Conjunctival S.epidermidis. rapidly develops resistance

Conjunctival S.epidermidis. repeatedly exposed to fluoroquinolone or azithromycin antibiotics quickly develops resistance in patients undergoing serial unilateral intravitreal (IVT) injections for choroidal neovascularization, states a paper published in Ophthalmmology.

A team led by Dr Stephen J. Kim, Vanderbilt Eye Institute, Nashville, Tennessee, USA, performed a prospective, controlled, longitudinal study with 1-year follow-up on 48 eyes of 24 patients. Each patient was administered 4 consecutive monthly serial unilateral intravitreal (IVT) injections for choroidal neovascularization.

The purpose of the study was to analyze the occurrence of multidrug-resistant Staphylococcus epidermidis after the repetition of conjunctival exposure topical macrolide or fluoroquinolone antibiotics. The main outcome measure was the antibiotic susceptibility patterns and multidrug resistance of Staphylococcus epidermidis.

After 4 consecutive treatments, 58 isolates of S. epidermidis were separated from control and treated eyes. In 69% of S. epidermidis isolated from control eyes there was resistance to 3 or more antibiotics, compared to 90% from treated eyes.

From control and treated eyes there was a total of 46 and 38 isolates of S. epidermidis, respectively. In 48% of control eyes and 71% of treated eyes there was a resistance to 5 or more antibiotics. S. epidermidis developed resistance to several fluoroquinolone-treated eyes compared to control eyes. The organisms also developed resistance to trimethoprim/sulfamethoxazole, gentamicin, and clindamycin.

A large number of azithromycin-treated eyes developed S. epidermidis resistant to macrolides, compared with control eyes. The azithromycin-treated eyes also developed a higher resistance to trimethoprim/sulfamethoxazole and doxycycline.