Open access peer-reviewed chapter

Ocular Infections Caused by Corynebacterium Species

By Hiroshi Eguchi

Submitted: April 20th 2012Reviewed: February 22nd 2013Published: May 29th 2013

DOI: 10.5772/56214

Downloaded: 2274

1. Introduction

1.1. The history of Corynebacteriumspecies

The most well-known Corynebacteriumspecies, Corynebacterium diphtheliae, causes diphtheria. However, in 1970, the clinical value of identification of Corynebacteriumdiphtheriae became less medically significant owing to the development of diphtheria toxoids and a decrease in the prevalence of diphtheritic infection in developed countries. Other Corynebacteriumspecies have been considered contaminants when found in clinical samples because they are organisms normally found in the skin, mucous membranes, and other human tissues. Given that Corynebacteriumspecies are one of the most commonly isolated bacteria from the ocular surfaces [1, 2], they are also considered non-pathogenic in the ophthalmic field.

Currently, in a clinical setting, many bacteriological laboratory technicians in hospitals report Corynebacteriumspecies as “Gram-positive rods”. Sometimes, the presence of Corynebacteriumspecies is not reported because it is considered to be contaminants. As a result, it is not possible for ophthalmologists to determine whether Corynebacteriumspecies are present in clinical samples by using laboratory tests. This makes the Corynebacteriumspecies to be nonpathogenic for ophthalmologists leading to therapeutic failure.


2. Bacteriological characteristics of Corynebacteriumspecies

Morphology: The size of Corynebacteriumspecies varies from 0.3–0.8 × 1–8 µm. They exsist in a variety of shapes, even in pure cultures. In the clinical samples, they mostly appear as rod-shaped bacteria in palisade-, ring-, or ‘I, N, T, V, W, or Y’ letter-shaped arrangments.

Lipophilicity: Few Corynebacteriumspecies generally have high lipophilicity. In vitro, they can be easily become unculturable if the final concentration of Tween 80 (polysorbate 80) in the medium is slightly different from the optimal concentration. Presumably, this is the reason why particular Corynebacteriumspecies prefer the ocular surfaces as these are area where fatty acids are always present because they are secreted from the meibomian gland. This requirement may also explain why Corynebacterium-induced endophthalmitis is very rare.

3. Corynebacteriumspecies as a pathogen: Case presentations

Case 1: In 2003, the author encountered the case of an elderly patient who had clear infectious conjunctivitis in his right eye. He had experienced mild conjunctival hyperaemia and mucopurulent discharge after cataract surgery performed 2 years before consultation (Fig. 1). He had continued to use a quinolone ophthalmic solution postoperatively, but had not undergone any ophthalmic examination. He had eye discomfort for more than 3 months. Gram staining smear of the discharge showed that many polymorphonuclear leukocytes phagocytizing Gram-positive rods (Fig. 2). Culture of the discharge sample detected quinolone resistant Corynebacteriumspecies, and the strain was susceptible to cephem antibiotics. Switching the quinolone ophthalmic solution to a cephem antibiotic resolved of the patient’s symptoms. The author determined this to be a clear case of conjunctivitis due to Corynebacteriumspecies. Thereafter, the author encountered a large number of cases of Corynebacteriumconjunctivitis in geriatric patient as well as several cases of Corynebacteriumkeratitis in patients who underwent keratoplasty. Thus, in 2012, Corynebacteriumspecies still appear to be pathogens of the ocular surface.

Figure 1.

Infectious conjunctivitis occurred in case 1. A mild infectious conjunctivitis was found.

Figure 2.

Gram stain of the discharge sample from case 1, original magnification ×1000 Gram-positive rods shaped bacteria in palisade- and ‘I, or V’ letter-shaped formations were found within polymorphonuclear neutrophil leukocytes.

Case 2: Figures 3 A & B show an ocular surface of a diabetic young man. He had intractable filamentous keratitis after 2 vitrectomies. When he was referred to the author’s clinic, a moxifloxacin ophthalmic solution has been prescribed for more than 6 months (from the perioperative stage of the first vitrectomy). After the diagnosis of infectious blepharoconjunctivitis with mucopurulent yellowish discharge, it was determined that the blepharoconjunctivitis may have caused swelling of the eyelid, and the swollen eyelid partially induced intractable filamentous keratitis. Analysis of a smear of the discharge showed a large number of polymorphonuclear leukocytes and Gram-positive rod-shaped bacteria in palisade- and ‘I, V, or W’ letter-shaped arrangements (Fig. 4). Corynebacteriumspecies were identified in the culture of the discharge by using a simple, commercially available identification kit (BBL Crystal, BD, Japan, Tokyo). The author also isolated Corynebacteriumspecies on a sheep blood agar plate from the discharge and identified the causative agent as Corynebacterium macginleyion the basis of its biochemical characters tested by API-Coryne (bioMérieux SA, Lyon, France). The minimum inhibitory concentration (MIC) of moxifloxacin and ceftriaxone for the strain (tested by E-test®, bioMérieux SA, Lyon, France) was >256µg/mL and 2 µg/mL, respectively. Switching moxifloxacin to topical cephmenoxim led to rapid improvement of blepharoconjunctivitis and filamentous keratitis (Fig. 5).

Figure 3.

Anterior segments of case 2. Moderate blepharoconjunctivitis, yellowish mucopurulent discharge, and corneal erosion with filamentous keratitis were found.

It is currently no exaggeration to say that Corynebacteriumspecies are among the major pathogens responsible for chronic conjunctivitis, especially in geriatric patients. These pathogens can also cause infectious keratitis in patients who are immune-compromised [3-5]. All such conditions may be triggered, when the bacterial flora of the ocular surface are disturbed, by opportunistic infections. Endophthalmitis caused by Corynebacteriumspecies is very rare. Although C. macginleyiis the common Corynebacteriumspecies to be isolated from the ocular surface [6, 7], it remains unclear whether C. macginleyiis the major species responsible for ocular infections because cases caused by other species have been documented as well [5].

4. Diagnostic techniques

According to Koch’s postulates, when establishing the specificity of a pathogenic microorganism, the first criterion is the organism must be present in all cases of the disease. Although quantitative analysis of a specific bacterium in samples by using real-time polymerase chain reaction may be useful, this technique is not readily available to practitioners. It is difficult to validate the other criteria of Koch’s postulate, always in clinical setting. Thus, most clinical ophthalmologists depend only on first criterion when identifying a pathogen.

The first step when diagnosing and treating Corynebacteriuminfections should be to subject the clinical samples, such as mucopurulent discharge or corneal scrapings, to Gram staining, examine them microscopically, and observe whether Gram-positive rods suggestive of Corynebacteriumspecies appear ingested by polymorphonuclear leukocytes (Fig. 2, 4). Finally, the culture results must be accounted.

Figure 4.

Gram stain of the discharge sample from case 2, original magnification ×1000 A large number of Gram-positive rods are phagocytised by polymorphonuclear neutrophil leukocytes.

Figure 5.

Post-medication. The blepharoconjunctivitis and filamentous keratitis are disappeared.

Although the culture results from discharge and corneal scrapings have clinical significance, we should also recognize the risk of overestimation. As a proof of this, the author has received culture results identifying Staphylococcus epidermidisas a pathogen even though plenty of Gram-positive rods are normally found on microscopy in some patients. In some cases, a ‘culture negative’ result is reported. Figure 6 shows the anterior segments of a bedridden elderly female patient (A) and a panorama Gram stain image of her eye discharge (B). She had a conjunctival hyperaemia with a large amount of yellowish white mucopurulent discharge that lasted for 1 week. The smear prepared from discharge was stained by Gram staining, which showed a large amount of Gram-postitive rods suggestive of Corynebacteriumspecies. Although she clearly had infectious conjunctivitis and no medication had been administered, the culture result from her discharge was reported as negative. Hence, the smear and microscopic examination of clinical samples contribute significantly to the diagnosis of ocular infections caused by Corynebacteriumspecies.

Figure 6.

Severe infectious conjunctivitis and a Gram-stained panoramic image of the discharge sample. A: A large quantity of yellowish-white mucopurulent discharge and conjunctival hyperaemia were found. B: A large amount of Gram-positive rods and a few polymorphonuclear leukocytes were found.

AntimicrobialMax MICMin MIC% Susceptible*

Table 1.

MICs of several antimicrobials to 20 bacterial strains. (μg/mL)

*: The susceptibility test follow the instruction of E-test.

5. Observation and result

The author found that Corynebacteriumspecies isolated from the ocular surfaces of elderly patients in Japan are very sensitive to cephem antibiotics (Table 1, unpublished data). Although they are also sensitive to aminoglycosides, most of the strains are highly resistant to quinolone [7].


6. Conclusion

When faced with the case of an elderly patient with chronic conjunctivitis, the first step should be to collect the discharge and to prepare a Gram stained smear and observation under microscope. Assessment should also determine whether the lacrimal duct is obstructed or not. Documenting a patient’s history of antimicrobial use will also contribute to the diagnosis. If the patient has a history of using an antimicrobial ophthalmic solution, and also has Gram-positive rods in palisade, ring or ‘N, T, V, W, or Y’ letter-shaped arrangement present in their discharge and if these Gram positive rods appear to be ingested by polymorphonuclear leukocytes, then a cephem-based ophthalmic solution should be prescribed first. It is possible that an organism other than a Corynebacteriumspecies is the causative pathogen if the cephem antibiotics do not resolve the infection. For Corynebacterium-induced keratitis, a systemic carbapenem and glycopeptide may be useful in additions to frequent applications of cephem, aminoglycoside, and glycopeptide eye drops.

© 2013 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite and reference

Link to this chapter Copy to clipboard

Cite this chapter Copy to clipboard

Hiroshi Eguchi (May 29th 2013). Ocular Infections Caused by Corynebacterium Species, Infection Control, Silpi Basak, IntechOpen, DOI: 10.5772/56214. Available from:

chapter statistics

2274total chapter downloads

3Crossref citations

More statistics for editors and authors

Login to your personal dashboard for more detailed statistics on your publications.

Access personal reporting

Related Content

This Book

Next chapter


By Lul Raka, Gjyle Mulliqi-Osmani, Lumturije Begolli, Arsim Kurti, Greta Lila, Rrezarta Bajrami and Arbëresha Jaka-Loxha

Related Book

First chapter

The IDEFICS Intervention Toolbox - A Guide to Successful Obesity Prevention at Community Level

By Vera Verbestel, Stefaan De Henauw, Staffan Marild, Stefan Storcksdieck genannt Bonsmann, Laura Fernández Celemín, Katharina Gallois, Holger Hassel and Ilse De Bourdeaudhuij

We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. We share our knowledge and peer-reveiwed research papers with libraries, scientific and engineering societies, and also work with corporate R&D departments and government entities.

More About Us