Staphylococcus cornubiensis is a gram-positive & cocci-shaped bacterial species. This bacterial strain was discovered in 2018 after it was isolated from the infected skin of a 64 year old man in Cornwall, UK. The medieval translation of this location is Cornubia, which served as inspiration for the bacterial species' name. Originally designated as the NW1T strain, scientists used multiple phenotypic and genomic comparisons in an attempt to identify this newly isolated species. These results identified S.cornubiensis as a novel species in the Staphylococcus intermedius Group (SIG). The SIG clade is a group of species including the following members: Staphylococcus intermedius, Staphylococcus psuedintermedius and Staphylococcus delphini. SIG members are best known as pathogens that typically reside on the mucosal surfaces of both wild and domesticated animals, with S.intermedius and S.psuedintermedius gaining increased attention for their role as common zoonotic threats. Species of the SIG clade can often be misidentified as Staphylococcus aureus since they demonstrate positive tube coagulase with rabbit plasma, a test used to identify the coagulase heat enzyme characteristic of S.aureus. Due to the questionable reliability of phenotypic tests used to identify SIG members, genotypic sequence comparison methods serve as much more trustworthy grounds for identification.
Genome & Genomic Comparisons
The genome of S.cornubiensis is 2,677,814 base pairs long with 2,465 open reading frames (ORFs). The bacteria's genetic code has a GC content of 37.3%, which is a value fairly similar to the other three members of the SIG clade. After finding approximately 369,267 SNPs in core genes shared amongst S.cornubiensis and the SIG clade, researchers used phylogenetic analysis software to construct a core genome phylogenetic tree that placed S.cornubiensis as a separate species within the SIG clade. S.cornubiensis showed a core genome nucleotide similarity ranking of 90.2% when compared with S.intermedius, 88.8% when compared S.pseudintermedius, 89.1% when compared with S.delphini and 78.6% when compared to S.schleiferi (a related coagulase-positive species). Scientists have not discovered any virulence factor genes when searching the S.cornubiensis genome. However, they noted that when using the same 90% nucleotide cut off parameter, no virulence genes are identified in any SIG members either. Researchers similarly have not detect any antibiotic resistance genes within the S.cornubiensis genome.
Energy & Carbon Metabolism
The production of acid from different sugars lead scientists to believe that S.cornubiensis uses fermentation as its method of energy metabolism. Fermentation is defined as the process of generating energy through the oxidation and reduction of the same initial organic compound, making the S.cornubiensis species chemoorganotrophs. All members within the SIG clade, including S.cornubiensis, produce acid from many of the same sugars (sucrose, lactose, galactose, mannose etc.). However, S.cornubiensis and S.intermedius do not produce acid from maltose, compared to S.pseudintermius and S.delphini who have been reported to ferment the sugar. Scientists can assume that the S.cornubiensis species is likely heterotrophic as well since it acquires ATP through fermentation. Heterotrophs are defined as organisms whose carbon sources are generated through the collection of organic compounds from their environments, as opposed to fixing carbon themselves.
When grown on Oxoid (sheep blood) agar and incubated overnight at 37C, Staphylococcus cornubiensis cultures were described as white, entire, convex and glistening. They were 2–3 mm in diameter and surrounded by double zone hemolysis. The second hemolysin zone developed following further incubation of the S.cornubiensis sample at 4C. Other experimentation involving culture growth revealed DNase activity, positive tube coagulase (a well known characteristic of the SIG clade) and negative latex agglutination which led scientist to infer that the species does not contain Protein A. This is a protein best known for its presence in the cell wall of S.aureus, where it suppresses B-cell responses from the host's immune system.
Due to the common misidentification of SIG species, researchers and medical professionals are continuously attempting to improve detection methods for these bacteria as they can cause harmful and dangerous infections. The SIG clade is of importance to both medical and veterinary professionals since it includes zoonotic pathogens. This type of pathogen is defined as one with the ability to spread from humans to animals and vice versa. At this point in time, researchers are still unaware if S.cornubiensus is a mutualist or opportunistic pathogen and if it has the ability to transfer from pets to owners. In Norway, researchers discovered a canine isolate (strain 2008-01-1056-2) that was strikingly similar to S.cornubiensus based phylogenetic comparisons of different marker genes (98% nucleotide similarity with hsp60 & 100% with sodA). If researchers are correct in believing that this isolate is of the S.cornubiensis species, it will be confirmed that this bacterial strain is in fact zoonotic. Luckily, no virulence genes or antibiotic resistance genes have been identified within the genome of S.cornubiensis. Researchers agree that future studies will be needed to detect this bacterial species prevalence in both humans and/or animals and the degree of potential harm it could bring to our own and our beloved pets' wellbeing.
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