Canvas Notes: Microbiology PDF

CANVAS NOTES Thursday, 18 July 2024 6:34 pm Learning outcome Understand Identify the four types of microorganisms and describe their characteristics Explain how bacteria are identified Identify the routes by which micro-org...

CANVAS NOTES Thursday, 18 July 2024 6:34 pm Learning outcome Understand Identify the four types of microorganisms and describe their characteristics Explain how bacteria are identified Identify the routes by which micro-organisms enter the body and relate these to clinical practice Identify potential sources of infection and the mechanisms of transmission of microorganisms with reference to clinical practice Distinguish between cleaning, disinfection and sterilisation Describe the role of cleaning, disinfection and sterilisation in preventing the spread of infections, with special reference to the hospital environment MICROBIOLOGY = the study of organisms that are not visible to the naked eye. - May only be observed and studied when magnified using some form of microscopy. Organisms include: bacteria, viruses, fungi and protozoa (widespread in the environment + c Other organisms exist happily within the human body and provide health benefits e.g. health NAMING CONVENTIONS FOR MICROORGANISMS (Unique way of identifying different types of organisms) Name is binomial (meaning made of two parts). 1. First word of the name stands for the genus - type of classification 2. Second word specifies the species Two-part name is written in italics e.g. humans (not microorganisms) are named Homo sapiens Common bacterium causing food poisoning = Escherichia coli (E. coli). TYPES OF MICROORGANISMS 1. BACTERIA 2. VIRUSES CHARACTERISTICS - Unicellular/Single-celled organisms. - Smaller again and - Classed as prokaryotes (cells have no nucleus) light microscope ( - Very small with a diameter of about 1 microscope micrometre - Nanometres in siz - Viruses are non-liv d Covered on notes Covered on cheat sheet can cause disease if they invade the human body). hy gut bacteria. 3. FUNGI 4. PROTOZOA cannot be seen using a regular - Multicellular, eukaryotic organisms (more Eukaryotic org (can be observed using an electron complex + genetic material is housed within or multicellula cells in the nucleus - organelle) EXAMPLES ze (1/1000th of a micrometre) - Feed on decaying/dead material 1. Amoeba ving comprising a protein coat that 2. Flagella A ganisms that may be unicellular ar. as ates CHARACTERISTICS - Unicellular/Single-celled organisms. - Smaller again and - Classed as prokaryotes (cells have no nucleus) light microscope ( - Very small with a diameter of about 1 microscope micrometre - Nanometres in siz - Viruses are non-liv encloses genetic m RNA. - Can only survive a organisms LOCATION Found in our environment + on and within the Viral diseases are se human body. The human body provides a perfect without the need fo environment for bacteria to thrive. - Viruses are a to bacteria so medications h value on viral are responsiv symptoms). EXAMPLES IN THE - Internally found in the human mouth, nasal - HIV (human immu HUMAN BODY cavity, throat, ears + gastrointestinal tract. - Rhinovirus (causes - Large colonies can be found on healthy human - Epstein-Barr virus skin particularly in the armpits, navel + behind ears (locations that are typically moist) - Drier areas of the skin contain bacteria  cannot be seen using a regular - Multicellular, eukaryotic organisms (more Eukaryotic org (can be observed using an electron complex + genetic material is housed within or multicellula cells in the nucleus - organelle) EXAMPLES ze (1/1000th of a micrometre) - Feed on decaying/dead material 1. Amoeba ving comprising a protein coat that 2. Flagella material in the form of DNA or 3. Ciliates 4. Sporozo and replicate in the cells of other elf-limiting (resolve spontaneously Can thrive on and in the human body. AMOEBAS or treatment). - Some strains of the fungus Penicillium Single-celled different type of micro-organism produce the metabolite penicillin extending a fl o antibiotic/antibacterial (antibiotic that kills bacteria) pseudopods. have no effect on viruses + no - Live in b infections. Some viral infections their ing ve to anti-viral drugs (lessoning via cont results DYSENTERY = which causes mixed with m abdominal dis unodeficiency virus) - Tinea causes athlete's foot + ringworm FLAGELLATES s common cold) - Candidal infection can result in thrush Have a long w (causes glandular fever) - Aspergillus infection can result in aspergillosis flagellum tha (occur in people with underlying illnesses e.g. with moveme tuberculosis/COPD and individuals who are EXAMPLE immunocompromised) Infection with (carried by ins African Sleepi - Early sy joint pa - Later st confusio  ganisms that may be unicellular ar. as ates oans protists that move by luid part of the cell called both fresh and salt water and gestion into the human body taminated food and water in dysentery infection of the intestines the passage of bloody stools mucus along with associated scomfort. S whip-like structure called a at beats to provide the cells ent. h the flagellate Trypanosoma sects/animals) can cause ing Sickness. ymptoms = fever, headaches, ains + itching tages = behavioural changes, on + poor coordination  Staphylococcus Ebolavirus - cause f BACTERIAL CLASSIFICATION Bacteria can be classified as gram-positive or gram-negative