Topic 4

    Cards (13)

    • Gram staining
      A common technique used to differentiate two large groups of bacteria based on their different cell wall constituents
    • Gram staining procedure
      1. Distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet
      2. Gram positive bacteria stain violet/blue due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with
      3. Gram negative bacteria stain red/pink, which is attributed to a thinner peptidoglycan wall, which does not retain the crystal violet during the de-coloring process
    • Antimicrobial chemotherapy
      Based on the principle of selective toxicity, which implies that a compound is harmful to a microorganism but less damaging to its host
    • Properties of drugs used in antimicrobial therapy
      • Antimetabolites
      • Inhibit cell wall biosynthesis
      • Inhibit protein synthesis
      • Inhibit nucleic acid synthesis
      • Alter or inhibit cell membrane permeability or transport
    • Drug resistance
      Occurs when microbes survive and grow in the presence of a drug that normally kills or inhibits the microbe's growth
    • Types of drug resistance
      • MRSA (Methicillin-Resistant Staphylococcus aureus)
      • VRE (Vancomycin-Resistant Enterococci)
    • Causes of antimicrobial drug resistance
      • Selective pressure
      • Mutation
      • Gene transfer
      • Inappropriate drug use
      • Inadequate diagnosis
      • Hospital use drugs
    • Chlamydia trachomatis
      • Gram-negative bacterium
      • Different types cause different diseases, most common strains cause disease in the genital tract, other strains cause trachoma and conjunctivitis
    • Escherichia coli
      • Motile, member of the Enterobacteriaceae, Gram negative, facultative anaerobe
      • Causes urinary tract infections (UTIs), neonatal sepsis and meningitis, and diarrheal diseases
      • All strains have endotoxin and constitutively produce common pili that adhere to colon cells
    • Haemophilus influenzae
      • Gram-negative, fastidious, pleomorphic rod
      • Most strains are opportunistic pathogens
      • Transmitted via respiratory droplets by direct contact
      • In infants and young children, H. influenzae type b (Hib) causes bacteremia, pneumonia, epiglottitis and acute bacterial meningitis
      • Causes exacerbations of chronic bronchitis in patients with chronic obstructive pulmonary disease (COPD)
    • Pseudomonas aeruginosa
      • Gram-negative rod with polar flagella, aerobe
      • Blue-green pus is a classic sign of P. aeruginosa cellulitis in burn patients
      • Frequent cause of nosocomial infections, with pneumonia in cystic fibrosis (CF), neutropenia, or ventilated patients
      • The capsule inhibits phagocytic uptake, pili also aid in adherence
    • Staphylococcus aureus
      • Gram-positive coccus found in grapelike clusters
      • Colonizes in the nasal passages mucosa and can be found on the skin
      • Transmitted by direct contact/fomites (e.g., bedrails)
      • Common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning
    • Streptococcus pyogenes
      • Gram-positive coccus
      • Colonizes skin and upper respiratory tract mucosa
      • Survives on hard surfaces; spread by fomites, respiratory droplets, and direct contact
      • Causes pharyngitis, impetigo, cellulitis (inflammation of subcutaneous connective tissue), scarlet fever
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