The use of bacteriophages to differentiate serologically cross-reactive isolates of Klebsiella pneumoniae

Abstract

Summary. In serological typing of Klebsiella pneumoniae strains from human, equine and environmental sources, the capsular identity of many isolates could not be determined because of serological cross-reactivity. A panel of 91 bacteriophages able to lyse each of the 77 capsular serotypes of K . pneumoniae was isolated and tested for the ability to distinguish between strains in a collection of 17 clinical isolates of K. pneumoniae which exhibited crossreactivity with two or more capsular type sera. Most isolates could be assigned a capsular type by performing a simple streak test with bacteriophage, although some required the application of an efficiency of plating analysis to discern capsular type. Bacteriophage typing was found to be an effective, inexpensive and clinically practical adjunct to serotyping in distinguishing serologically cross-reactive K. pneumoniae isolates, irrespective of their origin.

Two T7-like Bacteriophages, K5-2 and K5-4, Each Encodes Two Capsule Depolymerases: Isolation and Functional Characterization

“…After centrifugation, the supernatant was filtered using a 0.45-µm filter and spotted onto LB plates overlaid with the respective strain to detect phage plaques. An agar overlay method was used for isolation of a pure phage preparation and to determine phage titers as described previously 33 . Single plaque isolation, elution, and re-plating were performed repeatedly.…”

“…After overnight incubation at 37 °C, plates were observed for formation of lytic or semi-clear spots. An efficiency of plating assay was also used to quantify the ability of the phage to infect other strains, as described previously 33 . Briefly, samples of serial 10- fold dilutions (in SM buffer) of the respective phage suspensions were incubated for 15 min with the isolating host and with a heterologous host.…”

“…Phage depolymerases, which are often a part of the tail spike or tail fiber, can degrade bacterial capsular polysaccharides into their oligosaccharide units during infection. As such, the use of phages for Klebsiella capsular typing has been previously described 32, 33 . Such lytic phages can also be used as therapeutic agents 34–36 .…”

Klebsiella Phage ΦK64-1 Encodes Multiple Depolymerases for Multiple Host Capsular Types

“…An efficiency-of-plating (EOP) assay was used to quantitate the ability of phage to infect different hosts as previous described (18). The EOP value is a ratio indicating how well a bacteriophage plates on different strains compared to the host which the phage preparation made from.…”

“…Given the specificity of capsule depolymerases, capsule type-specific phage or depolymerases also have been used in capsular typing. Klebsiella phages have been reported since 1940 and have been used for determination of several K-types of Klebsiella (16)(17)(18)(19)(20)(21). However, little was known about the host specificity determinants of these phages until the recent characterization and identification of bacteriophageborne depolymerases (6,22).…”