Human Biological Science - Pathogens and Disease - Coursework Example

Human Biological Science (Pathogens and Disease) TAQ What is a pathogen? It is a microorganism which causes a disease. This microorganism usually has specific features which render it harmful to its host and gives it the ability to cause a disease. These features result in different classifications of pathogens. Hence, there are several examples of pathogens that include fungi, viruses, bacteria and protozoa. 2. Features Viruses Bacteria Fungus Protozoa Structure They have a protein coat. They have genetic material, either DNA or RNA They have a cell wall, a bacterial DNA, plasmid DNA and a flagellum. They have a nucleus, cytoplasm and a cell wall They have a cell membrane, nucleus, cytoplasm and a vacuole. They are unicellular. Reproduction They reproduce inside living cells by injecting their DNA or RNA into the host cell through Lytic infection or Lysogenic infection. They reproduce asexually through binary fission They reproduce sexually through fusion of 2 haploid nuclei. They reproduce asexually through division of nucleus by mitosis. They reproduce through binary fission. Nutrition They do not metabolize as they are non - living. They are heterotrophic meaning they need organic compounds of nitrogen and carbon for nutrition. They are heterotrophic meaning they need organic compounds of nitrogen and carbon for nutrition. They are holozoic meaning they acquire nutrition through ingestion and digestion of organic matter. Table 1: Features of pathogens. Baron, S. Ed., 1996. Medical Microbiology. [e-book] Galvestone (TX): University of Texas Medical Branch. Available at: http://www.ncbi.nlm.nih.gov/books/NBK7627/ [Accessed 17 March 2014]. TAQ 2: Outline transmission and development of infection by a bacterium, virus fungus and protozoan. Cholera Cholera is transmitted through taking in of water or food that has Vibrio cholera which is the infectious agent. Vibrio cholera has two specific life cycles, in the environment and in human beings. They are naturally found in coastal waters where they use crustaceans as hosts. On ingestion by humans, they colonize the ileum, multiply and secrete the cholera toxin. They are then passed on through human stool back to the environment through secretory diarrhoea. These are hyperinfectious and they function to increase the outbreak. To inhibit the spread of Cholera, various control measures can be used. One is the preventive measure where persons moving to areas susceptible to Cholera outbreak are advised on cautious water and food consumption while ensuring that what they consume is clean, washed or sterilised. Also, in case of a cholera outbreak, cholera cases may be controlled through quarantine as stated under the Commonwealth Quarantine Act 1908. Contacts between infected and non - infected persons should be controlled by monitoring contacts for 5 days from the date of exposure. The environment around cholera victims should be controlled. This can be done through disinfection of clothes and beddings used by cholera patients, and terminal cleaning of the rooms occupied by cholera patients (Department of Health, Victoria, Australia, 2007). Athlete’s Foot (Trichophyton) It is transmitted directly through contact with infected skin or indirectly through contact with material that holds the fungus. On infection, trichophyton cannot be detected within the first 48 hours. It is usually in its logarithmic stage. It stays in the stratum corneum of the skin. The rate at which it grows is dependent on the amount of available nutrients. If nutrients are not available, the fungus enters the log stage. In this stage, it degrades the keratin found in the stratum corneum forming the appropriate amino acids that provide nutrients for reproduction and growth. Once nutrients are available, it enters the stationary stage whereby degradation of keratin slows down. The trichophyton uses its enzymes, proteases in particular to degrade keratin cells and produce nutrients for its survival. To prevent and contain the spread of trichophyton, it is good to ensure that there is enough aeration to the feet, wearing of socks that absorb sweat away from the skin, avoid wearing of wet socks or sharing socks, avoid sharing of towels, drying the feet thoroughly after washing them, washing the feet habitually with water and soap and changing socks and shoes regularly (Department of Biology, Davidson College, 2007). Malaria (Plasmodium) Malaria is transmitted when a female anopheles mosquito takes in the plasmodium gametocytes from an infected person. After 8 – 35 days, the plasmodium develops into its infective form which is transmitted to another individual through a bite of the infected anopheles mosquito. The life cycle is divided into 4 stages that are; growth, development, transmission and reproduction. It is complex as it has varying phases, time length in the host and in the vector. The three main invasive phases in the lifecycle of the plasmodium include the liver phase, blood phase and the sporogonic phase. The liver phase entails asexual replication. The blood phase involves both asexual reproduction and the formation of female and male gametocytes. At this stage, symptoms are observed. The formed gametocytes develop into both male and female gametes which on fertilization develop into sporozoites that are capable of infecting the liver. To control the spread of malaria, anti - malarial drugs can be taken, use of nets and mosquito repellents to avoid being bitten by mosquitoes and individuals should be made aware of the major symptoms that are expressed during the blood phase (McConnell, Lin & Hurban, 2007). Influenza The influenza virus is transmitted through the respiratory route by either