INTRODUCTION
Actinomycosis is a chronic infection caused by Gram-positive, facultative anaerobic bacteria from the genus Actinomyces [1]. Actinomyces has also been reported as a causative agent of such ophthalmic infections as endophthalmitis, keratitis, and canaliculitis [2]. It was reported that Actinomyces israelii is responsible for 13%-25% of the cases of chronic lacrimal canaliculitis [3].
The severity of anaerobic ophthalmic infections can range from self-limiting to sight-threatening blindness. The emerging trend of antibiotic resistance further contributes to the development of this infection into a more dangerous and serious health threat in the future [4]. Here, we present three cases of an eye infection caused by the Actinomyces species.
MATERIALS AND METHODS
All patients participated in the study signed an informed consent. The aspirates from the eye lesions of patients with chronic and recurring ophthalmic infections were sent to a microbiology laboratory in Robertson’s Cooked Meat (RCM) media for the identification of the anaerobic culture and analysis of its sensitivity to antibiotics. The RCM was incubated for 48 h and then Gram staining was performed. Then, the blood agar plates were inoculated with the substructure from RCM in a triplicate manner – one plate was incubated at aerobic conditions for 24 h, another plate – in atmosphere containing 5%-10% CO2 for 24 h, and the third plate – at anaerobic conditions (sealed with parafilm) for 72 h in a Gas Pack Jar at 37°C (Fig. 1). The growth of bacteria in anaerobic conditions was confirmed by a VITEK® 2 test. The antibiotic sensitivity tests were performed using the Epsilometer strips (E-test) [5, 6, 7].
RESULTS
Participants
Case 1
In July 2021, a 45-year-old female patient visited the eye outpatient department (OPD) with complaints of severe itching, burning sensation, watering, and pain in the left eye lasting for six months. This patient has no diagnosed comorbidities other than hypertension for the past year. On examination, a small white lesion was found in the medial canthus of the left eye (Fig. 2). The vision was 20/20 in both eyes, with all other ophthalmic parameters being normal. The right eye was normal; no complaints were noted at all from the patient. The pus from the lesion of the left eye was aspirated after local anesthesia under sterile conditions. Then, the testing of the pus sample in order to check for the presence of anaerobic bacteria and their sensitivity to antibiotics has been suggested. To do this, an aspirate taken from the lesion was sent to a microbiological laboratory for analysis.
Case 2
The same patient as in the first case came again to the eye OPD after 30 days since the treatment of the first Actinomyces infection with the same complaints as during the first visit. The examination revealed one new lesion in the medial canthus of the same left eye. The analogous tests were performed as during the first visit.
Case 3
In September 2021, a 52-year-old female patient complained of ocular hypertension with pain and burning for 4.5 months in the left eye. She had diabetes for the past 4 years and had been taking anti-diabetic drugs (her sugar was under control). Visual acuity test showed a 20/20 score. The external examination revealed mild redness in the left eye and a grayish to white color lesion with a white pinhead in the lacrimal sac. An aspirate from the lesion was sent to a microbiology laboratory for analysis.
Both patients recovered after the treatment with Moxifloxacin eye drops three times a day for 10 days.
Microbiological analysis of the obtained samples
The plates inoculated with aspirates collected from the eyes of the patients were incubated at different conditions. The plates incubated under aerobic conditions for 24 h showed no culture growth in all three cases. On the contrary, plates incubated in a CO2 atmosphere for 24 h showed bacterial growth (Fig. 3A). The colonies growing at anaerobic conditions in a Gas Pack Jar were gray in color, 2-3 mm in size, low convex, flat with irregular margin, and non-hemolytic. Thin filamentous bacilli showed a positive result in Gram stain procedure (Fig. 3B). The anaerobic growth was confirmed by VITEK® 2. The isolated bacteria were identified as Actinomyces israelii (Case 1), Actinomyces odontolyticus (Case 2), and Actinomyces meyeri (Case 3).
