两澳大利亚人获诺贝尔医学奖(4)

Malignancies  associated  with  Helicobacter  pylori  infection

In  some  individuals  Helicobacter  pylori  also  infects  the  corpus  region  of  the  stomach.  This  results  in  a  more  widespread  inflammation  that  predisposes  not  only  to  ulcer  in  the  corpus  region,  but  also  to  stomach  cancer.  This  cancer  has  decreased  in  incidence  in  many  countries  during  the  last  half-century  but  still  ranks  as  number  two  in  the  world  in  terms  of  cancer  deaths.

Inflammation  in  the  stomach  mucosa  is  also  a  risk  factor  for  a  special  type  of  lymphatic  neoplasm  in  the  stomach,  MALT  (mucosa  associated  lymphoid  tissue)  lymphoma.  Since  such  lymphomas  may  regress  when  Helicobacter  pylori  is  eradicated  by  antibiotics,  the  bacterium  plays  an  important  role  in  perpetuating  this  tumour.



Disease  or  not  –  interaction  between  the  bacterium  and  the  human  host

Helicobacter  pylori  is  present  only  in  humans  and  has  adapted  to  the  stomach  environment.  Only  a  minority  of  infected  individuals  develop  stomach  disease.  After  Marshall's  and  Warren's  discovery,  research  has  been  intense.  Details  underlying  the  exact  pathogenetic  mechanisms  are  continuously  being  unravelled.

The  bacterium  itself  is  extremely  variable,  and  strains  differ  markedly  in  many  aspects,  such  as  adherence  to  the  gastric  mucosa  and  ability  to  provoke  inflammation.  Even  in  a  single  infected  individual  all  bacteria  are  not  identical,  and  during  the  course  of  chronic  infection  bacteria  adapt  to  the  changing  conditions  in  the  stomach  with  time.

Likewise,  genetic  variations  among  humans  may  affect  their  susceptibility  to  Helicobacter  pylori.  Not  until  recently  has  an  animal  model  been  established,  the  Mongolian  gerbil.  In  this  animal,  studies  of  peptic  ulcer  disease  and  malignant  transformation  promise  to  give  more  detailed  information  on  disease  mechanisms.



Antibiotics  cure  but  can  lead  to  resistance

Helicobacter  pylori  infection  can  be  diagnosed  by  antibody  tests,  by  identifying  the  organism  in  biopsies  taken  during  endoscopy,  or  by  the  non-invasive  breath  test  that  identifies  bacterial  production  of  an  enzyme  in  the  stomach. (责任编辑：泉水)

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两澳大利亚人获诺贝尔医学奖(4)