breathing it in or by touching infected material and then placing your hands near the nose, eyes or mouth. The life cycle of influenza can be divided into five phases: entry into the cell that hosts it, entry of vRNPs into the nucleus, transcription and replication of the viral genome, export of the vRNPs from the nucleus and assembly and budding at the host cell plasma membrane. Entry into the host cell involves binding of the HA spikes to the sialic acid found on the surface of the cell membrane of the host. On binding, endocytosis occurs and the virus enters the cell of the host in an endosome. Transcription and replication of the virus occurs in the nucleus which is released into the cytoplasm. The vRNP then enters the nucleus. The genome of the virus is then transcribed. Its RNA is composed of negative sense strands of RNA that are converted into positive sense to function as templates for production of viral RNA. The vRNPs are then exported from the nucleus. Assembly and budding occurs at the cell membrane of the host cells’. Influenza can be prevented with vaccines and controlled by observing personal hygiene habits (Samji, 2009). Department of Biology, Davidson College, 2007. Trichophyton: Lifecycle. [online] Available at: http://www.bio.davidson.edu/people/sosarafova/assets/bio307/jelahre/life%20cycle.html [Accessed 18 March 2014]. Department of Health, Victoria, Australia, 2007. Infectious Diseases: Cholera. [online] Available at: http://ideas.health.vic.gov.au/bluebook/cholera.asp [Accessed 18 March 2014]. McConnell, P., Lin, S. And Hurban, P., 2007. Methods of Microarray Data Analysis V. Springer. Samji, T., 2009. Influenza A: Understanding the Viral Life Cycle. The Yale Journal of Biology and Medicine, [e – journal] 82(4). Available through NCBI website: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2794490/ [Accessed 18 March 2014]. TAQ 3: Main Features and best Practice in the Control of Cross Infection Main Features in the control of cross Infection The presence of a strong leadership based on its ability to effect control measures. Policies that outline and give directions on evidence based hand hygiene practices. They can be made up by the hospital administration or policies that have been set up by recognized health bodies can be followed. Antimicrobial stewardship through which the hospital sets up programmes that are geared towards prevention, control and elimination of known pathogen and pathogen transmission means. Adequate and well trained hospital personnel who are well versed with means to prevent and control cross infection among patients. Surveillance techniques which monitor cross infection trends in the hospital is very important. Evidence based reduction strategies based on previous incidences of cross infection in the hospital are vital for control of cross infection (Motacchi & Kapoian, 2011). Under the Health and Social Care Act (2008), the Code of Practice on the Prevention Control of Infections and related guidance requires that patients, staff and visitors are protected from exposure to healthcare associated infections (Motacchi & Kapoian, 2011). Many hospital infections of staff, patients and visitors occur through Contact with infected material or patient Airborne exposure Droplet exposure How to control and Prevent Cross Infection There are several ways to control cross infection. The following ways are recommended: Cleaning of the hospital environment: This should be done through a program of thorough cleaning in the hospital. Observing hand hygiene: Hand hygiene should be made mandatory. Proper intravenous line care: An intravenous team devoted to intravenous line care should be set up. Antibiotic control: Firm antibiotic policies should be formulated to ensure correct use of antibiotics in the hospital. Motacchi, K., and Kapoian, T., 2011. An Illustrated Guide to Infection Control. Springer Publishing Company. TAQ 4: How does the body defend itself against pathogens which cause infectious diseases? Introduction Pathogens have unique and diverse ways of causing infections in human beings. But on numerous occasions, the body’s defence mechanisms protect humans from the pathogens and the infections. These defence mechanisms are an intricate, complex and interactive networks that overlap to ensure that body’s defence against the pathogens is paramount. This essay looks at the two kinds of defences found in humans; the non specific and the specific. The nonspecific defence mechanism of the human body is comprised of natural physical and mechanical barriers and the inflammatory reaction coupled with phagocytosis. The natural barriers of the body include the skin. It has defence mechanisms that include horny layer made of keratin which pathogens cannot pass through. It produces fatty secretions that have fatty acids which have antiseptic properties. The skin is dry and growth of pathogens on it is hindered by a high salt concentration that is as a result of sweating. It also is naturally acidic, this hinders bacterial growth. The other barrier is the respiratory tract. The nose and airways have cells that secrete mucus which lysozyme which is a mucolytic enzyme that destroys pathogens. The mucus also contains phagocytic cells which destroy pathogens. If a pathogen penetrates and reaches the alveoli, the alveoli are phagocytised by the alveolar macrophages. The digestive tract has a mucous membrane that also secretes lysozyme. Saliva which is produced in the mouth has mucopolysacchrides that inactivate various viruses. The stomach walls secrete acid which destroy pathogens. The intestines have normal bacteria flora which destroys pathogens (Berg & Viljoen, 1999). The urogenital tract’s defence mechanism can be attributed to urine acidity that is