A new biosensor for quantitative rapidly and easy detection for bacteria in planktonic and biofilm lifestyle.

Remarkable interest for human health concerns the microbiological risk assessment due infections by bacteria possessing the ability to adhere to host cell or abiotic surfaces as well as to live in aggregated and biofilm lifestyle. Biofilm is multicellular bacterial community held together by a self-produced extracellular matrix in response to several factors. These factors may include recognition of specific or non-specific attachment sites on cell surfaces, electrostatic interactions on abiotic surfaces, nutritional cues, or in some cases, exposure to stress conditions in the environment as well as into the host. Biofilm lifestyle is comparatively more common than the planktonic one and it has been shown that biofilm plays a crucial role in human health. As matter of fact, the eradication of bacterial biofilm by administration of antibiotics often fails due to the high drug resistance of bacteria in this lifestyle. Since 2008, European Centre for Disease Prevention and Control reports epidemiological data on the increasing of antimicrobial resistance constituting an important concern in public health hazard. For this reason, rapid assays to determine biofilm susceptibility to antibacterial drugs can significantly improve the outcome of infected patients by enabling a fast selection of efficient antibiotic treatments, thus decreasing the period and the related costs of hospitalization, as well as the incidence of morbidity and mortality. Therefore, a fundamental prerequisite in studying, counteracting and eradicating biofilm is the possibility to quantify the actual number of bacteria involved. Bacterial counts have deep implications in microbiological diagnosis and therapeutic treatments, in water and food quality analysis, in environmental applications and consumers‘ safety. The standard method used to evaluate the number of bacteria, based on determination of Colony Forming Units (CFUs) (ISO method), can be considered fully appropriate only when bacteria are in planktonic lifestyle but it is unreliable to count bacteria in aggregated, adherent and biofilm lifestyle. Even if different analytical strategies have been attempted to enumerate bacteria in biofilm, the detection of the actual number of bacteria in aggregated, adherent and biofilm lifestyle is still a great challenge for microbiologists.