According to the antibiotic susceptibility tests, all three species of Actinomyces showed sensitivity to Vancomycin, Moxifloxacin, and Imipenem but resistance to Metronidazole. The results are summarized in Table 1.
| Antibiotic | Minimum inhibitory concentration (MIC) | ||
|---|---|---|---|
|
A. israelii
Case 1 |
A. odontolyticus
Case 2 |
A. meyeri
Case 3 | |
| Penicillin | 0.2 μg/ml (S) | >256 μg/ml (R) | >256 μg/ml (R) |
| Ampicillin | 0.25 μg/ml (S) | >256 μg/ml (R) | 0.25 μg/ml (S) |
| Vancomycin | 1.5 μg/ml (S) | 1.5 μg/ml (S) | 1.25 μg/ml (S) |
| Moxifloxacin | 2 μg/ml (S) | 2 μg/ml (S) | 2 μg/ml (S) |
| Tetracycline | 8 μg/ml (S) | >256 μg/ml (R) | >256 μg/ml (R) |
| Imipenem | 0.5 μg/ml (S) | 2 μg/ml (S) | 3 μg/ml (S) |
| Metronidazole | >256 μg/ml (R) | >256 μg/ml (R) | >256 μg/ml (R) |
S – sensitive, R – resistant
DISCUSSION
Ocular infections caused by Actinomyces species are uncommon. Unilateral chronic conjunctivitis is usually caused by Actinomyces which might be associated with canaliculitis [8]. In the above-mentioned case series, we have isolated three species of Actinomyces, namely A. israelii and A. odontolyticus from the first patient and A. meyeri from the second one. Anaerobic bacteria like Actinomyces species have been reported as a causative organism in cases of canaliculitis. Propionibacterium acnes have been isolated from the lacrimal gland in 29 out of 55 healthy and diseased eyes, which show an anaerobic environment in eye, whereas Actinomyces meyeri has been reported as a causative organism of canaliculitis [9,10,11]. Actinomyces species have been commonly reported in cases of canaliculitis [12]. In addition, Actinomyces species has been associated with other ophthalmic infections, such as keratitis, dacryocystitis, conjunctivitis, and post operative endophthalmitis. Usually, no generalized systemic invasion is observed in these cases [13]. An incidence of bilateral blepharoconjunctivitis in the absence of canaliculitis due to Actinomyces species have been reported [14]. Nair et al. [15] also reported Actinomyces canaliculitis complicating congenital nasolacrimal duct obstruction in an infant showing the diversity of population amenable to this disease. An ocular actinomycosis mimicking meningioma caused by Actinomyces species in a 67-year-old female patient was described by Kobayashi et al. [1]. The case of chronic lacrimal canaliculitis caused by A. israelii in a 70-year-old retired male patient was described by Mohanty et al. [16]. Bhole et al. [17] described a case of keratoactinomycosis in a 50-year-old female farmer caused by Actinomyces species after vegetative trauma. The case of Actinomycotic lacrimal canaliculitis was described in a 60-year-old male patient [18]. Hickman et al. [19] also presented a case of lacrimal canaliculitis with bleeding from the eye caused by the Actinomyces species. The above-mentioned studies prove the significant role of Actinomyces species as a causative agent of ocular infections worldwide. To the best of our knowledge, there have been no reports published on cases with the infections caused by Actinomyces israelii and Actinomyces odontolyticus in the same patient in a 30-day gap. All of the above studies showed that the different species of Actinomyces cause ophthalmic infection in a broad diversity of patients.
CONCLUSION
Anaerobic bacteria should be considered as a possible causative agent of every chronic ocular infection, and the corresponding laboratory tests should be performed. Since we found the resistance to Metronidazole in all three reported here cases, antibiotic susceptibility tests should always be performed before any antibiotic treatment. Proper susceptibility testing before the treatment decreases the chance of the development of an antibiotic resistance pattern.