Bacteria Genomes - SALMONELLA PARATYPHI

Salmonella paratyphi is part of the Enterobacteriaceae family; it is a Gram-negative motile, aerobic rod which is facultatively anaerobic and there is serological identification of somatic and flagellar antigens.

Salmonella enterica serovars often have a broad host range and some cause both gastrointestinal and systemic disease. The serovar Paratyphi A is restricted to humans and causes only systemic disease. The sequence and microarray analysis of the Paratyphi A genome indicates that it is similar to the Typhi genome but suggests that it has a more recent evolutionary origin.

Salmonella paratyphi causes bacterial enteric fever which is characterised by an abrupt onset, continued fever, malaise, headache, anorexia, enlargement of spleen, bradycardia, rose spots on trunk occur on approximately 25% of Caucasians, constipation is more common than diarrhea in adults; complications include perforation/hemorrhage/ulceration of the intestines, less frequently psychosis, hepatitis, cholecystitis, pneumonitis, and pericarditis. It is clinically similar to typhoid fever but milder with lower fatality rate. Common enterocolitis may result without enteric fever this is characterised by headache, abdominal pain, nausea, vomiting, diarrhea and dehydration.

After entering the small intestine wall, the Salmonella invades through the lymphatic system to the lymph nodes and after a period of multiplication invades the blood stream. From there the bacteria invades the liver, gall bladder, spleen, kidney and bone marrow where it multiplies and causes infection of these organs. From here they again invade the blood stream causing secondary bacteremia. The secondary bacteremia is responsible for causing fever and clinical illness.

Salmonella paratyphi occurs sporadically or in limited outbreaks and is restricted to humans. It is transmitted by direct or indirect contact with faeces or rarely the urine of a patient or carrier, contaminated food, especially milk, milk products and shellfish, it may be contaminated by the hands of a carrier or flies may be a possible vector.

A few outbreaks related to water supplies have been documented. The incubation period is 1 to 3 weeks. Salmonella are excreted in the faeces of infected humans or animals. Faeces contamination of ground water or surface waters, as well as insufficiently treated and inadequately disinfected drinking water, are the main causes of epidemic waterborne caused by Salmonella species.

References:

Nat. Genet. 36(12):1268-1274(2004).
http://www.phac-aspc.gc.ca/msds-ftss/msds133e.html
http://www.sanger.ac.uk/Projects/S_paratyphiA/
http://www.medindia.net/patients/waterborne/enteric_fevers.asp