Studying pathogenic viruses requires strict laboratory protocols and sophisticated infrastructure. An alternative approach is to use surrogate viruses such as bacteriophages. Bacteriophages are viruses that only infect bacteria. Their specificity makes bacteriophages a promising agent to control bacteria, and their diversity makes them a promising surrogate for pathogenic viruses. This study focused on these two properties and used bacteriophage to control bacterial sulfide production and as a surrogate virus to study how the environment affects virucidal properties.

The first part of this study developed a protocol for harvesting bacteriophages from the environment to control malodor caused by bacterial hydrogen sulfide (H₂S). The electrostatic interaction of the Ti⁴⁺ and Al³⁺ function...[ Read more ]

Studying pathogenic viruses requires strict laboratory protocols and sophisticated infrastructure. An alternative approach is to use surrogate viruses such as bacteriophages. Bacteriophages are viruses that only infect bacteria. Their specificity makes bacteriophages a promising agent to control bacteria, and their diversity makes them a promising surrogate for pathogenic viruses. This study focused on these two properties and used bacteriophage to control bacterial sulfide production and as a surrogate virus to study how the environment affects virucidal properties.

The first part of this study developed a protocol for harvesting bacteriophages from the environment to control malodor caused by bacterial hydrogen sulfide (H₂S). The electrostatic interaction of the Ti⁴⁺ and Al³⁺ functionalized materials are reversible and recovered 0.64 ± 0.17% to 67.99±4.79% of bacteriophage T3. The results showed that both electrostatic interaction and covalent bonding between metal ions and the amino acids of the viral capsid protein are the primary mechanisms of capture. Sulfate-reducing bacteria (SRB) were cultured and isolated from Tsuen Wan Harbor and sludge samples from Stonecutters Island Sewage Treatment Works. Spot titration and plaque assay showed lytic bacteriophages. The H₂S production of Tsuen Wan SRB was suppressed by 84.66 ± 0.04% and 77.8 ± 0.04% using bacteriophage harvested from dry sludge and the developed protocol, respectively.

In the second part of the study, Plackett-Burman design showed that the most significant factors for inactivation are mixing speed and chemical agents. Mixing inactivation follows first-order decay. The inactivation rate constant is a linear function of the friction loss in the system and is significant above mixing at 100 rpm or a Reynolds number above 2,200. Bacteriophages T3, MS2, and Φ6 were used as a surrogate for enteric and enveloped, RNA and DNA viruses. Various compounds were screened, but only Benzalkonium chloride, chlorine dioxide (ClO₂), and Oxone^TM are virucidal at 1,000 mg/L. The minimum inhibitory concentration (MIC) of these compounds against the surrogate viruses is worst in 5% tryptone followed by sludge. The MIC improved in seawater for Oxone^TM and ClO₂ as these compounds interact with halides to form oxidizing species. These reduced the protein concentration detected by A280 absorbance, suggesting oxidation of the capsid protein consistent with the literature.

This study showed that bacteriophages can control the H₂S production of SRB and that the media greatly influences the efficacy of virucidal agents. This study is among the first to quantify variations in the MIC of virucidal agents in environmental samples.