Thursday, June 23, 2011

Epidemics of Diarrhea due to Escherichia coli (Shiga toxin producing enterohemorrhagic) in Europe

Recently, enterohemorrhagic Escherichia coli (EHEC) strain has infected over 3,500 and kills over 40 people in the Europe and most of them are German [1]. Initially, it was blamed to salad and vegetables and the farmers for the cause of transmission, as concluded by case-control study. But the causative bacterial strain, EHEC O104:H4 has not been found in any of these salad and vegetables samples. Then authorities realize farmers were not culpable. Then they withdraw the blame with apology and announce the compensation for farmers. Now suspecting on bean, sprout, and agricultural practice [2].

EHEC O104:H4 is a type of E. coli classified on the basis of somatic O-antigen (over 170 different type: 1-170), and flagellar H-antigen (over 50 different types: 1-50). In E. coli, there are different chemical structure and functional group comprising lipopolysaccharide of plasma membrane (O-antigen), polysaccharide of  capsule (K-antigen) and flagella (H-antigen). Combining of these different antigens there could be thousands of different types of E. coli. The infective EHEC O104:H4 is new to Europe but this strain was reported from Korea in 2006 [3]. Does this means this strain is shipped from Korea? Certainly not, or needs exigent research.

Every organism has the tendency to adapt the environment with necessary genotype reshuffle or addition, and phenotypic variation, suitable to survive, as Darwinism. Bacterial strains also, always tend to increase virulence and pathogenicity by adapted gene transfer and mutation. In latent type of infection, plasmid and/or gene transferred from virulent strain to non-virulent may get proliferated for several months without symptom and unknown to health professional. This may be the one of the possible reason for outbreak in Europe, which is still under research to find the source of infection. So, the organism whose reservoir is the environment, they proliferated when the environmental condition becomes optimum, as said by Rita Colwell [6].

Vibrio, Escherichia has the environmental reservoir unlike smallpox and polio virus. So they are always prone to infect mammal once environmental condition become favourable. E. coli is even more dangerous as it is opportunistic pathogen and can acquire antibiotic resistance as well as virulence.

In my study (in NAST), some strains of E. coli were found to be resistant against all commonly used antibiotics (courtesy: Nabaraj Dahal, Pankaj Baral, and Sanjiv Neupane). This shows it is the dreadful strain having most flexibility in genetic variation among bacterial kingdom. However, the innovation and more research on antibiotics may enervates its massive proliferation.
Multi-drug resistant E. coli reconfirmed on M-endo agar.
Antibiotics sensitive E. coli (ATCC 25922) reconfirmed on M-endo agar.
Even in the Europe, the bacterial strain can invade people where living standard is high as well as good sanitation, well managed health system. Also, Nepal had faced problem of diarrhoeal epidemics and hundreds of people died in remote area, two years ago. But it was different scenario, poor people were lack of medicine and ORS.
Few months ago, an unprecedented outbreak of cholera in Haiti was the reason to blame Nepalese peacekeeping soldier. But neither stool nor rectal swab nor antibody test of these soldiers showed positive result of V. cholera (or was not investigated). Even no one could be verified as carrier. And probably, the sample of drinking water, seawater and sewage from different source was not analysed properly to make a conclusion. Only the co-incidence was the bacterial strain found there resembled with the South Asian strain, which is not only confined in Nepal but also other South Asian countries like Bangladesh, India, Pakistan etc.

  1. European Centre for Disease Prevention and Control,  Stockholm, Sweden, 22 June 2011, 11:00
  2. Editorials, 16 June, 2011, Nature, Vol. 474, 251
  3. Woo Kyun Bae, et al., Jun 2006, Yonsei Medical Journal, Vol. 47(3), 437-439
  4. Marian Turner,  9 June, 2011, Nature, Vol. 474, 137
  5. Kai Kupferschmidt, 10 June 2011, Science, Vol. 332, 1249-1250
  6. Martin Enserink, 5 November 2010, Science, Vol. 330, 738-739

No comments:

Post a Comment