Salmonella are pathogenic bacilli which cause three kinds of infection to humans viz., enteric fever (Typhoid or Paratyphoid), Gastroenteritis and Septicemia.
Typhoid fever is caused by S.typhi. It is transmitted via Pathogen contained food and water. The disease is characterized by a continued fever, inflammation of the intestine, formation of intestinal ulcers and enlargement of the spleen.
Gastroenteritis is caused by Salmonella, but most commonly by S.choleraesuis. The bacteria reach the blood stream from the intestinal tract, where it multiplies. It causes recurring high fever, chills, loss of appetite and weight loss. When the bacteria infect the organs from blood they can cause meningitis, pneumonia, abscesses, nephritis, osteomyelitis, or endocarditis, etc.
Cholera is caused by Vibrio cholere. It is a disease of antiquity and has been the cause of untold sufferings and death. Cholera is transmitted in water and food contaminated with this bacteria. In the small intestine, the bacteria adhere to epithelium, multiply and produce the enterotoxin. The symptoms of cholera are vomiting, profuse diarrhoeal stool (rice water stool) Which results in severe dehydration, loss of minerals, increased blood acidity and haemoconcentration.
Plague is caused by the bacterial species Yersinia pestis, a non motile gram negative bacilli. There are two types of plagues. They are bubonic plague and pneumonic plague. Bubonic plague is characterized by enlarged and inflamed lymph glands (Bubos). The symptoms are shivering, fever, nausea, vomiting and general weakness. In untreated cases the bubonic plague can cause 58% mortality. Pneumonic plague is a pneumonia characterized by a thin watery sputum with bright red streaks of blood. The mortality is 100% in untreated cases.
The disease syphilis is a well known and dreadful sexually transmitted disease (STD). It is caused by Treponema pallidium. Syphilis occurs only in humans and is transmitted by direct sexual contact (Venereal syphilis) or through placenta from an infected mother to the foetus (Congenital syphilis). Venereal syphilis progresses in three stages viz., primary, secondary and tertiary stage. The symptoms are very prominent in the tertiary stage. It will lead to blindness, loss of hearing, brain damage, insomnia, headache and delusions and spinal cord damage.
Gonorrhoea is another sexually transmitted disease caused by Neisseria gonorrhoea. In the males the primary site of infection is the urethra. In the female it is the cervix. It causes pain during urination and a yellowish discharge from the urethra of males. In females also it causes painful urination and vaginal discharge. Other symptoms are fever, abdominal pain, arthritis, meningitis etc.