Citrobacter Freundii

Citrobacter freundii, are aerobic gram-negative bacilli. They are long, about 1-5 μm in length and are rod-shaped. A few of them are non-motile, but most of them move using their flagella. They contain two membranes, both the inner and outer.

The space in between the two membranes is called periplasmic space. Citrobacter freundii characteristics are described as opportunistic. They cause a number of infections. In fact, they are the one responsible for infections of the urinary tract, respiratory tract, and blood infections, to name a few.

About 29% of opportunistic infection is caused by Citrobacter freundii.

Citrobacter freundii have the ability to grow on glycerol. They can also metabolize lactose or citrate. On the positive note, Citrobacter freundii have a beneficial role in the environment. They reduce nitrate to nitrite in the environment, which plays an important part in the nitrogen cycle.

About 85% of the earth’s atmosphere contains nitrogen. (1, 2, 3, 4)

Citrobacter freundii habitat

The natural habitat of citrobacter freundii is the environment. It thrives in soil, water, sewage, food, and even in the human and animal’s intestinal tract. A water containing citrobacter freundii is an indication that it is contaminated. They can be found on the organs of diseases animals, especially amphibians, reptiles, mammals, and birds. (2)

Citrobacter freundii symptoms

Citrobacter freundii being an opportunistic microbe can cause severe infections. However, it can only affect humans with weak immune system or those immune compromised. If you are healthy, you are less likely to get infected by this microbe.

What are the citrobacter freundii symptoms? They vary on the types and severity of the infection. (6)

An imaging study of Citrobacter Freundii.photoImage 1: An imaging study of Citrobacter Freundii
Picture Source:


How C. freundii organism looks like.image

Photo 2: How C. freundii organism looks like
Image Source:

Urinary tract infection secondary to C. freundii

Citrobacter Freundii causes infection when spread into the urinary system. A sexual intercourse or wiping back to front after a bowel movement can lead to urinary tract infection. Symptoms include the following:

  • Pain (burning feeling) when urinating
  • Scanty urine
  • Presence of blood in the urine
  • Foul smelling urine
  • Fever
  • The urge to urinate increases
  • Pain in the pelvis and lower back (7)

Inflammatory changes in the intestine

Citrobacter freundii in stool is one of the reasons why there are inflammatory changes in the intestines. The usual symptoms include the following:

  • Nausea
  • Gastric upset
  • Weight loss (5)

Neonatal Meningitis

Citrobacter freundii is associated with neonatal meningitis. What is meningitis? It is the inflammation of the meninges (the covering of the brain). Citrobacter freundii can cross the blood-brain barrier. It can reside in the brain and even replicate too.

It is the primary reason why the mortality rate is high in people with meningitis. The usual clinical features of neonatal meningitis secondary to Citrobacter freundii include the following:

  • High grade fever
  • Seizure
  • Vomiting (projectile in nature) (8)

Respiratory Tract Infection

  • Fever and chills
  • Productive cough with a white to yellow sputum
  • Chest pain
  • Labored breathing
  • Gastric upset in some patients ( diarrhea and abdominal pain) (8)


To accurately diagnose the presence of Citrobacter freundii, various diagnostic procedures should be performed including x-ray, sonogram, bacterial culture and imaging. It is a must to come up with a quick and accurate diagnosis so that the infection will be treated right away. (9)

Treatments for Citrobacter freundii infection

Infections caused by Citrobacter freundii bacteria is treated using antibiotics. The usual antibiotics of choice are cephalosporins, fluoroquinolones, and carbapenems. The doctor will determine the right antibiotic of choice. Basically, the health care professional will take into consideration the vulnerability of the bacteria to antibiotics as well as the site of the infection. (9, 10)

Citrobacter freundii treatment using antibiotics is modified because some strain of citrobacter freundii developed resistance to a certain number of antibiotics. To hasten the healing process, supportive treatment is given to the patient along with tested and proven effective antibiotic of choice.

During the course of treatment, it is important to be open to your health care provider. If you have any allergy to antibiotics, you should inform your physician right away to prevent adverse reactions.

Antibiotics offer a quick relief from the symptoms that are currently bothering you. Even so, you should continue taking the antibiotics until your doctor tells you to stop. This is to prevent recurring infection. If you are experiencing any side effects, you should inform your doctor right away.

This is to avoid another infection and prevent worsening of your condition. If you are suffering from severe Citrobacter freundii infection, the antibiotic is given to you via intravenous route every eight hours until you no longer have fever. This typically lasts for three days. After that, you can take oral antibiotics.

On the other hand, if you are suffering from mild Citrobacter freundii infection, you will be required to take oral antibiotics for two weeks or until the infection subsides. (4, 5, 7)


Citrobacter freundii infection has a moderate prognosis. It is important to treat the infection right away. Neglected cases of Citrobacter freundii infection could lead to severely poor prognosis. If the infection is left untreated, the patient could die.

If you are suffering from urinary tract infection secondary to Citrobacter freundii infection, the prognosis is good. However, the prognosis is moderate to poor in patients with peritonitis (inflammation of the lining of the abdomen). In the case of people with meningitis caused by Citrobacter freundii infection, the prognosis is poor. In fact, the death rate ranges from 25% to 50%.

Those who survived the infection have a tendency to suffer from neurological problems. It affects about 75% of patients who survived meningitis. For good prognosis, early detection and treatment of the infection is a must. If you are ill for three days, you should consult your doing so, you will be able to prevent further infection and worsening of the condition. (4, 5, 9, 10)


  10. Principles and Practice of Pediatric Infectious Diseases E-Book By Sarah S. Long, Charles G. Prober, Marc Fischer

Leave a Reply

© 2017 All Rights Reserved. Privacy Policy
This website is for informational purposes only and Is not a substitute for medical advice, diagnosis or treatment.