Fluoroquinolone-resistant conjunctival bacteria are more frequent in dry eye cases

The study authors saw no links between steroid use, incidence of bacterial species and resistance to methicillin or fluoroquinolones.

Patients with dry eye were more likely than normal subjects to have fluoroquinolone-resistant conjunctival bacteria, but data showed no tangible reasons for the correlation, according to a study.

The findings may help prevent infectious keraconjunctivitis in patients with dry eye, the study authors said.

Yuichi Hori, MD, and colleagues published their results ahead of press in the American Journal of Ophthalmology.

In an e-mail interview with Ocular Surgery News, Dr. Hori cited ongoing uncertainty over why the fluoroquinolone susceptibility of various bacteria varied between patients with dry eye and those without the condition.

Yuichi Hori

"We speculated that some inflammatory conditions of the ocular surface of patients with dry eye may alter susceptibility patterns of conjunctival bacteria to fluoroquinolones," he said.

The authors found no significant relationship between the use of steroids and bacterial resistance to methicillin and fluoroquinolones.

"Initially, we had hypothesized that topical use of immunosuppressive agents to treat dry eye may alter the distribution of ocular bacteria of patients with dry eye," Dr. Hori said.

Patients, methods and results

The prospective, observational study included 67 eyes of 67 female dry eye patients who had a mean age of 60.3 years (range, 26 to 80 years). Dry eye treatments – eye drops and punctal occlusion – had not been changed in the previous 3 months.

A control group of 57 female patients without dry eye had a mean age of 63.4 years. The Schirmer 1 test and tear break-up test were used to diagnose tear film abnormalities. Fluorescein staining and rose bengal staining were used to diagnose ocular surface abnormalities.

Patients receiving topical or systemic antibiotics within the previous 3 months were excluded; those receiving topical steroids to treat dry eye were included, the authors said.

All patients received preservative-free artificial tears. Twenty-three patients received additional topical steroids as anti-inflammatory treatment for dry eye. Twenty-six patients received punctal plugs; none of those patients received additional topical steroids.

The results showed that 63 eyes (94%) had positive bacterial growth, with 88 bacterial strains isolated: 48 strains of Propionibacterium acnes; 26 strains of coagulase-negative Staphylococcus, including 12 methicillin-sensitive strains and 14 methicillin-resistant strains; six Staphylococcus aureus strains (five methicillin-sensitive and one methicillin-resistant); and eight other strains.

Patients with dry eye had a mean 1.27 bacterial species each; those without dry eye had a mean 1.51 species each, the authors reported.

More than half of isolated coagulase-negative Staphylococcus strains were methicillin resistant. The authors said the dry eye patients had a significantly higher rate of fluoroquinolone-resistant methicillin-sensitive coagulase-negative Staphylococcus (P = .018) and fluoroquinolone-resistant methicillin-resistant coagulase-negative Staphylococcus (P = .024) than the control group patients.

The authors saw no significant relationship between steroid use, the incidence of bacterial species and resistance to methicillin and fluoroquinolones.

Caveats and conclusions

The study had a few limitations, the authors said. For example, the patient group was all-female because dry eye syndrome is more prevalent in women than in men. Also, dry eye could not be completely ruled out in control patients who did not undergo the Schirmer 1 test. And moxifloxacin, a latest-generation fluoroquinolone, was not evaluated because it has not been approved by the Japanese government.

More research is needed to further probe factors that influence the susceptibility and resistance of some bacteria to fluoroquinolones, the authors said.

"Some inflammatory conditions or alteration of the defense system on the ocular surface of patients with dry eye may change the susceptibility patterns of conjunctival bacteria to fluoroquinolones," they said. "Further investigation should be needed in these matters."

Antibiotic eye drops show promise as prophylactic measure against ocular infection. However, more study is needed to identify factors that may reduce the risk of infection, Dr. Hori said.

"The application of preoperative antibiotic eye drops may be promising for sterilizing the preoperative ocular surface, even though fluoroquinolone-resistant strains are on the ocular surface," he said. "In the future, we would like to figure out the mechanism of the ocular surface barrier to prevent ocular surface infection." – by Matt Hasson

Reference:

• Hori Y, Maeda N, et al. Bacteriologic profile of the conjunctiva in the patients with dry eye. Am J Ophthalmol. 2008 July 29. [Epub ahead of print]

• Yuichi Hori, MD, can be reached at Department of Ophthalmology, Osaka University Medical School, 2-2 Yamadaoka, Room E7, Osaka 565-0871, Japan; +81-6-6879-3456; fax: +81-6-6879-3458; e-mail: hori@ophthal.med.osaka-u.ac.jp