Use of bacteriophage to inactivate pathogenic bacteria from wastewater.

The aim of this study was to enhance the rhizobacterium potential in horizontal subsurface flow constructed wetland (CW) system planted by Phragmites australis using specific and lytic phages. The bioinoculation of specific bacteriophage for target bacteria; Salmonella typhi, and the monitoring of bacterial inactivation under different conditions showed the effectiveness of this methodology to enhance bacteria reduction and consequentially ameliorate purification performance of this studied biological treatment system. The injection of the phage at a concentration equal to 103 UFP/mL within the rhizosphere of the inoculated filter (F) was allowed 1 U-Log10 of improvement of bacterial inactivation compared to the control filter (T) nearly 1 logarithmic unit thus, a 90% improvement of bacteria reduction. When we increased the phage titer (105 UFP/mL), the bacterial reduction equal to 2.75 U-Log10 (N/N0) was registered that corresponds to a decrease of nearly 99.9%. According to the first-order model, the inactivation coefficient is equal to 2.29 min-1 (0.88 min-1 for the first experiment) and the bacterial reduction rate is 5 times higher than that determined for the control filter. This results show the positive impact of the phage in the bacterial inactivation and the improvement of water treatment of the biofilter C.

Detection of active pathogenic bacteria under stress conditions using lytic and specific phage.

In this study, we have monitored the potential activity of a foodborne and waterborne pathogenic bacterium, Salmonella typhi, under starvation conditions. The interaction between lytic phage and starved-VBNC pathogenic bacteria was studied to establish reliable methods for the detection of active cells before resuscitation. The analysis of phage kinetic parameters has demonstrated the flexibility of lytic with the quantity and mainly the quality of host cells. After 2 h of phage-starved-VBNC bacteria interaction, the reduction of phage amplification rate can reveal the ability of specific-lytic phage to recognize and to attach to their host cells with a probability of burst and release of infectious phages by active bacteria. After an extension of the latent period, the boost of the phage amplification rate was directly related to the positive interaction between potential intracellular 'engaged' phages and potential active bacteria. Furthermore, the modeling of the Salmonella-specific phage growth cycle in relationship with starved host cells can highlight the impact of the viability and the activity state of the host cells on the phage's growth cycle.

Enhancement of rhizocompetence in pathogenic bacteria removal of a constructed wetland system.

The main goal of the present study was to enhance the rhizobacterium potential in a horizontal subsurface flow constructed wetland system planted with Phragmites australis, through environmentally friendly biological approaches. The bioinoculation of antagonist bacteria has been used to promote higher rhizosphere competence and improve pathogenic bacteria removal from wastewater. The experiment was performed both with single and sequential bioinoculation. The results showed that strain PFH1 played an active role in pathogenic bacteria removal, remarkably improving inactivation kinetics of the pathogenic tested bacterium Salmonella typhi in the plant rhizosphere. The single bioinoculation of selected bacteria into the rhizosphere of P. australis improved the kinetics of S. typhi inactivation by approximately 1 U-Log10 (N/N0) (N is the number of viable cultured bacteria at time t, N0 is the number of viable and cultivable bacteria at time t0) compared to the control. By a series of multi-bioinoculations, the enhancement of pathogenic bacteria reduction compared to the inhibition rate in the pilot-scale control was of 2 U-Log10(N/N0). These findings suggested that this strain represents a promising candidate to enhance water purification in constructed wetlands.

The application of phage reactivation capacity to sens bacterial viability and activity after photocatalytic treatment.

We purpose in this study to develop a reliable and low-cost method for the detection of Viable but nonculturable (VBNC) bacteria. Indeed, after water disinfection, injured-VBNC bacteria can be underestimated using conventional assessment methods, causing false-negative results and, posing a significant and potential health risk. The VBNC bacterial survival strategy can hide the real microbial quality of treated water. To overcome this bacterial assessment limitation, we were used a specific and lytic phage to monitor the presence of active bacteria; Pseudomonas aeruginosa after photocatalytic treatment. Within 2 h of phage-target bacteria contact, the reduction of phage amplification rate (At) can reveal the ability of specific-lytic phage to recognize and to attach to their host cells with a probability of new infectious phages release despite their lose of cultivability in the usual media. The determination of phage reactivation coefficient (Rt) after 2 and 8 h of phage-target cell contact time reveals the ability of phages to reactive their infectivity and their amplification in positive correlation with their host cells viability and activity. The increase in phage reactivation coefficient (Rt) after an extension of the latent period was directly related to the positive interaction between infectious phages and potential active bacteria. The use of this method can improve the water disinfection process and avoid public health-hazardous especially related to the resuscitation of active-nonculturable bacteria mainly for pathogenic bacteria.