Efficacy of bacteriophage cocktails administered through mucosal and non-mucosal routes for urinary tract infections caused by Enterobacter cloacae: A preclinical study

This preclinical study assessed the effectiveness of a phage cocktail in completely curing Enterobacter cloacae-associated urinary tract infections (UTIs) in a mouse model, employing various routes and dosages (both in quantity and frequency). Three lytic phages, designated ΦENT1, ΦENT2, and ΦENT3, were identified and characterised phenotypically using transmission electron microscopy (TEM) and genotypically through ERIC and restriction enzyme analysis. To induce a UTI, ten groups of female Swiss albino mice were inoculated with 100 μL containing 1 × 10⁹ CFU/mL via the urethral route with E. cloacae GNENT11213. The mice were subsequently treated with the phage cocktail via subcutaneous, oral, transurethral, and rectal routes. The efficacy of these routes was optimised at two doses of phages, namely 1 × 10⁹ PFU/mL (5 mice) and 1 × 10⁵ PFU/mL (5 mice). Furthermore, the levels of Endotoxins and Interleukin-6 (IL-6) were measured to assess the negative impact of phage therapy. Our findings indicated that E. cloacae GNENT11213 could be effectively eliminated with one dosage of 1 × 10⁹ Plaque-Forming Units per mouse (PFU/mouse) and two doses of the phage cocktail containing 1 × 10⁵ PFU/mouse administered through the urethra (local mucosa). Interestingly, higher concentrations of phage particles and multiple doses were necessary for other mucosal routes, such as oral and rectal administration, to effectively eradicate E. cloacae GNENT11213 at any stage of acute illness UTI. Furthermore, phage treatment did not significantly alter the levels of IL-6 and Endotoxins. Non-mucosal routes, such as subcutaneous, were ineffective in curing the infection.