Bacteria - Growth Requirements PDF

Bacteria - Growth Requirements Bacterial multiplication?? Temperature Most between 10oC – 39oC Variable depending on organism Pathogenic bacteria o...

Bacteria - Growth Requirements Bacterial multiplication?? Temperature Most between 10oC – 39oC Variable depending on organism Pathogenic bacteria o optimum ~37 C Thermophile Mesophiles Pyschrophiles (heat-loving) (love moderate temps) (cold-loving) Optimum 60oC Optimum 25 - 30oC Optimum 10oC 10 https://nationalvetcontent.edu.au/alfresco/d/d/workspace/SpacesStore/cebc7038-83d9-432d-97e0-8289f4f13e26/ims/page_03.htm ; & Bridges (2015) from http://slideplayer.com/slide/7272660/# Bacteria - Growth Requirements pH Most close to neutral ~ pH 7 Variable depending on organism Helicobacter pylori have enzymes which enable them to survive quite happily at pH 3.5 found in stomach antrum (area closest to small intestine) This enables them to survive and potentially cause ulcers.  Bacteria - Growth Requirements Oxygen Obligate aerobes Obligate anaerobes Can ONLY grow in Can NOT grow in the presence of O2 the presence of O2 Example Example Pseudomonas aeruginosa Clostridium perfringens Mycobacterium tuberculosis Clostridium botulinum Staphylococcus aureus Facultative +/- O 2 E.Coli, Salmonella…. anaerobes 12  Bacteria – Gram Stain Technique to visualise bacteria https://commons.wikimedia.org/wiki/File:Gram_stain_01.jpg; Y tambe; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-3.0,2.5,2.0,1.0  Bacteria – Gram Stain Structural difference in cell wall Gram Positive – Thick layer of peptidoglycan Gram Negative – Reinforced with 2nd membrane Gram +ve Gram -ve Capable of forming spores More difficult to kill! (spores survive extreme conditions – e.g. Clostridium difficle) Produce endotoxins (endotoxins released when bacteria Reinfection +++ die, can cause sepsis - ?fatal) e.g. Staphylococci, Streptococci, e.g. E. coli, Salmonella, Neisseria Pneumococci, Clostridia… Pseudomonas, Legionella… 14 Some antibiotics can work on both whilst others work on one type Normal Flora (Microbiota) Our bodies have microbes in residence on various areas Bacteria… 10 x more than human cells. Resident flora Colonised / transient Hygiene 15 https://commons.wikimedia.org/wiki/File:Microbiome_Sites_%2827058471125%29.jpg; https://www.flickr.com/people/142595545@N03; https://commons.wikimedia.org/wiki/Category:CC-BY-2.0 Normal Flora (Microbiota) Beneficial Roles Skin: Reduces pH Change environmental conditions Not ideal for other species Oral & Vagina: Competes & inhibits pathogens & yeasts Intestine: Excrete antibacterial chemicals Synthesise and secrete vitamins (esp. Vit. K) Stimulate local immunity (lymphatic tissue, Ig) 16 | School of Behavioural and Health Sciences Nat Rev Microbiol. 2011 Apr; 9(4): 244–253. doi: 10.1038/nrmicro2537 Normal Flora (Microbiota) Possible harmful effects Competition for nutrients Bacterial synergism: normal flora & pathogen Endogenous disease: fever, inflammation, ?cancer Opportunistic infection: overgrowth, infection 17 | School of Behavioural and Health Sciences Nat Rev Microbiol. 2011 Apr; 9(4): 244–253. doi: 10.1038/nrmicro2537 Normal Flora (Microbiota) Common causes of opportunistic infection Genetic predisposition Chemotherapy or other therapies that impact immunity HIV/AIDS Bone marrow disease Pregnancy 18 | School of Behavioural and Health Sciences What is an antigen? anything capable of inducing an immune response anything foreign to you as the host examples: – microbes or their parts – protein from other species rabbit serum, dust mite, cat hair, pollen – transplanted tissue from other humans/animals 4 | classes.midlandstech.edu Body defences non-specific (innate) general defence/attack on all antigens inborn first and second line defences specific (acquired or adaptive) Specialist/targeted defence against one type of antigen acquired during life third line defences 7 Non-specific defences General properties Do not distinguish between threats