Clostridia Botulinum Microbiology PDF

CLOSTRIDIA   Dr.  Alex  Owusu-­‐Ofori    General properties of Clostridia Taxonomy   Family  Bacillaceae.   Genus  Clostridia.       There  are  2  important  genera  in  this  family:   Bacillus  (aerobic  spore  formers)   Clostridium  (ana...

CLOSTRIDIA   Dr.  Alex  Owusu-­‐Ofori    General properties of Clostridia Taxonomy   Family  Bacillaceae.   Genus  Clostridia.       There  are  2  important  genera  in  this  family:   Bacillus  (aerobic  spore  formers)   Clostridium  (anaerobic  spore  formers)    Obligate  Anaerobes   In  the  presence  of  oxygen,  anaerobic  bacteria   produce  toxic  products  such  as  superoxide  and   hydrogen  peroxide,  but  they  lack  superoxide   dismutase  (SOD),  catalase  and  peroxidase  that   detoxify  these  products:   SOD:                        O2-­‐+2H+  →    H2O2     Catalase:            H2O2  →  H2O  +  O2     Peroxidase:      H2O2  →  H2O  /NAD  to  NADH    Anaerobes   No  oxidaNve  phosphorylaNon   InfecNon  caused  by  anaerobes  usually   occurs  in  the  sites  with  low  oxidaNon-­‐ reducNon  potenNal  such  as  periodontal   pocket,  intesNnal  tract  and  vagina.     Anaerobes  are  co-­‐infected  with  other   facultaNve  anaerobe  which  use  up  oxygen   to  establish  a  local  anaerobic  environment.      Source  of  anaerobic  infecNon   Endogenous  infecNon:  caused  by  anaerobes  of   normal  flora  which  are  non-­‐spore  formers.     Exogenous  infecNon:  The  pathogens  are   usually  anaerobic  spore-­‐formers  and  come   from  the  environment  (e.g.,  soil).  Clostridia    is   the  unique  genus  of  anaerobic  spore-­‐formers   to  cause  human  diseases.    Clostridia   There  are  at  least  118  species,  the  clinically   important  species:     Clostridia  tetani   Clostridia    perfringens   Clostridia  botulinum   Clostridia  difficile    Clostridia   Large  Gram  posiNve     Straight  or  slightly  curved  rods  with  slightly  rounded  ends     Anaerobic  bacilli     Spore  bearing     Spore  do  not  germinate  and  growth  does  not  normally  proceed   unless  a  suitably  low  redox  potenNal  exists     Saprophytes     Some  are  commensals  of  the  animal  &  human  gut  which   invade  the  blood  and  Nssue  when  host  die  and  iniNate  the   decomposiNon  of  the  corpse  (dead  body)     Causes  diseases  such  as  gas  gangrene,  tetanus,  botulism  &   pseudo-­‐membranous  coliNs  by  producing  toxins  which  aWack   the  neurons  pathways      Clostridia  of  medical  importance   Clostridium Causing diseases   Tetanus Botulism Gas gangrene   ِAntibiotic associated diarrhea e.g. Cl. tetani   e.g. Cl. botulinum   e.g. Cl. difficille   Saccharolytic Proteolytic e.g. Cl. perfringens &Cl. septicum   e.g. Cl. sporogenes   Mixed: Cl. histolyticum    Clostridia causing wound infections are: 1. C.tetani 2. C.perfringens 3. Additional agents causing gas gangrene C.hystolyticum C.novyi C.septicum C.sporogenes  Clostridia causing enteric infection are: 1. C. botulinum 2. C.difficile 3. C.perfringens (serogroup A)  Cultivation Clostridia are strictly obligate anaerobic to aerotolerant The optimum temperature is 370 C, optimum pH is 7-7.4 Special media for anaerobes Robertson´s cooked meat broth Litmus milk media. Kitt-Tarocci´s media C.  botulinum    Clostridium  botulinum   Botulism  is  caused  by  toxin  produced  by   the  bacterium  Clostridium  botulinum   Anaerobic,  gram  posiNve,  rod-­‐shaped   bacteria   Create  spores  that  can  remain  dormant   for  30  years  or  more   Spores  extremely  resistant  to   environmental  stressors,  such  as  heat  and   UV  light   