A case report of bacterial canaliculitis caused by Ottowia massiliensis Sp.nov

Abstract

Background

Ottowia massiliensis sp.nov. is a slow-growing and Gram-stain-negative bacillus, first isolated from the stool sample of a healthy volunteer. Due to its slow growth and challenging cultivation, it is easily overlooked in clinical microbiology laboratories. This case report is the first case of its pathogenicity.

Case presentation

This case report describes a case of canaliculitis caused by Ottowia massiliensis sp.nov. The patient, an 80-year-old woman, presented with bilateral epiphora and discharge lasting for 4 years, which worsened with redness and swelling over the past week. Microbial culture of the lacrimal duct secretion after 72 h on Columbia blood agar showed small colonies. MALDI-TOF MS did not yield accurate results, but 16 S rDNA sequencing identified the bacterium as Ottowia massiliensis sp.nov. (LT960589.1). Antimicrobial sensitivity tests showed high activity against most ophthalmic drugs.

Conclusions

In the case described here, we discuss the diagnosis and treatment strategies for eye infections caused by Ottowia massiliensis sp.nov., laying the foundation for improving clinical and laboratory awareness of this bacterium.

Background

The genus Ottowia was first described in 2004, and to date, nine species have been identified. The related literature mainly studies their biological characteristics, phylogenetics and taxono-genomics. There have been no cases of disease caused by Ottowia massiliensis sp.nov. reported until now. Canaliculitis is an inflammation of the proximal lacrimal drainage system, commonly seen in middle-aged and elderly women. Typical symptoms include redness, mucopurulent discharge, medial canthal swelling, epiphora, and punctal eversion [1]. The most common causative organisms are Staphylococcus, Streptococcus, and Actinomyces [2]. Current treatments include systemic and topical antibiotics, with systemic therapy using cefaclor or amoxicillin, and topical treatment with levofloxacin, tobramycin, or fluorometholone [3].We introduced a case of bacterial canaliculitis caused by this infection, explaining the rare isolation of this bacterium due to its slow growth and difficult identification. Therefore, clinical microbiology laboratories should enhance their understanding of this type of bacterium to avoid misdiagnosis or missed diagnosis.

Case presentation

An 80-year-old female patient with no underlying conditions presented with a four-year history of bilateral epiphora with discharge, worsening over the past week with increased redness and swelling. Examination revealed conjunctival hyperemia in both eyes, medial eyelid swelling, and abundant ocular discharge. Expression of the eyelids produced sebaceous secretion from the meibomian gland orifices, while pressure on the canaliculus and puncta resulted in purulent discharge. The cornea was clear, and the lens was cloudy.

Before performing lacrimal irrigation, use a lacrimal swab to wipe away the pus discharged from the pressed lacrimal canaliculus and lacrimal punctum and was cultured on blood agar and chocolate agar plates, incubated in 5% CO₂ and atmospheric pressure at 35 °C. After 72 h under atmospheric pressure, small colonies were observed on Columbia blood agar. After 5 days, the colonies spread over the agar surface, semi-transparent, grey, smooth, and sized 0.2–1.0 mm. After 10 days of incubation, colonies varied in size, were grey-white, semi-transparent, smooth, with no hemolysis or distinctive odor observed. Gram staining revealed Gram-stain-negative rods of variable length (1.50–2.50 μm), slightly curved, and diverse arrangements(Fig. 1). MALDI-TOF MS (Rapid Microbial Identification Mass Spectrum System) indicated Enterobacteriaceae bacteria with good quality spectral peaks, but it did not reach the species identification level. Anaerobic culture, fungal culture, amoeba culture, and viral PCR (HSV-1, HSV-2, VZV, CMV, EB, ADV) were all negative. Due to significant differences between the colony morphology, microscopic examination, and typical Enterobacteriaceae bacteria, 16 S rDNA sequencing was performed. Primers used were 27 F (5’-AGAGTTTGATCCTGGCTCAG-3’) and 1429R (5’-GGTTACCTTGTTACGACTT-3’) for PCR amplification, with a fragment length of 1400 bp. The PCR mix included 2×TsingKE Master Mix 12.5µL, forward primer (10µmol·L-1) 1.0µL, reverse primer (10µmol·L-1) 1.0µL, DNA template 5µL, and ddH2O 5.5µL, with a program set at 94 °C for 3 min, followed by 35 cycles of 94 °C for 1 min, 60 °C for 1 min, 72 °C for 1 min, and a final extension at 72 °C for 10 min, then preserved at 4 °C. The product was sent to Shanghai Sangon Biotech for sequencing. Sequence comparison with the NCBI database showed 99% similarity with Genbank entry LT960589.1, indicating the bacterium as Ottowia massiliensis sp.nov.

