Label-Free Detection of Escherichia coli from Mixed Bacterial Cultures Using Bacteriophage T4 on Plasmonic...

Consumption of water contaminated with pathogenic bacteria is a major cause of water-borne diseases. To address this challenge, we have developed a novel and sensitive sensing scheme for the rapid detection of bacteria (Escherichia coliB40) on a fiber-optic platform using bacteriophage (T4) as a bio-recognition element. The novelty of our sensing scheme is that instead of bacteriophages, bacteria (analyte) were first captured on the sensing surface and then the sensing surface was subjected to bacteriophages for specific detection of bacteria. The sensor was subjected to 100 to 10⁷ cfu/mL of E. coliB40 spiked in a lake water matrix, and the least concentration of bacteria that could be easily detected was found to be 1000 cfu/mL. The control studies were performed with nonhost bacteria Pseudomonas aeruginosa. Bacteriophage T4, being specific to its host E. coliB40, did not interact with P. aeruginosa captured on the sensing probe, giving a negligible nonspecific response. Due to the specificity of bacteriophages to its host bacteria, it is possible to use this scheme to carry out the detection of specific bacteria in a mixed sample (containing a combination of bacteria) using bacteriophages specific to it. The sensor was able to detect E. coliB40 (target bacteria) even in the presence of a very high concentration (1000 times higher) of P. aeruginosa (nontarget bacteria).