Isolation of gram-positive rods that resemble but are clearly distinct from Actinomyces pyogenes from mixed wound infections

Abstract

Beginning in 1990, gram-positive rods resembling Actinomyces pyogenes were found with increasing frequency in mixed cultures from various infectious processes, most of them from patients with otitis, empyema, pilonidal cysts, perianal abscesses, and decubitus ulcers. Ribotyping and hybridization showed that these gram-positive rods could be divided into five groups not related to known Actinomyces species. Biochemical markers for reliable differentiation into these groups, however, could not be found. Therefore, naming new species is not warranted unless parameters are discovered that allow identification without DNA hybridization. These gram-positive rods have been isolated only in mixed cultures with anaerobes, Staphylococcus aureus, Streptococcus "mileri," enterococci, and gram-negative rods. Their exact role in these possibly synergistic infections needs further investigation.

Identification of coryneform and other Gram‐positive rods with several methods

“…Our strains fit the enzymatic profiles for species published previously (9,10,15,16,36). Strains belonging to Corynebacterium spp.…”

“…The "gold standard" for the identification of an isolate was a combination of: traditional morphological and biochemical data provided by the schemes of Hollis & Weaver (20) and Hollis (19), cellular fatty acid profiles as published previously (2, 5, 9, 10, 11, 12, 15, 21, 28, 33, 34, 36), and production of metabolic fatty acids as reported for Gram-positive rods (7,9,18,29,31,32,36). Diagnoses provided by the API Coryne and MIDI systems were not used for identification.…”

“…Failure to identify Actinomyces strains was due to the absence of all species in the data base except for A. pyogenes. We had isolated eight strains of A. neuii (9,12), seven A. pyogenes-like strains (36), and one each of A. odontolyticus and A. naeslundii.…”

“…Recent studies from this (9,10,11,12,15,36) and other (1, 4, 6, 27, 28, 30, 35) laboratories, however, have shown that a precise identification of these organisms can be worthwhile in (a) detecting unsuspected species, (b) ascribing potential pathogenicity to species so far thought to be "non-pathogenic", and (c) outlining hitherto undescribed taxa. We thought it therefore appropriate to try to identify a large number of clinical isolates of aerobically growing GPR by using several techniques that are now at the disposal of many laboratories.…”

When Zoonotic Organisms Cross Over—Trueperella pyogenes Endocarditis Presenting as a Septic Embolic Stroke

“…Historically, it wasn't straightforward to differentiate between Actinomyces species, as most clinical laboratories were not equipped to detect them and they were often identified as Streptococci. This mismatch was due to their aerobic properties, gram-positive reaction, betahemolytic architecture on blood agar, and its subsequent reaction with Lancefield group G [14][15]. [12].…”