Microbiology and Pathogens. Teacher - Peter Mitchell

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1 Microbiology and Pathogens Teacher - Peter Mitchell BSc (Anatomy & Histology). Dip Health Science (Massage Therapy)

2 Microbiology is the study of organisms 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!

3 Not all microbes are harmful to humans Despite the fact that the microbial biomass outweighs the total animal biomass by a factor of 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)

4 There are many examples of microbes being 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

5 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 Bacteria are just one type of micro-organism, Bacteria are just one type of micro organism, alongside viruses, fungi and protozoa and parasites

6 Direct damage (lysis of cells by intracellular organisms) Toxin production (vomiting, diarrhea, paralysis, haemolysis, necrosis) Damage through inflammation and immune response

7 The presence of pathogens does not automatically ti imply disease. Context is important e.g.: p g E-coli is normally found in the gut and is not harmful in normal concentrations, however if e- coli 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.

8 Smallest Viruses Bacteria Fungi Protozoa & Parasites Largest

9 What is a virus? It is very small, typically 0.1um It is not a true cell It is not an independently living organism. It must be inside a living cell to replicate They have genetic material but lack cell membranes, cytoplasm and machinery

10 The virus uses the host s cell's machinery and enzymes to generate virus parts which are later assembled into new virus particles which h leave the cell to infect other cells It can infect bacteria, fungi, plants, animals and man It may remain viable for long time, even in dry conditions It can survive but does not grow in food

11 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: from colds and flu to chicken pox and measles from mumps and herpes to polio, hepatitis and HIV

12 From the Clinic Hygiene point of view, we are mainly concerned with virus infections relating to poor personal or surface hygiene, and are thus preventable Gastrointestinal infections Gastroenteritis Diarrhoea Infectious intestinal disease Respiratory infections Flu Common cold Bronchitis Skin presenting conditions o Papilloma Herpes simplex & Zooster Chicken pox (Poxivirus)

13 Papilloma Virus Herpes simplex Herpes zoster Poxivirus - Chicken pox

14 Bacteria are prokaryotes (membrane and cell wall) and have a characteristic cellular organisation. They are simple, 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

15 Spherical (coccus) e.g. Staphylococcus aureus Spiral/helical e.g. Treponema Rod (bacilli) e.g Escherichia coli

16 Sphere shaped Diplococci- bacterial pneumonia Staphylococcus aureus- wound infections, boils and infected acne. Streptococci- common culprits in throat infections Rod shaped- bacilli Spiral tetanus tuberculosis syphilis

17 Typical Growth Curve for a Bacteria Population Lag Phase growth is slow whilst they become used to their new environment and nutrients Log Phase once the metabolic machinery is running, they start multiplying exponentially, doubling in number every few minutes Stationary Phase as more and more bacteria are competing for nutrients which are decreasing, growth stops and the number of bacteria stabilises Death Phase toxic waste products build up, nutrients have run out and the bacteria begin to die

18 Impetigo Staphylococcus Aureus Golden Staph Streptococcus Pneumoniae meningitis Acne

19 Fungi are eukaryotic and exist in different growth forms in different environments. They range from small single cells such as yeasts (~5um) to large complex structures such as mushrooms (~5cm) The high humidity and temperatures often found in bathrooms and kitchens are conducive to fungal growth. Mould, or mildew as it is sometimes referred, likes warmth and moderate to high humidity

20 Fungi responsible for human disease can be divided into two distinct morphological forms Yeasts which grow as oval or spherical single cells like bacteria and multiply by budding and division Filamentous fungi more commonly known as moulds, consist of long, branching hyphae forming a mycelium. Asexual reproduction results in formation of spores

21 They can be responsible for infections They can cause an allergic response Fungi cause discolouration and deterioration of household surfaces giving the characteristic blackening of walls, tile grouting, plaster and around window frames

22 Can cause unpleasant odours which are difficult to disguise. Fungi such as Aspergillus, Penicillium, and Alternata have been found to produce volatile organic compounds N f i h b f d t d l til Numerous fungi have been found to produce volatile 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

23 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, possibly causing other effects e.g. skin lesions

24 Fungi cause 2 types of infection: Superficial mycoses Deep mycoses

25 Fungus grows on the body surface in skin, hair and nails Spread by direct contact Highly contagious and easily spread E.g. Candida albicans (thrush and nappy rash) Athlete s foot Ring worm

26 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 Some are part of the normal body flora and are harmless unless the body s defences are compromised in some way (e.g. Candida)

27 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, grass), house dust mites and moulds.

28 Tinea Pedis Tinea Corporis Tinea Cruris Tinea Versicolor

29 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

30 Cryptosporidium spp. infects the intestines causing Cryptosporidiosis. Large outbreaks are associated with contaminated water or treatment deficiency of water supplies Giardia lamblia 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 Entamoeba histolytica an amoeba infecting the large intestine, causes diarrhoea/dysentery, spread via contaminated t water or food Toxoplasma gondii causes toxoplasmosis, a very severe disease that can produce central nervous system disorders

31 Parasites are larger and more complex than protozoa. Common examples of parasites are: Tape worms Hook worms Pin worms

32 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

33 Micro-organisms are introduced continually into the clinic via: people, food, water, insects, air. Wet sites such as sinks, toilets, dishcloths and facecloths can also support microbial growth and themselves become reservoirs of potentially hazardous microorganisms. Towels, washing basket etc 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 into the body producing infection