Salmonella: significance as a pathogen
Two clinical entities cause by Salmonella are recognized: enteric fever (a severe, life threatening illness) and the more common food poisoning syndrome. In both cases, the organisms enter the body via oral route.
Enteric fever, commonly referred to as typhoid fever, is primarily caused by the one species Salmonella typhi, but other salmonella are potentially capable of producing this syndrome. The symptoms of enteric fever are generally not elicited through the intestinal tract, although the route of entry into the body is primarily oral. However, a short period of vomiting and diarrhea sometimes occurs in the first day or two in typhoid fever. The onset times vary considerably between typhoid and paratyphoid enteric fevers. Onset times for typhoid are usually 8 – 15 days, seldom as short as 30 – 35 days: while onset time for paratyphoid fever tends to be shorter, and may be so short as to suggest food poisoning. The usual symptoms of salmonellosis are headache, malaise, anorexia, and congestion of the mucous membranes, especially of the upper respiratory tract. Bacteremia generally occurs on the first week of illness.
The food poisoning syndrome is characterized by a self-limiting acute gastroenteritis. Contaminated food or water is the usual, but not the only, vehicle. The incubation period varies from 6 to 48 hours and generally falls within a range of 12 – 36 hrs. Variation in the incubation time may be attributed to the size of the infecting dose, the virulence (degree of pathogenicity) of the organisms, the susceptibility of the host, and the physicochemical composition of the transmitting food. Symptoms include diarrhea, abdominal cramps, vomiting and fever which generally last from 1 - 7 days. However, the organisms may be excreted in the feces for many weeks after symptoms subside.
Salmonellosis may be confused clinically with staphylococcal intoxications, but there are important distinctions. Salmonella has a longer incubation period than staphylococci and is usually accompanied by fever, which is absent in staphylococcal intoxication. And, unlike Salmonella food poisoning, the acute symptoms of staphylococcal food poisoning normally disappear within 24 hrs.
In some case, the gastroenteritis may be followed by extraintestinal invasion resulting in enteric fever, which is more, likely to occur in the very young, the aged and debilitated patients.
Salmonella: significance as a pathogen
