**7.4 Contact lenses biofilms**

*Bacterial Biofilms*

device.

devices. Few remarkable results are:

dextrose-heparin flush.

**7.2 Mechanical heart valve biofilms**

**7.3 Urinary catheter biofilms**

Many studies have been done to control or avoid biofilm formation in these

• It has been found in a research that microbial colonies of the left arterial catheter can be eliminated by addition of sodium metabisulfite to the

than those coated with chlorhexidine and silver sulfadiazine [5].

• Less colonization was seen on catheters coated with minocycline and rifampin

Microorganisms like *S. epidermidis*, *S. aureus, Streptococcus* species*,* Gram-negative

bacilli, diphtheroids*, Enterococci and Candida* species develop biofilm on the components of mechanical heart valves and surrounded heart tissues, which lead to a condition called prosthetic valve endocarditis. Also, it more often develops on the tissue surrounding the prosthesis or on the sewing cuff fabric that attaches a device to the tissue than on the valve itself. The source of the microorganism somehow tells its identity as, if it gets originate from an invasive process like dental work then it possibly belongs to *Streptococcus* species or it also might get originated during surgery (early endocarditis, mainly due to *S. epidermidis*) or from an indwelling medical

To prevent initial attachment of the microbes, anti-microbial agents are provided during valve replacement or any invasive process like dental work. It has also been found out that less inflammation was caused when silver coated sewing cuff of

Organisms which develop biofilm on these devices are *S. epidermidis*, *E. faecalis*, *E. coli*, *Proteus mirabilis*, *P. aeruginosa*, *K. pneumonia* and other Gram-negative organisms [17]. These catheters are tubular latex or silicone devices that are inserted via urethra into the bladder. It may be of an open system in which catheter drains into an open collection center or close system in which it vacates into a securely fastened bag. In open system, catheter gets quickly contaminated and chances of UTI (Urinary Tract Infection) are much more than in closed system. The chances of microbes to develop biofilm and hence causing UTI is more as long as the catheter remains on its place as it has been found out that approximately 10 to 50% of the patients undergoing short-term catheterization (up to 7 days) and around all the patients undergoing

It has been shown in studies that hydrophobicity of both organism and surface is responsible factors for microbial attachment on the catheter as a wide range of microbial colonies are found to be attached on the catheter's surface which displays both hydrophobic and hydrophilic regions [17]. Bacterial attachment is also enhanced by an increase in urinary pH and ionic strength by divalent cations (Mg and Ca). Urease is produced by some of the organisms of this biofilm which is responsible for hydrolyzing the urea to ammonium hydroxide. As a result, pH at the biofilm-urine interface gets higher, which causes precipitation of minerals such as struvite and hydroxyapatite. These biofilms having mineral components form

Several approaches have been done to control biofilm formation on urinary catheters like the use of antimicrobial ointments and lubricants, bladder instillation,

St. Jude mechanical heart valve was implanted than an uncoated one [5, 17].

long-term catheterization (>30 days) gets infected with UTI [5].

encrustations which can completely block the catheter's inner lumen [5].

**156**

Microbes get readily attached to the surface of both type of contact lenses i.e. soft contact lenses and hard contact lenses (differentiated according to the material used, design, wear schedule and frequency of disposal). Nature of substrate, water content, polymer composition, electrolyte concentration and type of bacterial strains governs the degree of adherence of microbes to the lenses. The storage case of a lens has been implicated as the primary source of contamination [5].

*Staphylococcus*, *Serratia* and *Pseudomonas* are some most common bacterial species obtained in contact lenses. *Staphylococci* are found affiliated with contact lens induced peripheral ulcer, blepharitis and conjunctivitis while *Serratia* and *Pseudomonas* species known to contribute in corneal inflammation and infection [18].
