Infective Endophthalmitis Caused by Bacillus cereus after Cataract Extraction Surgery
- 1Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin
- 2Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Hong Kong Eye Hospital, Kowloon, Hong Kong, People's Republic of China
- Reprints or correspondence: Dr. Wai-Man Chan, Dept. of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, 3/F, Hong Kong Eye Hospital, 147K Argyle St., Kowloon, Hong Kong (cwm6373{at}netvigator.com).
Abstract
We describe a 72-year-old Chinese man who developed fulminant Bacillus cereus endophthalmitis 36 h after an uneventful surgery for cataract extraction. Clinical progression of disease was extremely rapid, in spite of early vitrectomy and intravitreal injection of antibiotics. Results of Gram staining showed gram-positive bacilli, and the culture was positive for B. cereus. Endophthalmitis is rare after cataract surgery (cumulative probability within 1 year, ∼0.08%), and cases caused by B. cereus are even less common. The prognosis and plan of treatment are discussed.
Bacillus cereus is a ubiquitous, gram-positive, endospore-forming rod. Occasionally, it can cause wound infection, gastrointestinal infection, pneumonia, meningitis, or septicemia [1–3]. Intraocular infections caused by B. cereus are very rare, and most cases are related to trauma [4–7]. In several case series, vision outcomes were uniformly poor, with 75%–91% of patients experiencing a loss of light perception, eyeball evisceration, or enucleation [4, 5, 7]. We found only 2 culture-confirmed cases of postoperative B. cereus endophthalmitis in the English-language literature [6, 8, 9]. Here, we describe an elderly Chinese man who developed relentlessly progressive B. cereus endophthalmitis shortly after surgery for cataract extraction.
Case report. A 72-year-old Chinese man with an unremarkable medical history underwent an uneventful cataract extraction surgery on his left eye, which consisted of small corneal wound phacoemulsification and posterior capsule intraocular lens implantation in January 2002. The ocular examination at the first scheduled visit on the day after surgery was unremarkable. However, later that same evening, he developed escalating ocular pain, redness, thick yellowish discharge, and markedly reduced visual acuity and presented to the Casualty Department of the Prince of Wales Hospital ∼36 h after the cataract operation. Ocular examination of his left eye revealed a decrease in visual acuity to light perception only. He had diffuse eyelid swelling, conjunctival chemosis with intact corneal wound, marked anterior chamber reactions (including hypopyon and fibrin), and a hazy fundal view (figure 1). Ocular ultrasonography demonstrated generalized increases in the echogenecity of the vitreous cavity. The right eye was normal. The patient denied any history of ocular injury and did not have any features of systemic infection.
Figure 1
Photograph of the external surface of the patient's left eye at presentation, ∼36 h after an uneventful cataract surgery, showing severe conjunctival chemosis, subconjunctival hemorrhage, and corneal edema.
The patient was treated for acute postoperative infective endophthalmitis. Emergency vitreal biopsy and vitrectomy were performed, followed by intravitreal injection of 1 mg of vancomycin and 2 mg of cefuroxime [13, 14]. Hourly treatment with fortified topical antibiotics, including tobramycin (14 mg/mL) and cefuroxime (50 mg/mL), was begun. Examination of the vitreous sample showed gram-positive rods; neither mixed flora nor fungal hyphae could be seen. On the second day of infection, gram-positive rods grew on a culture of the initial vitreous biopsy specimen; these were suspected to be Bacillus species. Accordingly, topical fortified vancomycin (50 mg/mL) was substituted for tobramycin. On the fifth day of infection, heavy growth of B. cereus on the vitreous culture was seen. This organism was found to be sensitive to vancomycin.
In spite of the aggressive treatments, there was increasing opacification and thinning of the cornea associated with features of impending perforation (figure 2). After a thorough discussion with the patient and his family, evisceration was chosen and was performed on day 7 of infection. Histopathological examination of the left eye's eviscerated contents showed acute suppurative inflammation, and no further bacterial growth was seen on culture.
Figure 2
Photograph of the external surface of the patient's left eye 7 days after presentation, showing thinning and opacification of the cornea, with features of impending perforation, in spite of aggressive treatment with antibiotics.
To search for possible sources of contamination, the patient's postdischarge history was explored. Because there were no symptoms and signs of possible food poisoning or other foci of infection and because the patient denied that any obvious or gross soiling or contamination of the ocular wound by external agents had occurred, the chance that infection occurred by these routes was remote. Microbiologic samples were obtained from the autoclave oven and instruments. No infecting organism, however, could be identified by either culture or PCR.
Discussion. Cases of B. cereus endophthalmitis generally are trauma related, and the involved eyes typically have poor vision outcomes [4–7]. A large proportion of patients (75%–91%) experience a loss of light perception, phthisis bulbi, evisceration, or enucleation [5, 7].