bacteriostatic. The bladder has a mucous membrane which produces mucous that has phagocytic cells. The eye secretes tears contain vast amounts of lysozome which destroy pathogens, specifically gram – bacteria. Tears also rinse the eye very efficiently and pass on the pathogens to the nasopharynx through the nasocrimal duct. The inflammatory reaction and phagocytosis is triggered when pathogens attach to the cells of the host. An inflammatory reaction is triggered. The inflammatory reaction of body cells is in response to the invasion by the pathogen. Pathogens bind to epithelial cells lining inner body organs and are identified as foreign substances. This triggers the reaction. When the inflammatory reaction is due to a pathogen, it results in an infection. If the pathogen may cause a communicable disease, the local and systemic inflammatory reactions both occur. The reason why they both take place is because pathogens move from the local area of entry, through the lymph and the blood to the rest of the body organs. The local inflammatory reaction is composed of cellular changes, phagocytosis and production of an inflammatory fluid. The systemic inflammatory reaction results into a general reaction of inflammation (Berg & Viljoen, 1999). When the nonspecific defence fails, the specific defence is in line to defend the body against the pathogens. It is composed of cells, specifically white blood cells which fight of pathogens. They are of two types, lymphocytes and phagocytes. There are two types of lymphocytes that have a function in specific defence, namely T cells and B cells. The origin of these cells is the bone marrow. They are transported in the lymph and blood. They dwell in the thymus, spleen and lymph nodes. The T cells are processed in the bone marrow and mature in the thymus. Their capability to recognize pathogens is based on the antigens on the outer surface of the pathogens. Helper T cells trigger the particular immune response. One of which is the cell – mediated immune response whose primary reaction is that cytotoxic T cells identify and destroy infected body cells. When a helper T cell is triggered it secretes lymphokines which are chemical substances that aid the particular immune response. Activated inducer T cells activate maturation of lymphocytes in the thymus that have not yet matured. Cytotoxic T cells that have been activated destroy the cells of the body which have been infected. The other immune response is the antibody mediated response. When the helper T cells are made to react to unknown antigens, they trigger the antibody mediated response which the B lymphocytes play a role in (Alters, 2000). They mature in the bone marrow and their antibody reaction is called the humoral response because they release antigen particulate chemicals into the bloodstream. According to Alters (2000), B cells have a100, 000 replicas of a protein receptor on their surfaces which binds to antigens. Due to the fact that they have different antigen receptors, each B cell identifies a certain particular antigen. The receptors of one or several B cells bind to pathogens at the start of an infection, they then process and show the antigen of the pathogens. The B cells that are bound on the pathogen antigen are identified by helper T cells which also have bound to pathogens showing pathogen antigens on their surfaces. The helper T cells then bind to the antigen – B complex and secrete lymphokines that activate division of cells in the B cell. After many cell divisions, each B cell produces a big clone of cells. On formation of clones, B cells secrete replicas of the antibodies which reacted to the antigen. The B cells that secreted the antibodies are named as plasma cells. The antibodies mark the pathogens for destruction by the macrophages. The T cells that do not develop into plasma cells survive as memory T cells which react fast and strongly if the same foreign antigen recurs (Alters, 2000.) Alters, S., 2000. Biology: Understanding Life. Jones & Bartlett Learning. Berg, R. H.., & Viljoen, M. L., 1999. Communicable Diseases: A Nursing Perspective. Preston South Africa. TAQ 5: Complete the tables below that show the differences between the four types of immunities. Immunities Natural Acquired Similarities It involves antibodies It involves cell – mediated immunity. It involves antibodies It involves cell – mediated immunity. Differences It is an inborn ability to resist disease. It develops at birth and is identical with nonspecific resistance. It involves the chemical and physical defences to foreign antigens It begins after birth and is dependent on the reaction of T cells and antibodies. It may be active or passive. Table 2: Natural and acquired immunities; similarities and differences. Immunities Active Passive Similarities It involves the function of antibodies. B cells produce these antibodies. It may be induced. It also involves the function of antibodies. These antibodies are given directly. It may also be induced Differences It takes some hours or days to fully develop. However, it remains for a long duration, mostly the entire lifetime of an individual. Immunological memory present It is not inherited. It involves cell mediation and humoral immunity. A negative phase may take phase. It is utilised for prophylaxis It takes a short time to develop after foreign antibodies enter the body. However, it stays on for only a few days or weeks. Does not have immunological memory It may be inherited from the mother It precisely involves humoral immunity. It does not have a negative phase. It is utilised for immediate treatment. Table 3: Active and passive immunities; similarities and differences. Vasanthakumari, R., 2007. Textbook of Microbiology. BI Publications Pvt Ltd. Read More