Antimicrobial sensitivity testing was performed using the Kirby-Bauer disk diffusion method on blood agar plates. After 7 days, inhibition zone diameters indicated susceptibility to ceftazidime, ceftriaxone, cefuroxime, gentamicin, tobramycin, amikacin, levofloxacin, gatifloxacin, and moxifloxacin. The patient was empirically treated with 0.488% levofloxacin eye drops three times daily and 1% pranoprofen eye drops four times daily. Bilateral canalicular irrigation was performed after lacrimal secretion scraping. One month later, follow-up examination showed no epiphora or purulent discharge on lacrimal sac compression. The puncta and canaliculus remained free of exudate, and the skin over the lacrimal sac area was intact without tenderness.

Discussion and conclusion

Bacterial canaliculitis can be misdiagnosed due to clinical similarities with conjunctivitis, marginal meibomian gland cysts, and dacryocystitis, leading to delayed treatment and adverse outcomes [4]. Therefore, early diagnosis and accurate microbial identification are crucial. This study represents the first report of an Ottowia species causing an eye infection and provides insights into its antimicrobial susceptibility, which may aid clinicians and laboratory personnel in recognizing and effectively treating similar cases to prevent severe complications.

Ottowia massiliensis sp.nov. belongs to the bacterial kingdom, phylum Proteobacteria, class Gammaproteobacteria, order Sphingomonadales, family Sphingomonadaceae, genus Ottowia. Currently, nine species have been identified, among which Ottowia massiliensis sp.nov. was first isolated from the feces of a healthy individual in August 2022 [5]. According to the LPNS (List of Prokaryotic names with Standing in Nomenclature), bacteria of the genus Ottowia primarily originate from aquatic environments, such as sewage treatment plants, contaminated waters, and the intestines of aquatic animals [6]. Literature indicates that the bacterium is Gram-negative, non-motile, aerobic or facultatively anaerobic, with both catalase and oxidase tests negative, and colonies on blood agar measuring 0.2–1.0 mm in diameter. This isolate grew only in an atmospheric environment on Columbia blood agar and did not grow in 5% CO₂ or anaerobic conditions, suggesting that the Ottowia genus has specific cultural requirements.

To date, there has been relatively little research on the pathogenicity of Ottowia genus bacteria. This case is the first reported instance of chronic canaliculitis caused by this bacterium, notable for its persistence without cure in a patient with normal immune function and without evidence of mixed bacterial infection in the lacrimal secretion, which distinguishes it from common bacterial canaliculitis that typically shows a symbiosis of multiple bacteria. Literature suggests that 70% of canaliculitis cases require surgical intervention, but this patient showed significant improvement with topical treatment alone, avoiding surgery [7]. Due to the slow growth of this bacterium and its absence in mass spectrometry databases, identification becomes difficult, making its diagnosis challenging for clinical microbiology laboratories. Our study provides the first antimicrobial susceptibility data for this organism, offering a foundation for future research into Ottowia infections.

Fig. 1

Ottowia massiliensis sp.nov.colony morphology and bacterial smear (a):After 7 days of culture on blood agar, colonies of Ottowia massiliensis sp.nov. varied in size, displaying grey-white, semi-transparent, wrinkled colonies without a hemolysis ring or distinctive odor. (b): Gram staining revealed slightly curved, variable-length, diversely arranged Gram-negative rods under 1000× magnification