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A coccobacillus (plural coccobacilli) is a type of bacterium with a shape intermediate between cocci (spherical bacteria) and bacilli (rod-shaped bacteria).[1] Coccobacilli, then, are very short rods which may be mistaken for cocci. Haemophilus influenzae, Gardnerella vaginalis, and Chlamydia trachomatis are coccobacilli. Aggregatibacter actinomycetemcomitans is a Gram-negative coccobacillus prevalent in subgingival plaques. Acinetobacter strains may grow on solid media as coccobacilli. Bordetella pertussis is a Gram-negative coccobacillus responsible for causing whooping cough.

Coxiella burnetti is also a coccobacillus.[2] Bacteria from the Brucella genus are medically important coccobacilli that cause brucellosis. Haemophilus ducreyi, another medically important Gram-negative coccobacillus, is observed in sexually transmitted disease, chancroid, of Third World countries.[3]

Pasteurellae are small, nonmotile, Gram-negative coccobacilli often exhibiting bipolar staining. In cattle, they cause life-threatening pneumonia. They are non-pathogenic for cats and dogs, as they are part of the normal nasopharyngeal flora. In humans, they cause chronic abscesses on the extremities or face following cat/dog bites.[4]


  1. ^ "Dorlands Medical Dictionary:coccobacillus". 
  2. ^ "persistent rickettsial disease". 
  3. ^ Schaetchter's Mechanisms of Microbial Disease 4th Edition. ISBN 0-7817-5342-2
  4. ^ Collins FM. Pasteurella, Yersinia, and Francisella. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 29. Available from: