**4. Diagnostic techniques**

According to Koch's postulates, when establishing the specificity of a pathogenic microor‐ ganism, the first criterion is the organism must be present in all cases of the disease. Al‐ though 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 practi‐ tioners. It is difficult to validate the other criteria of Koch's postulate, always in clinical set‐ ting. Thus, most clinical ophthalmologists depend only on first criterion when identifying a pathogen.

The first step when diagnosing and treating *Corynebacterium* infections 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 *Cory‐ nebacterium* species appear ingested by polymorphonuclear leukocytes (Fig. 2, 4). Finally, the culture results must be accounted.

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 dis‐ charge 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 *Corynebacteri‐ um* species. 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 diag‐

**Figure 5.** Post-medication. The blepharoconjunctivitis and filamentous keratitis are disappeared.

**Figure 4.** Gram stain of the discharge sample from case 2, original magnification ×1000 A large number of Gram-posi‐

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nosis of ocular infections caused by *Corynebacterium* species.

tive rods are phagocytised by polymorphonuclear neutrophil leukocytes.

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 re‐ ceived culture results identifying *Staphylococcus epidermidis* as a pathogen even though plen‐ ty of Gram-positive rods are normally found on microscopy in some patients. In some cases,

**Figure 4.** Gram stain of the discharge sample from case 2, original magnification ×1000 A large number of Gram-posi‐ tive rods are phagocytised by polymorphonuclear neutrophil leukocytes.

**Figure 5.** Post-medication. The blepharoconjunctivitis and filamentous keratitis are disappeared.

very rare. Although *C. macginleyi* is the common *Corynebacterium* species to be isolated from the ocular surface [6, 7], it remains unclear whether *C. macginleyi* is the major species respon‐ sible for ocular infections because cases caused by other species have been documented as

B: Corneal erosion with filamentous keratitis was found.

A: Moderate blepharoconjunctivitis and yellowish mucopurulent discharge were found.

**Figure 3.** Anterior segments of case 2. Moderate blepharoconjunctivitis, yellowish mucopurulent discharge, and cor‐

Figure 3 Anterior segments of case 2.

A B

According to Koch's postulates, when establishing the specificity of a pathogenic microor‐ ganism, the first criterion is the organism must be present in all cases of the disease. Al‐ though 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 practi‐ tioners. It is difficult to validate the other criteria of Koch's postulate, always in clinical set‐ ting. Thus, most clinical ophthalmologists depend only on first criterion when identifying a

The first step when diagnosing and treating *Corynebacterium* infections 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 *Cory‐ nebacterium* species appear ingested by polymorphonuclear leukocytes (Fig. 2, 4). Finally, the

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 re‐ ceived culture results identifying *Staphylococcus epidermidis* as a pathogen even though plen‐ ty of Gram-positive rods are normally found on microscopy in some patients. In some cases,

well [5].

78 Infection Control

pathogen.

**4. Diagnostic techniques**

neal erosion with filamentous keratitis were found.

culture results must be accounted.

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 dis‐ charge 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 *Corynebacteri‐ um* species. 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 diag‐ nosis of ocular infections caused by *Corynebacterium* species.

**5. Observation and result**

quinolone [7].

**6. Conclusion**

**Author details**

Hiroshi Eguchi\*

**References**

The author found that *Corynebacterium* species isolated from the ocular surfaces of elderly patients in Japan are very sensitive to cephem antibiotics (Table 1, unpublished data). Al‐ though they are also sensitive to aminoglycosides, most of the strains are highly resistant to

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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 un‐ der 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 diag‐ nosis. 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 polymorphonu‐ clear leukocytes, then a cephem-based ophthalmic solution should be prescribed first. It is possible that an organism other than a *Corynebacterium* species 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

Department of Ophthalmology, Institute of Health Biosciences, The University of Tokushi‐

[1] Inoue Y, Usui M, Ohashi Y, et al. Preoperative disinfection of the conjunctival sac with antibiotics and iodine compound: a prospective randomized multicenter study.

[2] Hara J, Yasuda F, Higashitsutsumi M.Ophthalmologica1997; 211(suppl 1): 62-67

of cephem, aminoglycoside, and glycopeptide eye drops.

ma Graduate School, Tokushima-shi, Japan

Jpn J Ophthalmol. 2008; 52: 151-161

Address all correspondence to: hiroegu@clin.med.tokushima-u.ac.jp

**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.


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

**Table 1.** MICs of several antimicrobials to 20 bacterial strains. (μg/mL)
