Microbiology Lecture Notes PDF

MICROBIOLOGY Unit 303 LO 1 AIMS ► To describe the relevant micro-organisms and the diseases they cause. ► Different signs and symptoms of immunity. ► Describe other relevant diseases. OBJECTIVES ► Describe the structure of microorganisms and prions. ► Explain the relevant terms ► Des...

MICROBIOLOGY Unit 303 LO 1 AIMS ► To describe the relevant micro-organisms and the diseases they cause. ► Different signs and symptoms of immunity. ► Describe other relevant diseases. OBJECTIVES ► Describe the structure of microorganisms and prions. ► Explain the relevant terms ► Describe factors that impact susceptibility to infection ► Describe the bodies reaction to inflammation ►Explain the importance of immunisation ► Describe the chain of infection RELEVANT TERMS ► Micro-organism – an organism only seen by a microscope. ► Pathogenic – a micro- organism capable of causing harm. ► Non Pathogenic – incapable of causing harm. ► Commensal – causes harm if the environment changes. MICRO-ORGANISMS Divided into 4 groups PROTOZOA BACTERIA (not relevant to dentistry) VIRUSES FUNGI Structure of Bacteria ► Plasmid Bacteria ► Bacteria are single-celled microorganisms ► They have a rigid cell wall which varies in thickness ► A membrane controls substances that move in and out of the cell ► It is filled with a gel like substance known as cytoplasm ► They do not have a nucleus but have a nucleoid where DNA is found ► Flagella enables movement BACTERIA ► Single celled organisms. ► Aerobic bacteria thrives in the presence of oxygen. ► Anaerobic bacteria thrives in the absence of oxygen. BACTERIA Divided into 3 groups, defined by shape: ► Cocci – Round shaped. ► Bacilli – Rod shaped. ► Spirochaete – Spiral shaped. TYPES OF BACTERIA STREPTOCOCCUS MUTANS ► Round shaped. ► Grow in chains. ► Initiates dental caries. STAPHYLOCOCCUS ► Round shaped. ► Grows in clumps like grapes. ► Can cause soft tissue infections – skin or gum boils. ► Causes MRSA (Methicillin Resistant Staphylococcus Aureus) BACILLUS FUSIFORMIS ► Found in cases of ANUG (Acute Necrotizing Ulcerative Gingivitis). A.N.U.G ► Swollen gingiva. ► Ulceration. ► Grey/yellow film over the gingiva. ► Halitosis. SPIROCHAETES ► Spiral in shape. ► Found in cases of ANUG – Borrelia Vincenti ► Sometimes known as Treponema Vincenti Impetigo Is caused by streptococcus and staphylococcus bacteria Is it passed on by skin contact and is highly contagious Signs/Symptoms include itchy skin, and blisters on the skin that can look like cornflakes Treated by topical anti-biotics Tuberculosis Is a highly infectious bacterial condition that affects mainly the lungs but can affect other parts of the body It is passed on in droplets when a patient coughs or sneezes Symptoms night sweats, persistent cough and sometimes coughing up blood Can be prevented by immunisation ► Streptococcus sanguis is found in plaque, does not cause harm in the oral cavity but can settle on heart valves and cause a condition known as Endocarditis if the heart is weak. TREATMENT OF BACTERIAL INFECTIONS ► Can be treated either: ❖ systemically (swallowed). or ❖ topically (applied to the surface). ► If it kills the bacteria it is known as Bacterio-cidal. ► If it stops growth it is called Bacterio-static. TYPES OF ANTIBIOTICS ► A broad spectrum antibiotic commonly used: ❖ For Aerobic infections – Amoxicillin. ❖ If a patient is allergic to Amoxicillin – Erythromycin. ❖ For Anaerobic infections – Metronidazole. Learning check 1 ► Complete learning check of types of bacteria Structure of viruses ► Viruses are non-cellular particles ► They replicate within living cells, causing the cell to burst and infect other cells ► They either replicate the host cells nucleus or cytoplasm ► They vary is shape and complexity, very small can only be seen with an electron microscope ► They need a host but can survive outside the for sometime Relevant Viruses ► Hepatitis B ► Can either be acute or chronic ► Affects the liver ► Signs and symptoms can include fever, fatigue, abdominal pain and Jaundice ► It is highly virulent meaning is has a high risk of being passed on by bodily fluids ► It can