Question

Please answer ALL questions in three to four sentences.

Discuss a specific antibiotic of your choosing include its mechanism of action, spectrum and clinical uses.

Describe how antibiotics can promote some microbial infections? Include an example in your answer.

Compare and contrast endotoxins of gram-negative bacteria and the super antigens of some gram positive bacteria.

How does the ID50 relate to the pathogenesis and severity of disease cause by a pathogen?

Describe two different types of virulence factors and how they promote infection and disease.

Answer 1

Streptomycin-

1. Streptomycin is a protein synthesis inhibitor. It binds to the small 16S rRNA of the 30S subunit of the bacterial ribosome, interfering with the binding of formyl-methionyl-tRNA to the 30S subunit.

Streptomycin is an antibiotic that inhibits both Gram-positive and Gram-negative bacteria and is, therefore, a useful broad-spectrum antibiotic.

Streptomycin belongs to a class of drugs known as aminoglycoside antibiotics. It works by killing the organisms that cause the infection. Today it is widely used as a first line TB medicine in patients that have previously been treated for TB.  This drug may also be used to treat other serious infections e.g., tularemia, endocarditis, plague along with other medications.

3. Endotoxins are part of the outer membrane of the cell wall of Gram-negative bacteria such as Escherichia coli, Salmonella, Shigella, Pseudomonas, Neisseria.

Staphylococcus aureus and Streptococcus pyogenes (group A streptococci) are gram-positive pathogens capable of producing a variety of bacterial exotoxins known as superantigens. Superantigens' are protein antigen-like molecules produced by a diverse array of microbes that interact with MHC class II molecules and TCR in a manner that dramatically increases the frequency of T-cell responses compared to conventional peptide antigens. Superantigens are exotoxins.

4. The infective dose, or more specifically the ID₅₀, is the estimated number of organisms required to produce infection in 50% of normal adult humans exposed by a given route. For exaample, The ID₅₀ for S. flexneri, S. sonnei, and S. dysenteriae is approximately 5,000 organisms.

5. . Factors that are produced by a microorganism and cause disease are called virulence factors. Examples are toxins, surface coats that inhibit phagocytosis, and surface receptors that bind to host cells.