What is a Coccobacillus (Coccobacilli)?

It is a type of bacteria characterized by oval or rod shape. It comes from the words “cocci” and “bacilli.”

Cocci are bacteria with a sphere shape while the bacilli are bacteria with a rod shape. If the bacteria have these two shapes, then they are called coccobacilli.

There are different species of coccobacilli. Some of them cause illnesses while others are harmless.

Bacteria can be classified as gram-positive and gram-negative depending on their cellular wall. To differentiate the bacteria, a procedure called gram staining should be performed.  Staining is important as it is helpful in determining the right course of treatment. (1, 2, 3, and 4)

Coxiella burnetii coccobacillus bacteria image

Picture 1: A closer look at coccobacillus bacteria.

Image source: wikimedia.org

Gram staining of the culture gram negative coccobacilli image

Picture 2: The image shows gram-negative coccobacilli.

Image source: rgstatic.net

Gram positive rods image picture

Picture 3: The image shows gram-positive rods.

Image source: upei.ca

Medical conditions caused by Coccobacilli

  • Bacterial vaginosis – It is caused by coccobacillus G. vaginalis. The condition is characterized by yellowish to whitish vaginal discharge with a strong fishy odor.
  • Pneumonia – It is caused by Gram-negative coccobacillus H. influenzae. Clinical manifestations include fever and chills, coughing, excessive sweating, chest pain, difficulty breathing, and headache.
  • Chlamydia – it is caused by a gram-negative coccobacillus called C. trachomatis. It is a sexually transmitted disease characterized by unusual vaginal discharge, painful urination, and bleeding.
  • Periodontitis – it is caused by a gram-negative coccobacillus A. actinomycetemcomitans. It is a normal flora of the mouth but with poor oral hygiene the bacteria grow excessively leading to infection. Clinical manifestations include swollen and bleeding gums, halitosis (bad breath) and pain when chewing.
  • Whooping cough – It is caused by B. pertussis, which is a Gram-negative coccobacillus. Clinical manifestations are low grade fever, cough, and runny nose. When not treated could eventually lead to exhaustion, vomiting, and a cough characterized by a high-pitched whooping sound.
  • Plague – it is caused by Y. pestis, a gram-negative coccobacillus. Symptoms include a headache, fever and chills, body ache, weakness, and nausea and vomiting.
  • Brucellosis – It is caused by a gram-negative coccobacillus Brucella. It is common in animals but humans can be infected too by consuming unpasteurized dairy products. (2, 3, 4, and 5)
Haemophilus influenzae bacteria image

Picture 4: A haemophilus influenza belongs to the coccobacilli family.

Image source: eurekalert.org

Coccobacilli Treatment

There is a variety of ways to treat infections caused by coccobacilli. These are the following:

  1. Antibiotics – A full course of antibiotic should be taken religiously. Antibiotics for the treatment of coccobacilli infection require a doctor’s prescription.
  2. Vaccines – Some disease-causing coccobacillus can be prevented through vaccination. Examples are B. pertussis and Y. pestis. A vaccine for whooping cough should be given to babies and children. A booster dose should be given to teenagers. Pregnant women can also receive the vaccine as per the Centers for Disease Control and Prevention. (5, 6, and 7)
Acinetobacter baumannii image

Picture 5: The image shows Acinetobacter species.

Image source: wikimedia.org

Haemophilus species image

Picture 6: A glass slide containing Haemophilus species.

Image source: slidesharecdn.com

Francisella tularensis image

Picture 6: Francisella species on a petri dish.
Image source: wikimedia.org

Kingella species image

Picture 6: The image shows an example of Kingella species.

Image source: asm.org

Examples of Gram-Negative Coccobacilli

  1. Acinetobacter species – They cause a variety of diseases such as wound infections, blood infections, and pneumonia. They are usually present in open wounds without causing infection.
  2. Haemophilus species – They are associated with various diseases such as septic arthritis, meningitis, cellulitis with bacteremia, and epiglottitis, to name a few.
  3. Francisella species – They are facultative and intracellular bacteria.
  4. Kingella species – They are aerobic gram-negative coccobacilli and are the cause of skeletal infections in children. (7, 8, 9, and 10)


  1. https://en.wikipedia.org/wiki/Coccobacillus
  2. https://www.healthline.com/health/coccobacilli#common-conditions
  3. https://microbeonline.com/gram-negative-cocci-coccobacilli-medical-significance-list-bacteria-diseases/
  4. https://www.picmonic.com/pathways/medicine/courses/standard/microbiology-202/gram-negative-coccobacilli-1163
  5. https://jcm.asm.org/content/jcm/1/1/102.full.pdf
  6. https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/Coccobacillus.html
  7. https://biocyclopedia.com/index/medicinal_microbiology/small_gram_negative_coccobacilli.php
  8. https://microbiologylearning.weebly.com/gram-positive-coccobacilli.html
  9. https://www.revolvy.com/page/Coccobacillus
  10. Practical Handbook of Microbiology edited by Emanuel Goldman, Lorrence H Green

Leave a Reply

Your email address will not be published. Required fields are marked *