Atypical non-Typhi Salmonella enterica bacteremia, lactose-positive, lysine decarboxylase-negative

We describe here the first isolation in Argentina of a lactose-fermenting and lysine decarboxylase-negative non-Typhi Salmonella enterica from a blood culture of a patient with systemic lupus erythematosus. The microorganism was identified as S. enterica (score: 2.148) by mass spectrometry, as "Salmonella group" (discrimination: 86%) by the VITEK® 2 system and as Citrobacter freundii complex by biochemical tests. The serological test using the OMA antiserum for the somatic antigen was positive. The identification was confirmed as Salmonella subsp. I 4,[5],12:i:- atypical at the National Reference Center ANLIS Dr. Carlos G. Malbrán. Mass spectrometry is especially useful in microbial identification in the presence of atypia, while biochemical tests can lead to misidentification in these cases. This study warns about the circulation of this strain in Argentina.