Corynebacterium macginleyi

an under-reported cause of conjunctivitis

Corynebacterium macginleyi

Corynebacterium macginleyi is lipophilic, slow-growing, gram-positive bacteria first described in 1995 and was named after Kenneth McGinley, who made an essential contribution in the field of lipophilic coryneform bacteria.

It has been associated with conjunctivitis and other eye-related infections. It has also been implicated in various non-ophthalmic infections as an opportunistic pathogen.

It has been proposed that Corynebacterium macgileyi is a conjunctiva specific pathogen that colonises the lipid-rich environment of the meibomian glands/tarsal glands.

Meibomian glands/tarsal glands

Corynebactrium spp.

  • Corynebacterium is an aerobic gram-positive, non-motile rod, often with clubbed ends but could be pleomorphic. In gram stain, it may stain unevenly and appear beaded. They group in a characteristic way, which has been described as the form of a "V", "palisades", or "Chinese letters". Metachromatic granules are usually present representing stored phosphate regions.

  • Corynebacterium are facultative anaerobe or aerobe and may grow slowly. On blood agar, they produce small greyish colonies.

  • Selective and differential media for Corynebacterium is Hoyle's tellurite medium.

  • Three species of Corynebacterium, C. diphtheriae, C. ulcerans, and C. pseudotuberculosis, carry the phage borne diphtheria tox gene, which is required to produce toxin. These three species are capable of causing diphtheria or diphtheria like illness.

  • Other diphtheria species are usually the commensals of the skin and mucous membrane but can be opportunistic pathogens.

Diseases associated with Corynebacterium macginleyi

This bacteria has mostly been associated with eye infection [Sagerfors, Nature 2021][Fong, Pathology 2021].

  • conjunctivitis,

  • keratitis,

  • corneal ulcer,

  • preorbital cellulitis,

  • blebitis and

  • endophthalmitis

It has also been reported from various non-ocular infections. For example -

  • catheter-related urinary tract infection,

  • catheter-related blood-stream infection,

  • endocarditis,

  • pneumonia in an HIV infected individual or ventilated patients,

  • tracheostomy site infection in a patient with laryngeal carcinoma and

  • post orthopaedics surgery surgical site infection.

Pneumonia Caused by Corynebacterium macginleyi 

Ji An Hur, Sang-il Kim, Pneumonia Caused by Corynebacterium macginleyi in HIV-infected Patient, Infection & Chemotherapy 2010; 42(5): 319-322

Co-infection - In many ophthalmic cases (approx 50%), other pathogenic bacteria and viruses have also been isolated from the clinical specimens. The most common associated bacteria was Staph aureus.

What are the risk factors of Corynebacterium macginleyi infection?

Eye infection

  • Contact lens,

  • breach in epithelial surface,

Extra-ocular infection

  • Prosthetic material,

  • immunocompromised state (HIV, malignancy)

Laboratory identification

Gram stain:

Gram-positive, non-motile rod, often with clubbed ends but could be pleomorphic. It may stain unevenly and appear beaded. They group in a characteristic way, which has been described as the form of a "V", "palisades", or "Chinese letters". Metachromatic granules are usually present representing stored phosphate regions.

Corynebacterium gram stain

Colonies:

On blood agar, CM produces very small (<1mm diameter) non-haemolytic colonies after 48 hrs (large reddish-beige colonies can be seen when blood agar is supplemented with Tween-80).

Tests:

Catalase positive, oxidase negative, nitrate is reduced to nitrite, urease negative. [Riegel 1995]

Final identification can be made using – MALDI-ToF (reliable identification), API coryne, 16SrRNA sequencing supplemented with rpo B gene sequencing.

It is likely that many isolates are classed as contaminants and not followed up/reported.

Treatment

The reported susceptibility -

Eguchi et al reported high-level fluoroquinolone resistance from Japan, but it could be specific to the country or population group.

Reference