Polymicrobial Infection of the Cornea Due to Contact Lens Wear

Infectious keratitis is a sight-threatening complication of contact lens (CL) wear. Most types of lenses have been reported to be associated with infectious keratitis. For a favorable outcome, it is essential to identify the causative agent. To date, several microbiological agents including bacteria, fungi and protozoa have been reported. It is known that microorganisms can reside on lenses and lens storage cases, and CL solutions also act as reservoirs for microbial growth. The latter is more strongly correlated with keratitis.^1,2

The aim of this case report is to describe a case of polymicrobial keratitis due to CL wear. The causative agents identified were Pseudomonas aeruginosa, Alcaligenes xylosoxidans, and Acanthameoba. Ali and Reddy³reported a case of bilateral polymicrobial keratitis in which Pseudomonas aeruginosa, Alcaligenes spp., and Flavobacterium meningosepticum were involved. To the best of our knowledge, this is the first published case of CL-related polymicrobial keratitis with the aforementioned organisms.

All three causative organisms that were obtained from the current case are very well-known pathogens for CL-related keratitis, of which Pseudomonas aeruginosa is the most common.^1,2,3,4,5,6Acanthamoeba spp. are free-living protozoan parasites and are particularly reported to be associated with poor hygienic conditions.⁷On the other hand, despite its relatively low prevalence Alcaligenes (formerly Achromobacter) xylosoxidans is an important cause of infection in CL wearers. Alcaligenes spp. are gram-negative, aerobic bacilli; although rare, they may cause keratitis, particularly in compromised corneas.^5,6

Poor hygiene conditions enhance susceptibility to keratitis in CL wearers.7 Overnight CL wear is a common compromising factor for corneal infections.⁸It was clear that our patient did not take good care of his hygiene and did not have any follow-up visits with an ophthalmologist. He was also unable to provide information regarding the brands CL and cleaning solution he was using. He had a prior history of two nights sleeping with CLs, which he reported to be actually longer. Moreover, he had a history of regular and uncontrolled topical corticosteroid use. As a result of these factors the patient became susceptible to a polymicrobial keratitis with destructive organisms. Also, the relapsing nature of the infection can be attributed to the polymicrobial etiology due to poor hygiene.

Pseudomonas and Alcaligenes were involved in both eyes of our patient, whereas Acanthamoeba was isolated from the left eye. As the patient had no sign of keratitis in his right eye, Acanthamoeba, which was isolated only from the left eye, is strongly considered to be the causative agent. On the other hand, we believe that the role of the other two organisms must be discussed in terms of their contribution to the clinical outcome. It might be considered that the polymicrobial nature of the infection could affect its course, resulting in high recurrence rates and poor visual acuity. We also considered possible toxic effects of intensive topical therapy including fortified antibiotics; hence, the drops were tapered in the second hospitalization, which was three weeks after the first one. Our patient had no problem with compliance to therapy during follow-up; however, Alcaligenes is reported to be particularly associated with frequently recurrent keratitis.⁹

One must always consider accompanying topical anesthetic abuse in cases with severe pain. Topical anesthetic abuse itself is known to cause superinfections with poor outcome.^10,11

Silicone-hydrogel CLs are known to be associated with significantly lower Pseudomonas aeruginosa binding than conventional extended-wear soft CLs.⁴However, as we had no knowledge about the type of the CL our patient was wearing, we are not able to establish a relationship between the CL type and enhanced microbial binding.

Sharma et al.¹²stressed the risk of co-infection in their report, in which the patient did well following administration of propamidine isethionate 0.1%, chlorhexidine 0.02%, and polymyxine B eye drops in addition to previous anti-pseudomonal therapy. Immediately following presentation, we started fortified vancomycin and fortified amikacin. Both Pseudomonas and Alcaligenes were found to be sensitive to amikacin, piperacillin, and tazobactam. Hence, vancomycin was changed with piperacillin. As Acanthamoeba was identified by PCR, we started anti-amoebic therapy as well. Besides the polymicrobial nature, we believe that the intense topical therapy which would be expected to alter epithelial healing might also have played a role in the persistent course of the infection. As we tapered the topical regimen, the ulcer started to heal. Our plan was to administer topical therapy for an appropriate period of time, but the patient was lost to follow-up and later presented with recurrence.

To the very best of our knowledge this is the first report concerning these three organisms. Pseudomonas and Acanthamoeba are well known causes of CL keratitis, whereas because of the relative difficulty in its identification, the role of Alcaligenes might be underestimated.⁶Moreover, Alcaligenes spp. should be kept in mind in such persistent keratitis cases.