Characterization of methicillin-resistant Staphylococcus aureus strains in sewage treatment plants in Tehran, Iran

Hydrogen peroxide preoxidation as a strategy for enhanced antimicrobial photodynamic action against methicillin-resistant Staphylococcus aureus

Antimicrobial photodynamic treatment (aPDT) is a photooxidative process based on the excitation of a photosensitizer (PS) in the presence of molecular oxygen, under specific wavelengths of light. It is a promising method for advanced treatment of water and wastewater, particularly targeting disinfection challenges, such as antibiotic-resistant bacteria (ARB). Research in improved aPDT has been exploring new PS materials, and additives in general. Hydrogen peroxide (H2O2) a widely applied disinfectant, mostly in the food industry and clinical settings, present environmentally negligible residuals at the usually applied concentrations, making it friendly for the water and wastewater sectors. Here, we explored the effects of preoxidation with H2O2 followed by blue light-mediated (450 nm) aPDT using curcumin (a natural-based PS) against methicillin-resistant Staphylococcus aureus (MRSA). Results of the sequential treatment pointed to a slight hampering in aPDT efficiency at very low H2O2 concentrations, followed by an increasing cooperative effect up to a deleterious point (≥7 log10 inactivation in CFU mL-1), suggesting a synergistic interaction of preoxidation and aPDT. The increased performance in H2O2-pretreated aPDT encourages studies of optimal operational conditions for the assisted technology and describes potentials for using the described strategy to tackle the issue of ARB spread.

Isolation and Characterization of Bacteriophage Against Wastewater Isolates of Methicillin-resistant Staphylococcus aureus

Background: Methicillin-resistant Staphylococcus aureus (MRSA) not only is a notorious pathogen in clinical settings but also is an environmental issue that its presence in environmental wastewater is highlighted by several reports. Due to the negative impacts of antibiotics, alternatives like bacteriophages, as biocontrol, are considered safe. However, not all bacteriophages are safe. Thus, the characterization of bacteriophages is necessary. Objectives: This study aimed to, firstly isolate MRSA from wastewater and, secondly to perform bacteriophage isolation from the water samples to investigate its physical and genomic characteristics. Methods: Water samples were collected from seven locations across Nagpur city, India, bacteria were isolated on the S. aureus specific agar. For detecting MRSA, we followed the disc diffusion method. Isolation of bacteriophage against MRSA was performed by a modified enrichment method. We investigated its physical characteristics by the one-step growth rate, adsorption rate, host range, survivability, electron microscopy, and genomic sequencing for bioinformatics analysis. Results: Four MRSA were isolated from wastewater samples. We got a bacteriophage against an MRSA from the river Ganga. The bacteriophage belongs to the Podoviridae family, subfamily Autographivirinae. It was stable till 40°C and could survive at a highly alkaline pH. It is specific to its host. The bacteriophage DNA encodes 52 ORF, and all predicted genes are on the same strand; it also encodes a phage RNA polymerase. Conclusions: It is the first report of an S. aureus bacteriophage that belongs to the sub-family Autographivirinae. Our study and literature survey conclude that S. aureus bacteriophages of the Podoviridae family are safe for various downstream applications.