The Effect of Plasmids and Other Biomolecules on the Effectiveness of Antibiofilm Agents - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 154

The Effect of Plasmids and Other
Biomolecules on the Effectiveness
of Antibiofilm Agents
L.C. Gomes, P.A. Ara´ jo, J.S. Teod´sio, M. Sim˜es, and F.J. Mergulh˜o
Abstract This chapter describes the impact of cell transformation with a recom-
binant plasmid and the effects of the presence of selected biomolecules (bovine
serum albumin—BSA, alginate, yeast extract and humic acids) on biofilm resis-
tance to quaternary ammonium compounds (QACs), which are often used in
medical applications to prevent microbial contamination. Two case studies are
presented, the first concerning cell transformation with recombinant plasmids and
the second addressing potential interfering substances. In the first case study, the
pET28 and pUC8 plasmids were used to transform Escherichia coli JM109(DE3),
and biofilm formation, removal and antimicrobial susceptibility to the cationic
biocide benzyldimethyldodecylammonium chloride (BDMDAC) were assessed.
Plasmid-bearing cells formed biofilms with higher cell densities, whereas
non-transformed cells had higher viabilities. It was found that biocide treatment
was not efficient for biofilm removal and that the thickness of the biofilms formed
by non-transformed cells is less affected by the treatment, a fact that can be
associated with a higher protein content of the biofilm matrix. Despite being
unsuccessful at removing the biofilms, BDMDAC was very effective at killing
the cells since complete inactivation was attained for transformed and
non-transformed strains. In the second case study, it was possible to conclude that
BSA, alginate and yeast extract resulted in mild interferences in the antibacterial
activity of benzalkonium chloride (BAC) and cetyltrimethyl ammonium bromide
(CTAB) against Bacillus cereus and Pseudomonas fluorescens . Humic acids have a
severe impact on the activity of these QACs and can even trigger metabolic
activation in some circumstances. These observations suggest that the presence of
the tested biomolecules should be taken into account when using QACs as disin-
fection agents.