Principles of Infections Flashcards
What are microorganisms and how can they be classified?
Microorganisms are living organisms that are too small to be seen by the naked eye. They can be single-celled or a colony of cells. They can be classified into various categories, including bacteria, viruses, fungi, protozoa, and helminths. Pathogenic microorganisms are those that cause disease.
What are the key differences between Gram-positive and Gram-negative bacteria?
Gram-positive bacteria have a thick cell wall and a single plasma membrane. They are easier to treat with antibiotics because the antibiotics can easily penetrate the plasma membrane.
Gram-negative bacteria have a thinner cell wall and two plasma membranes (inner and outer). They are more difficult to treat with antibiotics because the dual membranes make it harder for antibiotics to penetrate.
How do viruses reproduce?
Viruses reproduce by invading host cells and forcing them to make new viral DNA or RNA. The infected cell produces hundreds of new viral particles, which are released to infect other cells. Viruses are considered microscopic parasites because they depend entirely on host cells for reproduction.
What is the role of the innate immune system?
The innate immune system is a non-specific defense mechanism that acts quickly to defend the body against pathogens. It includes physical and chemical barriers (like skin and mucus), as well as immune cells that respond rapidly to infections.
What is the difference between humoral and cell-mediated immunity?
Humoral immunity involves antimicrobial peptides and complement proteins in the blood that help eliminate pathogens.
Cell-mediated immunity involves cells like granulocytes and phagocytes that directly attack and remove pathogens from the body.
What is the human microbiota and microbiome?
The microbiota refers to all the microorganisms living in and on a human.
The microbiome refers to the collective genetic material of all the microorganisms that make up the microbiota.
What are the stages of infection and how do pathogens cause disease?
Transmission: The organism is acquired.
Infection: The pathogen reproduces inside the host.
Pathogenicity: The pathogen interacts with the host in a way that causes disease.
Virulence: The severity of the disease varies.
The immune system tries to prevent infection, but some interactions may result in disease.
What are some common routes of transmission for pathogens?
Common routes of transmission include air-borne spread, person-to-person spread, faeco-oral spread, consumption of infected material, vector-borne diseases, endogenous infections (from one’s own microbiome), and direct inoculation (e.g., through a needle).
What are virulence factors and how do they help microorganisms evade the immune system?
Virulence factors are components or structures of microorganisms that assist in establishing disease or infection. They help pathogens adhere to host tissues, evade immune defenses, proliferate, cause damage, produce toxins, and interact with the host in a way that promotes infection. For example, bacteria may have capsules to protect themselves from the immune system or produce toxins that damage host tissues.
What is antimicrobial resistance (AMR) and how does it develop?
Antimicrobial resistance occurs when microorganisms evolve to resist the effects of drugs meant to kill or inhibit them. This can happen naturally but is accelerated by the overuse and misuse of antimicrobials. Microorganisms can develop resistance through genetic mutations or by acquiring resistance genes from other organisms through horizontal gene transfer.
How do viruses develop resistance to antiviral drugs?
Viruses constantly mutate, which can change the proteins that antiviral drugs target. These changes can lead to resistance, as the virus may no longer respond to the drug. The use of antiviral drugs in combination can help reduce the emergence of resistant strains.
What is the difference between innate and adaptive immunity?
Innate immunity is the body’s immediate, non-specific defense response to pathogens, acting within minutes to hours.
Adaptive immunity is a specific immune response developed after exposure to a pathogen or vaccine, which takes hours to days to activate and provides long-lasting protection through memory cells (e.g., white blood cells and antibodies).
What is the role of antimicrobial stewardship in combating antimicrobial resistance?
Antimicrobial stewardship involves using antimicrobial drugs responsibly, only when necessary, to reduce the development of resistance. This approach helps preserve the effectiveness of existing drugs and prevents the spread of resistant microorganisms.
What is the role of anatomical barriers in the immune system?
Anatomical barriers are physical and chemical defenses that form the first line of defense against pathogens. This includes the skin, mucous membranes, and epithelial organs that prevent pathogens from entering the body.
How do bacterial capsules contribute to evading the immune system?
Bacterial capsules protect bacteria from the host’s immune system by preventing the immune cells from effectively recognizing and attacking the bacteria. They can also enhance an inflammatory response, making it more difficult for the immune system to clear the infection.
How do viruses evade the immune system through antigenic drift and shift?
Antigenic drift refers to small changes or mutations in the viral antigens that occur over time, making it harder for the adaptive immune system to recognize and respond to the virus.
Antigenic shift involves major changes in viral antigens, typically due to gene reassortment, which can make the virus unrecognizable to the immune system, leading to new and potentially more dangerous strains.
What is the significance of horizontal gene transfer in the spread of antimicrobial resistance?
Horizontal gene transfer allows bacteria to share genetic material, including genes responsible for antimicrobial resistance, with other bacteria. This enables the rapid spread of resistance traits across different bacterial species, making infections harder to treat.
Why are some bacterial infections harder to treat with antibiotics?
Bacterial infections can be harder to treat if the bacteria are Gram-negative, as they have two plasma membranes and a thinner cell wall. This structure makes it more difficult for antibiotics to penetrate and reach the target sites inside the bacteria, compared to Gram-positive bacteria, which have a thicker cell wall and a single plasma membrane.
What are the potential consequences of antimicrobial resistance in the future?
Antimicrobial resistance can lead to the failure of current treatments for infections, making it harder to manage diseases. This could result in longer hospital stays, more complicated surgeries, higher mortality rates, and the spread of resistant infections that cannot be easily treated with existing medications.
How do antiviral drugs differ from antibiotics in treating infections?
Antibiotics target bacterial infections and are ineffective against viruses, while antiviral drugs are designed to target specific stages of the viral replication cycle. Antiviral drugs work by interfering with the virus’s ability to reproduce, whereas antibiotics may kill bacteria or inhibit their growth.
