Endogenous endophthalmitis caused by bacteria with unusual morphology in direct microscopic examination of the vitreous.

Dear Editor,

Endogenous endophthalmitis is a rare condition in immunocompetent individuals. In this letter, we share our experience of two cases in apparently otherwise healthy individuals with unusual, misleading morphological forms of bacteria in vitreous samples, probably due to previous inadequate treatment. A 45-year-old man (case 1) and a 26-year-old lady (case 2) presented with redness, watering, photophobia, pain and diminution of vision (case 1: left eye, 15 days; case 2: right eye, 3 days). They had been previously treated with topical (chloramphenicol, ofloxacin) and subconjunctival antibiotic (amikacin) and corticosteroids. The presenting visual acuity in the affected eye was hand movement in the first patient and counting finger close to face in the second patient. B-scan showed low to medium reflective echoes in the vitreous cavity in both the cases. All systemic investigations were unremarkable. They were started on systemic and topical corticosteroids and antibiotics (ciprofloxacin). Pars plana vitrectomy with intraocular antibiotics (vancomycin, ceftazidime) and microbiological processing of the vitreous (smear and culture on aerobic and anaerobic media) was done in both. In case 1, the Gram-stained smear revealed gram-positive, thin, beaded, branching filaments and bacilli [Fig. 1a] suggestive of Actinomycetales, which were non-acid-fast (1% H2SO4). Gram stain of the culture [Fig. 1b] resembled Corynebacterium sp. [Fig. 1c]; however, it was identified as Cellulosimicrobium cellulans by API® CORYNE V-3.0 method. The Gram-stained smear of vitreous from case 2 showed gram-variable, thick, long, beaded bacilli with occasional vacuoles resembling spores and were suggestive of Bacillus sp. [Fig. 2a]. Dirty, moist, yellow colonies [Fig. 2b] grown in culture were gram-negative bacilli [Fig. 2c] and were biochemically identified as Escherichia coli. Thus, the initial microscopic examination of the vitreous fluid in both cases was misleading and the culture results were most unexpected. The organisms grew rapidly in ordinary culture media such as blood agar, chocolate agar, brain heart infusion broth and thioglycollate broth. Although the morphology was altered, the organisms remained sensitive to antibiotics tested by Kirby Bauer disk diffusion method. Abnormal forms of bacteria have been observed in clinical specimens including blood, sputum and cerebrospinal fluid of patients on antibiotic therapy.[1-3] This report highlights the observation of unusual morphological forms of bacteria in vitreous samples. We also report the first case of endogenous endophthalmitis caused by C. cellulans. Infections by C. cellulans have been reported in immunocompromised hosts[4] and traumatic endophthalmitis.[5] Post treatment, the final visual acuity was counting fingers at 2.5 m in the first and 20/400 in the second patient.

Figure 1

(a) Gram stain of vitreous of case 1 showing gram-positive, thin, beaded, branching filaments and bacilli under oil immersion magnification ×1000; (b) confluent, yellow, opaque colonies of C. cellulans on blood agar after 48 hours of aerobic incubation at 37°C; (c) Gram-stained culture smear showing beaded, gram-positive bacilli resembling Corynebacterium sp. with occasional branching (×1000)

Figure 2

(a) Gram stain of vitreous of case 2 showing gram-variable, thick, long, beaded bacillus with vacuoles resembling spore under oil immersion ×1000; (b) confluent, dirty yellow, opaque, moist colonies of E. coli on blood agar after 24 hours of aerobic incubation at 37°C; (c) Gram-stained culture smear showing gram negative bacilli (×1000)