Infectious Diseases
Microbiology is the study of microorganisms, including unicellular (single-celled) eukaryotes and prokaryotes, fungi, and viruses. Most of the work in microbiology is done using methods from biochemistry and genetics. It is also related to pathology, immunology, and epidemiology as many microorganisms are pathogens.
Notable Pathogens
Below is a listing of different types of notable pathogens as categorized by their structural characteristics.
- Bacteria - Most are minute, usually only 0.5-5.0 μm in size, though one type may reach 0.3 mm in diameter. They generally have cell walls, like plant and fungal cells, but with a very different composition.
- Viruses - is a small particle which can
infect other biological organisms.
A pathogen is a biological agent that can cause disease to its host.
Viruses are obligate intracellular parasites meaning that they can only reproduce by invading and taking over other cells as they lack the cellular machinery for self reproduction. - Protozoa - are single-celled creatures with nuclei that show some characteristics usually associated with animals, most notably mobility and heterotrophy.
- Fungi - A fungal infection of the human body is called a mycosis. The most common of human mycoses is caused by dermatophytes. Although seen in all areas of the body one of the more common is tinea pedis or Athlete's foot.
- Parasites - is an organism that lives in or on the living tissue of a host organism at the expense of it. Parasites are generally smaller than their hosts, absorbing nutrients from the host's body fluids, but this is far from a universal strategy
The Chain of Infection
A process that begins when an agent leaves its reservoir or host through a portal of exit, and is conveyed by some mode of transmission, then enters through an appropriate portal of entry to infect a susceptible host.
Portals of Entry and Exit
Entry - An opening allowing the microorganism to enter the host. Portals include body orifices, mucus membranes, or breaks in the skin. Portals also result from tubes placed in body cavities, such as urinary catheters, or from punctures produced by invasive procedures such as intravenous fluid replacement.
Mode of Transmission - Method of transfer by which the organism moves or is carried from one place to another. The hands of the health care worker may carry bacteria from one person to another.
Exit - A place of exit providing a way for a microorganism to leave the reservoir. For example, the microorganism may leave the reservoir through the nose or mouth when someone sneezes or coughs. Microorganisms, carried away from the body by faeces, may also leave the reservoir of an infected bowel.
Disease Terminology
Contacts - People who have been with someone infected and may too have become infected.Endemic - Disease that occurs continuously or recurrently in a particular geographic region.
Epidemic - Disease that attacks simultaneously a large number of persons living in a particular geographic region.
Fomites - articles capable of carrying germs from an infected person to another person, for example, clothes or bedding
Immunity - a body’s ability to resist a particular disease
Incubation Period - the period between the time somebody is infected with a disease and the appearance of its first symptoms.
Pandemic - Disease that occurs more or less over the entire world at the same time.
Quarantine - the period of time during which people or animals are kept in isolation to prevent the spread of disease
Sporadic - Disease that occurs in isolated cases in a locality where it is neither endemic nor epidemic.
Vector - A carrier that transmits disease-causing microorganisms from infected individuals to other persons, or from infected animals to human beings.
Blood Borne Viruses (BBVs)
Due to the nature of ambulance work, staff are at a greater risk of being in contact with those patients that may have a blood borne virus, e.g. hepatitis b, hepatitis c and HIV. The risk is greatly increased when the patient is being cannulated and ambulance personnel inadvertently sustain a 'sharps' or 'needlestick' injury.
Some patients may not even know that they have a BBV so all blood and body tissue should be treated as potentially infectious.
Hepatitis B - is transmitted through exposure to bodily fluids containing the virus. This includes unprotected sexual contact, blood transfusions, re-use of contaminated needles and syringes, vertical transmission from mother to child during childbirth.
Hepatitis C - In most cases, acute hepatitis C infection has no symptoms and becomes chronic, and can cause long term damage to the liver, including cirrhosis and hepatocellular carcinoma. Severe liver damage may not develop for 10-40 years after infection
Human immunodeficiency virus (HIV) - This is the virus that can lead to AIDS (Acquired Immune Deficiency Syndrome). HIV has a window period of three months after you are exposed to the virus before it is apparent on the tests used to detect HIV
Further info on HIV and AIDS - http://www.tht.org.uk/hiv_info/facts.htm
Methicillin Resistant Staphylococcus Aureus (MRSA)
Staphylococcus aureus is a bacterium, frequently living on the skin or in the nose of a healthy person, that can cause illnesses ranging from minor skin infections (such as pimples, boils, and cellulitis) and abscesses, to life-threatening diseases such as pneumonia, meningitis, endocarditis and septicaemia.
MRSA, or methicillin-resistant Staphylococcus aureus, is a bacterium that has developed antibiotic resistance, first to penicillin in 1947, and later to methicillin. Popularly termed a "superbug", it was first discovered in Britain in 1961 and is now widespread. While an MRSA colonisation in an otherwise healthy individual is not usually a serious matter, infection with the organism can be life-threatening to patients with deep wounds, intravenous catheters or other foreign-body instrumentation; or as a secondary infection in patients with compromised immune systems.
Infection Control
http://www.asancep.org.uk/InfControl.ppt
Further Reading