Bacteriophages are more virulent to bacteria with human cells than they are in bacterial culture; insights from HT-29 cells

Abstract

Bacteriophage therapeutic development will clearly benefit from understanding the fundamental dynamics of in vivo phage-bacteria interactions. Such information can inform animal and human trials, and much can be ascertained from human cell-line work. We have developed a human cell-based system using Clostridium difficile, a pernicious hospital pathogen with limited treatment options, and the phage phiCDHS1 that effectively kills this bacterium in liquid culture. The human colon tumorigenic cell line HT-29 was used because it simulates the colon environment where C. difficile infection occurs. Studies on the dynamics of phage-bacteria interactions revealed novel facets of phage biology, showing that phage can reduce C. difficile numbers more effectively in the presence of HT-29 cells than in vitro. Both planktonic and adhered Clostridial cell numbers were successfully reduced. We hypothesise and demonstrate that this observation is due to strong phage adsorption to the HT-29 cells, which likely promotes phage-bacteria interactions. The data also showed that the phage phiCDHS1 was not toxic to HT-29 cells, and phage-mediated bacterial lysis did not cause toxin release and cytotoxic effects. The use of human cell lines to understand phage-bacterial dynamics offers valuable insights into phage biology in vivo, and can provide informative data for human trials.

Bacteriophages inhibit biofilms formed by multi-drug resistant bacteria isolated from septic wounds

“…According to the recent reports, it is increasingly projected that the phages can be used for the eradication of both oral planktonic and biofilms formed by Actinomyces naeslundii, Aggregatibacter actinomycetemcomitans, Enterococcus faecalis, Fusobacterium nucleatum, Lactobacillus spp., Neisseria spp., Streptococcus spp. , and Veillonella spp (Ceri et al, 1999; Sillankorva et al, 2010; Cornelissen et al, 2011; Khalifa et al, 2018; Shan et al, 2018). The use of a phage cocktail (Phage DRA88 and phage K) exhibited intense lytic activity against the biofilm formed by S. aureus .…”

Bacteriophage and the Innate Immune System: Access and Signaling

“…These data indicated that transcytosis is likely both phage-and tissue-specific so that certain phages are able to move across specified tissues more easily while others, not at all. Other data suggesting a specificity of phage to epithelial cells come from Shan et al [52] who examined the ability of three different Clostridium difficile phages to adhere to either HT29 (human colonic) or HeLa (human cervical) monolayers. They found that two phages adhered to HT29, one better than the other, while the third did not adhere at all.…”

“…Extracellular recognition of a free phage is likely to occur either through binding of cell surface moieties, integrins, or currently unknown phage receptors [66,67]. C. difficile phage adhered to epithelial cells in a cell-specific, phage-specific manner [52], and Gorski et al [66] identified Lys-Gly-Asp (KGD) domains in the T4 capsid proteins with homologs involved in integrin binding [68,69] suggesting possible phage-integrin interactions. In addition to KGD domains, T4 and other members of Caudovirales also possess capsid proteins with Ig-like domains [70].…”

Bacteriophage adherence to mucus mediates preventive protection against pathogenic bacteria

“…on Clostridium difficile and phage interaction on human cell cultures concluded that the phage more efficiently reduces the number of planktonic and adherent bacterial cells in the presence of the human cells than occurs in vitro 35 . Although the hypothesis for this finding was that increased phage activity was related to strong phage adsorption to the cells, no data were presented regarding changes elicited by the human cells' effect on the bacterium.…”