Infection Flashcards
Talk to me about Bacteria
Bacteria are single-celled organisms that can cause a range of infections, from mild to life-threatening. They can be classified into two main groups based on their cell wall structure: Gram-positive and Gram-negative. Common bacterial infections include:
Staphylococcus aureus: Causes skin infections, pneumonia, and food poisoning.
Streptococcus pneumoniae: Leads to pneumonia, meningitis, and otitis media.
Escherichia coli (E. coli): Can cause urinary tract infections and is also a common cause of foodborne illness.
Salmonella: Associated with food poisoning and typhoid fever.
Talk to me about viruses
Viruses are much smaller than bacteria and require living hosts — such as people, plants, or animals — to multiply; otherwise, they cannot survive. Some well-known viruses include:
Influenza virus: Causes the flu, a respiratory infection that can be severe.
Human Immunodeficiency Virus (HIV): Attacks the immune system, leading to AIDS.
Herpes Simplex Virus (HSV): Causes cold sores and genital herpes.
Coronaviruses: Includes SARS-CoV-2, which causes COVID-19
Talk to me about fungi
Fungi can be found in air, soil, water, and plants. While many fungi are not harmful, some can cause infections, particularly in individuals with weakened immune systems. Common fungal infections include:
Candida: A yeast that can cause oral thrush, diaper rash, and vaginal infections.
Aspergillus: Typically found in decaying vegetation, it can cause aspergillosis, affecting the lungs.
Dermatophytes: Cause athlete’s foot, ringworm, and jock itch.
Talk to me about protazoa
Protozoa are microscopic, single-celled organisms that can be parasites or predators. They are often spread through water and can cause diseases such as:
Plasmodium: Causes malaria, transmitted by the bite of infected Anopheles mosquitoes.
Giardia lamblia: Causes giardiasis, a diarrheal illness spread through contaminated water.
Entamoeba histolytica: Causes amoebiasis, which can result in dysentery.
Talk to me about parasites
Parasitic infections are caused by organisms that live on or in a host organism, obtaining nutrients at the host’s expense. Common parasitic infections include:
Helminths: Such as roundworms, tapeworms, and pinworms, which can infect the gastrointestinal tract.
Ectoparasites: Such as ticks, fleas, and lice, which often act as vectors in transmitting diseases between hosts.
Give me the clinical manifestations of infections and the underlying physiology of them
The clinical manifestations of infections depend on the type of microorganism involved, the location of the infection, the host’s immune status, and various other factors. Despite this variability, there are several common signs and symptoms that are generally associated with infections, each with its own underlying physiological basis:
1. Fever
Physiology: Fever is typically induced by pyrogens, substances that can be either exogenous (from outside the body, like bacterial toxins) or endogenous (produced by the body, like interleukins and tumor necrosis factor). These substances act on the hypothalamus in the brain to raise the body’s thermostat.
Clinical Significance: Fever is a common response to infection that helps to inhibit the growth of many pathogens and enhances the immune response.
2. Chills and Rigors
Physiology: Chills and rigors often accompany fever as the body rapidly adjusts its temperature to a new set point. Rigors, or intense shivering, are a mechanism to generate heat and raise the body’s core temperature.
Clinical Significance: Often indicative of a systemic infection.
3. Fatigue and Malaise
Physiology: These symptoms are largely due to the production of cytokines and other inflammatory mediators which can affect the central nervous system, leading to feelings of tiredness and general discomfort.
Clinical Significance: Reflective of the body’s energy being diverted towards the immune response.
4. Pain and Tenderness
Physiology: Infections can cause pain through the direct irritation of nerve endings by the inflammatory process or via the release of chemicals like bradykinin and prostaglandins that sensitize pain pathways.
Clinical Significance: Pain and tenderness are especially common in infections of the skin, joints, and deep tissues, serving as a protective mechanism to prevent further injury of affected areas.
5. Redness and Swelling
Physiology: These are classic signs of inflammation. Increased blood flow to the infected area (redness) and leakage of fluid into tissues (swelling) are mediated by various inflammatory substances like histamine.
Clinical Significance: Serve to deliver immune cells and substances to the site of infection.
6. Loss of Function
Physiology: Depending on the site of infection, inflammation can lead to a functional impairment, as tissues either swell significantly or are damaged, impeding their normal function.
Clinical Significance: Particularly evident in infections of organs or systems like the lungs (respiratory infections leading to difficulty breathing) or the digestive system (gastrointestinal infections causing diarrhea or vomiting).
7. Pus Formation
Physiology: Pus is a collection of dead cells, pathogens, and immune cells, particularly neutrophils. It forms as a result of the body’s attempt to localize and control the infection.
Clinical Significance: Common in bacterial infections, the presence of pus can be a sign of an abscess or other localized infection.
8. Lymphadenopathy (Swollen Lymph Nodes)
Physiology: Lymph nodes swell in response to an influx of immune cells and materials filtered from lymphatic fluid, which increases when there is an infection nearby.
Clinical Significance: Indicates activation of the immune system, commonly seen in viral and bacterial infections.
How do we detect pathogens?
Microscopic Examination: Direct visualization of pathogens in clinical samples like blood, urine, or tissue using microscopes, often with the aid of stains (e.g., Gram stain) to differentiate types of organisms.
Culture Techniques: Growing pathogens in specific media, which helps in identifying the organism based on growth characteristics, colony morphology, and biochemical properties.
Molecular Diagnostics: Techniques like PCR (polymerase chain reaction) amplify the DNA or RNA of pathogens to detectable levels, allowing for rapid and specific identification, often within hours.
Serological Tests: Detect the presence of antibodies or antigens related to specific infections in a patient’s blood, indicating a current or past infection.
Biomarkers: Detect specific biomarkers produced in response to an infection, aiding in the quick diagnosis of conditions like sepsis.
Talk to me about the treatment of pathogens
Antibiotics: Used for bacterial infections, with the choice of antibiotic depending on the type of bacteria and its sensitivity pattern (determined via cultures and sensitivity tests).
Antivirals: Treat viral infections by inhibiting the development or replication of the virus. For example, oseltamivir for influenza and antiretrovirals for HIV.
Antifungals: Used to treat fungal infections. These can be topical (for skin infections) or systemic (for invasive infections), like fluconazole or amphotericin B.
Antiparasitics: Treat infections caused by parasites, such as antimalarials (chloroquine) for malaria or albendazole for worm infections.
Talk to me about antimicrobial resistance and stewardship
Antimicrobial Resistance (AMR) arises when microorganisms such as bacteria, fungi, viruses, and parasites change in ways that render the medications used to cure the infections they cause ineffective. Reasons for AMR include overuse, inappropriate prescribing, and suboptimal dosing of antimicrobials.
Antimicrobial Stewardship Programs (ASP) aim to optimize the treatment of infections and reduce adverse events associated with antimicrobial use, including AMR. Key components of ASPs include:
Optimizing Prescribing Practices: Guiding clinicians on the appropriate selection, dose, route, and duration of antimicrobial therapy.
Review and Feedback: Regularly reviewing antimicrobial usage and providing feedback to prescribers.
Education: Providing ongoing education and updates about antimicrobial resistance and stewardship practices to healthcare professionals.
Infection Prevention: Strengthening infection control measures to prevent the spread of resistant infections in healthcare settings.
Surveillance: Monitoring antimicrobial resistance patterns locally and globally to inform treatment guidelines and policies.
The combined approach of careful detection, targeted treatment, and robust antimicrobial stewardship is essential to effectively manage infections and mitigate the challenge posed by antimicrobial resistance, thereby preserving the efficacy of existing treatments and safeguarding global health.
