Klebsiella pneumoniae are opportunistic bacteria found in the gut. In recent years they have been associated with nosocomial infections. The increased incidence of multiple drug-resistant K. pneumoniae makes it necessary to find new alternatives to treat the disease. In this study, phage UPM2146 was isolated from a polluted lake which can lyse its host K. pneumoniae ATCC BAA-2146. Observation from TEM shows that UPM2146 belongs to Caudoviriales (Order) based on morphological appearance. Whole genome analysis of UPM2146 showed that its genome comprises 160,795 bp encoding for 214 putative open reading frames (ORFs). Phylogenetic analysis revealed that the phage belongs to Ackermannviridae (Family) under the Caudoviriales. UPM2146 produces clear plaques with high titers of 1010 PFU/ml. The phage has an adsorption period of 4 min, latent period of 20 min, rise period of 5 min, and releases approximately 20 PFU/ bacteria at Multiplicity of Infection (MOI) of 0.001. UPM2146 has a narrow host-range and can lyse 5 out of 22 K. pneumoniae isolates (22.72%) based on spot test and efficiency of plating (EOP). The zebrafish larvae model was used to test the efficacy of UPM2146 in lysing its host. Based on colony forming unit counts, UPM2146 was able to completely lyse its host at 10 hours onwards. Moreover, we show that the phage is safe to be used in the treatment against K. pneumoniae infections in the zebrafish model.

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The rise in in the number of drug-resistant bacteria that can resist almost all kinds of antibiotics is due to the overuse of these antibiotics (e.g., carbapenems). Thus, there is a need to find an alternative to antibiotic treatment such as the use of phages. In this study, phage UPM1705 was isolated from a polluted lake which can lyse its host Klebsiella pneumoniae ATCC BAA-1705. Based on morphological appearance from transmission electron microscopy, UPM1705 belongs to Caudovirales (Myoviridae). UPM1705 can reach a titer of 107 PFU/ml based on the double-layer method. It has a burst size of 298 PFU/bacteria cell and a latent period of 80 min, a rise period of 75 min, and adsorption time of 20 min based on a one-step growth curve assay using an MOI of 0.02. It was stable from 4°C to 80°C and retained its functionality at pH between 4 to 11, with pH of 7 being the optimum pH for the phage growth. The efficiency of UPM1705 was tested via a turbidity assay at MOI of 0.02, 0.2, and 2. UPM1705 was able to clear the turbidity of the host bacteria culture at all of these three MOIs. Thus, UPM1705 has the potential to be used for phage therapy.