React same each time as first time Present at (before) birth Second line defences respond to tissue damage caused by pathogens or “mechanical” means 8 | First line defences protect portals of entry https://commons.wikimedia.org/wiki/File:OSC_Microbio_17_02_Barrier.jpg; CNX 10 OpenStax; https://commons.wikimedia.org/wiki/Category:CC-BY-4.0 First line defences Non-specific Aim – keep every invader out/deny entry the SAME way via chemical and physical barriers 1.Skin – epidermis, sebum, sweat 2.Mucous membranes – mucous + hairs, cilia 3.Fluids that help protect these surfaces – tears, saliva, nasal secretions, urine, gastric juice 4.Defecation and vomiting, coughing and sneezing 12  Skin Colour 3 factors: Melanin - pigment made in skin (melanocytes) - exposure to UV increases melanin synthesis - darker skin due to more melanin, and type of melanin produced, not more melanocytes - Carotene - yellowish/orange pigment (found in carrots) - accumulates in the stratum corneum - Hemoglobin - red pigment of blood - gives fair-skinned people a ‘pinkish hue’ https://commons.wikimedia.org/wiki/File:CarotenemiaBefore_After.jpg; Norge0209; https://commons.wikimedia.org/wiki/Category:CC-BY-3.0  Skin Colour cont… Redness - embarrassment, fever, hypertension, inflammation, allergy etc Palour - fear, anger, anaemia, hypotension Jaundice - liver disorder (accumulation of yellow bile in tissues) Black/blue (bruises) - blood has escaped from vessels and clotted beneath the skin = hematoma (blood mass) https://commons.wikimedia.org/wiki/File:Jaundice08_-_censored.jpg; User:Doc James; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0  What, Where and Why? Nails - What: modifications of the epidermis, densely packed epithelial cells containing fibres of hard keratin (kera = horn) - Where: located distally on the posterior surface of the fingertips and distally on the superior surface of the toes - Why: https://www.flickr.com/photos/adaenn/453174242; https://creativecommons.org/licenses/by-nc/2.0 protection of the underlying nerves aids in picking things up, scratching, digging,  What, Where and Why? Glands - What: clusters of specialised epithelial cells that secrete a substance. eg, oil, sweat, wax, milk, etc - Where: sweat glands: whole body except nipples and parts of external genitalia sebaceous glands: whole body except palms and soles - Why: sweat glands: regulate body temp, remove wastes sebaceous glands: softens skin and hair, ↓bacterial growth, ↓ water loss  What, Where and Why? Hair - What: - shaft: slender filament of keratinised cells root: below the surface, embedded within skin follicle: group of cells that surround the root, holds hair in place - Where: whole body except palms, soles, lips, nipples and parts of the external genitalia - Why: warmth, protection against physical trauma, heat loss, sunlight, detect insects on skin, keep out foreign particles, etc https://commons.wikimedia.org/wiki/File:Cool_Hair,_Ethiopia_%289730522520%29.jpg; Rod Waddington from Kergunyah, Australia; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-2.0  Functions of the Skin Protection The skin is the most vulnerable organ of the body. It is constantly exposed to bacteria, abrasions, temperature extremes, chemicals, etc Acts as 3 types of barriers: - Chemical barrier: Skin secretions and melanin - Physical barrier: Continuity of skin, waterproof - Biological barrier: Langerhan’s cells, macrophages Functions of the Skin cont… Body temperature regulation Sweating - 500ml/day at rest (unnoticeable) - up to 12L/day during vigorous exercise Cutaneous sensation Sensory receptors on the skin allow us to feel light touch, pressure, vibration, tickling (mechanoreceptors), temperature (thermoreceptors), pain (nociceptors), etc Hair follicle receptors – insects, wind, etc Metabolic function Produces vitamin D (when exposed to UV) for calcium and phosphorous absorption (bone development) Functions of the Skin cont… Blood reservoir The dermis is highly vascularised