Isolation and Characterization of Two Klebsiella pneumoniae Phages Encoding Divergent Depolymerases

Abstract

The emergence of multidrug-resistant bacteria is a major global health concern. The search for new therapies has brought bacteriophages into the spotlight, and new phages are being described as possible therapeutic agents. Among the bacteria that are most extensively resistant to current antibiotics is Klebsiella pneumoniae, whose hypervariable extracellular capsule makes treatment particularly difficult. Here, we describe two new K. pneumoniae phages, πVLC5 and πVLC6, isolated from environmental samples. These phages belong to the genus Drulisvirus within the family Podoviridae. Both phages encode a similar tail spike protein with putative depolymerase activity, which is shared among other related phages and probably determines their ability to specifically infect K. pneumoniae capsular types K22 and K37. In addition, we found that phage πVLC6 also infects capsular type K13 and is capable of striping the capsules of K. pneumoniae KL2 and KL3, although the phage was not infectious in these two strains. Genome sequence analysis suggested that the extended tropism of phage πVLC6 is conferred by a second, divergent depolymerase. Phage πVLC5 encodes yet another putative depolymerase, but we found no activity of this phage against capsular types other than K22 and K37, after testing a panel of 77 reference strains. Overall, our results confirm that most phages productively infected one or few Klebsiella capsular types. This constitutes an important challenge for clinical applications.

Phages from Ganges River curtail in vitro biofilms and planktonic growth of drug resistant Klebsiella pneumoniae in a zebrafish infection model

“…Morphology of plaques from Ganges water showed a halo around the clear zone, which might indicate depolymerase activity of KpG that could target the capsule of the strain (Fig. 1 ) (Domingo-Calap et al 2020 ). The phage displayed stability at pH: 7.0, 9.0, 11.0 with a survival rate of 99%, 98% and 60% respectively (Fig.…”

“…Similar to our observation, another report showed that four lytic phages, belonging to the family Podoviridae , infecting K. pneumoniae capsular type K22, were isolated from environmental samples. They possessed narrow infectivity only against a K. pneumoniae clinical isolates with K22 capsular type (Domingo-Calap et al 2020 ). Moreover, the plaque morphology showed a halo around the lysis area, implying presence of depolymerase that lyses the capsule (Domingo-Calap et al 2020 ).…”

“…They possessed narrow infectivity only against a K. pneumoniae clinical isolates with K22 capsular type (Domingo-Calap et al 2020 ). Moreover, the plaque morphology showed a halo around the lysis area, implying presence of depolymerase that lyses the capsule (Domingo-Calap et al 2020 ). Interestingly, MTCC 432 strain produced capsule (Additional file 1 : Fig.…”

Antibiotics Act with vB_AbaP_AGC01 Phage against Acinetobacter baumannii in Human Heat-Inactivated Plasma Blood and Galleria mellonella Models

“…While, the host range of other Acinetobacter infecting phages varied between 2-68%, and in some reports, newly isolated phages infect only their propagation host [11,14,20]. Additionally, the host range of acinetobacter-infecting podoviruses mainly depended on pectate lyase depolymerase domains located on the tail fibers [16,[21][22][23][24]. It can be presumed that isolation and characterization of naturally occurring Acinetobacter phages is important and puts novel insights into their biology.…”

Engineering the Modular Receptor-Binding Proteins ofKlebsiellaPhages Switches Their Capsule Serotype Specificity

“…The number of RBPs with depolymerase activity per phage is highly variable. Phage KP36 produces a single RBP and is only active against serotype K63, corresponding to the substrate specificity of its RBP (8,16), whereas other phages (e.g., KP32, K5-2, K5-4, and UK64-1) encode more RBPs with depolymerase activity, recognizing a corresponding number of capsular serotypes (6,7,9,10,17) and resulting in a broader host spectrum. A similar relationship has also been described for Escherichia coli and Salmonella phages (18)(19)(20).…”