The cumulative probability of developing infective endophthalmitis within 1 year after cataract extraction has been estimated to be ∼0.08% [10]. Most cases of infective endophthalmitis were caused by gram-positive, coagulase-negative micrococci (70.0%), Staphylococcus aureus (9.9%), Streptococcus species (9.0%), and Enterococcus species (2.2%), as determined by the Endophthalmitis Vitrectomy Study (EVS) [11]. Bacillus species of all kinds as a cause of postoperative endophthalmitis has been reported only rarely (2 cases in 1918, 4 cases in 1981, 14 cases in 1996, and 5 cases in 1999) [6, 8, 9]. Compared with cases of endophthalmitis caused by trauma, postoperative endophthalmitis cause by Bacillus species other than by B. cereus did have a better vision outcome. Roy et al. [6] reported the largest case series of Bacillus endophthalmitis related to cataract extraction; 14 eyes were infected as a result of intraocular use of bacteria-contaminated viscoelastic material during the procedure. Only 7% of the infected eyes experienced a loss of light perception, and the authors concluded that cases of postoperative Bacillus endophthalmitis have a better prognosis than do cases of endophthalmitis caused by trauma, provided that vitrectomy is performed early. Most of the organisms grown in that series and in the others, however, were less-virulent Bacillus species, such as Bacillus circulans, Bacillus brevis, or Bacillus subtilis [6, 8, 12].
In our case, the organism grown was B. cereus, which is known to be the most virulent of the Bacillus species because of its unique exotoxins, including β-lactase and hemolysin BL (comprises a binding component, B, and 2 lytic components, L1 and L2), which are especially detrimental to ocular tissue [7, 13–15]. B. cereus rarely is the cause of the postoperative form of infective endophalmitis, and, to the best of our knowledge, only 2 culture-confirmed cases have been reported in the English-language literature [6, 8, 9].
In experimental animal models of induced B. cereus endophthalmitis, its destructive pathogenicity was clearly demonstrated histologically by the massive destruction of the corpus vitreous and rapid retinal necrosis [13–15]. The intraocular virulence of B. cereus is caused mainly by its secretion of exotoxins (tripartite hemolysin BL, phosphatidylcholine-preferring phospholipase C, and collagenase), the exuberant inflammatory response triggered by the potently immunogenic bacterial cell-wall components (peptidoglycan and teichoic acid), and the rapid intraocular migration of the organisms [13–15].
In the patient we describe here, disease activity followed the typical pathway of traumatic B. cereus endophthalmitis. The patient's condition deteriorated rapidly within 36 h after an uncomplicated cataract operation. Because his level of visual acuity at presentation was light perception only, vitreous biopsy, vitrectomy, and intravitreal injection of antibiotics, followed by fortified topical antibiotics, were adopted as the emergency treatment, in accordance with the recommendations of the EVS [11]. In spite of these aggressive treatment strategies, the disease continued to progress rapidly, and evisceration had to be performed to prevent corneal perforation.
The main factors determining the vision outcome in endophthalmitis include virulence, the inoculum size of the infecting organisms, and, most important, the time lapse between onset of symptoms, diagnosis, and institution of appropriate treatment [16]. Ophthalmic surgeons have no control of the first 2 factors; therefore, timely treatment once the diagnosis is established is the only key to success [5, 6, 16]. Bacillus species, B. cereus in particular, are known to be deleterious to ocular tissue because of their virulence, which has been clearly demonstrated in vitro [13–15]. The introduction of early vitrectomy may help reduce the infective bacterial dose and the associated exotoxin inside the vitreal cavity [6]. In the largest case series on postoperative Bacillus endophthalmitis, Roy et al. [6] postulated that the good vision outcome observed (1 case of phthisis bulbi among 14 cases of endophthalmitis) in postoperative Bacillus endophthalmitis may be attributed to early vitrectomy, irrespective of EVS recommendations. One of their major arguments is that the applicability of the EVS recommendations in these circumstances may be significantly hindered, because only 1 of the 323 the microbiologic isolates used in the EVS was B. cereus [12].
In the treatment of our patient, the early vitrectomy did not avert the ultimate poor vision outcome. Why did early vitrectomy fail in this case? There may be several possible explanations. First, the observation of Roy et al. [6] was based solely on more-benign Bacillus species, such as B. circulans and B. brevis, instead of the more-virulent B. cereus [6, 13–15]. Second, in experimental B. cereus endophthalmitis, a significant inflammatory response as early as 6 h after infection has been observed in the presence of small initial numbers of organisms [13]. In other words, an early vitrectomy may effectively decrease the inflammatory reaction by removing the infectious load, provided that it is performed within some critical time threshold. This intervention window is extremely narrow for B. cereus; in addition, there may be irreversible and progressive intraocular damage, as observed in our patient.
In conclusion, B. cereus endophthalmitis after cataract extraction is a difficult intraocular infection to treat. Time is the key factor for success, and the importance of the patient's awareness of and the clinician's alertness to symptoms have to be emphasized [5, 6, 16]. It seems that a prompt recognition of the condition and early vitrectomy and administration of antibiotics is the only way to salvage eye function in patients with acute, progressive Bacillus endophthalmitis. Demonstration of gram-positive bacilli in smears of samples from vitreous tapping may serve as a strong indication for prompt vitrectomy, because a high positive rate of 84% and a good correlation with culture have been demonstrated in a previous study. Adjunctive measures, such as intravitreal corticosteroid and ciprofloxacin therapy, are controversial and need to be tested further [17–19].
- Received January 22, 2003.
- Revision received March 25, 2003.
- © 2003 by the Infectious Diseases Society of America
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