Human pathogens include viruses, bacteria, fungi, protists and parasites; archaea are not known to cause human disease. Examples: cholera, malaria and food poisoning in IB Biology HL C3.2.1.
Outline the symptoms, mode of transmission and treatment of one named example of food poisoning.
symptom;
transmission;
treatment;
eg Salmonella food poisoning
symptoms: diarrhoea/fever/abdominal cramps/Reiter's syndrome.
transmission: by contact after poor personal hygiene/eating contaminated food (not properly cooked)/transferred from faeces of pets/from reptiles/poor kitchen hygiene/raw eggs/unpasteurised milk.
treatment: rehydration/lots of drinking/intravenous fluids/antibiotics.
Distinguish between intracellular and extracellular bacterial infection using Chlamydia and Streptococcus as examples.
| Intracellular (Chlamydia) | Extracellular (Streptococcus) |
|---|---|
| lives inside cells of host | lives outside host cells; |
| does not produce toxins/no toxins to irritate tissues/does not damage cells | produces toxins/damages cells; |
| host may not be aware of infection/asymptomatic | produces symptoms (sore throat) so host aware of infection; |
| not targeted by immune system / (usually) long-term infection | targeted by immune system / (usually) short-term infection; |
| sexually transmitted disease / infectious conjunctivitis | respiratory infection / pneumonia / skin infections; |