Blood can be temporarily shunted from the skin and relocated to another part of the body that requires it Excretion and Absorption Removal of nitrogenous wastes such as urea, ammonia, uric acid, and salts, etc in sweat. Absorbs vitamins A, D, E and K and oxygen  Effects of Aging on Skin ↓Basal cell activity, epidermis thins → ↑injuries, tears, infections, etc ↓Langerhan cells → ↓immune sensitivity → ↑skin damage and infections ↓ Vitamin D production → ↓calcium and phosphorus absorption → muscle weakness and bone degradation ↓ melanocyte activity → skin becomes pale and more likely to get sunburn, hairs go grey ↓ glandular activity → ↓thermoregulation, ↑dry skin Effects of Aging on Skin cont… ↓blood supply to dermis → cool skin → activates thermoreceptors → elderly often “feel cold” ↓elastic/collagen fibres in dermis → sagging and wrinkling ↑time taken for repairs The Skin Covers the entire body - surface area = 1.2 – 2.2 square meters Is the largest organ of the body - weighs 4-5kg (~7% of total body weight) Is a major component of the integumentary system - skin, glands, hair, nails Integument = covering Layers of the Skin Epidermis Outermost layer Dermis Deep to the epidermis Hypodermis Deep to the dermis, not really part of the skin Layers of the Skin https://commons.wikimedia.org/wiki/File:Structure_of_mammalian_skin_and_the_layers_typical ly_present_in_parchment.png; Sean P Doherty; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0  Epidermis Epi = upon Outermost layer Composed of epithelial cells - keratinised stratified squamous epithelium Thinner portion of the two Avascular - no blood vessels https://commons.wikimedia.org/wiki/File:Structure_of_mammalian_skin_and_the_layers_typical ly_present_in_parchment.png; Sean P Doherty; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0 Epidermis – 4 distinct cell types Keratinocytes most abundant, produces keratin, arises from the deepest layer of the epidermis Melanocytes spider-shaped cells, produces melanin, found in the deepest layer of the epidermis Langerhan’s cells star-shaped macrophage cells, activate immune system, originate from bone marrow Merkel cells present at the epidermis-dermis junction, associated with nerve endings, function as sensory receptors  Layers of the Epidermis Strata = layers - Stratum basale Deepest layer, sits on top of dermis - Stratum spinosum - Stratum granulosum Intermediate layers - Stratum lucida -Stratum corneum Outermost layer, what you see Thick and Thin The body is covered in two types of skin Thick skin - composed of all five layers - covers palms, fingertips, soles of feet Thin skin - missing the stratum lucida - all the layers are thinner than thick skin layers - covers the rest of the body  Dermis Derm = skin Deep to the epidermis Makes up the bulk of skin Composed of connective tissue - mainly collagen and elastin Highly vascularised Highly innervated https://commons.wikimedia.org/wiki/File:Structure_of_mammalian_skin_and_the_layers_typical ly_present_in_parchment.png; Sean P Doherty; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0 Dermis – Cell types Fibroblasts Macrophages Some mast cells White blood cells Layers of the Dermis Papillary - thinner of the two layers - superficial to the reticular layer - sits directly underneath the stratum basale of the epidermis Reticular - thicker of the two layers ~ 80% of the dermis - deep to the papillary layer - lots of collagen to stop penetration  Hypodermis Hypo = under - Subcutaneous layer, not really part of the skin - Lies beneath the dermis - Also called the superficial fascia (band) - Anchors the skin to underlying structures - Stores fat https://commons.wikimedia.org/wiki/File:Structure_of_mammalian_skin_and_the_layers_typical ly_present_in_parchment.png; Sean P Doherty; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0 2 The Lymphatic System - Structure https://commons.wikimedia.org/wiki/File:Blausen_0623_LymphaticSystem_Female.png; Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436; https://commons.wikimedia.org/wiki/Category:CC- BY-3.0 