Corynebacterium macginleyi isolated from a corneal ulcer

Clinical and genomic features of Corynebacterium macginleyi-associated infectious keratitis

Infectious keratitis is a potentially sight threatening ophthalmological emergency. Contact lens wear is a common risk factor. Diagnostic advances such as MALDI-TOF MS provides new insights into the spectrum of corneal pathogens and on microbes previously considered as commensals. Corynebacterium macginleyi was described in 1995, and in 2018, the genomic features of three isolates were reported after whole-genome sequencing. Here we describe the clinical characteristics of patients with infectious keratitis (n = 29) presumably caused by Corynebacterium macginleyi, and analyze the genomic features of C. macginleyi (n = 22) isolated from the corneal ulcers of these patients. The disease course was uneventful apart from minor interventions such as corneal cross-linking and amniotic membrane transplant. Genome sequencing and comparison revealed a highly conserved core genome of C. macginleyi. Based on the analyses of single nucleotide polymorphisms, the population could be divided into two main clades that also differed in a few clade-specific genomic islands. Patients infected with an isolate belonging to the minor clade (n = 7) presented a more severe disease. Comparisons with other corynebacterial species clearly separated C. macginleyi. C. macginleyi may be considered a corneal pathogen; genomic analysis provided insights into its population structure and disease-causing potential.

Current Evidence for Corynebacterium on the Ocular Surface

Corynebacterium species are commonly found in the conjunctiva of healthy adults and are recognized as non-pathogenic bacteria. In recent years, however, Corynebacterium species have been reported to be potentially pathogenic in various tissues. We investigated Corynebacterium species on the ocular surface and reviewed various species of Corynebacterium in terms of their antimicrobial susceptibility and the underlying molecular resistance mechanisms. We identified a risk for Corynebacterium-related ocular infections in patients with poor immunity, such as patients with diabetes or long-term users of topical steroids, and in those with corneal epithelial damage due to trauma, contact lens wear, lagophthalmos, and trichiasis. The predominant strain in the conjunctiva was C. macginleyi, and the species associated with keratitis and conjunctivitis were C. macginleyi, C. propinquum, C. mastitidis, C. pseudodiphtheriticum, C. accolens, C. striatum, C. xerosis, and C. bovis. Overall, Corynebacterium species present on the ocular surface were resistant to quinolones, whereas those in the nasal cavity were more susceptible. The prevalence of fluoroquinolone-resistant Corynebacterium has not changed in the past 10 years; however, Corynebacterium species remain susceptible to third-generation cephems. In conclusion, the use of third-generation cephems should be a reasonable and pragmatic approach for treatment of ocular infections caused by Corynebacterium species.

Microbiological Profile of Infectious Keratitis in a Portuguese Tertiary Centre

The microbiological profile of infectious keratitis has shown great differences across the world. Due to the continuous shifting trends in microbiological profile and antibiotic resistance patterns reported in several studies, constant local updates are crucial to provide an adequate treatment. The propose of this study was to analyze the incidence of infectious keratitis, possible changing trends in microbiological profile, and bacteria sensitivity to commonly used antibiotics, in our tertiary center, in the last 10 years. A retrospective study was performed, based on the survey review of electronic medical records of all patients with presumed infectious keratitis, between January 1, 2009, and December 31, 2018. Microbial cultures were performed, and patients were treated according to an internal protocol. A total of 1360 samples were included. We obtained a 35.1% culture-positive rate. Bacteria accounted for 76.78% of all positive scrapes (53.34% were Gram positive and 23.44% were Gram negative), Acanthamoeba for 12.13%, fungi for 8.16%, and virus for 2.93%. The most frequent agent identified was Corynebacterium macginleyi (18.41%), followed by Staphylococcus aureus (17.78%), Streptococcus pneumoniae (9.41%), and Pseudomonas aeruginosa (9.00%). We identified at least one ophthalmologic risk factor in 410 patients (85.77%). Trauma and contact lens wear were the most common risk factors found, accounting for 34.94% (n = 167) and 33.47% (n = 160) of cases. Sensitivity to fluoroquinolones and aminoglycosides was tested in all bacterial isolates, presenting values of 96.66% and 98.12%. In our region, the most common bacteria are Staphylococcus aureus, Streptococcus pneumoniae, and Pseudomonas aeruginosa, and they showed high sensitivity rates to first-line antibiotics, without any modification or emergence of antibiotic resistance trends during the 10 years of the study. For this reason, we decided to maintain the same internal protocol in our tertiary centre.

Contact Lens-Related Infectious Keratitis with White Plaque Formation Caused by Corynebacterium propinquum

We report the first case of Corynebacterium propinquum keratitis in the compromised cornea of a diabetic patient wearing therapeutic contact lenses. The strain was identified to the species level based on sequencing of the 16S rRNA gene and RNA polymerase β-subunit-encoding gene (rpoB). Ophthalmologists should be aware of nondiphtherial corynebacterial infection of compromised corneas.

First Human Case of Fungal Keratitis Caused by a Putatively Novel Species of Lophotrichus

We report an aggressive fungal keratitis caused by a putatively novel species of Lophotrichus in a patient with traumatic injury to the cornea from a dog paw. The organism was isolated from the patient's necrotic cornea, which perforated despite coverage with hourly fortified broad-spectrum topical antibiotic therapy. This report represents the first case of human infection caused by this species.