## 5 Types of Phage-Based Biosensors
### Phage-Based Optical Biosensors
#### 5.1.3 Fluorescent Bioassay  
Phage-based fluorescent bioassays have also been combined with fluorescently labeled bacteriophages that are involved in binding and detecting the host bacterium. An epifluorescent filter technique or flow cytometry has been used to detect phage-bacteria in teractions. The reported sensitivity of this assay is about \(10^{2}\)-\(10^{3}\) CFU/mL and \(10^{4}\) CFU/mL for epifluorescent and flow cytometry microscopy detection, respectively [84].  
[PERSON] and co-workers demonstrated the detection of enteric bacteria such as _E. coli_ and _S. Typhimurium in water using phage-based fluorescent biosensor prototypes developed using the intact temperate phages HK620 and P22, respectively. The method is robust, fast, and sensitive, enabling the detection of as low as 10 bacteria/mL without enrichment or a concentration step [85]. Table 1 summarizes the use of different phage-based biosensor techniques for foodborne bacterial pathogens.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Transducer** & **Host Bacterium** & **Bio-Receptor** & **LOD** & **Assay Time** & **Food** & **Ref.** \\ \hline \multirow{8}{*}{SPR sensor} & Methicillin-resistant & & & & & \\  & _Staphylococcus aureus_ & BP14 & \(10^{3}\) & NR & NR & [77] \\  & (MRSA) & & & & & \\ \cline{2-6}  & _Salmonella_ spp. & P22 & \(10^{3}\) & 3 min & \begin{tabular}{c} Chicken \\ carcass \\ (wash) \\ \end{tabular} & [52] \\ \cline{2-6}  & _S. aureus_ & 12,600 & \(10^{4}\) & NR & NR & [86] \\ \cline{2-6}  & _Campylobacter jejuni_ & NCTC 12,673 & \(10^{2}\) & 45 min & Milk & [87] \\ \cline{2-6}  & _E. coli_ O157:H7 & T4 & \(10^{3}\) & NR & Skim milk & [88] \\ \cline{2-6}  & _E. coli_ K12 & T4 & \(7\times 10^{2}\) & NR & Skim milk & [89] \\ \cline{2-6}  & _L. monocytogenes_ & scFv & \(2\times 10^{6}\) & NR & NR & [90] \\ \cline{2-6}  & _S. aureus_ & 12,600 & \(10^{4}\) & NR & NR & [86] \\ \hline \multirow{8}{*}{Bioluminescence sensor} & _E. coli_ G2-2 & AT20 & \(10^{3}\) & NR & NR & [42] \\ \cline{2-6}  & _E. coli_ & _E. coli_ phage & \(10^{3}\) & 60 min & NR & [91] \\ \cline{2-6}  & _Salmonella_ Newport & \begin{tabular}{c} Newport (Felix) \\ phage \\ \end{tabular} & \(10^{3}\) & NR & NR & [91] \\ \cline{2-6}  & _Salmonella_ Enteritidis & SJ2 & \(10^{3}\) & 120 min & NR & [42] \\ \cline{2-6}  & _E. coli_ & \begin{tabular}{c} Wild-type and \\ modified T4 \\ \end{tabular} & \(6\times 10^{3}\) & NR & NR & [39] \\ \cline{2-6}  & _Yersinia pestis_ & \begin{tabular}{c} Phage A1122 \\ with lux tag \\ \end{tabular} & \(10^{2}\) & NR & NR & [92] \\ \cline{2-6}  & _E. coli_ B & lacZ T4 phage & 10 & NR & Water & [93] \\ \cline{2-6}  & _P. aeruginosa_ & Pap1 & 56 & NR & Milk & [94] \\ \cline{2-6}  & _S. flexueri_ & Shfl25875 & \(10^{3}\) CFU/g & NR & NR & [95] \\ \hline \multirow{8}{*}{Fluorescent bioassay} & _E. coli_ & T7 & 20 & NR & NR & [30] \\ \cline{2-6}  & _E. coli_ & \begin{tabular}{c} QD-labeled \\ lambda phage \\ \end{tabular} & ND & NR & NR & [96] \\ \cline{2-6}  & \
\begin{tabular}{c} Staphylococcal \\ enterotoxin B (SEB) \\ peptides \\ \end{tabular} &
\begin{tabular}{c} phage- \\ displayed \\ peptides \\ \end{tabular} & \(1.4\) ng & NR & NR & [97] \\ \cline{2-6}  & _E. coli_ O157:H7 & PP01 & 1 & NR & Apple juice & [98] \\ \cline{2-6}  & _S. aureus_ & P-_S. aureus_-9 & \(2.47\times 10^{3}\) & NR & NR & [99] \\ \cline{2-6}  & _S. Typhimurium & P22 & \(1\) CFU/24 mL & NR & Milk & [100] \\ \cline{2-6}  & _B. anthracis_ & W\(\beta\) & \(10^{4}\) CFU/g & NR & NR & [101] \\ \cline{2-6}  & _E. coli_ TD2158 & HK620 & \(10^{2}\)–\(10^{4}\) & NR & NR & [85] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Optical phage-based biosensors.