remain infectious on surfaces for at least 7 days ► It can be prevented by vaccination HEPATITIS B ► A vaccination is available. ► It takes a cycle of 3 immunisations. ► A blood test is then done to check titre levels. ► A booster is administered 5 years after. Hepatitis C Like Hepatitis B this is a blood borne virus which affects the liver However there is no vaccine for Hep C at the moment Symptoms do not usually show until damage has been done to the liver but you can pass it on (Carrier) Symptoms are flu like, along with stomach aches. Human Immunodeficiency virus ► HIV attacks the immune system and weakens our ability to fight of infection and disease ► If left untreated it could lead to acquired immune deficiency syndrome (AIDS) ► It is passed on via bodily fluids ► Antiretroviral drugs can stop the virus from replicating and prevent further damage ► There is no vaccination for it. ► Post exposure prophylaxis available for inoculation injuries ► Oral affects can be thrush, canker sores and dry mouth. ► More advanced cases can manifest as Kaposi sarcoma EPSTEIN BARR ►Epstein Barr is a saliva borne virus which causes Glandular fever. ►Also can be known as Infectious mononucleosis ► Signs/Symptoms are swollen glands, sore throat, fatigue. HERPES FAMILY OF VIRUSES ► Herpes simplex – causes blisters (vesicles) on the corners of the lips known as a cold sore (herpes labialis). ► Can be treated by acyclovir. HERPES VIRUSES ► Herpes Varicella ► Herpes Zoster causes ‘chicken pox’. causes Shingles. ► Paramyxovirus, causes bi or uni-lateral swelling of the parotid glands. ► Commonly called mumps. ► Passed on the inhalation of droplets. Meningitis Can be caused by a virus or bacterial Causes inflammation of the meninges (the protective membrane around the brain) Signs and symptoms headaches, stiffness of the neck, dislike of bright lights, a rash that does not disappear when you roll a glass other it Human papillomavirus (HPV) ► HPV is a group of viruses that affect our mucosa and skin ► It is normally not harmful but in some cases can lead to types of cancer. It is responsible for more than 50% of oropharyngeal cancers. ► Passed on via skin contact. ► Can be prevented by vaccination. Covid 19 (Coronaviruses) Passed on via droplets from coughing or sneezing Signs and symptoms high temperature, loss of sense of taste and a new continuous dry cough Prevented by social distancing, regular handwashing, ventilation and the use of face masks Influenza (Flu) A group of viral infections passed on via droplets when coughing/sneezing Signs and symptoms include high temperatures, headaches, body aches and feeling tired Can be prevented by a vaccination, handwashing, binning tissues immediately Learning check 2 ► Carry out learning check on viruses Fungi ► The most relevant fungus is Candida albicans ► It lives naturally in our mouth and digestive system ► It does not normally cause harm and is considered a commensal microorganism ► It is a plant like organism ► It consists of a cell wall ► It has a nucleus ► A mass of hyphae filaments called mycelium ► A cell wall, membrane and cytoplasm CANDIDA ALBICANS ► Denture Stomatitis ► Thrush ORAL THRUSH ► Oral thrush commonly occurs when the patient’s immune system is compromised such as HIV or Diabetes or the environment has changed such as wearing dentures. ► This is known as commensal. CANDIDA ALBICANS Treatment Angular Cheilitis All can be treated by anti- fungal drugs such as: ⮚ Miconazole. ⮚ Amphotericin. ⮚ Fluconazole. PRIONS ► Abnormal infectious protein particles. ► Causes rare, fatal degenerative central nervous system infections. ❖ The commonest form is Creutzfeldt-Jacob disease (CJD) VARIANT CREUTZFELDT-JACOB DISEASE (vCJD) ► vCJD is caused by another type of Prion: ❖ Known as human form of “mad cow disease” ❖ Linked to consumption of meat products ► Prions may not be inactivated by sterilization. Current guidelines state RCT instruments should be single use only. Learning check 3 ► Complete learning check on fungi and prions PATHOLOGY PATHOLOGY ► Study of disease and its effects on the tissues of the body. Chain of infection INFECTION ► Introduction