Molecular quantification of virulence gene-containing Aeromonas in water samples collected from different drinking water treatment processes

Phenotypic, molecular detection, and Antibiotic Resistance Profile (MDR and XDR) of Aeromonas hydrophila isolated from Farmed Tilapia zillii and Mugil cephalus

In the present study, Aeromonas hydrophila was isolated from Tilapia zillii and Mugil cephalus samples collected during different seasons from various Suez Canal areas in Egypt. The prevalence of A. hydrophila, virulence genes, and antibiotic resistance profile of the isolates to the commonly used antibiotics in aquaculture were investigated to identify multiple drug resistance (MDR) and extensive drug-resistant (XDR) strains. In addition, a pathogenicity test was conducted using A. hydrophila, which was isolated and selected based on the prevalence of virulence and resistance genes, and morbidity of natural infected fish. The results revealed that A. hydrophila was isolated from 38 of the 120 collected fish samples (31.6%) and confirmed phenotypically and biochemically. Several virulence genes were detected in retrieved A. hydrophila isolates, including aerolysin aerA (57.9%), ser (28.9%), alt (26.3%), ast (13.1%), act (7.9%), hlyA (7.9%), and nuc (18.4%). Detection of antibiotic-resistant genes revealed that all isolates were positive for blapse1 (100%), blaSHV (42.1%), tetA (60.5%), and sul1 (42.1%). 63.1% of recovered isolates were considered MDR, while 28.9% of recovered isolates were considered XDR. Some isolates harbor both virulence and MDR genes; the highest percentage carried 11, followed by isolates harboring 9 virulence and resistance genes. It could be concluded that the high prevalence of A. hydrophila in aquaculture species and their diverse antibiotic resistance and virulence genes suggest the high risk of Aeromonas infection and could have important implications for aquaculture and public health.

A comparative analysis of drinking water employing metagenomics

The microbiological content of drinking water traditionally is determined by employing culture-dependent methods that are unable to detect all microorganisms, especially those that are not culturable. High-throughput sequencing now makes it possible to determine the microbiome of drinking water. Thus, the natural microbiota of water and water distribution systems can now be determined more accurately and analyzed in significantly greater detail, providing comprehensive understanding of the microbial community of drinking water applicable to public health. In this study, shotgun metagenomic analysis was performed to determine the microbiological content of drinking water and to provide a preliminary assessment of tap, drinking fountain, sparkling natural mineral, and non-mineral bottled water. Predominant bacterial species detected were members of the phyla Actinobacteria and Proteobacteria, notably the genera Alishewanella, Salmonella, and Propionibacterium in non-carbonated non-mineral bottled water, Methyloversatilis and Methylibium in sparkling natural mineral water, and Mycobacterium and Afipia in tap and drinking fountain water. Fecal indicator bacteria, i.e., Escherichia coli or enterococci, were not detected in any samples examined in this study. Bacteriophages and DNA encoding a few virulence-associated factors were detected but determined to be present only at low abundance. Antibiotic resistance markers were detected only at abundance values below our threshold of confidence. DNA of opportunistic plant and animal pathogens was identified in some samples and these included bacteria (Mycobacterium spp.), protozoa (Acanthamoeba mauritaniensis and Acanthamoeba palestinensis), and fungi (Melampsora pinitorqua and Chryosporium queenslandicum). Archaeal DNA (Candidatus Nitrosoarchaeum) was detected only in sparkling natural mineral water. This preliminary study reports the complete microbiome (bacteria, viruses, fungi, and protists) of selected types of drinking water employing whole-genome high-throughput sequencing and bioinformatics. Investigation into activity and function of the organisms detected is in progress.

Virulence factor activity relationships (VFARs): a bioinformatics perspective

Virulence factor activity relationships (VFARs) - a concept loosely based on quantitative structure-activity relationships (QSARs) for chemicals was proposed as a predictive tool for ranking risks due to microorganisms relevant to water safety. A rapid increase in sequencing capabilities and bioinformatics tools has significantly increased the potential for VFAR-based analyses. This review summarizes more than 20 bioinformatics databases and tools, developed over the last decade, along with their virulence and antimicrobial resistance prediction capabilities. With the number of bacterial whole genome sequences exceeding 241 000 and metagenomic analysis projects exceeding 13 000 and the ability to add additional genome sequences for few hundred dollars, it is evident that further development of VFARs is not limited by the availability of information at least at the genomic level. However, additional information related to co-occurrence, treatment response, modulation of virulence due to environmental and other factors, and economic impact must be gathered and incorporated in a manner that also addresses the associated uncertainties. Of the bioinformatics tools, a majority are either designed exclusively for virulence/resistance determination or equipped with a dedicated module. The remaining have the potential to be employed for evaluating virulence. This review focusing broadly on omics technologies and tools supports the notion that these tools are now sufficiently developed to allow the application of VFAR approaches combined with additional engineering and economic analyses to rank and prioritize organisms important to a given niche. Knowledge gaps do exist but can be filled with focused experimental and theoretical analyses that were unimaginable a decade ago. Further developments should consider the integration of the measurement of activity, risk, and uncertainty to improve the current capabilities.

New perspectives in monitoring drinking water microbial quality

The safety of drinking water is evaluated by the results obtained from faecal indicators during the stipulated controls fixed by the legislation. However, drinking-water related illness outbreaks are still occurring worldwide. The failures that lead to these outbreaks are relatively common and typically involve preceding heavy rain and inadequate disinfection processes. The role that classical faecal indicators have played in the protection of public health is reviewed and the turning points expected for the future explored. The legislation for protecting the quality of drinking water in Europe is under revision, and the planned modifications include an update of current indicators and methods as well as the introduction of Water Safety Plans (WSPs), in line with WHO recommendations. The principles of the WSP approach and the advances signified by the introduction of these preventive measures in the future improvement of dinking water quality are presented. The expected impact that climate change will have in the quality of drinking water is also critically evaluated.