KATERYNA KON / SCIENCE PHOTO LIBRARY KATERYNA KON / SCIENCE PHOTO LIBRARY
Haemophilic ducreyi, or Ducrey's bacillus, computer illustration. This bacterium is transmitted through sexual contact (an STD). It is extremely contagious, and exposure does not confer immunity. It causes chancroid, characterised by a bleeding ulcer associated with swollen lymph nodes.
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