## 2 Applications of Biosensors in Bacteria Detection
### Detection of Resistance Using Biosensors
The sensor was used for the sensitive and specific detection of synthetic blaNDM targets with a detection limit of 200 nM [33]. Its properties proved the suitability of the new electrode materials and manufacturing for further point-of-care test development [33]. The blaNDM gene encoding the NDM beta-lactamase (New Delhi metallo-beta-lactamase) has been identified as having an important role because organisms containing blaNDM are probably multiresistant and only susceptible to \"last option\" treatments like colistin and tigecycline, which have uncertain efficacies [33; 192]. Other selective electrochemical techniques exist for detecting methicillin-resistance from 57 fM genome DNA [193]. [PERSON] and co-workers developed a polymer layer on an electrochemical sensor, which can detect antibiotic-resistant bacteria after 4 mg/mL antibiotic treatment (kanamycin, tetracycline, and erythromycin) [194]. A low-cost, sensitive, and rapid (5 min) thin-film transistor nanoribbon sensor can detect cephalospor- and carbapenem-resistant bacteria [195]. [PERSON] and co-workers developed a rapid (5 min), sensitive, and miniaturzed graphene field effect transistor, with improved detection limit and time [164]. Among optical biosensors, the ultrasensitive nanophotonic bimodal waveguide interferometer is able to detect \(\beta\)-lactamase and carbapenemase coding gene with a detection limit of 28 nM. [161]. A SERS-based method was also claimed to have 100% accuracy identifying methicillin-resistant bacteria [161]. LSPR is shown to sense cephalospororin, ceftazidine, ceftaxone, and cefotaxime resistance more effectively than chromatography coupled mass spectroscopic techniques [196]. Rapid (30 min) and specific bead-based biosensing can detect ceftadizime and levofloxacin resistance in different bacterial strains [197]. Electro-photonic traps can be also used for bacteria monitoring even at a single-cell level [198; 199; 200] and resistance can be studied, too [201]. While the bacteria are trapped by optical tweezers based on photonic crystal cavities, antibiotics can be added to the medium and the subsequent changes in its optical properties and motility can be monitored via changes of transmission and the resonance wavelength [201]. Furthermore, the metabolic rate in response to the antibiotic treatment can be determined by the alteration of the impedance of the medium surrounding the bacteria [201]. This method allows the simultaneous investigation of the electrical and optical response of an individual bacterium and it offers a rapid response [201]. Antimicrobial agents are becoming ineffective against many pathogenic bacteria, especially in the presence of biofilms [202]. Thus, there is a need for methods that can rapidly detect and treat biofilm infections as well [203]. [PERSON] et al. proposed the design of a novel optoelectronic device based on a dual array of interdigitated micro- and nano-electrodes [202]. This method is capable of monitoring the growth and maturation of the biofilm and probably testing the efficiency of antibiotics [202]. [PERSON] and co-workers developed a threshold-activated feedback-based impedance sensor-treatment system for combined real-time detection and treatment of biofilms [203]. As a result, bioelectric effect treatment reduced the average biofilm surface coverage with ~74.8% compared to the untreated negative control [203]. In both cases, _E. coli_ biofilm was used for the experiments. These techniques may be also used in the future for testing resistance, real-time detection of biofilms, and their in situ treatment, even on the surfaces of, for example, medical implants [203].