Nosocomial infection of a pancreatic pseudocyst due to Corynebacterium xerosis

Clinical microbiology of coryneform bacteria

Coryneform bacteria are aerobically growing, asporogenous, non-partially-acid-fast, gram-positive rods of irregular morphology. Within the last few years, there has been a massive increase in the number of publications related to all aspects of their clinical microbiology. Clinical microbiologists are often confronted with making identifications within this heterogeneous group as well as with considerations of the clinical significance of such isolates. This review provides comprehensive information on the identification of coryneform bacteria and outlines recent changes in taxonomy. The following genera are covered: Corynebacterium, Turicella, Arthrobacter, Brevibacterium, Dermabacter. Propionibacterium, Rothia, Exiguobacterium, Oerskovia, Cellulomonas, Sanguibacter, Microbacterium, Aureobacterium, "Corynebacterium aquaticum," Arcanobacterium, and Actinomyces. Case reports claiming disease associations of coryneform bacteria are critically reviewed. Minimal microbiological requirements for publications on disease associations of coryneform bacteria are proposed.

Most Corynebacterium xerosis strains identified in the routine clinical laboratory correspond to Corynebacterium amycolatum

A comprehensive study was performed on 25 bacterial clinical isolates originally identified as Corynebacterium xerosis. Three reference strains of C. xerosis were also included in the study. On the basis of a variety of phenotypic characteristics tested, all strains could be divided into two separate clusters: reference strains ATCC 373 (the type strain of C. xerosis) and ATCC 7711 showed yellow-pigmented, dry, rough colonies, fermented 5-keto-gluconate, exhibited strong leucine arylamidase and alpha-glucosidase activities, produced lactate as the major end product of glucose metabolism, were susceptible to most of the 19 antimicrobial agents tested, and showed an inhibition zone around disks containing the vibriocidal compound O/129. In contrast, the remaining 26 strains including reference strain NCTC 7243 as well as all clinical isolates formed white-grayish, dry, slightly rough colonies, did not ferment 5-keto-gluconate, exhibited only weak leucine arylamidase and no alpha-glucosidase activity, produced large amounts of propionic acid as the end product of glucose metabolism, and were resistant to most antimicrobial agents tested, including O/129. Chemotaxonomic (cellular fatty acids, mycolic acids, and G+C content) and molecular genetic (16S rRNA gene sequence) investigations revealed that the strains of the second cluster unambiguously belonged to the species C. amycolatum. Our data suggest that most strains reported in the literature as C. xerosis are probably misidentified and correspond to C. amycolatum.

Antimicrobial susceptibilities of Corynebacterium species and other non-spore-forming gram-positive bacilli to 18 antimicrobial agents

The susceptibilities of 265 strains of Corynebacterium species and other non-spore-forming gram-positive bacilli to 18 antimicrobial agents were tested. Most strains were susceptible to vancomycin, doxycycline, and fusidic acid. Corynebacterium jeikeium and Corynebacterium urealyticum were the most resistant organisms tested. Resistance to beta-lactams, clindamycin, erythromycin, azythromycin, ciprofloxacin and gentamicin was common among strains of Corynebacterium xerosis and Corynebacterium minutissimum. Ampicillin resistance among Listeria monocytogenes was more prevalent than previously reported. Optochin, fosfomycin, and nitrofurantoin showed very little activity against most organisms tested, but the use of nitrofurantoin as a selective agent in culture medium may prevent the recovery of some isolates. Except for the unvarying activity of vancomycin against Corynebacterium species, the antimicrobial susceptibilities of the latter to other antibiotics are usually unpredictable, such that susceptibility tests are necessary for selecting the best antimicrobial treatment.