Characterization of Extended-Host-Range Pseudo-T-Even Bacteriophage Kpp95 Isolated on Klebsiella pneumoniae

Abstract

Kpp95, isolated on Klebsiella pneumoniae, is a bacteriophage with the morphology of T4-type phages and is capable of rapid lysis of host cells. Its double-stranded genomic DNA (ca. 175 kb, estimated by pulsed-field gel electrophoresis) can be cut only by restriction endonucleases with a cleavage site flanked either by A and T or by T, as tested, suggesting that it contains the modified derivative(s) of G and/or C. Over 26 protein bands were visualized upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the virion proteins. N-terminal sequencing indicated that the most abundant band (46 kDa) is the major coat protein (gp23) which has been cleaved from a signal peptide likely with a length similar to that of T4. Phylogenetic analyses based on the sequences of the central region (263 amino acid residues) of gp23 and the full length of gp18 and gp19 placed Kpp95 among the pseudo-T-even subgroup, most closely related to the coliphage JS98. In addition to being able to lyse many extended-spectrum ␤-lactamase strains of K. pneumoniae, Kpp95 can lyse Klebsiella oxytoca, Enterobacter agglomerans, and Serratia marcescens cells. Thus, Kpp95 deserves further studies for development as a component of a therapeutic cocktail, owing to its high efficiencies of host lysis plus extended host range.The Klebsiella spp., ubiquitous in nature, are opportunistic human pathogens attacking primarily immunocompromised individuals who are hospitalized and suffering from severe underlying diseases such as diabetes mellitus or chronic pulmonary obstruction. It is estimated that Klebsiella spp. cause 8% of nosocomial bacterial infections in the United States and in Europe, placing these bacteria among the eight most important infectious pathogens in hospitals (35). Nosocomial Klebsiella infections are caused mainly by K. pneumoniae, the most clinically important species of the genus, present as a saprophyte in the human mouth, the nasopharynx, and the intestinal tract (35). In Taiwan, the high prevalence of K. pneumoniae has also been observed. For example, a survey taken during 1991 to 2003 at a university hospital in Taiwan indicates that K. pneumoniae ranked second among gram-negative bacteria causing nosocomial infections, only after Escherichia coli (22). Recently, Klebsiella infection-induced liver abscess was first reported in Taiwan, and K. pneumoniae has surpassed E. coli, the historically predominant causative agent of hepatic abscesses, as the number one isolate from patients with this disease (56,57). Since the initial description of extended-spectrum ␤-lactamase production by K. pneumoniae strains in 1983 (24), this organism's resistance to expanded-spectrum ␤-lactam antibiotics has emerged quickly (7). A similar situation was encountered in Taiwan (61), and it has caused increasingly serious problems in treating K. pneumoniae infections. Thus, a different approach, such as treatments with specific lytic bacteriophages, could be a possible alternative therapy (for a review, see references 3, 9, 25, 46, 47, and 48)....

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