High-Level Fluoroquinolone Resistance in Ophthalmic Clinical Isolates Belonging to the Species Corynebacterium macginleyi

Abstract

The clinical importance of nondiphtherial Corynebacterium, a ubiquitous member of the normal human microflora of the skin and mucous membrane, for ocular surface infections has been recognized recently. We performed an antimicrobial susceptibility test with Etest strips for three fluoroquinolones (ciprofloxacin, norfloxacin, and levofloxacin) and a taxonomic analysis on 21 isolates of Corynebacterium from ophthalmic samples. Of these, 16 isolates were identified as C. macginleyi at the species level on the basis of 16S rRNA gene sequence comparisons. The remaining five isolates were determined to be C. mastitidis (four) or C. accolens (one). Eleven of the C. macginleyi isolates showed high levels of resistance to all of the fluoroquinolones tested, and one isolate was resistant to norfloxacin alone. An analysis of the amplified quinolone-resistance-determining regions of the gyrA genes revealed that a single amino acid substitution in position 83 of the gyrA product was sufficient to generate the norfloxacin resistance phenotype, and double mutations leading to amino acid changes in positions 83 and 87 were necessary for high-level resistance against the other fluoroquinolones. We conducted the first example of multilocus sequence typing (MLST) analysis on C. macginleyi. The MLST analysis grouped the majority of C. macginleyi isolates into a single lineage, and another molecular strain typing by random amplified polymorphic DNA fragment patterns supported the finding, indicating that a particular lineage of C. macginleyi is dominant on the human ocular surface. This type of population might be particularly adaptable to the milieu on the human ocular surface.

Mechanisms of Antibiotic Resistance in Corynebacterium spp. Causing Infections in People

“…A double mutation has been also found, leading to amino acid changes in positions 83 and 87, which conditioned resistance to all fluoroquinolones. It was observed that double mutations occurred in Ser-83 and Asp-87 in all strains of C. macginleyi with a high level of resistance (Eguchi et al, 2008).…”

Corynebacterium macginleyi Conjunctivitis in Canada

“…Additional resistance phenotypes, however, are emerging, including to fluoroquinolone, co-trimoxazole, clindamycin, tobramycin, and erythromycin (8,18). Our isolate was resistant to erythromycin and clindamycin, supported by ermX gene expression.…”

“…Extraocular involvements, such as urinary tract infection, central venous catheter infection, endocarditis, and septicemia, have also been reported (7,13,18,19). In 2007, suture-related keratitis caused by this agent was described by Suzuki et al (17), and in 2008, Eguchi et al described C. macginleyi isolates from among ocular infections studied in Japan (8). In this instance, the patient was clearly symptomatic, with a bilateral ocular infection, and the same bacterium was recovered from both eyes, with no other aerobic or facultatively anaerobic organism being found.…”

“…Our findings, along with the cited literature, make culture and susceptibility testing highly advisable. Clinicians also empirically prescribing topical antibiotics without performing culture may encounter resistant strains (8).…”

“…This is the first such case of conjunctivitis reported in Canada and the second in North America, as a case involving C. macginleyi recovered from a corneal ulcer scraping has recently been described (16), suggesting a worldwide distribution of this organism. The strain described here was con- (8).…”