Reader and Industry Forum
Options When Treating Bacterial Conjunctivitis and Keratitis
BY NABA KHAN, OD, & AGUSTIN GONZALEZ, OD, FAAO
Bacterial conjunctivitis is caused by bacteria that infects the eye through various sources of contamination—contact with an infected individual, exposure to contaminated surfaces, or even by sinus infections. The most common types of bacteria that cause bacterial conjunctivitis include Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, and Pseudomonas aeruginosa. Both Pseudomonas aeruginosa and Streptococcus pneumoniae are major isolates in microbial keratitis in North America. Pseudomonas aeruginosa can be derived from various endogenous and environmental factors, but it is most commonly associated with contact lenses (Al-Mujaini et al, 2009).
Risks for Infection with Contact Lens Wear
One risk factor for bacterial infections is extending contact lens wearing time beyond the U.S. Food and Drug Administration (FDA)-indicated period of wear, which significantly increases the risk of complications of contracting bacterial conjunctivitis. When prescribed, patients are educated regarding the significant risks of sleeping in contact lenses that are not indicated for extended wear and the disadvantages of wearing their lenses for longer than their replacement schedule.
It is worth noting that at times, the perception of a device can also lead to abuse. Purchasing contact lenses from unregulated sources, such as the Internet, has been linked to the development microbial keratitis (Hoffman and Pelosini, 2016). Extended wear soft contact lens users have a higher annual incidence of ulcerative keratitis compared daily wear soft contact lens users. Extended wear cosmetic lenses are also more prone to Pseudomonas infections (Al-Mujaini et al, 2009).
Eighty percent of bacterial corneal ulcers are caused by Staphylococcus aureus, Streptococcus pneumonia, and Pseudomonas species. In addition, Pseudomonas aeruginosa is the most frequent and the most virulent ocular pathogen; it can cause corneal perforation in as fast as 72 hours. Pseudomonas may contaminate ophthalmic solutions such as fluorescein, ocular cosmetics such as eyeliner and mascara, and any other substance containing traces of organic carbon (Hoffman and Pelosini, 2016).
Contact lens wearers are more prone to bacterial infection, especially with gram-negative organisms. The contact lens induces hypoxia and decreases tear flow over the corneal surface, and the gram-negative corneal bacterial infections are more rapid in onset and progress much faster. The most common and virulent gram-negative ocular pathogens belong to Pseudomonas species (Hoffman and Pelosini, 2016).
Treating Bacterial Conjunctivitis and Keratitis
Common medications for bacterial conjunctivitis include topical tobramycin and levofloxacin as well as oral levofloxacin (Accorinti et al, 2015). In addition, treating patients who have Pseudomonas aeruginosa infections with besifloxacin ophthalmic suspension 0.6% can lead to bacterial eradication of Pseudomonas aeruginosa with high rates of clinical resolution (Silverstein et al, 2012). To compare, in a study conducted by Sanders et al (2011) using the ciprofloxacin/levofloxacin-resistant strain, clinical scores of besifloxacin-treated eyes had significantly lower resistant strain compared to those treated with moxifloxacin. Besifloxacin-treated eyes had significantly lower colony forming units (CFU) recovered as compared with that of eyes treated with gatifloxacin or moxifloxacin.
Most encountered eye infections, especially those involving contact lens use, are treated empirically without cultures; these results support guidance in treating patients at risk for developing Pseudomonas keratitis (Sanders et al, 2011). Besifloxacin 0.6% has also demonstrated high rates of eradication against multi-drug resistant gram-positive organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), and gram-negative pathogens, including Pseudomonas aeruginosa (Mah, 2013).
It Helps to Be Prepared
Wearing contact lenses changes the bacterial environment of the eye. Contaminated contact lens cases can act as reservoirs for microorganisms that could potentially compromise contact lens wear. Many of these factors can lead to sight-threatening adverse events through Pseudomonas aeruginosa and other bacterial species (Wu et al, 2015). Understanding the source and different antibiotic treatment options available to clinicians provides a guide to safely treat empirically when cultures are not available and Pseudomonas sp. is a concern. CLS
For references, please visit www.clspectrum.com/references and click on document #246.
Dr. Khan is a 2016 graduate of Inter American University School of Optometry in Puerto Rico (IAUPR), where she was the AOSA Committee Chair of the Cornea and Contact lens section. She now resides in Houston, Texas. Dr. Gonzalez is a graduate from IAUPR and has been in practice in Texas since 1995. He is a recognized industry expert in adoption and usage of ophthalmic medications by optometrists and is a board certified Clinical Medical Optometrist who has lectured extensively, including at AOA’s Optometry’s Meeting and the American Academy of Optometry.