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.

Clinical microbiology of coryneform bacteria.

We report the genome of the facultative intracellular parasite Rhodococcus equi, the only animal pathogen within the biotechnologically important actinobacterial genus Rhodococcus. The 5.0-Mb R. equi 103S genome is significantly smaller than those of environmental rhodococci. This is due to genome expansion in nonpathogenic species, via a linear gain of paralogous genes and an accelerated genetic flux, rather than reductive evolution in R. equi. The 103S genome lacks the extensive catabolic and secondary metabolic complement of environmental rhodococci, and it displays unique adaptations for host colonization and competition in the short-chain fatty acid–rich intestine and manure of herbivores—two main R. equi reservoirs. Except for a few horizontally acquired (HGT) pathogenicity loci, including a cytoadhesive pilus determinant (rpl) and the virulence plasmid vap pathogenicity island (PAI) required for intramacrophage survival, most of the potential virulence-associated genes identified in R. equi are conserved in environmental rhodococci or have homologs in nonpathogenic Actinobacteria. This suggests a mechanism of virulence evolution based on the cooption of existing core actinobacterial traits, triggered by key host niche–adaptive HGT events. We tested this hypothesis by investigating R. equi virulence plasmid-chromosome crosstalk, by global transcription profiling and expression network analysis. Two chromosomal genes conserved in environmental rhodococci, encoding putative chorismate mutase and anthranilate synthase enzymes involved in aromatic amino acid biosynthesis, were strongly coregulated with vap PAI virulence genes and required for optimal proliferation in macrophages. The regulatory integration of chromosomal metabolic genes under the control of the HGT–acquired plasmid PAI is thus an important element in the cooptive virulence of R. equi.

https://www.pure.ed.ac.uk/ws/files/7875998/The_Genome_of_a_Pathogenic_Rhodococcus_Cooptive_Virulence_Underpinned_by_Key_Gene_Acquisitions.pdf

The genome of a pathogenic rhodococcus: cooptive virulence underpinned by key gene acquisitions.

The susceptibility patterns of 480 isolates representing six recently defined species of coryneform bacteria (Corynebacterium amycolatum [n = 101], Corynebacterium auris [n = 48], Corynebacterium glucuronolyticum [n = 86], Brevibacterium casei [n = 50], Dermabacter hominis [n = 49], and Turicella otitidis [n = 146]) to 17 antimicrobial agents were determined by an agar dilution method. Most significantly, for C. amycolatum strains the MICs at which 90% of isolates are inhibited were > or = 32 micrograms/ml for nearly all agents. However, all 480 strains examined were susceptible to glycopeptide antibiotics.

Antimicrobial susceptibility patterns of some recently established coryneform bacteria.

Phylum XXVI. Actinobacteria phyl. nov.

Background. We present 2 case reports in the United States and investigations of diphtheria-like illness caused by toxigenic Corynebacterium ulcerans. A fatal case occurred in a 75-year-old male Washington resident who was treated with clindamycin but did not receive equine diphtheria antitoxin. A second, nonfatal case occurred in a 66-year-old female Tennessee resident who received erythromycin and diphtheria antitoxin. Methods. Both case patients and close human and animal contacts were investigated by their respective state health departments. Results. C. ulcerans isolated from the patient who died was resistant to erythromycin and clindamycin. For both isolates, conventional polymerase chain reaction results were positive for A and B subunits of diphtheria toxin gene tox, and modified Elek tests confirmed toxin production. The source of infection remained undetermined for both cases. Neither patient was up-to-date with diphtheria toxoid vaccination. Conclusion. These case reports highlight the importance of early treatment with diphtheria antitoxin, the selection of effective antimicrobial agents, and prevention through up-to-date vaccination.

https://www.jstor.org/stable/pdfplus/40306993.pdf

Investigations of 2 Cases of Diphtheria-Like Illness Due to Toxigenic Corynebacterium ulcerans

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.

/pdf/antimicrobial-susceptibilities-of-corynebacterium-species-2t4gl6r326.pdf

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

Five patients with non-urinary tract infections caused by Corynebacterium urealyticum were seen during an 8-year period at a university hospital in Madrid. Bacteremia (one case) and wound infections (four cases) were the most relevant features of these cases. Treatment with vancomycin, surgery, and supportive measures contributed to a favorable outcome for four of the five patients.

Non-Urinary Tract Infections Caused by Multiply Antibiotic-Resistant Corynebacterium urealyticum

Two Cases of Soft-Tissue Infection Caused by Arcanobacterium haemolyticum

A new selective medium (CBU agar) was compared with blood agar (BA) medium for primary isolation of Corynebacterium urealyticum from urine and skin samples of hospitalised patients. Overall, the CBU agar detected C. urealyticum in 14 (4.6%) of 302 urine samples and the BA medium detected the organism in four (1.3%), but most cultures which were positive only on CBU agar had < 10(4) cfu/ml. Six strains of C. urealyticum were isolated from 60 skin samples with CBU agar, whereas none was detected with BA. Although most skin samples had heavy inocula, the selective agar facilitated the recognition of low colony counts (< or = 10 cfu/plate) of C. urealyticum by reducing the growth of competing flora. Challenge of the selective medium with reference and clinical strains showed that CBU agar was inhibitory for gram-negative bacteria and reduced the gram-positive flora, allowing the growth of C. urealyticum strains. The new selective medium appears to be a useful epidemiological tool to study urinary and skin colonisation by C. urealyticum.

Evaluation of a New Selective Medium for the Isolation of Corynebacterium Urealyticum

clearly positive with lactoferrin controls), coarse agglutination with the control antibody as provided by TechLab might provide a clue that breast milk may be present in the specimen. In conclusion, our experience and experiences in several other laboratories would certainly concur with that of Quiroga and colleagues; fecal lactoferrin appears to be a more sensitive test than fecal leukocytes in the evaluation of patients with acute diarrhea. However, as with any laboratory test, this should be interpreted in the context of the clinical presentation (which, with fecal lactoferrin, may include the possibility of false positives with breast-fed infants when tested with certain antibodies).

J. Zapardiel

Papers

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

Non-Urinary Tract Infections Caused by Multiply Antibiotic-Resistant Corynebacterium urealyticum

Two Cases of Soft-Tissue Infection Caused by Arcanobacterium haemolyticum

Evaluation of a New Selective Medium for the Isolation of Corynebacterium Urealyticum

Use of selective media for isolating Corynebacterium urealyticum from urine specimens.