The specific name pyogenes, used in various bacterial genera, was derived from the Greekpuon or Latinpyum and suffix -genes, yielding pyogenes, meaning "pus-producing".
Microbiology
The cells typically measure 0.5 by 2.0 μm. They appear as pleomorphic or coccoid rods. They tend to be grouped singly or in short chains but are sometimes grouped into V-shaped pairs. Short diphtheroid shapes can also be observed, especially in young cultures.
It is not a particularly fastidious organism, however, media enriched with blood or serum must be used. Colonies create a zone of beta-hemolysis on blood agar plates and test negative for catalase. Although it can thrive in either anaerobic or aerobic environments, it is ideally suited to one with high (about 7%) levels of carbon dioxide.
The pathogenicity of this bacterium is believed to arise from its virulence factors, such as pyolysin, collagen-binding proteins, neuraminidases, fimbriae and exoenzymes. These factors support tissue colonization, immune evasion and tissue destruction. Interestingly, there are no obvious differences in the virulence genotypes of commensal and clinical isolates.
Despite its large impact on animal husbandry, the T. pyogenes transmission cycle is poorly characterized, although endogenous infection and environmental contamination are likely sources.
While T. pyogenes can be the primary etiological agent, it is more commonly found in polymicrobial diseases, and is frequently associated with Gram-negative anaerobes, such as Escherichia coli,Fusobacterium necrophorum, Bacteroides spp., and Peptoniphilusindolicus. In particular, there is a very strong synergistic relationship between T. pyogenes and F. necrophorum.
In humans, T. pyogenes infection is rare, and is typically associated with occupational exposure to farm animals and in immunocompromised populations, and most commonly presents as sepsis, endocarditis, and pneumonia. Patients presenting with intraabdominal infections, skin ulcers, arthritis, and pyelitis have also been reported. The clinical course of suppurative infections caused by T. pyogenes can be quite severe, with mortality rates increasing with misdiagnosis or incorrect treatment.
Microscopy, in vitro culture, and molecular techniques can be used to diagnose T. pyogenes infection. Treatment usually includes antibiotics such as beta-lactams, tetracyclines, and macrolides, although there is concern for emerging resistance to these antibiotics due to their overuse in agriculture.
References
12Yassin AF, Hupfer H, Siering C, Schumann P. (2011), "Comparative chemotaxonomic and phylogenetic studies on the genus Arcanobacterium Collins et al. 1982 emend. Lehnen et al. 2006: Proposal for Trueperella gen. nov. and emended description of the genus Arcanobacterium", Int J Syst Evol Microbiol, 61 (6): 1265–1274, doi:10.1099/ijs.0.020032-0, PMID20622055
