Abstract
Background
Ochrobactrum anthropi is widely distributed and primarily infects patients with compromised immune functions . Historically, O. anthropi has been considered to possess low toxicity and pathogenicity; however, recent studies suggest that it may in fact cause severe purulent infections. In this case study, we examine a case of O. anthropi infection following corneal transplantation, exploring the occurrence and outcomes of such post-operative infections.
Case presentation
A retrospective analysis of cases involved examinations, genetic testing for diagnosis, and subsequent treatment. In patients undergoing partial penetrating keratoplasty with a fungal corneal ulcer perforation, anterior chamber exudation and purulence were observed post-surgery. Despite antifungal treatment, genetic testing of the anterior chamber fluid and purulent material confirmed O. anthropi infection. The use of antimicrobial treatment specifically targeting O. anthropi was found to be effective in treating the infection.
Conclusion
Inflammatory reactions following corneal transplantation should be should be monitored for the presence of other infections. Genetic testing has significant implications for clinical diagnosis and treatment.
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Introduction
Ochrobactrum anthropi, a conditional pathogenic bacterium, is a Gram-negative rod that exhibits oxidase and catalase production and lacks fermentation capability. It is widely distributed and primarily infects patients with compromised immune functions [1, 2]. Reports also indicate infections in hosts without prior illnesses and with normal immune functions [3, 4]. The clinical presentation of infections caused by O. anthropi is not specific and the bacteria demonstrates robust drug resistance. This poses challenges in clinical diagnosis and treatment [5].
Historically, Ochrobactrum anthropi has been regarded as having low toxicity and pathogenicity. However, it can cause severe purulent infection [6]. Reports exist of post-organ transplantation bacteremia [7], and in ophthalmology, occurrences of intraocular inflammation following cataract surgery [8, 9]. However, cases of O. anthropi infection after corneal transplantation have not been documented. Here, we present a case of O. anthropi infection following corneal transplantation surgery.
Case report
A 51-year-old male patient presented with a 19-day history of redness and pain in the eye. The diagnosis was fungal keratitis (Fig. 1). Treatment included frequent instillation of natamycin eye drops (50mg/ml, North China Pharmaceutical, China) and intermittent application of intracorneal voriconazole injection (1mg/ml, Pfizer Limited, US). Following one month of treatment, examination results indicated that the sign of corneal ulcer healing, with no observable progress. However, there was a concerning sign of corneal perforation. (Fig. 2). B-ultrasound demonstrated the absence of abnormalities in the vitreous and retina. Consequently, a partial penetrating keratoplasty was performed with a favorable outcome. Intraoperatively, aqueous humor samples and the affected corneal tissue were collected for subsequent culture and identification of bacteria and fungi. Voriconazole injection was used throughout the procedure for corneal margin and anterior chamber irrigation. The donor cornea, sourced from our eye bank, and residual donor cornea, along with corneal preservation solution (Corneal Chamber, Alchimial, Italy), were sent for bacterial and fungal culture postoperatively. The postoperative regimen consisted of local administration of natamycin and tacrolimus eye drops (0.1%, Senju Pharmaceutical Co, Japan), as well as levofloxacin eye drops (0.5%, Senju Pharmaceutical Co, Japan). Additionally, itraconazole capsules (200 mg daily, **s with Gram staining. D. Corneal scra**s with potassium hydroxide (KOH) wet mount demonstrate the presence of fungal hyphae
A After treatment, the corneal ulcer has healed, with localized margins and corneal perforation. B No fungal hyphae are observed in corneal scra**s with Gram staining, but inflammatory cells are present
Following corneal transplantation, the graft remained transparent. However, the aqueous humor exhibited gradual turbidity, and by the fourth postoperative day, anterior chamber pus accumulation was observed, prompting concern regarding a potential recurrence of fungal infection. Consequently, the anterior chamber was aspirated to remove the pus, and a voriconazole injection was administered for anterior chamber irrigation and medication. Intraoperatively, it was noted that the anterior chamber pus was thin and watery in consistency, in contrast to the thicker purulent fluid observed in fungal infections. An examination of the anterior chamber pus revealed the absence of fungal hyphae (Fig. 3D). Postoperatively, there was no significant improvement in the anterior chamber reaction, and the cornea exhibited mild edema.
