Block 9 Bacteria Exotoxin & Capsule MCQ's

Explanation
The ability to form biofilms on plastic devices is a major virulence factor for S. epidermidis. One probable cause is surface proteins that bind blood and extracellular matrix proteins. The organism's capsule, known as polysaccharide intercellular adhesion (PIA), is made up of sulfated polysaccharide. It allows other bacteria to bind to the already existing biofilm, creating a multilayer biofilm. Such biofilms decrease the metabolic activity of bacteria within them. This decreased metabolism, in combination with impaired diffusion of antibiotics, makes it difficult for antibiotics to effectively clear this type of infection. S. epidermidis strains are often resistant to antibiotics, including penicillin, amoxicillin, and methicillin.
As mentioned above, S. epidermidis causes biofilms to grow on plastic devices placed within the body. This occurs most commonly on intravenous catheters and on medical prostheses.Infection can also occur in dialysis patients or anyone with an implanted plastic device that may have been contaminated. Another disease it causes is endocarditis. This occurs most often in patients with defective heart valves. In some other cases, sepsis can occur in hospital patients.

Antibiotics are largely ineffective in clearing biofilms. The most common treatment for these infections is to remove or replace the infected implant, though in all cases, prevention is ideal.
The drug of choice is often vancomycin, to which rifampin or aminoglycoside can be added.Hand washing has been shown to reduce the spread of infection.

Identification

The normal practice of detecting S. epidermidis is by using the Baird-Parker agar with egg yolk supplement. Colonies appear small and black. They can be confirmed using the coagulase test. Increasingly, techniques such as real-time PCR and quantitative PCR are being employed for the rapid detection and identification of Staphylococcus strains.[

Explanation
Tracheal cytotoxin, involved in the pathogenesis of whooping cough by Bordetella pertussis, is released from the bacterial cell via a cell wall-degrading enzyme. This enzyme is responsible for breaking down the cell wall of the bacteria, allowing the release of the cytotoxin into the surrounding environment. This mechanism enables the cytotoxin to interact with the host cells and contribute to the development of the disease.

Explanation
The toxin produced by the Gram-positive rod in this man's leg most likely degrades lipids in host cell membranes. This can lead to the destruction of the cell membrane, causing cell death and contributing to the symptoms observed, such as swelling, discoloration, and exudate.

Explanation
Antitoxin is an important component in the treatment of food-borne botulism. Food-borne botulism is caused by the ingestion of food contaminated with the toxin produced by Clostridium botulinum bacteria. Antitoxin works by neutralizing the toxin and preventing it from causing further harm to the body. Therefore, the use of antitoxin is crucial in the treatment of food-borne botulism to counteract the effects of the toxin and aid in the recovery of the patient.

Explanation
Iron is the factor that causes the inhibition of the diphtheria toxin repressor. In certain circumstances, such as in a patient, the repressor becomes inactive. Iron is known to play a crucial role in the regulation of diphtheria toxin production. When iron levels are low, the repressor is active and prevents the production of the toxin. However, when iron levels are high, the repressor becomes inactive, allowing the production of the toxin to occur. Therefore, iron acts as a factor that inhibits the diphtheria toxin repressor.

Explanation
Erythrogenic toxin is the correct answer because it is a known bacterial toxin that is produced by Streptococcus pyogenes, the bacteria responsible for causing scarlet fever. This toxin is responsible for the characteristic rash seen in scarlet fever, as it causes the dilation and leakage of blood vessels in the skin. Streptokinase is not associated with scarlet fever, as it is an enzyme produced by bacteria that helps dissolve blood clots. Pneumolysin is a toxin produced by Streptococcus pneumoniae, a different bacteria that is not associated with scarlet fever. Panton-Valentine leukocidin (PVL) is a toxin produced by certain strains of Staphylococcus aureus, which is also not associated with scarlet fever.

Explanation
Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, whose genes are considered to be part of the genome of -lambdoid prophages.- The most common sources for Shiga toxin are the bacteria Shigella dysenteriae and the Shigatoxigenic group of Escherichia coli (STEC), which includes serotypes O157:H7, O104:H4, and other enterohemorrhagic E. coli (EHEC).

Explanation
Corynebacterium diphtheria does not possess a capsule. Capsules are an important feature of pathogenic bacteria as they help protect the bacteria from the host's immune system. Streptococcus pneumoniae, Haemophilus influenzae type b, and Neisseria meningitidis are known to possess capsules, which contribute to their pathogenicity. However, Corynebacterium diphtheria does not possess a capsule, making it an exception among the given organisms.

Explanation
The capsule surrounding Streptococcus pneumoniae inhibits phagocytosis by preventing the activation of complement and the binding of C3b to bacteria. This means that the bacteria are able to evade the immune system's response, making them more pathogenic. The complement system is an important part of the immune response, as it helps to tag bacteria for destruction by phagocytes. By preventing the activation of complement and the binding of C3b, the capsule allows the bacteria to avoid being recognized and destroyed by the immune system.

Explanation
1) Capsules are a type of exopolysaccharide, which means that they are composed of long strands of sugar and are found on the outer surface of the microbe.
• They are often anchored into either the plasma or outer membrane.
• Capsules may be composed of a wide variety of sugars. Many bacterial capsules, including those of most pathogens, include anionic sugars, which imparts an overall negative charge to the surface of the cell. The sugars are organized in repeating units, which may be a single sugar or short oligosaccharides. These are polymerized to make the long polysaccharide chain. Some may contain amino acids, but the capsules of Bacillus anthracis and Yersinia pestis are exceptional in that they are made solely of amino acids (poly-D-glutamate and F1 protein, respectively).