Quiz Over Chapter 15 Microbiology

Capsules are a protective layer around the cell wall of microbes that can help them evade a host's immune system. The glycocalyx covering of the capsule can prevent phagocytosis, which is the process by which immune cells engulf and destroy foreign particles. However, it is important to note that host antibodies can enable phagocytosis by binding to the capsule and marking the microbe for destruction by immune cells. Therefore, capsules are indeed one way for microbes to evade a host's defenses, making the statement "True."

The given answer is correct because coagulases, kinases, hyaluronidase, collagenase, and IgA proteases are all enzymes or exoenzymes produced by microbes that help them evade a host's defenses. These enzymes play various roles in immune evasion, such as breaking down host tissues, degrading antibodies, and manipulating the host's immune response. By producing these enzymes, the microbes can successfully colonize and infect the host without being effectively eliminated by the immune system.

Antigenic variation refers to the ability of certain pathogens, like the influenza virus, to change their surface antigens. This allows them to evade the immune system and continue to infect individuals who may have previously developed immunity to a different strain. Therefore, the statement that the ability to change surface antigens refers to antigenic variation is true.

Lysogenic conversion is a process in which a bacterium acquires new abilities or traits as a result of incorporating genes from a phage (a type of virus that infects bacteria) into its own genome. This process can lead to the bacterium gaining new functions or characteristics that it did not previously possess. Therefore, the statement that the process in which bacterium gains new abilities due to phage genes refers to lysogenic conversion is true.

Lysogenic conversion refers to the process in which a bacterium acquires new genetic traits as a result of incorporating lysogenic phages into its genome. In this example, the genes for diphtheria toxin, botulinum neurotoxin, and the ability of Streptococcus pneumoniae to produce a capsule are carried by lysogenic phages. This means that these traits can be transferred to other bacteria when the lysogenic phages infect them. Therefore, the statement is true.

Viruses often evade host defenses by both growing inside cells and gaining access through attachment sites that match host receptors. Growing inside cells allows viruses to hide from the immune system and take advantage of the cellular machinery for replication. Gaining access through attachment sites that match host receptors enables viruses to enter and infect host cells more efficiently, evading the immune response. Therefore, both strategies help viruses to evade host defenses effectively.

Virulence refers to the degree or extent to which a microbe is pathogenic. It is a measure of the ability of a microorganism to cause disease or harm in a host organism. The term virulence encompasses factors such as the microbe's ability to invade and colonize the host, evade the host's immune system, and produce toxins or other harmful substances. Therefore, virulence is the correct answer as it directly relates to the given question about the degree of pathogenicity of a microbe.

Exotoxins are indeed secreted into the surroundings or released when the cell is lysed. Exotoxins are toxic substances produced by certain bacteria and are released outside the bacterial cell. They can cause damage to host cells and tissues, leading to various diseases. The secretion of exotoxins allows bacteria to exert their harmful effects on the host organism, making the statement true.

Endotoxins are a lipid portion (lipid A) of lipopolysaccharides found in the outer membrane of Gram (-) bacteria. They are released when bacteria die and are heat resistant. Unlike exotoxins, endotoxins cannot be converted to toxoids for vaccination. Therefore, the correct answer is endotoxins.

The statement is false because cytopathic effects are indeed visible signs of viral infection. Cytopathic effects refer to the changes that occur in infected cells as a result of viral replication. These effects can include cell death, changes in cell shape or size, formation of inclusion bodies, and alterations in cellular functions. These visible signs are often used to identify and diagnose viral infections in laboratory settings.

The correct answer explains the different portals of entry through which a microbe can enter the host cell. It mentions that mucous membranes in the gastrointestinal, respiratory, urogenital tracts, and conjunctiva can serve as portals of entry for microbes. It also states that the skin can be a portal of entry, but typically it must be broken for pathogens to gain access and cause disease. Some pathogens, like hookworm, can bore through the skin. Additionally, the answer mentions the parenteral route, which involves the direct deposition of microbes beneath the skin or into mucous membranes through punctures, injections, wounds, bites, etc.

Endotoxins are toxins released by certain bacteria when they are destroyed. These toxins can cause a range of symptoms in all species, including fever, chills, weakness, aches, and even shock and death. The release of endotoxins can lead to a systemic inflammatory response, triggering these symptoms. Swelling, although not mentioned in the question, can also be a possible symptom caused by the release of endotoxins.

Endotoxins are substances found in the cell walls of certain bacteria. When released into the bloodstream, they can trigger an immune response that activates blood clotting proteins. This activation leads to the formation of small clots, which can decrease blood flow. Therefore, the presence of endotoxins can cause a disruption in normal blood circulation.

The correct answer is cell wall components. This is because proteins in the cell wall can enhance attachment and help the cell resist phagocytosis, as seen in the M protein of Streptococcus pyogenes. Additionally, M tuberculosis has waxy lipids in its cell wall, which allows it to evade the host's defenses and multiply within phagocytosis. Therefore, the presence and composition of cell wall components play a crucial role in enabling microbes to evade a host's defenses.

This description of bacteria using host actin to form indention on the plasma membrane and be engulfed into the cell, as well as using host actin to move from cell to cell, suggests that the bacteria are penetrating into the host cell cytoskeleton. By manipulating the host cell's actin, the bacteria are able to evade the host's defenses and gain entry into the cytoskeleton, where they can establish infection and spread to other cells.

The correct answer is cytopathic effects. Cytopathic effects refer to the structural and functional changes that occur in host cells as a result of viral infection. These effects can lead to cell death and are caused by various mechanisms such as inhibition of cell division (stopping mitosis), destruction of the host cell (lysis), formation of viral replication sites (inclusion bodies), fusion of infected cells (syncytium), changes in cell surface antigens, production of interferons, alterations in chromosome structure, and transformation of the cell.