Bacteria| Can be helpful, can be an aid in digestion, able to break down sewage, can be used in food (yoghurt), affects odour, taste and texture. Needs nutrients, pH, time, temperature, +/- Oxygen and water activity to grow. | Lyme disease, Tuberculosis| Viruses| Exist only to replicate, need a host, infect all types of cells, found in soil, water and air. | Hepatitis A, Norovirus, Measles, Mumps| Parasites| Need a host (nourishment, protection, complete life cycle), found in soil, water air and animals, acquired via contaminated food, water and contact with a contaminated source.
| Anisakiasis, Giardiasis, Cryptosporidiosis, Trichinosis, Taeniasis| Fungi| Reproduce via spores e. g. yeasts, moulds. | Tinea pedis, Oral thrush| A Pathogen is an agent that produces disease. There are four categories; Bacteria, Viruses, Parasites and Fungi. Here is a table, which shows the differences between them: 1. 3 An 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, it is called 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). In certain circumstances, the germs that colonise our bodies may go on to give an infection. 1. 4 Systemic infection is a generic term for an infection caused by microorganisms in animals or plants, where the causal agent (the microbe) has spread actively or passively in the host’s anatomy and is disseminated throughout several organs in different symptoms of the host.
Systemic infections are also called disseminated infections, and they can be caused by bacteria and bacteria-like prokaryotes, fungi, protozoa in the broad sense, and viruses. Localised infections are confined to one specific area. The skin around a localized infection may be red, swollen, tender, and warm to touch. The wound may have pus-like drainage and fever may develop. 1. 5 Poor practices that may lead to the spread of infection: * Not washing hands regularly * Not using PPE * Not storing or cooking foods properly.
* Not covering your nose or mouth when sneezing or coughing * Not cleaning surroundings 2. 1 The conditions needed for the growth of microorganisms are: * Food – they need nutrients to grow on * Acidity – pH 7. 5-4. 6 * Temperature – they grown best between 40-141 degrees F * Time – if you leave food in the danger zone for 4 hours or more, the levels of Microorganisms can be high enough to make some ill * Oxygen – some but not all need oxygen to grow * Moisture – some but not all need moisture to grow 2. 2 There are four main routes for infections to enter the body: 1.
Down the respiratory tract into the lungs. Coughs, colds, influenza and other common airborne infections are contracted in this fashion. 2. Breaks in the skin. One of the many functions of the skin is to act as a barrier against infection. Anything that penetrates the skin, or for that matter the mucous membrane that lines the mouth or nose, provides a route for infection to enter. Typically, bites, scratches, puncture wounds by needles etc. increase the risk of infection. 3. Down the digestive tract. Food, drink or other infected products can be swallowed and infect the stomach or bowels.
Most people have experienced an ‘upset stomach’, which reveals itself in the form of diarrhoea and or vomiting. 4. Up the urinary and reproductive systems. The infectious agent may remain localized or may enter the blood stream. Sexually transmitted diseases most commonly infect the genitals. HIV, the AIDS virus, is carried in bodily fluids and can be transmitted in saliva, seminal fluid, or blood. 2. 3 2. 3 Common sources of infection: A person can be a source of infection; either for him/her self (endogenous) or to other people (directly through contact, or indirectly, e.g. by contaminating food or beverages).
Objects may be sources of infection; food, water, air-conditioning systems, showers, medical instruments, recreational waters, doorknobs, cotton handkerchiefs etc. Most man-made products that may be sources of infection are required to be produced while limiting the risk of contamination. In addition to people, also animals can be sources of infection. 2. 4 Infective agents can be transmitted to a person. There are two different modes of transmission; direct and indirect.
Direct transmission refers to the transfer of an infectious agent from an infected host to a new host, without the need for intermediates such as air, food, water or other animals. Direct modes of transmission can occur in two main ways: * Person to person – the infectious agent is spread by direct contact between people through touching, biting, kissing, sexual intercourse or direct projection of respiratory droplets into another person’s nose or mouth during coughing, sneezing or talking. * Transplacental transmission – this refers to the transmission of an infectious agent from a pregnant woman to her foetus through the placenta.
Indirect transmission is when infectious agents are transmitted to new hosts through intermediates such as air, food, water, objects or substances in the environment, or other animals. Indirect transmission has three subtypes: * Airborne transmission – the infectious agent may be transmitted in dried secretions from the respiratory tract, which can remain suspended in the air for some time. * Vehicle-borne transmission – a vehicle is any non-living substance or object that can be contaminated by an infectious agent, which then transmits it to a new host.
Contamination refers to the presence of an infectious agent in or on the vehicle. * Vector-borne transmission – a vector is an organism, usually an arthropod, which transmits an infectious agent to a new host. Arthropods, which act as vectors, include houseflies, mosquitoes, lice and ticks. 2. 5 Key factors that will make it more likely that infection will occur: * Environment * Diseases such as HIV/AIDS which suppress immunity * * Poorly developed or immature immunity, as in very young children * Not being vaccinated * Poor nutritional status (e. g. malnourished children) * Pregnancy.