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BIOL 2230 3/29 and 3/31 notes

by: Allison Collins

BIOL 2230 3/29 and 3/31 notes BIOL 2230

Marketplace > Middle Tennessee State University > Biology > BIOL 2230 > BIOL 2230 3 29 and 3 31 notes
Allison Collins
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These notes cover the lectures on 3/29 and 3/31. We finished the unit 2 material and started the unit 3 material. Topics include antibiotics, combinations of drugs, antibiotic resistance, classific...
Anthony L Newsome
Class Notes
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This 7 page Class Notes was uploaded by Allison Collins on Thursday March 31, 2016. The Class Notes belongs to BIOL 2230 at Middle Tennessee State University taught by Anthony L Newsome in Fall 2015. Since its upload, it has received 24 views. For similar materials see Microbiology in Biology at Middle Tennessee State University.


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Date Created: 03/31/16
3/29   Antibiotic:  a  metabolite  produced  by  one  microorganism  that  inhibits  the   metabolic  pathway  of  another  microorganism   •   Certain  bacteria  are  more  sensitive  to  certain  bacteria  –  identify  bacteria   when  possible   •   Don’t  use  antibiotics  to  prevent  wound  infections   o   Exception:  post-­‐surgical  wounds   •   About  half  of  antibiotics  from  the  genus  Streptomyces   o   Common  genus  because  they  produce  chemicals  that  inhibit   other  microorganisms’  processes   o   Other  common  MO’s  –  Bacillus,  Penicillium   o   The  vast  majority  of  antibiotics  are  produced  by  other  organisms   Spectrum  of  activity  –  action  of  antibiotics   •   INHIBIT:   •   1.  cell  wall  formation   •   2.  protein  synthesis   •   3.  DNA  synthesis   •   4.  metabolic  pathways   o   The  newest  antibiotics  also  function  in  these  ways   Problem  when  pathogen  is  a  eukaryotic  cell/MO:   •   Example:  fungus,  yeast,  protozoan,  worm  (helminth)   •   Share  many  of  the  same  metabolic  pathways  that  our  cells  do,  thus   making  these  MO’s  difficult  to  selectively  inhibit   Viral  infections  are  also  difficult  to  treat   •   Don’t  have  their  own  metabolic  pathways  –  use  enzymes  from  our  cells   Desirable  criteria  for  antibiotics     •   1.  Selective  toxicity   •   2.  Don’t  produce  hypersensitivity     •   Ex:  many  people  are  allergic  to  Penicillin   •   3.  MO  not  easily  resistant   •   4.  Soluble  in  body  fluids  and  not  rapidly  broken  down  or  excreted   Action  of  antimicrobial  drugs     1.  Inhibition  of  cell  wall  synthesis   •   Most  effective  against  Gram  positive  bacteria   o   Interfere  with  synthesis  of  peptidoglycan   •   A)  Penicillin(s)  –  have  β  lactam  ring  –  central  to  structure  of  molecule   o   Many  bacteria  that  are  resistant  to  Penicillin  are  able  to  break   down  the  beta  lactam  ring   o   β  lactamase  –  AKA  penicillinases  –  enzyme  that  breaks  open  the   beta  lactam  ring   o   Penicillin  then  can’t  work  to  inhibit  cell  wall  function   •   B)  Cephalosporins  (another  type  of  antibiotic)  –  also  inhibits  cell  wall   synthesis   2.  Inhibit  protein  synthesis   •   Streptomycin  –  attach  and  change  shape  of  bacteria’s  ribosomes  –  mRNA   is  then  read  incorrectly   o   Bacteria  produce  non-­‐functional  protein   •   Tetracyclines  –  inhibit  attachment  of  tRNA  to  mRNA     o   Amino  acid  chain  not  constructed   3.  Injury  to  plasma  membrane   •   Amphotericin  B  –  antifungal  –  very  toxic,  users  must  be  hospitalized   2   •   Polymyxin  B  –  OTC  –  topical  use  only   •   Polypeptide  antibiotics   o   Hot  area  of  research  for  new/better  antibiotics   o   Found  when  studying  salamander  limb  regeneration   –  noticed   that  when  limbs  were  cut  off,  salamanders  never  got  skin   infections     o   Removed  skin,  ground,  and  added  to  bacterial  cultures   –   inhibited  bacterial  growth   o   Salamanders,  frogs,  goldfish,  etc  produce  magainins   –  new  class   of  antibiotics   o   Old  Russian  tradition:  keeping  a  frog  in  a  bucket  of  milk  will  keep   it  from  spoiling   4.  Inhibit  nucleic  acid  synthesis   •   Inhibit  unwinding  of  DNA   o   Ex:  Nalidaxic  acid  blocks  DNA  gyrase  (unwinds  bacterial  DNA  so   that  it  can  replicate)   •   Inhibit  DNA  polymerase     5.  Inhibit  metabolism/enzyme  activity   •   Sulfanilamide:  sulfa  drug   o   Prevents  folic  acid  synthesis  –  necessary  vitamin  for  bacteria   Ocean  bacteria  –  untapped  source  of  vast  number  of  organisms  –  constant   search  for  new  antibiotics   Who  use  the  most  antibiotics?  