3 The Lymphatic System - Functions 1. Drains excess fluid & proteins from all tissues back to blood circulation 2. Defends the body against external and internal threats (immunity / resistance to diseases) 3. Transports fats and vitamins from gut to liver (digestion) 4 The Lymphatic System - Components 1. Immune cells 2. Lymph fluid 3. Lymph vessels 4. Lymphatic organs & tissues 5 1. Immune cells ⚫ Lymphocytes - key players ⚫ Produced from the same precursor cell in the bone marrow ⚫ Mature in bone marrow or thymus  6 BIOL121/2016/ACU/Santha James https://pressbooks.ccconline.org/bio106/chapter/cardiovascular-levels-of-organization/; Colorado Community College; CC-BY-3.0 Lymph 2. Lymph ⚫ Means “fluid” ⚫ Fluid connective tissue ⚫ Contains lymphocytes & macrophages + enemies they seek out & destroy ⚫ foreign cells (microbes) ⚫ foreign proteins ⚫ cancer cells ⚫ Plasma proteins & RBC usually not found 10 8 3. Organs (for flow of lymph) 3. Lymph flows through special tubes from tissues to the venous system and heart ⚫ Lymph/atic capillaries ⚫ Lymph/atic vessels, trunks & ducts 9 The Lymphatic Circulation ⚫ blood plasma(from capillaries)  ⚫ interstitial/tissue fluid  ⚫ lymphatic capillary  ⚫ lymph vessels, trunks & ducts  ⚫ blood plasma (vein at base of neck) 1 0 Lymphatic Capillaries ⚫ Capillaries that begin as blind ended tubes ⚫ Structure similar to blood capillaries ⚫ One layer of epithelial (endothelial) cells supported by basement membrane ⚫ Structure helps to let fluid in, but not out ⚫ overlapping endothelial cells open when tissue fluid pressure is high (one-way valve) ⚫ Fluid inside is called “lymph” ⚫ Lymph capillaries in intestinal villi = Lacteals  11 BIOL121/2016/ACU/Santha James https://commons.wikimedia.org/wiki/File:2202_Lymphatic_Capillaries.jpg; OpenStax College; https://commons.wikimedia.org/wiki/Category:CC-BY-3.0 1 2 Lymph Vessels ⚫ Thin walls ⚫ Resemble veins; have more valves ⚫ Have lymph nodes at intervals ⚫ Respiratory & muscular pumps promote flow of lymph towards large veins/heart https://commons.wikimedia.org/wiki/File:2202_Lymphatic_Capillaries.jpg; OpenStax College; https://commons.wikimedia.org/wiki/Category:CC-BY-3.0; cropped to show valves  1 3 Lymph Ducts ⚫ Vessels unite to form 2 thoracic ducts ⚫ Right side head, arm & chest empty into right lymphatic duct ⚫ Left side and lower body empties into main thoracic duct (largest vessel) ⚫ Lymph from ducts flow into left & right https://commons.wikimedia.org/wiki/File:2203_Lymphatic_Trunks_and_Ducts_System.jpg; OpenStax subclavian veins College; https://commons.wikimedia.org/wiki/Category:CC-BY-3.0 2 4. Lymphatic organs & tissues ⚫ Primary lymphatic organs ⚫ red bone marrow ⚫ thymus ⚫ Secondary lymphatic organs ⚫ spleen ⚫ lymph nodes ⚫ Diffuse lymphatic tissue ⚫ tonsils, adenoids & Peyer’s patches  3 Primary Red bone lymphatic organ - 1 marrow ⚫ In flat bones ⚫ At end of long bones ⚫ Contains haemopoietic stem cells ⚫ Produces & matures B cells and make pre -T cells (lymphocytes) https://commons.wikimedia.org/wiki/File:Bone_Marrow.png; OpenStax; CC-BY-4.0 ThymusPrimary gland: in the lymphatic organ -2 mediastinum ⚫ large in infancy ⚫ max size (70g) at puberty ⚫ atrophied (3 g),but functional in adulthood https://commons.wikimedia.org/wiki/File:OSC_Microbio_18_01_thymus.jpg; CNX OpenStax; CC-BY-4.0 ⚫ T cells mature here ⚫ Thymus makes thymosin hormones for development and maturation of T cells Lymph nodes Secondary lymphatic organ -1 ⚫ Size 1 - 25 mm ⚫ Along lymphatic vessels (esp. near neck, axillae & inguinal area) ⚫ Multiply lymphocytes; “finishing school” for B cells ⚫ Filter lymph: Afferent vessels brings lymph with foreign material into node ⚫ foreign matter trapped in fibres ⚫ destroyed by macrophages, B & T cells ⚫ Efferent vessel leaves node with cleaner lymph https://commons.wikimedia.org/wiki/File:Lymph_Node_Diagram_Unlabeled.jpg; Andrewmeyerson; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0 