Postkeratoplasty Keratitis Caused by Abiotrophia defectiva: An Unusual Cause of Graft Infection.

Abiotrophia defectiva is a nutritional variant of Streptococci. We describe a case of microbial keratitis due to A. defectiva in a patient who had undergone penetrating keratoplasty and was on corticosteroid therapy for recent graft rejection. Isolation of this organism confirmed this to be an opportunistic infection.

INTRODUCTION

To report Abiotrophia defectiva as the etiological agent in the case of graft infection isolated using the VITEK-2 (BioMerieux SA, France) compact system.

CASE REPORT

A 77-year-old patient presented for a follow-up for his ongoing ocular condition. Past ocular history was significant for a known diagnosis of bilateral lattice stromal corneal dystrophy, left eye more severe than the right eye, with his first visit to our center 10 years ago. There was positive family history of a similar condition in his mother and younger brother. He had undergone multiple surgeries: Phototherapeutic keratectomy, followed by cataract surgery with intraocular lens implantation in the right eye 9 years ago and a penetrating keratoplasty combined with cataract surgery and posterior chamber intraocular lens implantation in the left eye 8 years ago. He was on regular follow-up and had a best-corrected visual acuity of 20/60 in the right eye (with residual lattice dystrophic opacities) and 20/20 in the left eye until 6 months prior to his last presentation. A month prior presentation, the patient presented with a significant reduction in vision and was diagnosed with acute allograft rejection, which was treated with intensive corticosteroid therapy. However, the graft failed to recover.

At the time of presentation, the patient complained of sudden pain and redness lasting 1-week. The patient was still using prednisolone acetate 1% eye drops once a day. Best-corrected visual acuity was 20/80 in the right eye and counting fingers at 2 m in the left eye. Examination of his left eye indicated the corneal graft was in place, with an oval, well-defined epithelial defect measuring 3 mm in diameter with an underlying stromal infiltrate and 25% thinning, located at the periphery of the graft at the 9’o clock position. The surrounding cornea showed grade 3 stromal edema. Corneal Scrapping were performed for laboratory assessment (see below). Based on microbiology results of the corneal scrapings, treatment was initiated with fortified topical cefazolin 1% and topical ciprofloxacin 0.3% every hour, along with topical atropine sulfate 1% 3 times a day. At follow-up 3 weeks later, the infiltrate resolved with scarring. Final visual outcome was 20/400, the graft remained edematous due to the secondary graft failure following allograft rejection [Figure 1].

Figure 1

Slit lamp photograph of the left eye showing area of corneal scar at the graft-host junction (arrow) corresponding to the resolved infiltrate

Microbiological studies

After instilling 0.5% topical proparacaine, corneal scrapping were collected using a number 15 sterile blade. Corneal scrapings were processed based on our institute's microbiology protocol. The scrapping were first transferred on slides for 10% potassium hydroxide (KOH) with calcoflour white white (CFW) preparation, gram and giemsa staining as well as inoculation in the following enriched media: Chocolate agar, blood agar, broth including brain heart infusion broth, thioglycolate broth and for fungal isolation media including, Sabroud's dextrose agar and potato dextrose agar. Gram's stain showed the presence of polymorphs 0–2/oil immersion field (OIF), epithelial cells 0–2/OIF and Gram-positive cocci (GPC) in pairs and chains 0-plenty/OIF [Figure 2a]. Giemsa stain showed the presence of polymorphs 0–2/OIF, cocci in pairs and chains 0-plenty/OIF. KOH + CFW was negative. Small translucent colonies were noted on blood agar with β-hemolysis after 24 h [Figure 2b]. Culture smear revealed GPC in chains. The organism was catalase negative and optochin resistant. For the identification of the organism, the culture was subjected to the VITEK-2 compact system (BioMerieux SA, France). The organism was identified as A. defectiva with a record of excellent identification with 99.9% probability. Antibiotic drug sensitivity using Kirby-Baeur disc diffusion showed sensitivity to amikacin, cefazolin, ofloxacin, cefuroxime, gentamicin, vancomycin, gatifloxacin, moxifloxacin, ciprofloxacin and chloramphenicol.

Figure 2

(a) Direct smear shows the presence of Gram-positive cocci in corneal scrapping. (b) Translucent colonies were noted on blood agar with β-haemolysis

DISCUSSION

Abiotrophia (which means “life nutrition deficiency”) is the nutritional variant of Streptococci. It is part of the normal flora of the oral cavity, the urogenital and intestinal tracts, but is not normally found in the conjunctival flora.1 In humans, it has been reported to cause serious infections, including endocarditis,2 brain abscesses,3 septic arthritis,4 and bacteremia.5

This organism has rarely been implicated as a cause of ocular infections and has been previously reported in cases of endophthalmitis and keratitis.678 Keay et al. were the first to report the association of this organism with infiltrative keratitis associated with extended wear with hydrogel lenses.9 Rudolph et al. described Abitrophia in keratitis cases.10 A study from France reported A. defectiva as the cause of infectious crystalline keratopathy.11 In most cases, the infection responded to vancomycin, and the final visual outcome was reasonably good.11 With improvement in microbiological techniques including the application of the VITEK-2 Compact system, rare organisms, which may have been missed earlier can now be identified. The VITEK-2 compact system is used for identifying the organisms. It is an automated platform, and the identification is rapid and accurate. This system detects growth of the bacteria based on the metabolic changes and is based on fluorescence technology. It accurately identifies the organisms up to the species level and a good level discrimination between species.1213

The current report shows that the clinical presentation of A. defectiva was similar to graft infections due to other GPC, such as Streptococcus or Staphylococcus sp. with hallmark features of well-circumscribed infiltrate and intense inflammatory reaction. It was noted that the organism was sensitive to most of the commonly used antibiotics and was associated with a good outcome in the present case. It is possible that this organism has been under-reported as it may not be identified by other techniques and may have been grouped with other GPC-related infections. The clinical presentation does not help in differentiating this entity. The use of enriched media for culture and isolation, application of VITEK-2 compact system (BioMerieux SA, France), lead to the detection of rare, fastidious organism.