[The Microbiological Analysis of a Rhizobium radiobacter Outbreak After Intravitreal Injection]

Rhizobium radiobacter, which is found in nature and causes tumorigenic plant diseases can lead to opportunistic infections, especially in people with underlying diseases. In our study, endophthalmitis that observed in ten patients caused by R.radiobacter bacteria after intravitreal ranibizumab injection in Ophthalmology Clinic were examined microbiologically. Vitreous fluid samples of 13 patients who received intravitreal ranibizumab injection were sent to the Microbiology Laboratory from Van Yuzuncu Yil University Faculty of Medicine's Ophthalmology Clinic for microbiological examination in December 21, 2016. Samples were examined under microscope after staining with Gram and cultured with 5% sheep blood agar and Eosin Methylene Blue (EMB) agar. The culture plates were incubated for 18-24 hours at 37°C in 5% CO2. At the end of this period, catalase, oxidase, and urease tests were performed on the colonies. The identification and antibiotic susceptibility tests of microorganisms growing in vitreous fluid samples were performed using BD Phoenix (Becton Dickinson, USA), Vitek 2 Compact (BioMerieux, France), and Vitek MS (BioMerieux, France) systems. In addition, 16S rDNA sequence analysis was performed and the pulsed field gel electrophoresis (PFGE) method was used to determine the clonal relationship between the isolates. After growing in cultures (one day after the procedure), culture samples were collected from the objects, medical tools and equipment, hands of healthcare staff and a new injection solution in the area where the procedure was performed. R.radiobacter was isolated in 10 of the vitreous fluid samples of 13 patients, and no bacterial growth was detected in 3. The microorganisms were found to be gram-negative bacilli, non-fermenter, motile, catalase/oxidase/urease positive, in compliance with R.radiobacter. All isolates were identified as R.radiobacter by BD Phoenix (Becton Dickinson, USA), Vitek 2 Compact (BioMerieux, France), and Vitek MS (BioMerieux, France) (database v2.0) systems. R.radiobacter isolates were found to be resistant to ampicillin, amoxicillin/clavulanate, trimethoprim/ sulfamethoxazole, cefotaxime and ceftazidime; susceptible to cefuroxime, cefepime, amikacin, gentamicin, imipenem, meropenem, ciprofloxacin, levofloxacin and piperacillin/tazobactam. The isolates were identified as R.radiobacter by 16S rDNA sequence analysis. PFGE showed that all isolates had the same band profile. R.radiobacter isolates with the same band profile likely revealed that the contamination was from the same source. However, the growth of R.radiobacter was not detected in the cultures made from the objects, medical instruments and supplies, the hands of healthcare professionals and the new injection solution in the area where the procedure was performed, and the source of the agent could not be determined. The results have shown that intravitreal injection procedure carries a risk for R.radiobacter infection. Disinfection and antisepsis conditions, before and during the procedure, is important for the prevention of such infections. This study is the first epidemic outbreak report of endophthalmitis caused by the same strain of R.radiobacter and the second article in which R.radiobacter was reported as the cause of endophthalmitis after intravitreal injection.