Juan Jofre

Even in countries with extensive sanitation systems, outbreaks of waterborne infectious diseases are being reported. Current tendencies, such as the growing concentration of populations in large urban conurbations, climate change, aging of existing infrastructures, and emerging pathogens, indicate that the management of water resources will become increasingly challenging in the near future. In this context, there is an urgent need to control the fate of fecal microorganisms in wastewater to avoid the negative health consequences of releasing treated effluents into surface waters (rivers, lakes, etc.) or marine coastal water. On the other hand, the measurement of bacterial indicators yields insufficient information to gauge the human health risk associated with viral infections. It would therefore seem advisable to include a viral indicator—for example, somatic coliphages—to monitor the functioning of wastewater treatments. As indicated in the studies reviewed herein, the concentrations of somatic coliphages in raw sewage remain consistently high throughout the year worldwide, as occurs with bacterial indicators. The removal process for bacterial indicators and coliphages in traditional sewage treatments is similar, the concentrations in secondary effluents remaining sufficiently high for enumeration, without the need for cumbersome and costly concentration procedures. Additionally, according to the available data on indicator behavior, which is still limited for sewers but abundant for surface waters, coliphages persist longer than bacterial indicators once outside the gut. Based on these data, coliphages can be recommended as indicators to assess the efficiency of wastewater management procedures with the aim of minimizing the health impact of urban wastewater release in surface waters.

The emergence of multi-drug resistant bacteria has undermined our capacity to control bacterial infectious diseases. Measures needed to tackle this problem include controlling the spread of antibiotic resistance, designing new antibiotics, and encouraging the use of alternative therapies. Phage therapy seems to be a feasible alternative to antibiotics, although there are still some concerns and legal issues to overcome before it can be implemented on a large scale. Here we highlight some of those concerns, especially those related to the ability of bacteriophages to transport bacterial DNA and, in particular, antibiotic resistance genes.

Here we describe the detection, enumeration, and isolation of bacteriophages infecting Bacteroides. The method is based on the infection of Bacteroides host strains and the production of visible plaques in a confluent lawn of the host strain using the double-layer agar method. This is a straightforward methodology that can be applied for the detection, enumeration and isolation of bacteriophages for other anaerobic bacteria, using an appropriate host strain and culture conditions. In the case of bacteriophages of Bacteroides the results can be obtained in less than 24 h, although the time could vary depending on the growth rate of the host strain.

Bacteriophages are increasingly being used as water quality indicators. Two groups of phages infecting Escherichia coli , somatic and F-specific coliphages, are being considered as indicators of fecal and viral contamination for several types of water around the world. However, some uncertainties remain regarding which coliphages to assess. Recently, E. coli strain CB390 has been reported to be suitable for simultaneous detection of both groups, which seems to be more informative than determining only one of the groups. Here, a significant number of samples from different settings, mostly those where F-specific phages have been reported to outnumber somatic coliphages, are analyzed for somatic coliphages, F-specific RNA phages by standardized methods and coliphages detected by host strain CB390. The results presented herein confirm that the numbers of phages counted using CB390 are equivalent to the sum of the somatic and F-specific coliphages counted independently in all settings. Hence the usefulness of this strain for simultaneous detection of somatic and F-specific coliphages is confirmed. Also, sets of data on coliphages presence in reclaimed and groundwater are reported.

Two groups of bacteriophages that infect Escherichia coli, somatic and F-specific coliphages, have been used in academia as both fecal and viral indicators for many years. Regulatory authorities in different parts of the world are beginning to consider coliphages as indicators of water quality in a range of settings. However, issues such as their potential replication in natural water environments, the cumbersome detection and enumeration methods, a lack of definition concerning which of the two groups should be included in future regulations, and the lack of a clear correlation between coliphages and human viruses and health risks in different water settings remain controversial. This review attempts to shed some light on these contentious issues. The conclusions are that: 1) supposing that they can replicate in some natural water settings, the contribution of coliphages replicated outside the gut will not affect the numbers contributed by fecal pollution and detected by strains recommended for standardized methods; 2) there are easy, fast, and cost-effective methods that can be used in routine laboratories after a little training; 3) perhaps the best option is to determine both groups in a single step; and 4) the low correlation of coliphages with human viruses and health risks is no worse than the correlation between different human viruses.

Environments without any contact with anthropogenic antibiotics show a great abundance of antibiotic resistance genes that use to be chromosomal and are part of the core genes of the species that h...

The idea that bacteriophage transduction plays a role in the horizontal transfer of antibiotic resistance genes is gaining momentum. Such transduction might be vital in horizontal transfer from env...