When Good Bugs Go Bad: Epidemiology and Antimicrobial Resistance Profiles of Corynebacterium striatum, an Emerging Multidrug-Resistant, Opportunistic Pathogen

Abstract

Infections with Corynebacterium striatum have been described in the literature over the last 2 decades, with the majority being bacteremia, central line infections, and occasionally, endocarditis. In recent years, the frequency of C. striatum infections appears to be increasing; a factor likely contributing to this is the increased ease and accuracy of the identification of Corynebacterium spp., including C. striatum, from clinical cultures. The objective of this study was to retrospectively characterize C. striatum isolates recovered from specimens submitted as part of routine patient care at a 1,250-bed, tertiary-care academic medical center. Multiple strain types were recovered, as demonstrated by repetitive-sequence-based PCR. Most of the strains of C. striatum characterized were resistant to antimicrobials commonly used to treat Gram-positive organisms, such as penicillin, ceftriaxone, meropenem, clindamycin, and tetracycline. The MIC₅₀ for ceftaroline was >32 μg/ml. Although there are no interpretive criteria for susceptibility with telavancin, it appeared to have potent in vitro efficacy against this species, with MIC₅₀ and MIC₉₀ values of 0.064 and 0.125 μg/ml, respectively. Finally, as previously reported in case studies, we demonstrated rapid in vitro development of daptomycin resistance in 100% of the isolates tested (n = 50), indicating that caution should be exhibited when using daptomycin for the treatment of C. striatum infections. C. striatum is an emerging, multidrug-resistant pathogen that can be associated with a variety of infection types.

Keywords: Corynebacterium; Corynebacterium striatum; antimicrobial agents; opportunistic infections; susceptibility testing; telavancin.

FIG 1

Morphological characteristics of C. tuberculostearicum, C. simulans, and C. striatum. (a) Colony morphology of C. tuberculostearicum. At 24 h of growth on sheep blood agar, colonies are pinpoint and barely visible. (b) Colony morphology of C. simulans. At 24 h of growth on sheep blood agar, colonies are large and white. (c) Colony morphology of C. striatum. At 24 h of growth on sheep blood agar, colonies are large and white. (d) Gram stain of C. striatum showing typical coryneform morphology of palisading Gram-positive bacilli.