Bacteria are single-celled prokaryotes. They can reproduce very rapidly — doubling every 20 minutes under ideal conditions.
Bacteria cause disease in two main ways:
PRODUCING TOXINS — many bacteria secrete chemicals (toxins) that damage cells and tissues. It is often the toxins, not the bacteria themselves, that cause the symptoms of disease.
DIRECT CELL DAMAGE — some bacteria invade and destroy body cells directly.
Unlike viruses, bacteria CAN be treated with ANTIBIOTICS — drugs that specifically target bacterial structures (e.g. cell walls) that human cells don't have.
Salmonella Food Poisoning
CAUSE: Salmonella bacteria (various species).
TRANSMISSION: Eating food contaminated with Salmonella — most commonly undercooked poultry, raw or undercooked eggs, unpasteurised milk. Also spread through poor kitchen hygiene (cross-contamination from raw to cooked food) and unwashed hands.
SYMPTOMS: Begin 12–72 hours after eating contaminated food:
Fever.
Stomach cramps and abdominal pain.
Vomiting.
Diarrhoea (which can be severe and bloody).
Symptoms usually last 4–7 days.
MECHANISM: Salmonella bacteria survive cooking if the food isn't heated properly. They reach the small intestine, colonise the gut lining and produce toxins — causing the symptoms.
PREVENTION: Thorough cooking (bacteria are killed by heat), good hygiene (wash hands, clean surfaces), refrigeration (slows bacterial growth), pasteurisation of dairy products, vaccination of poultry flocks.
TREATMENT: Most cases resolve without antibiotics — rest and plenty of fluids. Severe cases may need antibiotics and hospital treatment.
Gonorrhoea
CAUSE: Neisseria gonorrhoeae bacteria.
TRANSMISSION: Sexual contact — a sexually transmitted infection (STI). Passed during vaginal, anal or oral sex without barrier contraception.
SYMPTOMS:
IN FEMALES: Often NO symptoms (asymptomatic) — this makes it particularly dangerous as it can spread unknowingly. When symptoms occur: thick yellow/green vaginal discharge, pain when urinating.
IN MALES: Thick yellow/green discharge from the penis, burning pain when urinating.
COMPLICATIONS: If untreated:
Pelvic inflammatory disease (PID) in females → can cause infertility.
Increased risk of HIV infection.
Can be passed from mother to baby during birth → eye infection in newborn.
PREVENTION: Using condoms (barrier contraception), reducing number of sexual partners, regular STI testing.
TREATMENT: Antibiotics — however, ANTIBIOTIC-RESISTANT strains have emerged, making gonorrhoea increasingly difficult to treat. This is a serious and growing public health problem.
ANTIBIOTIC RESISTANCE in gonorrhoea happens through natural selection:
Random mutations in bacteria can produce resistance.
Antibiotics kill non-resistant bacteria but resistant ones survive.
Resistant bacteria reproduce, passing on resistance genes.
Over time, the population becomes resistant.
⚠️ Common Mistake
Gonorrhoea IS treatable with antibiotics — but antibiotic-resistant strains are emerging. Do not say 'gonorrhoea cannot be treated'. Say instead: 'it can be treated, but resistance is a growing problem'. Also: Salmonella causes disease primarily through TOXINS — not just by the bacteria damaging cells directly.
📌 Key Note
Salmonella: bacteria, contaminated food, symptoms = fever/vomiting/diarrhoea, prevented by cooking thoroughly. Gonorrhoea: bacteria, STI, discharge and pain, treated by antibiotics (resistance growing).
🎯 Matching Activity — Match the Bacterial Disease to its Features
Match each feature to Salmonella or Gonorrhoea. — drag the symbols on the right to match the component names on the left.
Salmonella
Drop here
Gonorrhoea
Drop here
Salmonella
Drop here
Gonorrhoea
Drop here
Salmonella
Drop here
Bacteria produce toxins in the gut — causing vomiting and diarrhoea
Spread through undercooked food — prevented by thorough cooking and hygiene
Often resolves without antibiotics — rest and fluids usually sufficient
Antibiotic-resistant strains have emerged — major public health concern
Sexually transmitted — thick discharge and pain when urinating
🎯 Test Yourself
Question 1 of 2
1. How is Salmonella food poisoning prevented?
2. Why is gonorrhoea becoming harder to treat?
⭐ How Well Do You Understand This Topic?
Be honest with yourself — this helps you know what to revise!
Don't get itGetting thereNailed it!
🤖 Ask Mr Badmus AI
Stuck? Just ask! 💬
I'll use FIFA for calculations and flag Higher/Triple content clearly.