Traumatic endophthalmitis caused by Nocardia kruczakiae in a patient with traumatic eye injury

A 5-year-old boy suffered trauma in his left eye (OS) by a palm tree leaflet in October
2009. Two months later, he was diagnosed with traumatic infectious uveitis and intumescent
cataract with anterior capsule rupture. Treatment with systemic and topical vancomycin,
ceftazidime and methylprednisolone began. In January 2010, the patient underwent phacoemulsification
with intraocular lens implantation (IOL). Aqueous humour samples were cultured with
negative results. Every reduction in treatment led to several episodes of anterior
uveitis. Inflammation continued although systemic and topical clarithromycin plus
antimycotic treatment and antiglaucoma eye drops were prescribed.

The patient was admitted to our centre (Centre Oftalmología Barraquer) in July 2010. He was being treated with topical dexamethasone, atropine, ciprofloxacin,
voriconazole and antiglaucoma eye drops: oral acetazolamide, deflazacort, fluconazole,
omeprazole and calcium carbonate/colecalciferol. Visual acuity (VA) was 0.95 in the
right eye and 0.1 in the OS. Examination revealed yellowish nodules above the iris
and IOL (Fig. 1). Ultrasounds only revealed a slight inflammatory reaction. The patient’s medical
history was unremarkable. Anterior vitrectomy and IOL and capsular bag removal were
performed, adding intraocular vancomycin and ceftazidime injection. The latter treatment
was continued and oral clarithromycin restarted. Now, the aqueous humour culture showed
an aerobic gram-positive bacillus compatible with Actinomycetes. Antimycotic treatment
was stopped, and topical polymyxin B plus trimethoprim and oral trimethoprim/sulphamethoxazole
were therefore provided. Two weeks after vitrectomy, the patient showed reduction
of inflammation, but retinal detachment with macular involvement was diagnosed. Scleral
buckling, endophoto-coagulation and pneumatic retinopexy were performed.

Fig. 1. Left eye N. krckzakiae endophthalmitis. The slit lamp examination shows yellowish
nodules in anterior chamber above iris and intraocular lens

The Actinomycetes was further identified and antimicrobial susceptibility tested 1]. The 16S RNA, 65-kDa heat-shock protein (hsp65), ?-subunit type II DNA topoisomerase (gyrB) and RNA polymerase subunit ? (rpoB) genes were examined 2]–4]. Sequences were compared with those in the GenBank (http://www.ncbi.nlm.nih.gov/BLAST) and Bacteria Identification Bioinformatics (BIBI) databases (http://umr5558-sud-str1.univ-lyon1.fr/lebibi/lebibi.cgi). Similarities of ?99.0 % were deemed to denote the same species.

In terms of 16S, the bacterium was most similar (99.0 %) to Nocardia nova IFM 0272. Similarity with N. nova DSM 44481 and DSM 43207 5] was lower at 98.7 %. Ninety-eight percent similarity was detected with the sequences
for Nocardia africana, Nocardia aobensis, Nocardia cerradoensis, Nocardia kruczakiae and Nocardia veterana. The hsp65 gene showed 99 % similarity with respect to those of N. aobensis DSM 44805, N. nova DSM 44481, N. veterana NRRL B-24136 and N. kruczakiae DSM 44877 5].

The gyrB gene was most similar (99 %) to that of N. kruczakiae W9710/DSM 44877, N. aobensis DSM 44805 and N. cerradoensis W8368 3]. Among four detected polymorphisms (N. kruczakiae DSM 44877 numbering), one produces the replacement Trp(TGG)???Cys(TGC). A fully matching
rpoB sequence was obtained with N. kruczakiae DSM 44877. Similarity fell to 99 % with respect to N. aobensis DSM 44805 and N. cerradoensis DSM 44546 and to 98 % with respect to N. nova OAHPP13857-1633 5]. The studied bacterium, CNM997/10, was therefore identified as N. kruczakiae. The sequences were deposited in GenBank under accession numbers JX443642–JX443645.

Ocular inflammation resolved after 2 months with specific treatment. Two months after
retinal surgery, the patient underwent iris reconstruction, secondary IOL fixation
and Ahmed valve implantation. VA improved to 0.2. Three years after treatment discontinuation,
no inflammation was observed.

Discussion

Ocular infections caused by Nocardia species previously unknown in immunocompetent patients have recently been reported
6], 7]. The cornea and anterior chamber of the eye are immune-privileged tissues; this may
explain the appearance of ocular infections or surgically related endophthalmitis
in such patients 6], 8].

This report describes an immunocompetent child who suffered ocular trauma by a palm
tree leaflet inoculating N. kruczakiae. Nocardial infection should be considered in patients with such plant-inflicted trauma
since 31–67 % of postoperative nocardial endophthalmitis have occurred in those living
in rural areas 6], 9]. Initial management with rounds of corticosteroids probably encouraged chronic infection.
Long corticosteroid treatment predisposes patients to nocardial endophthalmitis 9]. A large proportion of patients (75–83 %) show nodules on the corneal endothelium
or on the iris; however, the posterior segment is usually normal or only slightly
involved 6], 9]. Surgical procedures are frequently used to eradicate nocardial endophthalmitis.
The outcome of nocardial endophthalmitis can be poor due to its delayed presentation
and extensive involvement of the anterior chamber. The present patient showed an improvement
to a VA of 0.2 OS from 0.1, despite late diagnosis and the retinal detachment that
occurred after IOL removal.

N. kruczakiae is difficult to distinguish from N. africana, N. nova and N. veterana by phenotyping 2] but can be identified by molecular technique even when the samples available are
very small and patients have undergone treatment with antibiotics 7], 10]. 16S analysis commonly provides a definitive identification, but certain closely
related species cannot be differentiated, a consequence of the low level of interspecies
polymorphism and the existence of multiple and different copies of 16S in N. nova11], 2]. Indeed, several species, such as N. africana, N. aobensis, N. cerradoensis, N. nova, N. kruczakiae and N. veterana, cluster together even when examined by multilocus sequence typing 5].

The rpoB and gyrB genes are known to show greater diversity than 16S and hsp65 and therefore allow for more precise identification 5]. Those of the causal agent were found similar (100 and 99.3 %, respectively) to those
of the N. kruczakiae DSM 44877, confirming that it belonged to this specie.

N. kruczakiae CNM997/10 also showed the same susceptibility profile to that first described for
N. kruczakiae ATCC BAA-280 2], except for ampicillin (Table 1). Treatment with amikacin, clarithromycin, imipenem, linezolid and trimethoprim/sulphamethoxazole
would therefore appear appropriate.

Table 1. Antimicrobial susceptibility of N. kruczakiae CNM997/10, the causal agent of endophthalmitis in the present patient

The suggested empirical treatment for severe ocular bacterial infections is topical
and intravitreal vancomycin and ceftazidime 12]. Unfortunately, this led to the recurrence of iris nodules in this patient. His endophthalmitis
was finally brought under control after surgical removal of the lens-bag complex with
associated inflammatory materials, which allowed the detection of N. kruczakiae. Specific treatment for 8 weeks resolved the condition.

N. kruczakiae, previously described as a causal agent of pneumonia 2], is reported here as the causal agent of ocular endophthalmitis. Ophthalmologists
should be aware of infections caused by Nocardia and suspect nocardial endophthalmitis after plant-inflicted trauma.