6 https://pressbooks.ccconline.org/bio106/chapter/lymphatic-structures-and-functions/; Colorado Community College; CC-BY-SA-3.0  7 Spleen Secondary lymphatic organ - 2 ⚫ Between stomach and diaphragm ⚫ Macrophages remove worn- out or defective RBCs, WBCs, and platelets. ⚫ Stores & releases blood & blood cells ⚫ Site of production of blood cells during the second trimester of pregnancy ; https://commons.wikimedia.org/wiki/File:Milz_-_spleen.jpg; Beat Ruest; CC-BY-SA-4.0  8 ⚫ Lymphoid tissues MALT: mucosa-associated lymphoid tissue ⚫ Nodules scattered in connective tissue layer in the mucous membranes ⚫ Examples ⚫ Tonsils ⚫ Peyer’s patches in the small intestine ⚫ Appendix https://commons.wikimedia.org/wiki/File:Peyer%27s_patch_%28improved_color%29.jpg; User:Plainpaper; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-3.0 What is oedema? ⚫ Excessive accumulation of interstitial fluid in tissue spaces due to: ⚫  blood pressure ⚫ obstruction to lymph flow https://commons.wikimedia.org/wiki/File:My_leg_with_cellulitis_and_oedema.jpg;Ujb 98; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-3.0-migrated-with-disclaimers 9  Second line defences Act once microbes have entered the body Non-specific: ANY invader inside is attacked the SAME way 1. Antimicrobial chemicals 2. Phagocytes 3. Natural killer cells 4. Inflammation 5. Fever Is this innate (inborn) or acquired immunity? 14 1. Antimicrobial chemicals Interferon interferes with viral replication and activates immune cells made by infected host cells and WBC effective against bacteria as well Complement is a set of plasma proteins that ‘complements’ all aspects of the immune response promote phagocytosis and cell lysis All of these “support” the immune cells 15 |  2. Phagocytes Phagocytosis = “cell eating” Phagocyte = “cell that eats” Fixed or free Attracted to the affected site by chemotaxis Destroy bugs and clean up dead tissues Where? https://commons.wikimedia.org/wiki/File:Phagocytosis2.png; en:User:Graham Beards; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-3.0 Connective tissue Wandering 17 |  3. Natural killer cells Immune surveillance – targets abnormal cells Abnormal cells? e.g. bacteria in interstitial fluid, virus infected cells, cancer cells https://commons.wikimedia.org/wiki/File:Antibody-dependent_cell- mediated_cytotoxicity.png; Simon Caulton; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-3.0 18 | 4. Inflammation Localised response damaged cells send out chemical messages body responds with inflammation this process is supported by phagocytosis Destroys & removes antigens: immune response Limits effects of injurious agent Cleans up dead tissue & debris Promotes healing 19 |  https://commons.wikimedia.org/wiki/File:2213_Inflammatory_Process.jpg; OpenStax 20 | College; https://commons.wikimedia.org/wiki/Category:CC-BY-3.0 5. Fever systemic response temperature regulator in hypothalamus is reset body tries to attain temperature above 37.20 C help by destroying bugs whose enzymes cannot work at high temperature higher metabolic rate to help healing 21 | Third line defences Specific immunity (aka adaptive or acquired immunity) develops on exposure to a particular antigen Antigens from microbes, “wrong” cells… uses B and T lymphocytes made in bone marrow B cells mature in bone marrow; T cells mature in thymus 23 | Properties of specific defences Specific: 1 antigen ⃗ 1 response Versatile: many threats! Memory formed after first exposure Tolerance must exist toward own cells (antigens) 24 |  Overview of the specific immune response https://commons.wikimedia.org/wiki/File:Primary_immune_response_1.png; 25 https://commons.wikimedia.org/wiki/User:Sciencia58; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0 Humoral immunity: B-lymphocytes B-cells make antibody (immunoglobulin) against the antigen; antibody-mediated immunity aka humoral immunity = antibodies work in the body humours (body fluids) destroy microbes/toxins that circulate