Antimicrobial Coatings to Prevent Biofilm Formation on Medical Devices - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 173

reduced catheter colonization and the incidence of CRBSIs (Darouiche et al. 1999 ;
Raad et al. 1997 ). In comparison with the first generation CH-SS catheters,
minocycline/rifampicin catheters reduced the rate of catheter colonization by
threefold and the rate of CRBSIs by 12-fold (Raad et al. 1997 ). Among critically
ill patients, minocycline/rifampicin CVCs significantly reduced nosocomial blood-
stream infections and the length of stays in intensive care units (Hanna et al. 2003 ).
The catheters also reduced the risk of catheter-related infections in patients with
acute renal failure (Chatzinikolaou et al. 2003 ). In vivo analysis revealed that
following 21 days of sequential exposure to different Gram-positive pathogens,
including methicillin-resistant S. aureus , methicillin-resistant Staphylococcus
epidermidis (MRSE), and vancomycin-resistant enterococci (VRE), minocycline/
rifampicin catheters retained their antibacterial activity (Aslam and Darouiche
2007 ). In vitro and in vivo studies using a rat subcutaneous implantation model
showed that when challenged with rifampicin-resistant S. aureus , antiseptic-coated
catheters were less susceptible to colonization than the minocycline/rifampicin
catheter (Sampath et al. 2001 ).
2.2.4 Organoselenium Coating of Hemodialysis Catheters
Selenium catalyzes the formation of superoxide radicals (O 2 •- ) which inhibits
bacterial attachment to solid surfaces. The detailed mechanism of function of
selenium compounds is described in the “Antimicrobial mechanism of selenium”
section. Covalent binding of organoselenium to solid surfaces prevents bacterial
colonization of those surfaces (Tran et al. 2009 ).
Cellulose discs coated with organoselenium methacrylate polymers inhibited
colonization and biofilm formation by S. aureus and P. aeruginosa (Tran
et al. 2009 ). Using in vitro and in vivo biofilm assays, Tran et al. demonstrated
the effectiveness of hemodialysis catheters coated with the organoselenium agent
(selenocyanato diacetic acid, SCAA) in preventing biofilm development by
S. aureus (Tran et al. 2012b ). Small pieces of uncoated polyurethane decathlon
high flow, long-term catheters were coated internally and externally by covalent
attachment of SCAA (Tran et al. 2012b ). To visualize the biofilm by confocal laser
scanning microscopy (CLSM), Tran et al. utilized the S. aureus strain AH133
(Malone et al. 2009 ; Tran et al. 2012b ). This strain carried plasmid pMC11 which
contains the gene that codes for green fluorescent protein (Malone et al. 2009 ). The
inhibitory effect of SCAA-coated catheter pieces in vitro was examined using two
systems: the static biofilm system and the flow-through continuous culture system
(Schaber et al. 2007 ). In the static biofilm system, catheter pieces were incubated
with AH133 in Tryptic Soy broth (TSB) for 24 h using 24-well microtiter plates.
The pieces were then rinsed and vigorously vortexed to detach bacterial cells, and
the amount of the biofilm was assessed using a crystal violet assay. In addition, the
number of S. aureus AH133 cells within the biofilm was determined. In comparison
with uncoated catheter pieces, SCAA-coated pieces reduced AH133 biofilm by
over 5 logs (Tran et al. 2012b ). To assess the stability of the SCAA coating, catheter