Micro-organisms that cause infections are known as pathogens. They may be classified as follows: Bacteria: minute organisms about one-thousandth to five-thousandths of a millimetre in diameter. They are susceptible to a greater or lesser extent to antibiotics.
Viruses: much smaller than bacteria and although they may survive outside the body for a time they can only grow inside cells of the body. Viruses are not susceptible to antibiotics, but there are a few anti-viral drugs available which are active against a limited number of viruses. Pathogenic Fungi: can be either moulds or yeasts.For example, a mould, which causes infections in humans, is Trichophtyon rubrum, which is one cause of ringworm, and which can also infect nails. A common yeast infection is thrush caused by Candida albicans. Protozoa: are microscopic organisms, but larger than bacteria. Free-living and nonpathogenic protozoa include amoebae and paramecium.
Examples of medical importance include: Giardia lamblia, which causes enteritis (symptoms of diarrhoea). Worms: are not always microscopic in size but pathogenic worms do cause infection and some can spread from person to person. Examples include: threadworm and tapeworm.Prions: are infectious protein particles. Example: the prion causing New Variant Creutzfeldt-Jacob Disease. Illnesses/infections caused by : * bacteria: Salmonellosis, tuberculosis, MRSA, coccidiosis, food poisoning, dysentery, bronchitis, ear infections, strep throat/tonsilitis, pneumonia, gonorrhea, syphilis, chlamydia— * Viruses: Influenza, common cold, stomach flu, pneumonia, ear infections, HIV/AIDS, herpes, warts, dengue, West Nile Virus, encephalitis * Fungi: Valley fever, athlete’s foot, ringworm, yeast infection * Parasites: Worms, schistosomiasis, malaria, sleeping sickness (trypanosomiasis), leishmaniasis.Infection, in general terms, is the illness caused by the growth of a germ on or in a person.
Sometimes the infection does not give any symptoms – this is called an ‘asymptomatic’ infection. When the germ is commonly found on our body without causing an illness, we call it carriage or colonisation. Carriage may be very short term (transient). For example, acquired by touching someone but quickly removed by washing your hands, or persistent with the germ multiplying on your body (usually called colonisation).
Colonisation of infection to the body is when the body as being invaded by disease, bacteria that can cause the body immune system to breakdown. A systemic infection is generally more serious. It can include things like Lyme Disease, AIDs, or tuberculosis. It can also be a chest or urinary tract infection, depending upon how serious it gets.
What seperates a systemic infection to a localised infection is that for it to be a systemic infection the bacteria or virus must enter the bloodstream. When bacteria or viruses are in the bloodstream there is the potential for the infection to spread to other organs and functions.Symptoms of a systemic infection include, headache, pains, nausea, seizures, cardiac problems and even death by scepticemia (blood poisoning) if medical treatment is not sought. A localised infection always has the potential to turn into a systemic infection. As another poster said, a loalised infection often starts as a cut or small wound. Usually these do not require treatment, only good self care. However, if it starts to get infected, like pus comes out or it is very hot to touch, anti-biotics may be required from your doctor.
If not treated, then a systemic infection may result.