C. botulinum Found  in  soil,  sediments  of  lakes/ponds,   decaying  vegetaNon   May  also  be  found  in  intesNnal  tracts  of   birds,  mammals  and  fish    History  of  Botulism   Germany  (1793)  earliest  recorded  human  outbreak   Organism  isolated  in  1895   Mortality  rate  of    5-­‐50%;  long  recovery  period   Weaponized  by  several  naNons  including  the  U.S.,  Japan,   and  Soviet  Union,  beginning  in  the  1930’s   Iraq  (1980’s)  produced  19,000  L  of  concentrated   botulism  toxin   Japan  (1990’s)  Aum  Shinrikyo  cult   PS:  Bioterrorism  is  not  an  infecNon  but  resembles  a   chemical  aWack.    What  Makes  Botulinum  Toxin  a   Good  Weapon?   Botulinum  toxin  is  the  most  poisonous  substance   known   High  lethality:  1  aerosolized  gram  could  potenNally  kill   1  million  people   Isolated  fairly  easily  from  soil   Could  be  released  as  an  aerosol  or  as  a  contaminant  in   the  food  supply   Expensive,  long-­‐term  care  needed  for  recovery      Clostridium  botulinum   7  types  of  botulin  A  through  G,  based  on  the  anNgenic   properNes  of  the  toxin  produced     – toxins  A,  B,  E  and  F  cause  illness  in  humans   – toxins  C  and  D  cause  illness  in  birds  and  mammals   – toxin  G   Type  A  is  the  most  common  –  62%   Type  G  is  plasmid  endoded    Categories  of  Botulism   Foodborne  botulism   – caused  by  eaNng  foods  that  contain  botulin  toxin   IntesNnal  botulism  (infant  and  child/adult)   – caused  by  ingesNng  spores  of  the  bacteria  which   germinate  and  produce  toxin  in  the  intesNnes   Wound  botulism     – C.  botulinum  spores  germinate  in  the  wound   InhalaNon  botulism   – Aerosolized  toxin  is  inhaled   – does  not  occur  naturally  and  may  be  indicaNve  of   bioterrorism    Botulism  Pathogenesis   IncubaNon  period   – ingesNon:  unknown   – foodborne:  6  hours-­‐8  days     – wound:  4-­‐14  days     – inhalaNon:  (esNmated)  24-­‐36  hours   Toxin  enters  bloodstream  from  mucosal  surface  or  wound     Binds  to  peripheral  cholinergic  nerve  endings   Inhibits  release  of  acetylcholine,  prevenNng  muscles  from   contracNng   Symmetrical,  descending  paralysis  occurs  beginning  with   cranial  nerves  and  progressing  downward   Normal functionality of neuromuscular junction Neurotoxin (botulotoxin) Mechanism of action  Botulism  Pathogenesis  (cont.)   Can  result  from  airway  obstrucNon  or  paralysis   of  respiratory  muscles     Secondary  complicaNons  related  to  prolonged   venNlatory  support  and  intensive  care  Botulism  Clinical  PresentaNon   Classic  symptoms  of  botulism  poisoning  include:   – blurred/double  vision   – muscle  weakness   – drooping  eyelids   – slurred  speech   – difficulty  swallowing   – paNent  is  afebrile  and  alert   Infants  with  botulism  will  present  with:     – weak  cry   – poor  feeding   – consNpaNon   – poor  muscle  tone,  “floppy”  baby  syndrome    Diagnosis     ---by clinical symptoms alone ---differentiation difficult. --- most direct and effective: serum or feces. ---most sensitive and widely used: mouse neutralization test. 48h. Culturing of specimens 5-7d. Diagnosis     Diagnosis      Botulism  Clinical  Treatment   AnNtoxin  administraNon   SupporNve  Care   – mechanical  venNlaNon   – body  posiNoning   – parenteral  nutriNon   EliminaNon     – Induced  vomiNng   – High  enemas    Botulism  Transmission   Home-­‐canned  goods  (foodborne)   – parNcularly  low-­‐acid  foods  such  as  asparagus,  and   corn   Honey  (ingesNon)   – can  contain  C.  botulinum  spores   – not  recommended  for  infants