Characterization of Corynebacterium pseudotuberculosis biofilm / Mohamad Fakhri Yaacob

Caseous lymphadenitis (CLA) is a ruminant disease caused by Corynebacterium
pseudotuberculosis, a Gram-positive facultative intracellular pathogen. To date, the
biofilm formation by C. pseudotuberculosis is not well understood. The present
work was performed to characterize C. pseudotuberculosis biofilm. Determination
of biochemical composition, morphology, antimicrobial susceptibility pattern and
whole-cell protein expression of C. pseudotuberculosis biofilm was carried out
using Raman spectroscopy, field emission scanning electron microscopy (FESEM),
microplate biofilm assay and sodium dodecyl polyacrylamide gel electrophoresis
(SDS-PAGE) respectively. Results showed that the 24-h-old biofilm was
characterized by Raman spectral peaks at 615 cm-1 (CCC symmetric bend phenyl
ring), 668 cm-1 (Valine) and 825 cm-1 (Ring breath Tyr.) whilst the 48-h-old and
72-h-old biofilms were characterized by Raman spectral peaks at 1400 cm-1 (COOsym.),
1450 cm-1 (COO- sym.), 1581 cm-1 (Ring breath Trp.), 1650 cm-1 (COOasym.)
and 1725 cm-1 (C-O str.). Raman spectra also revealed the biochemical
heterogeneity in C. pseudotuberculosis biofilm. FESEM images clearly showed the
biofilm cells which were surrounded by the extracellular matrix. Treatment with
nalidixic acid, streptomycin, tetracyclin, ethylenediaminetetraacetic acid (EDTA)
and dimethyl sulfoxide (DMSO) significantly (p < 0.05) inhibited the viability of
C. pseudotuberculosis biofilm. The major protein bands of C. pseudotuberculosis
biofilm were found to be in the range between 33.7 kDa and 150 kDa. Differential
protein expression in C. pseudotuberculosis biofilm was observed following the
treatment with antimicrobial agents. The present study suggests that the
biochemical composition of C. pseudotuberculosis biofilm may vary across
different developmental stages. Meanwhile, nalidixic acid, streptomycin,
tetracyclin, EDTA and DMSO may be useful in the treatment of CLA.