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Question: 1) How does prolonged antimicrobial therapy compromise the host immunologically? 2) Why are infections and malignancy common among the elderly? 3) Describe the type of infections that are likely to occur in an organ transplant patient. 4) Patient's with Hodgkin disease are especially susceptible to certain infections. Name several and the reason why they are more susceptible. 5) In neutropenic patients, what type of infection is most common and why? 6) Who is at greatest risk of infection after a splenectomy and why? 7) What type of infections have been reported in patients with chronic lymphocytic leukemia and lymphoma? 8) Briefly describe what happens to the immune defense mechanism in a burn patient. Questions on Antibiotic Mechanisms of Action and Resistance: 1)Describe the mechanism of action of the different classes of antimicrobials based on the five targets of antibiotics. 2)Describe intrinsic and acquired resistance, and provide examples. 3)List the different groups of antibiotics discussed in the chapter, and describe how they act on bacteria. Answer: How does prolonged antimicrobial therapy compromise the host immunologically? Immunocompromised patients are very much prone to bacterial or viral-mediated infections. Antimicrobial therapy helps the patient to treat the infection by recognizing the deficit properties of the immune system, performing the early diagnosis step and promoting intervention. Why are infections and malignancy common among the elderly? Aging is the main cause of infections and malignancy among elderly people. The immune system of elderly people lost declined the capability to respond to the invading pathogens and restriction against tumor formation. However, the malignancy itself can expose the elderly to infections caused by Pseudomonas aeruginosa and cytomegalovirus infection (Mahon et al., 2014). Describe the type of infections that are likely to occur in an organ transplant patient. Some specific types of infections are associated with the organ transplant patient in several interval. During the first month, the patient suffers infections results from E.coli, M.tuberculosis. Immunosuppressive therapy sometimes activates CMV infection during the third-month results in GI disease, hepatitis. Some infections may occur after six months of post-transplantation; which are associated with viral influenza and food related illness. Patients with Hodgkin disease are especially susceptible to certain infections. Name several and the reason they are more susceptible. Patients suffering from Hodgkin disease associated with impaired phagocytosis, inability of neutrophiles to migrate to the site of inflammation and a decreased number of neutrophiles which leads to infections. The infections often occurs from the facultative intracellular parasites such as Mycobacterium tuberculosis, Listeria monocytogenes etc. In neutropenic patients, what type of infection is most common and why? Septicemia is very common with the neutropenic patients. Neutrophils play a crucial role in maintaining the infection at the local site caused by E. coli, K. pneumonia. Pneumonia associated with gram-positive bacteria creates the major problem for neutropenic patients as it results in an inadequate immune response, infection of pulmonary. The patients fail to show symptoms of pneumonia. Who is at greatest risk of infection after a splenectomy and why? The people who compromised their spleen organ are at greatest risk of infection. The largest lymph node of the body is the spleen. So castration of spleen results in weakening the immunity of host. The loss in immunity power leads to severe infections, which are termed as post-splenectomy sepsis. The infections mainly associated with S. pneumonia, H. influenza etc (Mahon et al., 2014). What type of infections has been reported in patients with chronic lymphocytic leukemia and lymphoma? The infections associated with chronic lymphocytic leukemia and lymphoma results in increased creatinine level, a decrease in IgG, and a decline in neutrophil function. The infections more often associated with the endogenous bacteria originate from GI tract and cutaneous layer. Briefly, describe what happens to the immune defense mechanism in a burn patient. The humoral and cell-mediated defense mechanism in burn patient declined due to lowering in the concentration of IgG. The fibronectin level in plasma and matrix also reduced. Thus, the function of reticuloendothelial cell disrupted. The risk of fungal infection also increased with the extent of the burning nature. Serratia, Candida, Fusarium are the critical causes of infection in burn places (Mahon et al., 2014). Questions on Antibiotic Mechanisms of Action and Resistance: Describe the mechanism of action of the different classes of antimicrobials based on the five targets of antibiotics. As stated by Mahon et al. (2014), different antibiotics have a various mode of action based on the target host. The mechanism of action of different classes of antimicrobials are- Inhibition of the cell wall synthesis- Cell wall is the critical structure for the survival of bacterial species. These groups of antibiotics interfere with the cell wall machinery and prevent the cell wall formation. Inhibition of cell membrane function- Disruption of the cell membrane by the group of antibiotics create leakage in membrane which in turn results in loss of essential solution from the cell Inhibition of protein synthesis- Most of the cellular machinery is made up of proteins. Several types of antibacterial agents target the protein binding site of 30s ad 50s ribosome subunit. Inhibition of protein synthesis disrupts the metabolism action of the host. Inhibition of nucleic acid synthesis- Some antibiotics inhibit the DNA and RNA synthesis by restricts its component. Thus, the bacterial multiplication and survival stop. Inhibition of metabolic process- Some kind of antibiotics selectively blocks some important metabolic pathways of bacterial survival. As folic acid pathway disruption halts some vitamin synthesis in bacteria (Snell Arora, 2012). Describe intrinsic and acquired resistance, and provide examples. The innate ability exerts by a bacteria that prevent the activity of a certain antimicrobial substance both in structural and functional aspects is referred to as intrinsic resistance. This is due to the lack of affinity of antimicrobial towards the target or by the enzyme secretion from the target that inactivates the antimicrobial. Some examples of the intrinsic resistance- Stenotrophomonas shows resistance against Imipenem via producing beta- lactamases enzyme that degrades the drug before it can reach protein binding site. When a particular microorganism gains the ability to resist the effect of a particular antimicrobial to which the organism was susceptible previously, it termed as acquired resistance. This may results due to change in cells of microorganism due to mutation, horizontal gene transfer. For example- Mycobacterium tuberculosis become resistant to rifampicin due to a point mutation in receptor rpoB where rifampicin binds (Tille, 2013). List the different groups of antibiotics discussed in the chapter, and describe how they act on bacteria. Fluoroquinolones (Nalidixic acid, gemifloxacin), Trimethoprim-sulfamethoxazole, Rifamycins (rifampin)- Inhibits the DNA and RNA synthesis Lactams (Penems, Cephems, Carbapenems, Monobactams), Glycopeptides (vancomycin), lipopeptides (daptomycin)- Cell wall synthesis inhibitor Aminoglycosides (gentamicin, kanamycin), Tetracyclines, Macrolides (Erythromycin), Streptogramins (pristinamycin), Phenolics (chloramphenicol)- Inhibits protein synthesis. References: Mahon, C. R., Lehman, D. C., Manuselis Jr, G. (2014).Textbook of diagnostic microbiology. Elsevier Health Sciences. Snell, J. F., Arora, K. L. (2012).Mechanism of action of antimicrobial and antitumor agents(Vol. 3). J. W. Corcoran, F. E. Hahn (Eds.). Springer Science Business Media. Tille, P. (2013).Bailey Scott's diagnostic microbiology. Elsevier Health Sciences.