Antimicrobials Flashcards
Describe the key clinical signs & symptoms of infection
Fever: A body temperature higher than the normal range (98.6°F/37°C) may be a sign of an infection. The body raises its temperature to help fight off the infection.
Pain: Pain or discomfort in the affected area may indicate inflammation caused by the infection. For example, a sore throat may be a sign of a viral or bacterial infection.
Swelling: Swelling or redness at the site of infection may indicate an immune response to the infection.
Fatigue: Feeling tired or lethargic may be a sign of an infection. The body uses energy to fight off the infection, which can lead to fatigue.
Nausea and vomiting: These symptoms may be caused by the infection itself or as a side effect of medications used to treat the infection.
Diarrhea: An infection in the digestive tract may cause diarrhea as the body tries to eliminate the infectious agent.
Cough: A persistent cough may be a sign of a respiratory infection, such as a cold or flu.
Shortness of breath: Difficulty breathing or shortness of breath may be a sign of a serious respiratory infection, such as pneumonia or bronchitis.
Skin rash: An infection may cause a rash or redness on the skin, which can be accompanied by itching or discomfort.
Understand the laboratory markers of infection
White blood cell (WBC) count: WBCs are an important component of the immune system and help fight infections. An increase in the number of WBCs, particularly neutrophils (a type of WBC), may indicate an active infection.
C-reactive protein (CRP): CRP is a protein produced by the liver in response to inflammation. High levels of CRP in the blood may indicate the presence of an infection.
Erythrocyte sedimentation rate (ESR): ESR measures how quickly red blood cells settle to the bottom of a test tube over time. Elevated ESR levels may indicate the presence of inflammation and infection.
Blood cultures: Blood cultures are tests that check for the presence of bacteria or fungi in the blood. These tests can help diagnose a bloodstream infection or sepsis.
Urine culture: Urine culture is a test that checks for the presence of bacteria or fungi in the urine. This test can help diagnose a urinary tract infection.
Viral antigen testing: Viral antigen testing can detect the presence of viral antigens, which are proteins produced by a virus, in a sample such as blood or nasal secretions. This test can help diagnose a viral infection.
Serology: Serology involves testing for the presence of antibodies to a specific infectious agent in the blood. This test can help diagnose a past or current infection and can also help determine the effectiveness of vaccination.
Describe main structural features of bacteria
Cell wall: Bacteria have a cell wall that surrounds the cell membrane and provides shape, structure, and protection to the cell. The composition of the cell wall varies between different types of bacteria and can be an important target for antibiotics.
Plasma membrane: Bacterial plasma membrane is a lipid bilayer that separates the cytoplasm from the external environment. It is responsible for regulating the passage of molecules in and out of the cell.
Cytoplasm: The cytoplasm is a fluid-filled region that contains all the cellular components and organelles necessary for bacterial metabolism and growth. The cytoplasm also contains the bacterial DNA, which is not enclosed in a nucleus.
Ribosomes: Ribosomes are responsible for protein synthesis in bacteria. They are smaller than eukaryotic ribosomes and have a different structure.
Flagella: Some bacteria have flagella, which are whip-like appendages that allow the bacteria to move. Flagella are made up of proteins and rotate like propellers to propel the bacteria through the environment.
Pili: Pili are hair-like appendages that are used by bacteria to attach to surfaces and other cells. They can also be involved in the transfer of genetic material between bacteria.
Capsule: Some bacteria have a capsule, which is a protective layer of polysaccharides that surrounds the cell wall. The capsule can help protect the bacteria from phagocytosis by the host immune system.
Describe the metabolic characteristics of bacteria
Bacteria can use a variety of energy sources to produce ATP, including carbohydrates, lipids, proteins, and even inorganic compounds such as hydrogen gas. Energy can be generated through a variety of metabolic pathways, such as glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation.
In glycolysis, glucose is converted to pyruvate, generating ATP in the process. Pyruvate can then be further metabolized in the TCA cycle to generate additional ATP, as well as reducing equivalents in the form of NADH and FADH2. These reducing equivalents are used to generate a proton gradient across the cell membrane, which is then used by ATP synthase to generate additional ATP through oxidative phosphorylation.
In addition to aerobic respiration, some bacteria can use alternative electron acceptors such as nitrate, sulfate, or carbon dioxide in place of oxygen in the electron transport chain to generate energy through anaerobic respiration. Other bacteria can generate energy through fermentation, which involves the conversion of organic compounds such as glucose into lactic acid, ethanol, or other products.
