We speak of polymorphic flora when biological cultures reveal several different bacteria in an analyzed fluid (urine, vaginal samples, sputum, stool, etc.). Nothing to worry about when it is associated with an absence of white blood cells.

Many microorganisms (bacteria) are normally present in or on the human body of healthy subjects. Unlike pathogenic bacteria (which are responsible for diseases), these commensal bacteria (which live in symbiosis with the human body) actively participate in the defense of the organism, its functioning and the good condition of its mucous membranes.

These commensal bacteria can be divided into 4 main flora:

• cutaneous (skin),
• respiratory (respiratory tree),
• genital,
• digestive.

Among the most complex flora, that of the digestive tract permanently carries around 100 billion bacteria mainly located in the colon.

A human being thus lodges 10¹⁴ bacterial cells constantly.

“It is therefore normal to find several typologies of bacteria during a culture examination of a fluid, whether it is on the skin, the ENT sphere, the digestive tract or even the vagina”, confirms Professor Franck Bruyère, Urological surgeon. . But in the context of a search for infection, it is necessary to be able to identify and quantify them ”.

We can thus speak of polymorphic flora if several bacteria are present in a biological analysis examination. This is often the case in ECBU (urinary cytobacteriological examination); but also in stool cultures (stool samples), skin smears, vaginal smears or sputum examinations (ECBC).

In usual culture, in usually sterile media, such as in urine, the presence of a polymorphic flora in an ECBU, for example, indicates contamination of the sample with external bacteria or an infection.

“If the patient has no symptoms and their ECBU comes back polymorphic or poly-bacterial, that’s not a cause for concern. It is generally a stain: at the time of the sample, the urine may have touched the vulva, the urethral meatus or the fingers or the collection vial was not sterile. As a result, germs have developed ”. To have reliable results, urine must be collected under perfect hygienic conditions.

“In contrast, in a patient with fever and suspected of infection, an ECBU with polymorphic flora is more problematic. The doctor needs to know which germs are found in the fluid at a rate of more than 1000 bacteria per milliliter in order to specify the most indicated medical treatment ”.

The doctor will then ask the microbiologist to identify the germs using an antibiogram: this technique makes it possible to test the sensitivity of a bacterial strain to several antibiotics.

The simultaneous presence of germs (polymorphic flora) and white blood cells (leukocyturia) in the urine indicates the existence of a urinary tract infection. It is then necessary to redo an ECBU.

In some cases, the presence of polymorphic flora can be a problem. “For example, it is common to request an ECBU a few days before a procedure where there is a risk of UTI such as prostate resection, bladder resection or removal of a stone in a kidney. If the ECBU comes back with a polymorphic flora, there is no time to re-culture, which generally takes 3 days. We will then ask for a direct analysis, without cultivation in order to assess the risks ”.

The antibiogram will allow the doctor to choose the best individualized antibiotic treatment against the bacterial strain responsible for the infection.