Carbuncle due to Salmonella Enteritidis: A novel presentation

Background: Salmonella Enteritidis causes intestinal and extra-intestinal infections, but rarely cutaneous infections. It has never been reported to cause carbuncle (a collection of interconnected furuncles with multiple pustular openings). We report a case of carbuncle due to S. Enteritidis. Case presentation: An adult Bangladeshi patient with type 2 diabetes presented with a carbuncle on the left-side of his neck. A pure culture of S. Enteritidis was grown from the pus of the carbuncle. The patient was successfully treated with ciprofloxacin to which the isolate was susceptible. Whole genome sequencing of the strain showed that it possessed three additional virulence genes - pef (for plasmid-encoded fimbriae), spv (for salmonella plasmid virulence), rck (for resistance to complement killing) -responsible for systemic infections that were absent in the genome of a reference S. Enteritidis strain. In phylogenetic analysis, the strain clustered with other S. Enteritidis strains from different parts of the world. Conclusions: A weakened immune system of the patient due to diabetes mellitus and the additional virulence genes of the isolate may have contributed to the unusual presentation of carbuncle. The possibility of S. Enteritidis to cause carbuncle should be considered.