Lab act 7

• Antimicrobials


  Chemical agents used to kill microorganisms outside of the body, more commonly used as a treatment for a disease
• Types of antimicrobials


  • Antibiotics derived from microorganisms
  • Semisynthetics (chemically modified antibiotics)
  • Synthetics (chemically developed drugs)
• The use of antimicrobics involves the prescription of a medical doctor (MD) or a physician
• The MD must be sure that a particular prescribed drug is specific for a particular microorganism causing the disease
• Pathogenic microbes are able to acquire and express resistance to antimicrobial agents used to treat infections
• Antimicrobial susceptibility testing


  A laboratory procedure done in order to detect antimicrobial resistance
• Mechanisms of action of antimicrobials

  1. Inhibition of cell wall synthesis

  2. Disruption of cell membrane function

  3. Inhibition of protein synthesis

  4. Inhibition of nucleic acid synthesis

  5. Inhibition of metabolic pathways
• Purpose of antimicrobial susceptibility test

  To determine which antimicrobials will inhibit the growth of the bacteria or fungi causing a specific infection
• Clinical implications of susceptibility test results

  • Resistant (bacteria can grow even if drug is present)
  • Intermediate (uncertain therapeutic effect)
  • Susceptible (antibiotic is likely an effective treatment)
• Examples of antimicrobial drug families


  • Aminoglycosides
  • Carbapenems
  • Cephalosporins
  • Penicillins
  • Monocyclic Beta-Lactams
  • Chloramphenicols
  • Lincosamides
  • Macrolides
  • Quinolones
  • Sulphonamide combinations
  • Glycylcyclines
  • Tetracyclines
  • Glycopeptide antibiotics
  • Antituberculosis
  • Antileprosy
  • Antihelminthics/antihelmintics
  • Antifungal
  • Amebicides
  • Antimalarial
  • Antiviral
  • Antiprotozoal
• Gram stain


  When freshly grown bacterial cells are treated with the reagents used in the Gram stain, they can be categorized into one of two classes: Gram (+) or Gram (-). Gram (+) class will appear blue or violets while the Gram (-) class will appear red or pink.
• Cell wall


  • A tough and rigid structure surrounding the cell. The rigid part is the peptidoglycan. Peptidoglycans are the structural elements of almost all bacterial cell walls. They constitute almost 95% of the cell wall in some Gram positive bacteria and as little as 5-10% of the cell wall in Gram negative bacteria
• Gram-negative bacteria


  Have an outer membrane
• Bacterial cytoplasmic membrane


  Composed of a PHOSPHOLIPID LAYER and thus has all of the general functions of a cell membrane such as acting as a permeability barrier for most molecules and serving as the location for the transport of molecules into the cell
• Cytoplasm


  The TOTAL OF EVERYTHING INSIDE of the cytoplasmic membrane. It contains the Cytosol or the Amorphous Matrix to which nearly all other functions not conducted by the cell membrane occur and it is where interior structures are suspended. It contains ribosomes, storage granules, nucleoid, plasmids, and transposons.
• Acid-fast staining


  A differential stain used to identify acid-fast organisms such as members of the genus Mycobacterium. Acid-fast organisms are characterized by wax-like, nearly impermeable cell walls; they contain mycolic acid and large amounts of fatty acids, waxes, and complex lipids
• Acid-fast staining methods


  • ZIEHL NEELSEN
  • KINYOUN
• ZIEHL NEELSEN


  Heating required, acid fast stain, bacteria will be red
• KINYOUN


  Heating not required, acid fast stain, bacteria will be red
• Acid-fast staining counterstains


  • methylene blue
  • brilliant green/malachite green
• Eukaryotic cell functions


  • Nuclear envelope provides structural framework of the nucleus
  • Chromatin packages long DNA molecules into more compact,denser structure
  • Nucleolus for rRNA transcription,rRNA processing and ribosome subunit assembly
  • Peroxisome carries out oxidative reactions using molecular oxygen
  • Endoplasmic reticulum transports synthesized proteins in vesicles
  • Smooth E.R. synthesizes essential lipids such as cholesterol and phospholipids
  • Microtubules help to move cells organized genetic material during cell division and providing proper shape and help with intracellular transport
  • Centrosome organizes the microtubule and provide structure to the cell
  • Intermediate filaments provide support and structure for cells
  • Microfilaments assist with cell movement and are made of a protein called actin
  • Plasma membrane provides protection for a cell,regulates the passage of nutrients,waste products, and secretion into and out of the cell
  • Lysosomes serve as the digestive system of the cell,serving both to degrade material and to digest obsolete components of the cell
  • Golgi apparatus transports,sorts,modifies both protein and lipid
  • Cytoplasm is responsible for holding the components of the cell and protects them from damage
  • Mitochondria serve as the generation of metabolic energy in eukaryotic cell
  • Nuclear Membrane is a barrier that physically protects the cell's DNA from the chemical reactions that are occurring elsewhere in the cell
• Prokaryotic cell parts


  • Plasmid - Non-chromosomal DNA structures, not involved in reproduction
  • Cell membrane - Control what enters and leaves the cell
  • Cell wall - Provides rigidity, strength, and protection
  • Capsule - An outer protective covering, helps in moisture retention, protects the cell walls
  • Pili - Hair-like structures to anchor/adhere to surfaces which facilitates infection and virulence characteristics
  • Flagella - Threadlike protein appendages that assist cells to move, to swim from one location to a more desirable one
• Types of flagellum


  • Monotrichous - a single flagellum is present at one end
  • Lophotrichous - multiple flagella clustered at one or both ends
  • Amphitrichous - Single flagellum at both ends
  • Peritrichous - distributed all over their surface
• Diseases and causative agents


  • Diplococcus - pneumonia - Streptococcus pneumoniae
  • Streptococcus - Streptococcal throat/pharyngitis - Streptococcus pyogenes
  • Staphylococcus - Staphylococcal skin infections - Staphylococcus aureus
  • Bacillus - anthrax - Bacillus anthracis
  • Vibrio - Cholera - Vibrio cholerae
  • Spirillum - Rat-bite fever - Spirillum minus
  • Spirochetes - Lyme Disease - Borrelia burgdorferi
  • Gram positive bacteria - Toxic Shock Syndrome - Staphylococcus aureus
  • Gram negative bacteria - Urinary Tract Infection - Escherichia coli
  • Spore-forming bacteria - anthrax - Bacillus anthracis
• 10 most dangerous antibiotic-resistant bacteria


  • Streptococcus pyogenes - Streptococcal infections - low virulence - deadly
  • Neisseria gonorrheae - Gonorrhea - medium virulence - worrying
  • Mycobacterium tuberculosis - Tuberculosis - medium virulence - deadly
  • Acinetobacter baumannii - Nosocomial infection,pneumonia,meningitis - high virulence - worrying
  • Escherichia coli - Urinary tract infection - high virulence - worrying
  • Klebsiella pneumoniae - pneumonia - medium virulence - worrying
  • Clostridium difficile - diarrhea - low virulence - dangerous
  • Pseudomonas aeruginosa - pneumonia - medium virulence - worrying
  • Burkholderia cepacia - Cystic fibrosis,pneumonia - low virulence - worrying
  • Staphylococcus aureus (MRSA) - Skin infections, Pneumonia, Fish eating disease - medium virulence - dangerous