Bacteriophages have re-emerged as powerful regulators of the bacterial populations in natural ecosystems. As in natural environments, phages invade the human body and they are the most numerous group of virus in human viromes of healthy individuals. This is revealed in recent metagenomic studies, despite the presence of phages in human bodies was described decades ago. The influence of the presence of phages in humans has yet to be evaluated, but it could be envisaged a clear influence in the regulation of bacterial populations, that might have later an impact in human health.
To explore the presence of phages in clinical samples and to evaluate how these phages could interfere in clinical diagnosis.
Clinical samples (blood, ascitic, urine, cerebrospinal fluid and serum) were evaluated for the presence of infectious bacteriophages able to propagate and lyse E. coli and Pseudomonas host strains. The presence of phage particles was confirmed by electron microscopy.
Infectious tailed phages were detected in >46% ascitic and urine samples. The presence of phages was shown to hinder bacterial isolation in some of these samples, either by preventing the confluent bacterial growth required for an antibiogram assay, by reducing the bacterial growth in liquid enrichment or by killing the bacteria present in a sample, confounding the diagnostic. The presence of phages in human samples, most of the times not considered, can influence and bias the results of microbiological and molecular results, suggesting that more attention should be paid to their interference.