Some bacteria are capable of producing their own organic compounds from inorganic molecules through processes such as photosynthesis or chemosynthesis. For example, photosynthetic bacteria such as cyanobacteria can use light energy to generate ATP and reduce carbon dioxide to produce organic compounds. Chemosynthetic bacteria such as sulfur bacteria can oxidize inorganic compounds such as hydrogen sulfide to generate reducing equivalents that can be used to produce ATP and organic compounds.
Understand the various methodologies used to distinguish, classify & identify bacteria
Morphological characteristics: Bacteria can be differentiated based on their morphological features such as shape, size, and arrangement. For example, cocci are spherical bacteria, bacilli are rod-shaped bacteria, and spirilla are spiral-shaped bacteria.
Staining properties: Bacteria can be stained using dyes such as Gram stain or acid-fast stain, which can help to differentiate them based on their cell wall structure.
Biochemical tests: Bacteria can be tested for their ability to utilize or metabolize specific nutrients, such as carbohydrates or amino acids, to identify their metabolic characteristics.
Serological tests: Bacteria can be identified based on the presence or absence of specific antigens or antibodies in their cell wall or surrounding environment.
Genetic analysis: Bacteria can be identified based on their DNA sequences, which can be analyzed using techniques such as polymerase chain reaction (PCR), DNA sequencing, or ribosomal RNA sequencing.
Culture characteristics: Bacteria can be grown on specific types of media and observed for their growth characteristics such as colony morphology, color, and texture.
Virulence factors: Bacteria can be identified based on the presence of specific virulence factors, such as toxins or adhesins, that are associated with their ability to cause disease.
Phage typing: Bacteria can be identified based on their susceptibility to specific bacteriophages, which are viruses that infect bacteria.
differences between gram positive and gram negative bacteria
Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which is primarily composed of a sugar called N-acetylglucosamine and a short peptide chain. This thick layer is stained blue-violet by the crystal violet dye in the Gram staining process, and the cell appears purple under a microscope. Gram-positive bacteria also have a cytoplasmic membrane and may have an additional outer layer made of lipoteichoic acid or teichoic acid.
In contrast, Gram-negative bacteria have a thin peptidoglycan layer, which is surrounded by an outer membrane composed of lipopolysaccharides, lipoproteins, and phospholipids. This outer membrane is not stained by the crystal violet dye and appears colorless under a microscope. The thin peptidoglycan layer does not retain the stain, and the counterstain, safranin, which is applied after washing with alcohol, stains the cells red.
Some of the other differences between Gram-positive and Gram-negative bacteria include:
Size and shape: Gram-positive bacteria are typically larger and have a spherical or cylindrical shape, while Gram-negative bacteria are generally smaller and have a more diverse range of shapes, including spherical, rod-shaped, and spiral.
Antibiotic resistance: Gram-negative bacteria are often more resistant to antibiotics than Gram-positive bacteria due to the presence of the outer membrane, which acts as a barrier to many antimicrobial agents.
Toxins: Gram-negative bacteria produce endotoxins, which are released when the cell is destroyed, while Gram-positive bacteria produce exotoxins, which are secreted into the surrounding environment.
Sensitivity to physical agents: Gram-negative bacteria are generally more sensitive to physical agents such as detergents, disinfectants, and ultraviolet radiation due to the fragility of their outer membrane.
To be able to describe the treatment paradigm for management of infection – empiric v directed
Empiric therapy is the initial treatment given to a patient before the causative organism of the infection has been identified. This approach is often used in cases where the infection is severe or where there is a high likelihood of infection. Empiric therapy is based on the likely pathogens that are commonly associated with the type of infection, as well as the patient’s clinical presentation and risk factors.
Directed therapy, on the other hand, is the treatment given after the causative organism of the infection has been identified through laboratory testing. This approach involves tailoring the treatment to the specific pathogen responsible for the infection. Directed therapy is often preferred over empiric therapy as it can provide a more targeted and effective treatment, reducing the risk of antibiotic resistance and minimizing the risk of adverse effects.
To be aware of the drug & patient factors impacting on choice of antimicrobial
Age: The age of the patient can impact the choice of antimicrobial agent, as some drugs may be contraindicated or require dose adjustments in pediatric or elderly patients.
Renal and hepatic function: The patient’s renal and hepatic function can impact the choice of antimicrobial agent, as some drugs may be cleared through these organs and may require dose adjustments in patients with impaired function.
Allergies: The patient’s history of allergies to specific antimicrobial agents should be considered when selecting an appropriate agent.
Pregnancy and lactation: The use of certain antimicrobial agents may be contraindicated or require dose adjustments in pregnant or lactating women.
