Antimicrobial Coatings to Prevent Biofilm Formation on Medical Devices - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 181

et al. 1989 ). When daily disposable CLs became available (1995-1999), it was
supposed that frequent replacement of the lenses would reduce the risk of microbial
keratitis. However, an epidemiological study from the Netherlands reported that the
expected reduction in cases did not happen (Cheng et al. 1999 ). This is also seen in
the more recent study by (Yildiz et al. 2012 ), where they also saw an increase in the
number of cases with time.
Bacterial colonization of CLs has also been implicated in CL-induced inflam-
mation. Specifically, CL acute red eye (CLARE), CL peripheral ulcer (CLPU), and
infiltrative keratitis have all been associated with adherence of bacteria to hydrogel
CLs. In particular, many CLARE cases have been associated with Haemophilus
influenzae (Sankaridurg et al. 1996a ), Acinetobacter sp. (Corrigan et al. 2001 ),
Pseudomonas aeruginosa (Holden et al. 1996 ; Sankaridurg et al. 1996b ),
Aeromonas hydrophila (Sankaridurg et al. 1996b ), Serratia liquefaciens
(Sankaridurg et al. 1996b ), Serratia marcescens (Holden et al. 1996 ), and Pseudo-
monas putida (Holden et al. 1996 ). Infiltrative keratitis and CLPU have been
associated with Staphylococcus aureus (Jalbert et al. 2000 ), Streptococcus
pneumoniae (Sankaridurg et al. 1999 ), Abiotrophia defective (Keay et al. 2000 ),
Acinetobacter sp. (Corrigan et al. 2001 ).
Fungal biofilms are also associated with contact lens-related infections. Fusar-
ium keratoplasticum sp. nov. and Fusarium petroliphilum stat. nov. are two phylo-
genetic species that are among the most frequently isolated fusaria in outbreaks of
contact lens-associated keratitis (Short et al. 2013 ). Other in vitro studies showed
that Acanthamoeba castellanii trophozoites (Beattie et al. 2011 ) and Candida spp.
( albicans , parapsilosis , tropicalis , glabrata , and krusei ) (Estivill et al. 2011 ) are
also capable of forming biofilms on different medical devices. In addition, bacteria
are thought to have a role in fungal attachment. For instance, Pseudomonas had
been shown to enhance the absorption of Acanthamoeba to contact

lenses

(Simmons et al. 1998 ).
While bacterial contaminates that colonize contact lenses have been studied for
many years (Hovding 1981 ), and biofilms themselves have been studied for almost
20 years (Costerton et al. 1978 ), until recently most of the studies on contact lens
biofilms were devoted to looking at methods of sterilization (Szczotka-Flynn
et al. 2010 ). However, it is known that the biofilms on lenses protect bacteria and
fungi from disinfectants. It has been shown that fungal hyphae can penetrate the
surface of most types of CLs (Willcox 2013 ). Also, Acanthamoeba adhere in
greater numbers to first-generation silicone hydrogel lenses compared with the
second-generation or hydroxyethyl methacrylate-based soft lenses (Willcox 2013 ).
Bacteria that are known to form biofilms on contact lenses include: Pseudomo-
nas aeruginosa (Burnham et al. 2012 ; Henriques et al. 2005 ); Staphylococcus
epidermidis and S. aureus (Catalanotti et al. 2005 ; Henriques et al. 2005 ); and
Serratia marcescens (Hume et al. 2003 ). Also, in a study of 28 contact lens patients
with keratitis, the bacterial genera, Achromobacter, Stenotrophomonas , and Delftia ,
were found in all clinical groups (Wiley et al. 2012 ).