in blood & body fluids e.g. bacteria 26 | Humoral immunity: Antibodies Made against antigens Stay in blood & lymph nodes or attached to B-cells Can be measured in blood: “titre” 1 antibody type for each antigen….. a match! Inactivate and/or target https://commons.wikimedia.org/wiki/File:Antigen- antigens for destruction antibody_interactions_%28antibody_dependent_cell_mediated_cytoto xicity%29_ku_.png; https://openstax.org/; https://commons.wikimedia.org/wiki/Category:CC-BY-4.0, image cropped 27 | Defence against bacteria Bacteria live between cells, on epithelial surfaces, in fluids Attacked mostly by antibodies from B cells Helped by non- specific defences (e.g. fever, pH) https://commons.wikimedia.org/wiki/File:Primary_Immune_Response.svg; https://commons.wikimedia.org/w/index.php?title=User:Mr.Sneaky64&action=edit&redli nk=1; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0 28 | Two ways to activate B-cells 1. Phagocyte (APC) engulfs bacteria & “presents” antigens to helper T-cell……. 2. Antigen attaches to antibodies on surface of B-cells 29 | “Humoral immunity” has memory EVERY different antigen will cause a dedicated plasma and memory cell to be made… the memory cell will remember …. and produce antibodies instantly next time it sees that same antigen 30 Cell-mediated immunity: T lymphocytes T cells kill abnormal cells directly - don’t make antibody viruses inside your host cells fungal cells transplanted tissue cancer cells Also form memory cells…immune memory 31 https://commons.wikimedia.org/wiki/File:Primary_immune_response_1.png; Sciencia58 an the makers of the single images Domdomegg, , Fæ, Petr94, Manu5; https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0 Types of T-cells Type Function Helper Aid in maturing B cells, activation of other T cells and macrophages Cytotoxic (killer) Destroy virus-infected cells, tumour cells Memory Hold memory of specific antigen for next infection Regulatory/suppressor Decrease T cell response at end of infection 33 References Martini, F., Nath, J.L., & Bartholomew, E.F. (2018). Fundamentals of anatomy and physiology (11th Global ed.) Pearson, Harlow, Essex, UK. Tortora, G.T., Derrickson, B.H., Burkett, B., Peoples, G., Dye, D., Cooke, J., Diversi, T., McKean, M., Samalia, L., & Mellifont, R. (2019). Principles of anatomy and physiology (2nd Asia-Pacific ed.) John Wiley & Sons, Milton, Qld, Australia. 35 Mode of transmission Contact is contact between people; either directly via touch or indirectly via two people touching the same inanimate object Vehicle is transmission of pathogens via vehicles such as air, water,food (COVID) Vector transfer of pathogens via an animal (often arthropods like mosquitos or ticks). 20 School of Behavioural and Health Sciences http://www.katecampbell.ca/_images/illustrations/transplacentalTransmission_thumbnail.jpg Mode of transmission Others… Vector-Borne Mosquito - Ross-River, Barmah Forrest, Malaria… Tick – Australian tick typhus… Fomite-borne Transmission via an inanimate object (COVID) Vertical (transplacental) Intrauterine, and postpartum 20 School of Behavioural and Health Sciences http://www.katecampbell.ca/_images/illustrations/transplacentalTransmission_thumbnail.jpg Chain of Infection Infectious Agent Reservoir Susceptible Host Portal of Exit Portal of Entry Mode of Transmission 22 | School of Behavioural and Health Sciences Environmental control Differentiate between sterilisation, disinfection & sanitisation Sterilisation Destruction/elimination of ALL microbes Methods Heat– dry (e.g. burning) / moist (e.g. boiling) Heat & pressure – e.g. autoclave Radiation Filtration Chemical – e.g. bleach, hydrogen peroxide 23 School of Behavioural and Health Sciences Environmental control Disinfection Elimination of MOST pathogens from inanimate objects NOT bacterial spores Methods Chemical – e.g. alcohol, chlorine Gas – e.g. formaldehyde SANITATION Safe disposal of human urine and faeces 24 School of Behavioural and Health Sciences WHO (2016)