1.1 and 1.2
Bacteria – are micro-organisms that consist of only one cell. Bacteria multiply by splitting themselves in two, which is called a binary fission. Because of this they can increase in number rapidly. The majority are harmless, but some can be pathogenic which results in bacterial infection occuring. Bacterial infections can be treated by using antibiotics. Bacteria can evolve a resistance to antibiotic e.g. MRSA. Some diseases caused by bacteria include tuberculosis, pneumonia, salmonella, tetanus and syphilis.
Viruses – are extremely small particles made from protein and either DNA or RNA. They are not made up of cells instead they invade the living cells of other organisms and use them to produce many copies of themselves. Viruses are smaller than bacteria and are enclosed in protective coating. This makes it more difficult to kill them. Antibiotics do not kill viruses. Some diseases caused by viruses include common cold, influenza, AIDS, chickenpox and shingles.
Fungi unlike bacteria may consist of more than one cell. Most of them are invisible to the naked eye, but sometimes they can grow to the size as large enough to be noticed. Many fungi multiply and spread by producing tiny spores that are carried in the air. Sometimes they multiply by splitting themselves in two like bacteria. They thrive in warm and moist areas of the body. They are treated using antifungal medications. Some infection caused by fungi include trush, ringworm and athlete’s foot.
Parasites are dependent on the host for their existance. They are multicellular organisms. They can be divided in two groups: ectoparasites (live on human body – on skin or in the hair e.g. scabies, lice, ticks and fleas), endoparasites (live inside of the human body e.g tapeworm, liver fluke).
An infection occurs when the body is unable to protect itself from micro-organisms such as viruses, bacteria and fungi. Parasites can also enter the body, resulting in infection occuring. Micro-organisms that cause a disease are known as pathogens. Infectious diseases are spread when the pathogens are transmitted from person to person or from environment to person. Infection can affect any organ or system of the human body. Infection usually cause the sufferer to experience certain symptoms and to look and feel unwell. Infection can range in their severity and some can cause death. Most infections are treatable.
Colonisation occurs when some micro-organisms are present on our skin or in our gut and cause no infection within the person, who still has the potential to infect others. However if this micro-organisms invade tissue or cause harm to the person then colonisation becomes an infection.
Systemic infection affect the whole body and are usually very serious and can be life threatening, they often cause symptoms like fever, shaking chills, joint aches and general weakness (e.g. Septicaemia – blood poisoning). Localised infection affect one specific area and tends to cause swelling, redness, tenderness and feel of warm around affected area. Pus may form as well as presence of a fever (e.g. a pimple is a localised infection of the skin).
Poor hand hygiene, not wearing personal protective equipment when required, unsafe use and disposal of sharps (needles, vials), lack of routine cleaning with antibacterial solutions and sprays, lack of reproccesing appropriately any reusable medical equipment and instruments, lack of good respiratiry hygiene and cough etiquette (cover mouth during cough or sneeze and wash hands after), not effective handle of waste (incontinence pads being carried without getting bagged) and linens (dirty linen being left on the floor beside bed while sheets are being changed, rather than in the laundry skip or dirty linen being carried by the staff without first being bagged), wearing work uniforms outdoors etc.
Micro-organisms to grow need reservoir, food, moisture, temperature and time.Reservoir – pathogens need a reservoir to grow in, which has all the conditions the pathogen needs to grow and thrive. All pathogens need a source of food to provide them with a source of energy and nutrients they need to multiply. Often they get it from the body of the infected individual. All human pathogens require moisture to grow, that is why food is preserved by drying, which deprive mico-organisms of moisture. The pathogens that infect humans grow best at body temperature of 37*C. Higher temperatures inactivate and kill most of the micro-organisms, while low temperatures slow or stop their grow. That is why heat is used to steralize objects, while freezing is used to preserve food.
It takes time for the pathogen to multiply to the point where it starts to cause symtomps of infection. This is called an incubation time.
There are four main ports of entry:
– inhalation into the nose, throat and lungs (pathogens in the air or droplets, which can cause e.g. TB), – ingestion into the stomach and gut (pathogens ingested and swallowed, which can cause e.g. salmonella and norovirus), – sexual contact (pathogens transmitted in any sexual contact, which can cause e.g. HIV, gonorrhoea), – wounds and breaks in the skin (pathogens enter the body through mucus membranes, nose, mouth, gut, genital urinary track – catheters, or wounds like surgical incisions which can cause e.g. MRSA).
The sources of infection can be divided in two main groups. These are exogeneous and endogeneous sources. A source of the infection is endogeneous if the infectious agent comes from the patien’t own body, usually from his own normal flora in cases of contamination during surgery, malnutrition, impairment of blood supply, diseases such as AIDS, diabetes etc.
The exogenous sources of infection introduce organisms from anywhere outside to inside the body, which is the case most of the time. The exogenous sources of infection can be either human, animal or environmental in origin. Humans can be source of infection in three cases, either when thay are clinically infected (symptomatic infection), when they are asymptomatically infected or when they are carriers. Animals are another source of infection and an infection derived from this source is called zoonotic infection. Such infections are usually maintained in animals and are aquired accidentally.
Animal products such as meat, milk, eggs can be sources of infection. Food is another and very common source of infection due to everyday pattern of dealing with such material. Food can be contaminated and hence a source of infection at several stages – at its origin (infected animal or plant) or at the time of processing when handled with hands or contaminated tools. It is not only a vehicle when transmission is considered, but it is also a good enviroment, where bacteria and any other pathogen can multiply and produce toxins. Water is a major source of infection only in case of being in contact with sewage. Soil, air and dust usually contain non pathogenic organisms of numerous types, but this is not always a case since pathogenic organisms can be introduced through them to humans causing infection.
Soil can be contaminated with human and animal feaces or pathogenic fungi, air can be contaminated with organisms shed from skin or the respiratory tract. Dust can be infected with organism, especially bacteria and viruses that are shed from humans and any other source. Fomites are another source of infection, which can be defined as any porous substance that can absorb and pass on contagion. Nosocomial infections are infections that were not present or were incubating at the timme of admittance to a health care facility. They include infections patients aquire during their stay in a health care facility or infections they may manifest after discharge.