Bacterial pathogens

Some bacteria can enter a host and cause disease. These pathogenic bacteria are microorganisms made of a single cell. Once inside a host, they can multiply rapidly by cell division, increasing the number of bacteria present.

Some pathogenic bacteria also produce toxins: poisonous substances that damage the host’s tissues. This damage contributes to the symptoms of illness.

Bacterial populations can therefore harm a host through their multiplication and, when the bacteria produce toxins, through the effects of those toxins.

Salmonella food poisoning

Salmonella food poisoning is a bacterial disease caused by eating food contaminated with Salmonella bacteria. Food can become contaminated when it is prepared in unhygienic conditions.

The bacteria and the toxins they secrete cause symptoms including fever, abdominal cramps, vomiting and diarrhoea.

Control through poultry vaccination

Poultry can carry Salmonella, so vaccinating them helps control the spread of the bacteria and reduces the risk of food becoming contaminated. Poultry are vaccinated for this purpose in the UK.

Gonorrhoea

Gonorrhoea is a bacterial sexually transmitted disease that spreads through sexual contact. Symptoms can include a thick yellow or green discharge from the vagina or penis and pain when urinating. Some infected people have no noticeable symptoms.

Gonorrhoea: Treatment and control

Gonorrhoea was once easily treated with penicillin, but many strains of the bacterium have become resistant to it. Penicillin may therefore no longer kill those bacteria. Treatment with an appropriate antibiotic can clear the infection and help prevent it from spreading.

Using a barrier method of contraception, such as a condom, reduces the chance of gonorrhoea passing between sexual partners.