Antibiotics and Bacteria

Gram Negative Cocci Neisseria meningitidis Corticosteroids such as prednisone

Comparing Prokaryotic and Eukaryotic Cells Prokaryote comes from the Greek words for prenucleus. Eukaryote comes from the Greek words for true nucleus.

Fig. 4.25

Fill In Your Chart and Create a Definition for Each Nucleoid Plasmid Ribosomes Cell wall Plasma membrane (cell membrane) Capsule (outer membrane) Flagella Pili Gruanules

Fig. 4.1

Flagella A) Monotrichous B) Lophotrichous C) Amphitrichous D) Peritrichous

Fig. 4.4

Fig. 4.7

Fig. 4.8

Cell Wall Prevents osmotic lysis Made of peptidoglycan (in bacteria) Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) Linked by polypeptides

Fig. 4.9

Fig. i4.1

Fig. 4.11

Gram positive versus gram negative

Crystal violet-iodine crystals form in cell Gram-positive Gram Staining Crystal violet-iodine crystals form in cell Gram-positive Alcohol dehydrates peptidoglycan CV-I crystals do not leave Gram-negative Alcohol dissolves outer membrane and leaves holes in peptidoglycan CV-I washes out

Fig. i4.2

Fig. 4.14

Gram-Positive vs. Gram-Negative Gram summary Gram-Positive vs. Gram-Negative Thick peptidoglycan Teichoic acids In acid-fast cells, contains mycolic acid Thin peptidoglycan No teichoic acids Outer membrane

Examples Gram Positive Gram Negative Streptococcus (cocci) Staphylococcus (cocci) Bacillus (bacilli, protective spore) - causes anthrax and gastroenteritis Clostridium (bacilli, protective spore) - causes botulism, tetanus, gas gangrene, and pseudomembranous colitis Corynebacterium (bacilli, no protective spore) - causes diphtheria Listeria (bacilli, no protective spore) - causes meningitis Spirochetes (spiral-shaped) - causes syphilis, lyme disease Neisseria (cocci) - causes meningococcus, gonorrhea

Fig. 4.22

Fig. 4.23

Fig. 4.29

Structure of a Bacterial Cell Cell Wall -maintains cell structure -composed of peptidoglycan, a polymer of sugars and amino acids Flagella -tail-like structure used for locomotion Plasma Membrane -phospholipid bilayer surrounding cell -contains proteins that play a role in transport of ions, nutrients, and wastes http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Gram positive and gram negative refers to how a bacteria reacts to a gram stain. If it takes the initial stain, it will be purple and be considered gram positive. If it doesn't take the initial stain, it will be pink and gram negative. The difference is the outer casing of the bacteria. A gram positive bacteria will have a thick layer of peptidoglycan (a sugar-protein shell) that the stain can penetrate. A gram negative bacteria has an outer membrane covering a thin layer of peptidoglycan on the outside. The outer membrane prevents the initial stain from penetrating.

Structure of a Bacterial Cell Nucleoid -region DNA is found in prokaryotes DNA -single double-stranded circular chromosome -no histone proteins Plasmid -small circular chromosome -may carry an antibiotic resistance gene Ribosomes -site of protein synthesis (translation) http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Some Features of an Infectious Bacteria virulence factors: molecules produced by a pathogen that aid in its survival in a host capsule: surrounds bacterial cell wall; protects bacteria from phagocytosis pili: allows bacteria to attach to and invade other cells despite mucous and cell-turnover enzymes: break down matrix between cells allowing bacteria to spread throughout tissues http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg Toxins exotoxins: cause lysis of specific host cells enterotoxins: cause secretion of fluid into the small intestine leading to vomiting and diarrhea endotoxins: cell-bound lipopolysaccharides; causes fever and inflammation Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Fleming and Penicillin

Antibiotic/Antimicrobial Antibiotic: Chemical produced by a microorganism that kills or inhibits the growth of another microorganism

Microbial Sources of Antibiotics

Antibiotic Spectrum of Activity No antibiotic is effective against all microbes

Mechanisms of Antimicrobial Action Bacteria have their own enzymes for Cell wall formation Protein synthesis DNA replication RNA synthesis Synthesis of essential metabolites

Beta-lactam antibiotics Mode of Action The beta-lactam antibiotics inhibit the last step in peptidoglycan synthesis It is Bactericidal (Bacteria Killing) Bacteriostatic = Bacteria Inhibiting Examples: Penicillin Ampicillin Amoxycillin

Beta-lactam antibiotics Spectrum Some are effective against both Gram-positive and Gram-negative bacteria whereas others are more effective against Gram-positive than Gram-negative bacteria or vice versa.

Penicllins Derived from the fungus Penicillium Therapeutic concentration in most tissues Poor CSF penetration Renal excretion Side effects: hypersensitivity, nephritis, neruotoxicity, platelet dysfunction

Inhibitors of Cell Wall Synthesis

Tetracyclines Tetracyclines consist of eight members, and may be considered as a group of antibiotics, obtained as byproducts from the metabolism of various species of Streptomyces .

Tetracyclines Tetracycline Spectrum (effective against) Mode of action Biological source Streptomyces species Spectrum (effective against) Gram-positive and Gram-negative bacteria, Rickettsias Mode of action Inhibit translation (protein synthesis) Bacteriostatic

Tetracyclines Isolated from Streptomyces aureofaciens Reversibly bind 30S ribosomal subunit Penetrate sinus mucosa, saliva and tears Metabolized in liver-->excreted in bile--> reabsorbed-->eliminated in urine Side effects: GI upset, hepatotoxicity, photosensitivity, bony deposition Contraindicated in pregnant or breast feeding women, children under 8 y/o

Sulfonamides Derived from prontosil Act as competitive inhibitors of the enzyme dihydropteroate synthetase (DHPS), an enzyme involved in folate synthesis Wide distribution, penetrate CSF, cross placenta Metabolized in liver, eliminated in urine Side effects: rash, angioedema, Stevens-Johnson syndrome, kernicterus Avoid in pregnancy and infants

Inhibitors of Nucleic Acid Function/Synthesis Fluoroquinolones (Bactericidal) Bind to bacteria DNA Concentrate in sinus and middle ear mucosa, penetrate cartilage and bone Treat bone and joint infections, skin infections, urinary tract infections, inflammation of the prostate, serious ear infections, bronchitis, pneumonia, tuberculosis, some sexually transmitted diseases (STDs), and some infections that affect people with AIDS Partially metabolized in liver-->GI or renal excretion Side effects: nausea, dizziness, phototoxicity, nephrotoxicity Avoid in pregnant or nursing women Use in children--possible effect on articular cartilage

Antibiotic Therapy Identify infecting organism Evaluate drug sensitivity Target site of infection Drug safety/side effect profile Patient factors Cost