This paper reports the development of microencapsulated bacteriophage Felix O1 for oral delivery using a chitosan-alginate-CaCl₂system. In vitro studies were used to determine the effects of simulated gastric fluid (SGF) and bile salts on the viability of free and encapsulated phage. Free phage Felix O1 was found to be extremely sensitive to acidic environments and was not detectable after a 5-min exposure to pHs below 3.7. In contrast, the number of microencapsulated phage decreased by 0.67 log units only, even at pH 2.4, for the same period of incubation. The viable count of microencapsulated phage decreased only 2.58 log units during a 1-h exposure to SGF with pepsin at pH 2.4. After 3 h of incubation in 1 and 2% bile solutions, the free phage count decreased by 1.29 and 1.67 log units, respectively, while the viability of encapsulated phage was fully maintained. Encapsulated phage was completely released from the microspheres upon exposure to simulated intestinal fluid (pH 6.8) within 6 h. The encapsulated phage in wet microspheres retained full viability when stored at 4°C for the duration of the testing period (6 weeks). With the use of trehalose as a stabilizing agent, the microencapsulated phage in dried form had a 12.6% survival rate after storage for 6 weeks. The current encapsulation technique enables a large proportion of bacteriophage Felix O1 to remain bioactive in a simulated gastrointestinal tract environment, which indicates that these microspheres may facilitate delivery of therapeutic phage to the gut.

Multidrug-resistantKlebsiella pneumoniae(MRKP) has steadily grown beyond antibiotic control. However, a bacteriophage is considered to be a potential antibiotic alternative for treating bacterial infections. In this study, a lytic bacteriophage, phage 1513, was isolated using a clinical MRKP isolate KP 1513 as the host and was characterized. It produced a clear plaque with a halo and was classified as Siphoviridae. It had a short latent period of 30 min, a burst size of 264 and could inhibit KP 1513 growthin vitrowith a dose-dependent pattern. Intranasal administration of a single dose of 2 × 10⁹ PFU/mouse 2 h after KP 1513 inoculation was able to protect mice against lethal pneumonia. In a sublethal pneumonia model, phage-treated mice exhibited a lower level ofK. pneumoniaeburden in the lungs as compared to the untreated control. These mice lost less body weight and exhibited lower levels of inflammatory cytokines in their lungs. Lung lesion conditions were obviously improved by phage therapy. Therefore, phage 1513 has a great effectin vitroandin vivo, which has potential to be used as an alternative to an antibiotic treatment of pneumonia that is caused by the multidrug-resistantK. pneumoniae.