Microbiological assessment and antibiotic susceptibility of species isolated from forceps used for suture removal after penetrating keratoplasty

Abstract

Purpose : To document the bioburden, microbial diversity and antibiotic resistance among isolates recovered from forceps used for suture removal after penetrating keratoplasty (PKP).

Methods : Fifty five samples were collected from forceps and sutures of 11 healthy patients post PKP at 5 different time points during the removal of corneal sutures: after opening the sterile pouch (t1), after the suture was removed (t2), 5 minutes after the forceps were disinfected with alcohol pads (t3) and at the end of the day after spending several hours in the surgeon’s lab coat (t4). Samples were placed in broth (trypticase soy and or thioglycollate) and sent for culture. Positive broths were inoculated on to chocolate agar for species identification. Standard microbiological procedures were used for identification. The Kirby Bauer diffusion test was used to screen for antibiotic resistance to 21 different antibiotics.

Results : The overall contamination rate was 9.1% for both sutures (1/11) and forceps (4/44). A positive culture was recovered for time t1, t2 and t4. All positive cultures grew coagulase negative Staphylococcus spp. The positive isolate from the suture was identified as S. epidermidis. For the forceps, the isolates were identified as S. epidermidis, S. chromogenes, S. sciuri and coagulase negative not otherwise speciated. All isolates were susceptible to fluoroquinolones, aminoglycosides, sulfas and vancomycin. All isolates were resistant to Penicillin, Erythromycin and Polymyxin B. The S. chromogenes was also resistant to Oxacillin and other beta-lactams. None of the 4 patients with positive culture developed infectious keratitis, endophthalmitis or other ocular infection after 3 month.

Conclusions : Coagulase negative Staphylococci were the only bacteria identified on suture or forceps after corneal suture removal. All species identified are part of the normal bacterial flora of the skin and known to cause endophthalmitis and keratitis. Corneal suture removal is a task routinely performed in clinic that needs strict hygiene protocol to prevent ocular infection and antibiotic resistance.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.