than 600 nm with the digital image acquisition device; and, detecting the presence and/or location of a bacterial strain at the target in real-time, based on the detected fluorescence; and displaying on the viewing screen of the digital image acquisition device an image of the bacterial strain detected, in real-time. labelling a selected biomarker at the target with at least one exogenous bacteria-specific fluorescing contrast agent, wherein the labelling comprises topically applying the contrast agent to the target; with a device for fluorescence-based imaging and monitoring of the target comprising: a light source for emitting light for illuminating the target, the emitted light including at least one wavelength or wavelength band causing at least one biomarker associated with the target to fluoresce; an optical filter holder configured to accommodate one or more optical filters; a power supply; a digital image acquisition device having a lens and configured to acquire a fluorescence based image of the target, wherein the digital image acquisition device is a digital camera, video recorder, camcorder, cellular telephone with a built-in digital camera, smart phone with a digital camera, or a personal digital assistant, or a webcam, and comprises a viewing screen; and a housing that houses the all the components of the device in one entity and comprises means of securing the digital image acquisition device within the housing, wherein the housing is configured to be hand-held, compact and portable, illuminating the target with the light source of the device with a wavelength of 400 nm to 450 nm, preferably 405 nm; detecting fluorescence having a wavelength of 500 to 550 nm and greater than 600 nm with the digital image acquisition device; and, detecting the presence and/or location of a bacterial strain at the target in real-time, based on the detected fluorescence; and displaying on the viewing screen of the digital image acquisition device an image of the bacterial strain detected, in real-time.