Farmers   •   Poultry,  seafood,  etc.     •   Promotes  antibiotic  resistance   •   Aureomycin  –  sold  at  co-­‐op  for  cheap  –  very  effective  –  fed  to  animals   Treatments   3   •   Antibiotic  susceptibility  resistance   •   All  healthcare  systems  follow  the  same  protocol   •   Kirby-­‐Bauer  test   o   Determine  if  bacteria  are  sensitive  to  a  particular  antibiotic   o   Isolate  bacteria  and  look  for  zone  of  inhibition       3/31   Combinations  of  drugs   •   Synergism  –  effect  of  2  drugs  taken  simultaneously  is  greater  than  the   sum  of  each  drug’s  individual  effects   o   Ex:  penicillin  (inhibition  of  cell  wall  synthesis)  +  streptomycin   (inhibition  of  protein  synthesis   •   Antagonistic  effect:  effect  of  2  drugs  taken  simultaneously  is  less  than   the  sum  of  each  drug’s  individual  effects   Resistance   •   1.  Bacteria  produce  enzymes  that  destroy  antibiotics   o   Ex:  beta  lactamace  (penicillinase)   •   2.  Inhibit  entry  of  antibiotic  into  cell  so  it  can’t  inhibit  protein  synthesis,   DNA  synthesis,  etc.   o   Ex:  thick  capsule  on  a  bacterium   Principle  of  treatment:  give  a  large  initial  dose  of  antibiotic   Principle  of  use   •   Some  bacteria  are  resistant  before  antibiotic  use  begins   •   This  occurs  through  genetic  variation  –  likely  to  happen   •   Give  large  amount  to  quickly  reduce  number  of  bacteria  to  manageable   levels  so  that  our  bodies  can  quickly  clear  before  resistant  forms  emerge   4   •   If  unable  to  clear  resistant  forms,  they  start  to  multiply  and  you  get  sick   again  –  same  bacteria  but  different  variety     •   At  this  point  you  need  to  try  a  different  antibiotic     •   A  well-­‐functioning  immune  system  is  essential  to  fighting  bacterial   infections   o   Compromised  immune  systems  include  very  young,  very  old,   organ  transplant  patients  (take  immunosuppressant),  cancer,   HIV/AIDS     Antibiotics  –  2  types   •   1.  Broad  spectrum     o   Kills  both  gram  negative  and  gram  positive  bacteria   o   Use  when  you  aren’t  sure  which  bacteria  you’re  dealing  with   o   Also  kills  normal  flora,  which  kill  pathogens  naturally   §   Ex:  human  mouth  and  urogenital  tract  are  lined  with   bacteria  and  some  yeast  (Candida  albicans)   §   Broad  spectrum  abx  kills  normal  flora  à  yeast  able  to   multiply   §   Candidasis  à  systemic  candidiasis   •   Massive  amount  of  Candida  albicans  in  intestines,   which  causes  a  yeast  allergy   •   2.  Narrow  spectrum     o   Kills  only  gram  positive  OR  gram  negative  bacteria       *******end  of  test  2  material********         5   UNIT  3     Few  of  the  many  species  of  bacteria  cause  disease   <1%  of  bacteria  from  nature  can  be  cultured   Virulence  –  severity  of  disease  caused  by  MO   •   The  more  virulent,  the  more  severe   Attenuated  –  MO  has  lost  ability  to  cause  disease   •   Ex:  rubella  and  mumps  vaccines  –  contain  live  viruses   Etiology  –  study  of  the  cause  of  a  disease   •   Etiologic  agent  –  MO  that  causes  specific  disease  or  condition   Toxins   •   Endotoxin  –  LPS  (lipopolysaccharide)  –  only  in  gram  negative  bacteria   •   Exotoxin  –  released  into  environment   o   Ex:  tetanus     •   Enterotoxin  –  acts  on  intestines   o   Not  as  common  as  other  types   Classification  of  bacteria   •   Binomial  nomenclature  –  genus  +  species   o   Developed  by  Carolus  Linnaeus     •   Bergey’s  Manual  –  major  sourcebook  of  all  classified  bacteria   –  now   available  online   •   Classification  based  on:   •   1.  Morphological  features  –  shape/appearance   •   2.  Differential  staining   o   Gram,  acid  fast,  etc.   •   3.  Biochemical  tests   6   •   4.  Serology  –  how  bacteria  react  to  antibodies   o   ^^traditional  classification   More  recently:   •   5.  Protein  analysis   •   6.  Base  composition  of  nucleic  acids   Normal  flora   •   Humans  are  germ  free  at  birth   •   Soon  acquire  flora  within  hours/days   •   Lactobacillus  –  acquired  when  passing  through  birth  canal   •   Also  soon  acquire  E.  coli   Areas  of  body  with  normal  flora   •   Skin     •   2  predominant  bacteria:  Staphylococcus  aureus  &  Staphylococcus   epidermidis   •   Skin  is  a  salty/hypertonic  environment   •   MRSA  –  major  human  pathogen  –  20%  of  us  are  carriers       7  


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