To have an appreciation of the concepts of pharmacokinetics & pharmacodynamics & how they apply to antimicrobials
Pharmacodynamics is typically described in terms of two key parameters: minimum inhibitory concentration (MIC) and time above MIC. MIC refers to the lowest concentration of an antimicrobial that is needed to inhibit the growth of the microorganism causing the infection. The time above MIC refers to the duration of time during which the drug concentration remains above the MIC level, and this parameter is considered critical to the success of antimicrobial therapy.
For example, the pharmacodynamics of antimicrobial agents may influence the selection of a dosing regimen that maximizes the time above MIC, which is often necessary for effective treatment. Additionally, the development of antimicrobial resistance can also be influenced by pharmacodynamics, as the selective pressure created by sub-therapeutic drug concentrations can lead to the emergence of resistant strains.
describe laboratory methods for susceptibility testing
Disk diffusion method: This method involves inoculating a culture of the microorganism onto a solid agar plate, followed by placing filter paper disks impregnated with various antimicrobial agents onto the surface of the agar. The plate is incubated, and the zones of inhibition around each disk are measured to determine the susceptibility of the microorganism to the agent.
Broth microdilution method: This method involves preparing a series of dilutions of the antimicrobial agent in a liquid broth, followed by inoculating the broth with the microorganism. The broth is incubated, and the lowest concentration of the antimicrobial agent that inhibits the growth of the microorganism is determined.
Etest method: This method involves placing a strip containing a gradient of the antimicrobial agent onto an agar plate inoculated with the microorganism. The plate is incubated, and the MIC is determined by reading the point at which the growth of the microorganism intersects with the strip.
Automated systems: Automated systems use computer-controlled technology to perform susceptibility testing. These systems can rapidly determine the susceptibility of microorganisms to multiple antimicrobial agents using minimal amounts of culture material.
To describe the most commonly encountered infections in clinical practice
Upper respiratory infections (URIs): These are infections that affect the upper respiratory tract, including the nose, sinuses, throat, and larynx. URIs can be caused by viruses, bacteria, or fungi and may present with symptoms such as cough, congestion, sore throat, and fever.
Urinary tract infections (UTIs): UTIs occur when bacteria enter and infect the urinary tract, including the bladder, urethra, and kidneys. Symptoms can include frequent urination, pain or burning during urination, and lower abdominal pain.
Skin infections: Skin infections can be caused by bacteria, fungi, or viruses, and can present with symptoms such as redness, swelling, and pain. Common skin infections include impetigo, cellulitis, and fungal infections like athlete’s foot.
Gastrointestinal infections: These infections can affect the digestive system and cause symptoms such as nausea, vomiting, diarrhea, and abdominal pain. They can be caused by viruses, bacteria, or parasites.
Sexually transmitted infections (STIs): STIs are infections that are spread through sexual contact and can include gonorrhea, chlamydia, herpes, and human papillomavirus (HPV). Symptoms can vary depending on the specific infection, but can include discharge, pain during sex, and genital sores.
Bloodstream infections: Also known as sepsis, these infections occur when bacteria enter the bloodstream and can lead to life-threatening complications. Symptoms can include fever, chills, rapid heart rate, and low blood pressure.
pathogenesis & microbiology behind Pneumonia
Pneumonia is an inflammatory condition of the lung tissue, which can be caused by different microorganisms including bacteria, viruses, fungi, and other agents. The pathogenesis of pneumonia involves the inhalation of the causative agent into the lungs, colonization of the respiratory tract, and activation of the host immune response. The microorganisms that cause pneumonia can produce virulence factors that allow them to adhere to and invade host cells, evade the host immune response, and cause tissue damage. The inflammatory response to the microorganisms can cause symptoms such as fever, cough, and shortness of breath.
Pathogenesis and microbiology behind UTI
UTIs are infections that affect any part of the urinary system including the kidneys, ureters, bladder, and urethra. The most common cause of UTIs is the bacterium Escherichia coli (E. coli), which is normally found in the intestines. The pathogenesis of UTIs involves the colonization of the urinary tract by the bacteria, which can be facilitated by factors such as sexual activity, improper hygiene, or obstruction of urine flow. The bacteria can produce virulence factors that allow them to adhere to and invade host cells, evade the host immune response, and cause tissue damage. The immune response to the bacteria can cause symptoms such as pain or burning during urination, frequent urination, and lower abdominal pain.
Cellulitis and erysipelas
Cellulitis and erysipelas are skin infections caused by bacteria, most commonly by Streptococcus pyogenes or Staphylococcus aureus. The pathogenesis of cellulitis and erysipelas involves the entry of bacteria through a break in the skin, such as a cut or scratch. The bacteria can produce virulence factors that allow them to adhere to and invade host cells, evade the host immune response, and cause tissue damage. The inflammatory response to the bacteria can cause symptoms such as redness, warmth, swelling, and pain in the affected area.
