zoonoses and communicable diseases common to ... - PAHO/WHO

SALMONELLOSIS 233SALMONELLOSISICD-10 A02.0 salmonella enteritis; A02.1 salmonella septicaemia;A02.8 other specified salmonella infectionsSynonyms: Nontyphoid salmonellosis.Etiology: The genus Salmonella belongs to the family Enterobacteriaceae. It ismade up of gram-negative, motile (with a few exceptions), facultatively anaerobicbacteria. Salmonellae grow between 8°C and 45°C and at a pH of 4 to 8. They donot survive at temperatures higher than 70°C. Pasteurization at 71.1°C for 15 secondsis sufficient to destroy salmonellae in milk.These bacteria can resist dehydration for a very long time, both in feces and infoods for human and animal consumption. In addition, they can survive for severalmonths in brine with 20% salinity, particularly in products with a high protein or fatcontent, such as salted sausages; they also resist smoking. It has been indicated thatthey can survive for a long time in soil and water (WHO Expert Committee onSalmonellosis Control, 1988).A study conducted in Great Britain showed that S. typhimurium can survive 4 to14 months in the environment of facilities with infected calves, an important epidemiologicalfactor (McLaren and Wray, 1991). It can survive in ripening cheddarcheese for 10 months at 7°C (el-Gazzar and Marth, 1992).Le Minor and Popoff (1987) used DNA:DNA hybridization to show that they aregenetically a single species. Various classification schemes have been proposed,leading to controversy and confusion. At present, the trend is to return to the schemeconceived by Kauffmann-White due to its simplicity and because it is clearer andmore useful from a clinical and epidemiological standpoint. The nomenclaturescheme of Edwards and Ewing that was frequently used, particularly in theAmericas, is being abandoned (Farmer et al., 1984). As a result, the serotype termis used directly as a species. Thus, S. enterica serotype Typhimurium according toone scheme or Salmonella subspecies I serotype typhimurium according to anotherscheme would currently be S. typhimurium.The Kauffmann-White scheme divides salmonellae into serotypes. O somatic, Hflagellar, and Vi capsular antigens are distinguished primarily on the basis of theirantigenic structure. Currently, there are close to 2,200 serotypes.Some serotypes have several different phenotypes, and their identification can beimportant in epidemiologic investigation. For example, biochemical tests were ableto differentiate three biotypes of S. typhimurium, each of which was associated witha geographic and ecological region. S. gallinarum and S. pullorum are two nonmotilesalmonellae adapted to birds. Some authors consider them a single species orserotype because they are antigenically identical. However, each of these serotypescauses a different disease (fowl typhoid and pullorum disease). They can be distinguishedbecause, unlike S. gallinarum, S. pullorum does not use dulcitol or d-tartrate(D’Aoust, 1989).Phage typing is also useful for some serotypes. The Scottish SalmonellaReference Laboratory studied 2,010 cultures of S. typhimurium and differentiated137 different groups of phage types/biotypes. Four major epidemic clones were recognizedthat accounted for 52% of the cultures, with a predominance of bovine and