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Transcript
Microbiology and Pathogens Teacher - Peter Mitchell BSc (Anatomy & Histology) Histology). Dip Health Science (Massage Therapy) Microbiology gy is the study y of organisms g not visible to the naked eye. Thus requiring the use of a microscope to see them. Microscopic organisms are sometimes called microbes The biomass of the microbial kingdom outweighs that of the animal kingdom! Not all microbes are harmful to humans “ Despite the fact that the microbial biomass outweighs the total animal biomass by a factor of 100, 100 most of us sail through life unbothered by the microbial ocean. They are the host; we the pampered and tolerated guest. ” William Boyd (Pathologist) There are manyy examples p of microbes being g beneficial to humans • Some bacteria live in our gut and help digest food • Some yeasts and bacteria are used in baking, brewing and cheese making What are Germs? Micro organisms are found in abundance throughout the environment. Germs are micro organisms that are likely to cause disease. Only a very small number of microbes are pathogenic, i e capable of causing disease i.e. Bacteria are just one type of micro-organism, micro organism, alongside viruses, fungi and protozoa and parasites y Direct damage (lysis of cells by intracellular organisms) y Toxin production (vomiting, diarrhea, paralysis, haemolysis, necrosis) g p y y y Damage through inflammation and immune g g response The presence of pathogens does not automatically t ti ll iimply l di disease. Context is important p e.g.: g E-coli is normally found in the gut and is not harmful in normal concentrations, however if ecoli numbers increase problems can arise. OR If sufficient numbers of e-coli enter the blood via non-intact skin or mucous membranes, serious disease can occur. Smallest Viruses Bacteria Fungi Protozoa & Parasites Largest Wh t is What i a virus? i ? y It is very small small, typically 0 0.1um 1um y It is not a true cell y It is not an independently living organism. It must be inside a living cell to replicate y They have genetic material but lack cell membranes, cytoplasm and machinery y The virus uses the host’s cell's machinery and enzymes to generate virus parts which are later assembled bl d iinto t new virus i particles ti l which hi h lleave th the cell to infect other cells y It can infect bacteria, fungi, plants, animals and man y It may remain viable for long time, even in dry conditions y It can survive but does not grow in food Nearly 1000 different types of viruses are known to infect humans and it has been estimated that they account for approx. 60% of human infections. The young, elderly and immuno-compromised are particularly at risk from virus infections Many viral diseases are well known and easily identified: y from colds and flu to chicken pox and measles y from mumps and herpes to polio, hepatitis and HIV From the ‘Clinic Hygiene’ point of view, we are mainly concerned with virus infections relating to poor personal or surface hygiene hygiene, and are thus preventable y Gastrointestinal infections Gastroenteritis Diarrhoea Infectious intestinal disease y Respiratory infections Flu Fl Common cold Bronchitis y Skin S presenting p ese t g co conditions dto s Papilloma Herpes – simplex & Zooster Chicken pox (Poxivirus (Poxivirus)) Papilloma Virus Herpes zoster Herpes simplex Poxivirus - Chicken pox Bacteria are p prokaryotes y ((membrane and cell wall)) and have a characteristic cellular organisation. They are simple, simple small, small unicellular organisms varying in size between 1-20 um long Damage tissue directly Also damage tissue by releasing toxins Bacteria can be classified by shape Spherical (coccus) e.g. Staphylococcus aureus Spiral/helical e.g. Treponema Rod (bacilli) e.g Escherichia coli Sphere shaped Diplococci- bacterial pneumonia Staphylococcus aureus- wound infections, boils and infected acne. Streptococci- common culprits in throat infections Rod shapedshaped bacilli tetanus tuberculosis Spiral syphilis Typical Growth Curve for a Bacteria Population y Lag Phase growth is slow whilst they become used to their new environment and nutrients y Log Phase once the metabolic machinery is running, they start multiplying exponentially, doubling in number every few minutes y Stationary Phase as more and more bacteria are competing for nutrients which are decreasing, growth stops and the number of bacteria stabilises y Death Phase toxic waste products build up, nutrients have run out and the bacteria begin to die Impetigo Staphylococcus Aureus “Golden Staph” Streptococcus Pneumoniae “meningitis” Acne Fungi g are eukaryotic y and exist in different g growth forms in different