according to the staining proper Gram staining is a 4-step process: STEP 1: Cells are exposed to the primary stain crystal violet and appear purple/blue. STEP 2: Iodine is added so that the crystal violet dye sticks to the cell wall. STEP 3: Alcohol is added and the crystal violet stain that has not adhered to the cell wall is w  African Sleepi - Early sy joint pa - Later st confusio CILLIATES Unicellular m hair-like proje cell membran - Cilia bea movem EXAMPLE Balantidium c causes dysent fatal haemolytic disease Candida albicans - yeast infection that can cause thrush rties of their cell walls. washed away.  ing Sickness. ymptoms = fever, headaches, ains + itching tages = behavioural changes, on + poor coordination micro-organisms that have small ections on the surface of their nes. at and assist the organisms ment in water. coli found in the pig colon tery in humans BACTERIAL CLASSIFICATION Bacteria can be classified as gram-positive or gram-negative according to the staining proper Gram staining is a 4-step process: STEP 1: Cells are exposed to the primary stain crystal violet and appear purple/blue. STEP 2: Iodine is added so that the crystal violet dye sticks to the cell wall. STEP 3: Alcohol is added and the crystal violet stain that has not adhered to the cell wall is w STEP 4: A secondary stain (safranin) stains cells pink/red. GRAM-POSITIVE BACTERIA GRAM-N Have a thick cell wall that retains the primary stain (crystal violet) during the Have a th decolourising step. - App - Retain purple after the staining procedure because the crystal violet - Som dominates the light red/pink colour of the secondary counterstain e.g. some (safranin). reagents Bacteria can also be classified according to their: morphology or shape - More detailed identification involves metabolic + genetic characterisation. EXAMPLE Two common bacterial morphologies = the round 'coccus' (a single sphere) and rod-like 'bac Two spheres joined together = Diplococcus Streptococcus are chains of cocci Staphylococcus are clusters of cocci  rties of their cell walls. washed away. NEGATIVE BACTERIA hin cell wall and the crystal violet washes away during the decolourising step. pear light red/pink after staining with the safranin. me bacteria don't react with Gram stain = atypical bacteria e Mycoplasma and Chlamydia lack a cell wall and cannot retain the gram-stain cillus'.  - More detailed identification involves metabolic + genetic characterisation. EXAMPLE Two common bacterial morphologies = the round 'coccus' (a single sphere) and rod-like 'bac Two spheres joined together = Diplococcus Streptococcus are chains of cocci Staphylococcus are clusters of cocci Bacillus is a single rod Streptobacillus is a chain of rods ACQUIRING INFECTION SOURCES OF INFECTION Two different ways infection can be acquired: 1) ENDOGENOUS INFECTION (LEAST COMMON) Caused by an infectious agent that is already present in the body, but has previously been u EXAMPLE - Bowel perforations may lead to peritonitis or infection within the peritoneum. cillus'. unapparent/dominant (usually occurs when microorganisms gain access to locations where they don n’t normally reside) SOURCES OF INFECTION Two different ways infection can be acquired: 1) ENDOGENOUS INFECTION (LEAST COMMON) Caused by an infectious agent that is already present in the body, but has previously been u EXAMPLE - Bowel perforations may lead to peritonitis or infection within the peritoneum. - Aspiration of stomach acid into the respiratory system can lead to pneumonia - Staphylococcus aureus that is normally found in the nose may cause wound infection i 2) EXOGENOUS INFECTION Acquired from the environment. The most important source of human infection is other hum Some agents e.g. measles are more transmissible than others. EXAMPLE - Nosocomial infections (acquired in a hospital environment) ROUTES OF ENTRY (RESULTING IN EXOGENOUS INFECTION) Inhalation of aerosols involves the entry of pathogens e.g. rhinovirus or mycobacteriu These pathogens can cause the common cold and tuberculosis. Ingestion of pathogens found on contaminated food and water e.g. salmonella can re inoculation often enabled by an insect vector causes African sleeping sickness and HIV Congenital transmission from mother to unborn child PREVENTION OF INFECTIONS Good hygiene reduces infections. 3 means of preventing infections are: 1) CLEANING = the physical removal of dirt, blood and sputum that may allow the growth - Source of nutrition for the micro-organisms is removed limiting the possibility for grow 2) DISINFECTION = renders an object non-infective. - Micro-organisms may still be present, but their numbers are greatly reduced, limiting p 3) STERILISATION (MOST STRINGENT) = where all living organisms, including fungal spore - For surgical procedures where instruments are directly contacting the interior of the b unapparent/dominant (usually occurs when microorganisms gain access to locations where they don if inoculated into a surgical wound. mans and animals. um via the respiratory system. esult in food poisoning V. h of an organism. wth. However, viable micro-organisms may remain at the location. probability of infection es are destroyed and rendered non-infective. body it is crucial that all equipment is thoroughly sterilised usually via auto valving (treats the instrum n’t normally reside) ments with steam at a high pressure).