of disease into the body by pathogenic micro-organisms. ► Can be: ► Direct – person to person such as skin contact or inhaling droplets. ► Indirect – via an item such as inoculation injury. Chain of Infection ► Infectious agent i.e. the flu virus ► Reservoir where the flu virus naturally lives i.e. a person ► Portal of exit how does the flu leave for example via the nose when sneezing ► Mode of transmission ie airborne ► Portal of entry ie new host breathing the droplets in ► Susceptible host the individual has a lower immune system for example elderly FIRST LINE OF DEFENCE Intact skin, hair and tears. Forms a physical barrier which prevents micro-organisms from entering the body. IMMUNITY ► The resistance to disease. ► The body produces ‘anti-bodies’ which fight off the disease. ► The response is started by the body being invaded by ‘anti-gens’. IMMUNITY Passive Immunity This is temporary only, the anti-bodies are from a donor not formed by your own body It is fast acting Once they have fought off the infection they disappear They can be natural from breast feeding Or artificial from an injection of pre-formed antibodies Acquired Immunity This is where the body produces it’s own antibodies It is slow acting But provides long term protection Natural caused by exposure to disease Artificial by vaccines DO YOU HAVE UP TO DATE VACCINATIONS ? ► Hepatitis B. ► Poliomyelitis. ► Chicken pox. ► Meningitis. ► MMR. ► TB & whooping cough. ► Diphtheria & tetanus. Vaccinations ► A vaccine is an artificially produced version of a pathogen which causes the same immune response as contact with the real disease does ► However the pathogen does not replicate so does not infect other cells so does not cause illness ► Vaccines not only protect the vaccinated person but also creates herd immunity, if enough people are immune to a disease is stops its spread and protects those with weakened immune systems 5 SIGNS OF ACUTE (IMMEDIATE) INFLAMMATION 1. Redness.(Erythema) 2. Swelling. 3. Heat. 4. Pain. 5. Loss of function. Learning check 4 ► Complete learning check on immunity Factors that impact on infection There are many factors that impact on the host’s susceptibility to infection This means some people are more likely to have worse symptoms and less likely to be able to fight off the infection Factors that affect susceptibility​ ► Age babies and young children have not yet developed their immune systems ► As we get older our immune system weakens ► Pregnancy the immune system goes through many changes to prevent the embryo being rejected and help the baby grow ► Illnesses such as diabetes lower the immune system ► Also other issues such as immunisation, diet, smoking and stress can impact on our immune system. Other relevant terms ► Chronic – long term disease (longer than 3 months) ► Acute – Short term disease ► Localized infection, an infection that effects a specific part of the body such as an abscess around a tooth. ► Systemic infection where the whole body is effected and is spread through the blood stream such as the flu or pneumonia ► Or can be non-infectious such as diabetes Pus Production ► Pus is a byproduct of your body’s response to infections ► When the body detects infection it sends a type of white blood cell to destroy the bacteria. ► This process causes pus which contains dead white blood cells, dead tissue cells and dead bacteria. ABSCESS ► A localised collection of pus CELLULITIS ► Diffuse pus in the soft tissues. CYST Abnormal sac of fluid ► e.g. dentigerous cyst ► Occurs around the crown of a partially erupted or unerupted tooth. TUMOUR ► A tumour is a swelling caused by an abnormal and uncontrolled growth of body cells. TYPES OF ORAL TUMOURS Benign Malignant ► Non invasive, ► Very aggressive, slow growing, non potentially fatal recurrent (not e.g. squamous fatal). cell carcinoma. LEUKOPLAKIA ► Immovable white patches which may be premalignant. ERYTHROPLAKIA ► Red patches in the mouth which can be described as sinister. CONGENITAL DEFECTS ► Defects present at birth caused by abnormal facial development during gestation, for example: ❖ Cleft palate and harelip ❖ Heart defects