Infectious Diseases - Session 3

Acquired Immunodeficiency Syndrome is a complex condition caused by the Human Immunodeficiency Virus. Human Immunodeficiency Virus is a retrovirus that attacks the immune system, particularly CD4 cells. These cells are also known as T-helper cells. T helper cells are a type of white blood cells. T helper cells undertake a crucial role in coordinating the body's immune response.

Human Immunodeficiency Virus can be transmitted through vaginal, anal, or oral sex with an infected person. Human Immunodeficiency Virus can be spread by sharing needles or syringes contaminated with the blood of an infected person. This can occur during injection drug use or through the use of contaminated needles for medical procedures or tattoos. Human Immunodeficiency Virus can be passed from an infected mother to her child during pregnancy, childbirth, or breastfeeding. However, the risk of transmission can be significantly reduced with proper medical care and interventions.

When Human Immunodeficiency Virus enters the body, it replicates and gradually weakens the immune system by destroying CD4 cells. However, many people with Human Immunodeficiency Virus do not experience symptoms immediately after infection. The initial phase of HIV infection is also known as acute HIV infection. Many people with acute HIV infection experience an unexplained fever, often accompanied by other symptoms.

A sore throat is a common symptom during acute HIV infection. It often resembles the symptoms of a cold or flu. Some individuals develop a rash on the skin, typically appearing as red, raised bumps or patches. This rash can occur on various parts of the body and can be itchy or painful.

Lymph nodes, which are part of the body's immune system, can become enlarged and tender. Swollen lymph nodes are particularly common in the neck, armpits and groin. Other symptoms that can occur during acute HIV infection include muscle aches, joint pain, headache, fatigue, nausea, vomiting and diarrhea. These symptoms typically last for a few days to a few weeks before resolving on their own.

Acquired Immunodeficiency Syndrome is the final stage of HIV infection, characterized by a severely weakened immune system. It is diagnosed when the individual’s CD4 cell count falls below a particular threshold. This threshold can be two hundred cells per cubic millimeter of blood. People diagnosed with Acquired Immunodeficiency Syndrome can develop particular opportunistic infections or cancers known as AIDS defining illnesses.

These infections and cancers are typically rare in individuals with healthy immune systems but can be life threatening in people with Acquired Immunodeficiency Syndrome. Some examples of AIDS defining illnesses include tuberculosis, Pneumocystis jirovecii pneumonia, Kaposi's sarcoma, cryptococcal meningitis, and cytomegalovirus retinitis. As the immune system becomes severely compromised, individuals with AIDS might experience a wide range of symptoms and complications. These include recurrent infections, chronic diarrhea, weight loss, fatigue, night sweats and neurological symptoms.

While there is currently no cure for HIV or AIDS, advances in medical treatment have transformed it into a manageable chronic condition for many people. Antiretroviral therapy is the cornerstone of HIV treatment. It consists of a combination of medications that suppress the replication of the virus, reduce viral load and slow-down the progression of the disease. When taken consistently and correctly, antiretroviral therapy can significantly prolong the lives of people with HIV. It can improve their quality of life, and reduce the risk of transmission to others.

Additionally, preventive measures such as safer sex practices, needle exchange programs, pre-exposure prophylaxis, and post-exposure prophylaxis can help reduce the risk of HIV transmission. Overall, AIDS remains a significant global health challenge, particularly in regions with limited access to healthcare resources.

Penicillin is an antibiotic that works by interfering with the ability of bacteria to build their cell walls. It ultimately leads to their destruction. Many bacteria have a cell wall that provides structure and protection to the cell. This cell wall is made up of a complex molecule called peptidoglycan. Peptidoglycan consists of sugar and amino acid chains cross linked to form a mesh-like structure surrounding the bacterial cell.

Penicillin belongs to a class of antibiotics known as beta lactams. It contains a beta lactam ring-structure that mimics the shape of the D-alanine-D-alanine portion of the peptidoglycan precursor molecules. When bacteria are actively growing and dividing, they synthesize new peptidoglycan molecules to expand and maintain their cell wall integrity. Penicillin works by binding to and inhibiting enzymes called penicillin binding proteins. These enzymes are responsible for cross linking the peptidoglycan chains during cell wall synthesis.

By inhibiting the activity of penicillin binding proteins, penicillin prevents the cross linking of peptidoglycan chains. This weakens the bacterial cell wall. Without a fully functional cell wall, the bacterial cell becomes fragile and susceptible to rupture. The internal pressure of the cell causes it to swell and burst. This leads to the death of the bacterial cell.

One of the key advantages of penicillin and other beta lactam antibiotics is their selective toxicity towards bacteria. Mammalian cells lack cell walls. Due to lack of cell wall, the mammalian cells are not affected by penicillin. This allows the antibiotic to target bacterial cells specifically while minimizing harm to the host organism.

Antibiotics are medications specifically designed to target and kill bacteria, but they do not affect viruses. This is because bacteria and viruses are two distinct types of microorganisms with different structures, life cycles and mechanisms of infection.Because viruses lack the cellular machinery found in bacteria, they cannot be targeted by antibiotics that interfere with bacterial cellular processes.

Antibiotics are designed to selectively target and kill bacteria while minimizing harm to human cells. They achieve this by exploiting differences in cellular processes between bacteria and human cells. For example, antibiotics might target bacterial cell walls or protein synthesis machinery processes that are not seen in human cells. Since viruses replicate inside host cells, targeting viral replication without harming host cells is much more challenging. Antiviral medications are specifically designed to target viral processes or components, such as viral enzymes or proteins involved in viral replication.

Antibiotic resistance occurs when bacteria evolve mechanisms to withstand the effects of antibiotics, rendering the medications ineffective against them. Some bacteria produce enzymes that can chemically modify antibiotics, rendering them inactive. For example, beta-lactamase enzymes can break-down beta-lactam antibiotics like penicillin, preventing them from inhibiting bacterial cell wall synthesis. Bacteria can modify the structure of their target sites, such as enzymes or proteins targeted by antibiotics. This alteration prevents antibiotics from binding effectively to their targets and inhibiting bacterial growth.

Bacteria can develop mechanisms to reduce the entry of antibiotics into their cells or actively pump out the drugs once they enter. This decreases the concentration of antibiotics inside the bacterial cell, making them less effective in killing or inhibiting bacterial growth. Some bacteria can bypass the inhibited metabolic pathway targeted by antibiotics by using alternative pathways to fulfill their metabolic needs. This allows them to survive and replicate in the presence of antibiotics. Overuse and misuse of antibiotics leads to antibiotic resistance.