Klebsiella pneumoniae is a healthcare-associated bacterial pathogen which causes
severe diseases in immunocompromised individuals. Concanavalin A (conA), a lectin which
recognizes proteins with mannose or glucose residues, has been reported to agglutinate K.
pneumoniae and hence, is postulated to have therapeutical potential for K. pneumoniaeinduced
liver infection. This study investigated the conA binding properties of a large collection
of clinical isolates of K. pneumoniae. ConA agglutination reaction was demonstrated by 94
(51.4%) of 183 K. pneumoniae isolates using a microtiter plate assay. The conA agglutination
reactions were inhibited in the presence of 2.5 mg/ml D-mannose and 2.5 mg/ml glucose, and
following pretreatment of the bacterial suspension with protease and heating at 80ºC. Majority
of the positive isolates originated from respiratory specimens. Isolation of conA-binding
proteins from K. pneumoniae ATCC 700603 strain was performed using conA affinity column
and the conA binding property of the eluted proteins was confirmed by western blotting
analysis using conA-HRP conjugates. Proteins with molecular weights ranging from 35 to 60
kDa were eluted from the conA affinity column, of which four were identified as outer
membrane protein precursor A (37 kDa), outer membrane protein precursor C (40 kDa),
enolase (45 kDa) and chaperonin (60 kDa) using mass spectrometry analysis. Several conA
binding proteins (including 45 and 60 kDa) were found to be immunogenic when reacted with
rabbit anti-Klebsiella antibody. The function and interplay of the conA binding proteins in
bacterium-host cell relationship merits further investigation.