An underestimated pathogen: Corynebacterium species

Corynebacterium species are a diverse group of organisms historically considered to be non-pathogenic, outside of the C. diphtheriae complex. Over the last few decades, this belief has been disproven with many notable non-diphtheriae Corynebacterium species being found to be pathogenic, often in certain clinical scenarios and/or anatomical sites. C. striatum and C. jeikeium are responsible for a large portion of bloodstream infections and orthopedic infections related to coryneform Gram-positive rods (GPRs). Eye and ear infections have commonly been attributed to C. macginleyi and C. otitidis, respectively. Pneumonia in critically ill and immunosuppressed individuals has been frequently reported by the C. propinquum/pseudodiphtheriticum group and occasionally in C. striatum. C. urealyticum is the primary pathogen associated with encrusted cystitis. Granulomatous lobular mastitis and breast abscesses have a strong association with C. kroppenstedtii. Erythrasma (C. aurimucosum/minutissimum group), trichobacteriosis (C. flavescens), and hidradenitis suppurativa are cutaneous disorders caused by or associated with Corynebacterium species. Biofilm formation by these bacteria leads to hardware/medical device-associated infections involving endovascular catheters, cerebrospinal fluid shunts, peritoneal dialysis catheters, and prosthetic joints. Clinical microbiology laboratories must be aware of this and optimize laboratory identification and reporting of these organisms when appropriate. Matrix-associated laser/adsorption ionization time-of-flight mass spectrometry, currently available in most large clinical microbiology laboratories, offers laboratories the ability to rapidly, accurately, and affordably accomplish this task.