A Following corneal transplantation, there was an accumulation of pus in the anterior chamber of the eye, exhibiting a thin and watery consistency. B Subsequent to treatment, there was a discernible reduction in anterior chamber pus. C The corneal graft appeared grayish-white and opaque, and the anterior chamber pus completely disappeared. D Gram staining of corneal scra**s did not reveal any fungal hyphae, but did indicate the presence of a considerable number of inflammatory cells. E Turbidity was observed in the vitreous cavity, resembling sediment. F The vitreous opacities exhibited a noticeable reduction in comparison to the pre-treatment state
A microbiological examination of the recipient corneal ulcer, aqueous humour, donor cornea, and preservation solution yielded negative results for bacteria and fungi, which is thought to be the consequence of preoperative antifungal and antibacterial treatment. However, given the possibility of other infections occurring postoperatively, aqueous humour and anterior chamber pus from the operated eye were collected for metagenomic next-generation sequencing (mNGS) test. Total genomic DNA was extracted using a nucleic acid extraction kit, then fragmented to 200 bp and used to build a library with end-repaired, adapter-ligation, and polymerase chain reaction amplification. The prepared library was sequenced on the MGISEQ-2000 sequencing platform (MGI, China). The reads were finally aligned to the Microbial Genome Databases, which contain the whole-genome sequences of 8,472 viruses, 10,537 bacteria, 903 fungi and 288 parasites. During the aforementioned interval, the previously administered eye drops were maintained. This was accompanied by an increase in the rate of anterior chamber pus leakage, culminating in the clouding of the corneal graft (Figure 3A). The mNGS results identified O. anthropi, with 321 sequences with a relative abundance of 98.98%. Additionally, a vitreous opacity was revealed through a B-ultrasound examination. (Fig. 3E). To treat O. anthropic, ceftazidime (25 mg/ml), an amikacin (4 mg/ml), and vancomycin (10 mg/ml) were administered to the anterior chamber and vitreous, respectively, three times each. The oral antifungal medication was discontinued, and a cefuroxime injection (1.0 g, administered three times a day) was administered intracamerally. To prevent a recurrence of fungal infection, natamycin eye drops were administered four times daily, in conjunction with tobramycin eye drops (0.3%, Tobramycin Eye Drops, Alcon-Couvreur n. v, Belgium), and levofloxacin eye drops (0.5%, Senju Pharmaceutical Co, Japan) at 1-hour intervals. Following three days of treatment, there was a reduction in anterior chamber pus (see Fig. 3B). After a further ten days of treatment, the anterior chamber pus had been absorbed completely. However, the corneal graft remained cloudy (Fig. 3C), with ultrasound indicating that the vitreous opacities had reduced (Fig. 3F). The patient's condition remained stable, with effective infection control being maintained.
Six months following corneal transplantation, the operated eye exhibited corneal opacities and pseudo-pterygium (Fig. 4A). B-ultrasound examination did not reveal any abnormalities. To enhance visual function, a secondary partial penetrating keratoplasty was conducted concurrently with a cataract removal procedure. Postoperatively, Tobramycin eye drops were administered for the purpose of prophylaxis against infection, in conjunction with Tacrolimus and Prednisolone Acetate Ophthalmic Suspension (1%, Allergan Pharmaceuticals Ireland) for the prevention of rejection. One month following the procedure, the corneal graft was observed to be transparent, with a corrected visual acuity of 0.1 (Fig. 4B).
A Pseudo-pterygium and corneal opacities developed six months after corneal transplantation. B After the second corneal transplantation, the corneal graft became transparent
