A 17 year old adolescent, presented with fever since one week which is step-ladder in pattern. He also has loose stools which are "pea-soup" in consistency. Rose spots are seen on his body. He is most probably infected with:

Enteric fever is a clinical syndrome characterized by constitutional and gastrointestinal symptoms and by headache. It can be caused by any Salmonella species. During the prodromal stage, there is increasing malaise, headache, cough, and sore throat, often with abdominal pain and constipation, while the fever ascends in a stepwise fashion. There may be marked constipation, especially early, or "pea soup" diarrhea; marked abdominal distention occurs as well. The rash (rose spots) commonly appears during the second week of disease. The individual spot, found principally on the trunk, is a pink papule 2-3 mm in diameter that fades on pressure. It disappears in 3-4 days. Ref: Schwaz B.S. (2014). Chapter 33. Bacterial & Chlamydial Infections. InPapadakis M.A., McPhee S.J., Rabow M.W. (Eds), CURRENT Medical Diagnosis & Treatment 2014.