Infectious diseases Flashcards
(23 cards)
Define infectious diseases
They can be transmitted from person to person, and they are caused by disease-causing microorganisms called pathogens, which include bacteria and viruses
Define non-infectious diseases
They are not caused by pathogens and cannot be transmitted from person to person.
How can infectious diseases be spread
Droplets in the air, coming into contact with body fluid of an infected person, contaminated food and water
Describe characteristics of bacteria(1)
Possess cell wall, cell membrane, cytoplasm and genetic material
No nucleus or membrane-bounded organelles
Genetic material consists of circular chromosome consisting of coiled up, circular strand of DNA, may have smaller rings of DNA called plasmid
Bacterial cell wall made of peptidoglycan (sugars and amino acids) and proteins
Describe characteristics of bacteria(2)
Mobile bacteria possess long thread-like structures called flagella which allow them to move either toward or away from stimuli
Bacteria have slime capsule, sticky layer of polysaccharide or protein that can help cell adherence or evasion of host’s immune system
Some are pathogenic and some are non-pathogenic
Describe structure of virus
Smallest disease-causing particles known, virus always made up of genetic material surrounded by protein coat known as capsid. Some viruses surrounded by envelope derived from host cell’s membrane. Viruses usually infect specific cell types.
Describe mode of life of viruses
Viruses are biochemical parasites as they take control of a living cell, known as host cell. First step involves getting genetic material of virus, together with viral proteins, across cell membrane of the host cell into the cytoplasm
Why are viruses not considered living
Viruses cannot reproduce or carry out metabolic activities outside of a host cell
What is similarity between bacteria and virus
Both contain genetic material
What are differences between bacteria and virus
Bacteria genetic material typically DNA, virus may not be DNA. Bacteria has cell membrane, virus has protein coat. Bacteria has ribosomes while virus do not. Bacteria can reproduce itself, virus needs host cell to reproduce
How is influenza transmitted
Spread from person to person through respiratory droplets propelled by coughing and sneezing. Influenza passed on through contact with contaminated surfaces.
How to reduce transmission of influenza
Annual influenza vaccination is recommended to protect against influenza, especially for individuals belonging to populations at higher risk of complications of influenza
Describe pneumococcal disease
Disease caused by bacterium called Streptococcus pneumonia, known as pneumococcus. Attacks lungs, blood, coverings of brain and spinal cord, middle ear
How is pneumococcus transmitted from person to person and what are the symptoms
Can spread from person to person by direct contact, droplets from infected person through coughing or sneezing, articles contaminated with infected droplets
Symptoms: Fever, headache, vomiting, cough, chest pain and rapid breathing
How to reduce transmission of pneumococcus bacteria
Get pneumococcal vaccination
Prompt treatment with antibiotics, especially penicillin. However, in recent years treatment has become more challenging with emergence of strains resistant to antibiotics, especially penicillin.
What are antibiotics
Substances that kill or inhibit growth and replication of bacterium
How do antibiotics target bacteria
Inhibit synthesis of bacterial cell wall - when cell wall is weakened, unable to resist expansion when water enters cell, hence bacterium bursts and dies
Inhibit cell membrane functions by breaking it up
Inhibit protein synthesis in ribosomes, antibodies bind to ribosomes, preventing ribosomes from synthesising polypeptide chains, inhibiting growth
Inhibit enzyme action in cytoplasm, action of enzyme required for bacterium to synthesise folic acid inhibits growth of bacterium
Why are antibiotics not effective on viruses
They act on bacterial cell walls, virus do not have
They break up cell membranes, virus do not have
They act on ribosomes, inhibiting protein synthesis and growth. Viruses do not have ribosomes and do not grow
How do antibiotic-resistant bacteria emerge
Antibiotic resistance occurs when bacteria develop resistance to specific antibiotics after being exposed to it. Due to variation in bacteria population, there may be bacteria which may be less sensitive to antibiotics, manage to evade action of antibiotics, especially when prescribed course of antibiotics not completed. When they survive, they reproduce and more bacteria in population are less sensitive antibiotics. Bacteria will acquire resistance to antibiotics. Drug becomes less effective or ineffective when used to treat the infection
Define superbugs
‘Superbugs’ are bacteria that are resistant to many types of antibiotics. Superbugs may make it harder for doctors to effectively treat infections, leading to prolonged illness, higher healthcare costs and death
Describe vaccine
Vaccine is technique used to induce immune system to develop acquired immunity to specific disease using a vaccine. A vaccine contains agent that resembles pathogen and prevents infectious diseases by stimulating white blood cells to quickly produce antibodies when pathogen invades
How do vaccines work
Substances that trigger production of antibodies are called antigens. When foreign particles such as pathogens enter bloodstream, they stimulate white blood cells to produce antibodies against them. When vaccine which contains agent that resembles pathogen enters the body, stimulates the white blood cells to produce antibodies. Antibodies are proteins that are produced to destroy pathogen. They are specific in action. Antibodies that destroy one type of pathogen will be ineffective against another type of pathogen, can tag pathogen for destruction by white blood cells
Describe primary and secondary immune response
When vaccine given, white blood cells become activated and produce antibodies just as they do when they encounter actual disease-causing organism. Called primary immune response. The next time person is exposed, there will be sharp increase in level of antibodies produced, secondary immune response
As time passes, level of antibodies begins to fall, remains high only if person repeated exposed to same antigen, either by accident or booster shot. If natural exposure does not occur, amount of antibody falls slowly, reaching low unprotective level
