Ultraviolet Disinfection of Antibiotic Resistant Bacteria and Their Antibiotic Resistance Genes in Water and Wastewater

Abstract

Disinfection of wastewater treatment plant effluent may be an important barrier for limiting the spread of antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs). While ideally disinfection should destroy ARGs, to prevent horizontal gene transfer to downstream bacteria, little is known about the effect of conventional water disinfection technologies on ARGs. This study examined the potential of UV disinfection to damage four ARGs, mec(A), van(A), tet(A), and amp(C), both in extracellular form and present within a host ARBs: methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), Escherichia coli SMS-3-5, and Pseudomonas aeruginosa 01, respectively. An extended amplicon-length quantitative polymerase chain reaction assay was developed to enhance capture of ARG damage events and also to normalize to an equivalent length of target DNA (∼1000 bp) for comparison. It was found that the two Gram-positive ARBs (MRSA and VRE) were more resistant to UV disinfection than the two Gram-negative ARBs (E. coli and P. aeruginosa). The two Gram-positive organisms also possessed smaller total genome sizes, which could also have reduced their susceptibility to UV because of fewer potential pyrimidine dimer targets. An effect of cell type on damage to ARGs was only observed in VRE and P. aeruginosa, the latter potentially because of extracellular polymeric substances. In general, damage of ARGs required much greater UV doses (200-400 mJ/cm² for 3- to 4-log reduction) than ARB inactivation (10-20 mJ/cm² for 4- to 5-log reduction). The proportion of amplifiable ARGs following UV treatment exhibited a strong negative correlation with the number of adjacent thymines (Pearson r < -0.9; p < 0.0001). ARBs surviving UV treatment were negatively correlated with total genome size (Pearson r < -0.9; p < 0.0001) and adjacent cytosines (Pearson r < -0.88; p < 0.0001) but positively correlated with adjacent thymines (Pearson r > 0.85; p < 0.0001). This suggests that formation of thymine dimers is not the sole mechanism of ARB inactivation. Overall, the results indicate that UV is limited in its potential to damage ARGs and other disinfection technologies should be explored.

Removal of bacterial contaminants and antibiotic resistance genes by conventional wastewater treatment processes in Saudi Arabia: Is the treated wastewater safe to reuse for agricultural irrigation?

“…In places 611 that only rely on treatment processes as outlined in this study, existing infrastructure may have to 612 be retrofitted with other technologies such as ultraviolet disinfection and/or membrane filtration 613 to ensure a substantial removal of antibiotic resistant bacteria and their incorporated resistance 614 genes. To illustrate, 10-20 mJ/cm 2 of UV doses can be used to reduce gram-negative ARB by 4 615 to 5 logs (McKinney and Pruden 2012). However, a high UV dose is required to reduce 616 antibiotic resistance genes by more than 2 logs (McKinney and Pruden 2012, Zhuang et al 617 2014.…”

“…To illustrate, 10-20 mJ/cm 2 of UV doses can be used to reduce gram-negative ARB by 4 615 to 5 logs (McKinney and Pruden 2012). However, a high UV dose is required to reduce 616 antibiotic resistance genes by more than 2 logs (McKinney and Pruden 2012, Zhuang et al 617 2014. This is not economically viable for routine operation.…”

Use of a stainless steel washer platform to study Acinetobacter baumannii adhesion and biofilm formation on abiotic surfaces

“…(ii) Effect of UV light irradiation on A. baumannii planktonic cells and mature biofilms. The effects of irradiation by UV light on biofilms formed by A. baumannii or planktonic cells were determined by exposing bacterial cells to various doses (100, 200, 300 and 400 mJ cm 22 ) of UV light (254 nm) generated by a GS Gene Linker UV chamber (Bio-Rad) (McKinney & Pruden, 2012). The viability of planktonic cells or biofilms post-irradiation with UV light was measured by c.f.u.…”

Control of Microbiologically Influenced Corrosion using Ultraviolet Radiation

“…Key target of UV induced damage is deoxyribonucleic acid (DNA) in a variety of organisms, ranging from bacteria and human. Due to this damage, the bacteria cannot duplicate and hence it exterminates bacteria colonies (Mckinney & Pruden 2012). Previous studies of UV disinfection in mitigating the MIC in oil and gas system has proven to be an effective method and eliminate 99% reduction in bacteria present in the water (Clark et al 1984;Gloe et al 2010;Lawal et al 2010;Wang et al 2005).…”