environments. They range from small single cells such as yeasts (~5um) to large complex structures such as mushrooms (~5cm) ( 5cm) The high humidity and temperatures often found in g bathrooms and kitchens are conducive to fungal growth. Mould, or mildew as it is sometimes referred, likes warmth and moderate to high humidity Fungi responsible for human disease can be divided into two distinct morphological forms y Yeasts which grow as oval or spherical single cells like bacteria and multiply by budding and division y Filamentous fungi more commonly known as moulds, consist of long, branching hyphae forming a mycelium mycelium. Asexual reproduction results in formation of spores The can be responsible for infections They They can cause an allergic response Fungi cause discolouration and deterioration of household surfaces giving the characteristic blackening of walls walls, tile grouting grouting, plaster and around window frames Can cause unpleasant odours which are difficult to disguise. Fungi such as Aspergillus, Penicillium, and Alternata have been found to produce volatile organic compounds d Numerous ffungii h N have b been ffound d tto produce d volatile l til organic compounds (VOC) and it has been suggested that these affect the health of persons living in mouldy houses. Symptoms include headache, eye, nose and throat irritation and fatigue VOC’s have been implicated in health issues relating to sick building syndrome Spores of toxigenic fungi contain mycotoxins (toxic secondary metabolites). Many fungal spores are small enough to reach the alveoli in the lungs. The mycotoxins may be transported via the blood from the lung to other body sites, sites possibly causing other effects e.g. skin lesions Fungi cause 2 types of infection: y Superficial mycoses y Deep mycoses Fungus grows on the body surface in skin, hair and nails Spread by direct contact Highly contagious and easily spread E.g. y Candida albicans ((thrush and nappy ppy rash)) y Athlete’s foot y Ring worm Involve internal organs, usually life-threatening Rare except in immunocompromised people Caused by opportunistic fungi (e.g. Aspergillus) Acquired by inhalation of spores or by entry through wounds Some are part of the normal body flora and are harmless unless the body’s defences are compromised in some way (e.g. Candida) Almost all microbial allergens are fungal in origin Allergic rhinitis (hay fever) Bronchitis Asthma Extrinsic allergic alveolitis Asthma can be initiated and provoked by allergens commonly encountered in the general environment, for example pollens (trees, (trees grass), grass) house dust mites and moulds. Tinea Pedis ed s Tinea Cruris Ti Tinea C Corporis i Tinea Versicolor Protozoa are single-celled eukaryotes Live in water or moist places or other organisms as parasites Have a resistant transmissible cyst stage Transmission to humans via insect bite or accidental ingestion of infective stages y Cryptosporidium spp. infects the intestines causing Cryptosporidiosis Cryptosporidiosis. Large outbreaks are associated with contaminated water or treatment deficiency of water supplies y Gi Giardia di lamblia l bli causes giardiasis, an infection of the small intestine, spread via contaminated food and water and by direct person-to-person contact. Ingestion of one or more cysts may cause disease y Entamoeba histolytica an amoeba infecting the large intestine, causes di h diarrhoea/dysentery, /d t spread d via i contaminated t i t d water t or ffood d y Toxoplasma gondii causes toxoplasmosis, p , a very y severe disease that can p produce central nervous system disorders Parasites are larger and more complex than protozoa. Common examples of parasites are: y Tape worms y Hook worms y Pin Pi worms Worms are very contagious and are transmissible via the faecal – oral route. That is; the worm eggs are normally ingested due to poor hand hygiene and cross contamination of inanimate objects Micro-organisms are introduced continually into the clinic via: people food, people, food water, water insects, insects air. air Wet sites such as sinks, sinks toilets, toilets dishcloths and facecloths can also support microbial growth and themselves become reservoirs of potentially hazardous microorganisms. T Towels, l washing hi b basket k t etc t Many organisms occurring in the clinic are of little consequence. Some organisms have the potential to cause infectious disease Some people carry highly pathogenic organisms without themselves being affected - other family members unaware of hazard Hands, and a whole range of food and hand contact surfaces, combine to provide transfer routes that can move pathogens around the home and ultimately y into the body y producing g infection