A novel method for rapid and sensitive detection of viable Escherichia coli cells using UV-induced PMA-coupled quantitative PCR

• Published in: Brazilian journal of microbiology Vol. 51; no. 2; pp. 773 - 778
• Main Authors: Deshmukh, Rehan, Bhand, Sunil, Roy, Utpal
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2020; Springer Nature B.V
• Subjects: Amplification; Azides - chemistry; Biomedical and Life Sciences; Cross-Linking Reagents - chemistry; Crosslinking; Deoxyribonucleic acid; DNA; DNA, Bacterial - genetics; Drinking water; E coli; Environmental Microbiology - Short Communication; Escherichia coli; Escherichia coli - isolation & purification; Food Microbiology; Heat; Hot Temperature; Indicators and Reagents; Life Sciences; Luminous intensity; Medical Microbiology; Microbial Ecology; Microbial Genetics and Genomics; Microbial Viability; Microbiology; Mycology; Phorbol esters; Polymerase chain reaction; Propidium - analogs & derivatives; Propidium - chemistry; Real-Time Polymerase Chain Reaction - methods; Sensitivity and Specificity; Ultraviolet radiation; Ultraviolet Rays; Water analysis; Water Microbiology; Water sampling; Viable; Propidium monoazide; qPCR; Ultraviolet; Monitoring; Escherichia coli
• ISSN: 1517-8382; 1678-4405
• DOI: 10.1007/s42770-019-00161-8

We report a specific and sensitive method to improve the coupling of propidium monoazide (PMA) with DNA derived from killed cells of Escherichia coli using UV light of 365 nm. UV light of three different intensities mainly 2.4 × 10 3 , 4.8 × 10 3 , and 7.2 × 10 3  μJ/cm 2 was applied to E. coli cells each for 1, 3, and 5 min. PMA was found to be successfully cross-linked with the DNA from killed cells of E. coli at 4.8 × 10 3  μJ/cm 2 in 3 min leading to the complete inhibition of PCR amplification of DNA derived from PMA-treated heat-killed cells. In spiked phosphate-buffered saline and potable water samples, the difference of the Cq values between PMA-treated viable cells and PMA-untreated viable cells ranged from −0.17 to 0.2, demonstrating that UV-induced PMA activation had a negligible effect on viable cells. In contrast, the difference of the Cq values between PMA-treated heat-killed cells and PMA-untreated heat-killed cells ranged from 8.9 to 9.99, indicating the ability of PMA to inhibit PCR amplification of DNA derived from killed cells to an equivalent as low as 10 0  CFU. In conclusion, this UV-coupled PMA-qPCR assay provided a rapid and sensitive methodology to selectively detect viable E. coli cells in spiked water samples within 4 h.