There is some evidence that the source of infection is a signature for the bacteria associated with the keratitis. For example,
P. aeruginosa is frequently associated with contact lens wear.
4 We recently reported that a subpopulation of
P. aeruginosa better able to survive in environmental water is associated with keratitis infections.
9,10 This association suggests that there is a link between a subset of bacteria with particular phenotypic properties and their possible transmission routes, in this instance through water, and that these are associated with contact lens use. In contrast to
P. aeruginosa , the source of
S. aureus responsible for keratitis may be autocthonous, as nasopharyngeal colonization with
S. aureus is recognized as a risk for certain systemic infections.
11–15 Approximately 20% of the healthy human population are persistently colonized with
S. aureus , and the same strain can persist over months or years.
16–18 A key feature of nonocular
S. aureus infection is its recurrence, which is seen in approximately 30% of all cases.
19 Persistent carriage might predispose these individuals to recurrent
S. aureus keratitis, especially those with underlying ocular surface disease. It is not known, however, whether treatment of patients who have
S. aureus keratitis with antibacterials (topical, nasal, and systemic) would concomitantly eliminate nasopharyngeal carriage.