Proteus mirabilis


00:00 / 00:00



Proteus mirabilis


Introduction to bacteria

Bacterial structure and functions

Gram positive bacteria

Staphylococcus epidermidis

Staphylococcus aureus

Staphylococcus saprophyticus

Streptococcus viridans

Streptococcus pneumoniae

Streptococcus pyogenes (Group A Strep)

Streptococcus agalactiae (Group B Strep)


Clostridium perfringens

Clostridium botulinum (Botulism)

Clostridium difficile (Pseudomembranous colitis)

Clostridium tetani (Tetanus)

Bacillus cereus (Food poisoning)

Listeria monocytogenes

Corynebacterium diphtheriae (Diphtheria)

Bacillus anthracis (Anthrax)


Actinomyces israelii

Gram negative bacteria

Escherichia coli

Salmonella (non-typhoidal)

Salmonella typhi (typhoid fever)

Pseudomonas aeruginosa


Klebsiella pneumoniae


Proteus mirabilis

Yersinia enterocolitica

Legionella pneumophila (Legionnaires disease and Pontiac fever)

Serratia marcescens

Bacteroides fragilis

Yersinia pestis (Plague)

Vibrio cholerae (Cholera)

Helicobacter pylori

Campylobacter jejuni

Neisseria meningitidis

Neisseria gonorrhoeae

Moraxella catarrhalis

Francisella tularensis (Tularemia)

Bordetella pertussis (Pertussis/Whooping cough)


Haemophilus influenzae

Haemophilus ducreyi (Chancroid)

Pasteurella multocida


Mycobacterium tuberculosis (Tuberculosis)

Mycobacterium leprae

Mycobacterium avium complex (NORD)

Other bacteria

Mycoplasma pneumoniae

Chlamydia pneumoniae

Chlamydia trachomatis

Borrelia burgdorferi (Lyme disease)

Borrelia species (Relapsing fever)


Treponema pallidum (Syphilis)

Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species

Coxiella burnetii (Q fever)

Ehrlichia and Anaplasma

Gardnerella vaginalis (Bacterial vaginosis)


Proteus mirabilis


0 / 6 complete

USMLE® Step 1 questions

0 / 2 complete

High Yield Notes

17 pages


Proteus mirabilis

of complete


USMLE® Step 1 style questions USMLE

of complete

A 44-year-old man presents to the emergency department due to severe abdominal pain for the past 12 hours. The patient also has nausea and dark red urine. Past medical history is significant for Crohn disease. Urinalysis shows numerous bacteria and pH >7. A CT scan of the abdomen is shown below. Which of the following characteristics is associated with the organism causing the kidney stone found in this patient?  

External References

First Aid








Proteus mirabilis

cephalosporins p. 186

kidney stones p. 628

penicillins for p. 185

urinary tract infections p. 625

UTIs p. 179

External Links



Alexandru Duhaniuc, MD

Kaylee Neff

Victoria Cumberbatch

Proteus mirabilis is a Gram-negative bacillus which belongs to a family of bacteria called the Enterobacteriaceae.

It is widely distributed in soil and water and can also be found in the normal human intestinal flora.

In humans, it causes urinary tract infections, or UTIs for short.

Now, Proteus mirabilis has a thin peptidoglycan layer, so it doesn’t retain the crystal violet dye during Gram staining. Instead, like any other Gram-negative bacteria, it stains pink with safranin dye.

And since it’s a Gram-negative bacillus, it looks like a little pink rod under the microscope.

Alright, now Proteus mirabilis is non-spore forming and highly motile.

It’s also facultative anaerobic which means it can survive in both aerobic and anaerobic environments, non-lactose fermenter, oxidase negative which means it doesn’t produce this enzyme, and urease positive which means it can produce an enzyme called urease.

Now, it grows well on blood agar and MacConkey agar.

On blood agar, it has a swarming growth, so it moves and forms a thin filmy layer of concentric circles, which look like the ripples after you throw a rock into a lake.

On MacConkey agar, however, it doesn’t swarm so it forms smooth, pale or colourless colonies.

Finally, the triple sugar iron test, or TSI for short can be done to assess hydrogen sulfide production.

This medium contains three sugars - lactose, glucose and sucrose, as well as iron and a pH sensitive dye.

Proteus mirabilis produces hydrogen sulfide, that reacts with the iron, and a black precipitate forms in the test tube.

Ok, now Proteus mirabilis has a number of virulence factors, that are like assault weaponry that help it attack and destroy the host cells, and evade the immune system.

First, Proteus mirabilis has flagella, which are lash-like appendages that comes out from the cell body, and confer the bacteria its motility.

Now, when Proteus mirabilis comes in contact with solid surfaces, especially urinary catheters, it has the ability to differentiate from short swimmer cells into elongated swarm cells that express hundreds to thousands of flagella, and interact with each other to form multicellular rafts.


Proteus mirabilis is a gram-negative, facultatively anaerobic, rod-shaped bacterium. It is commonly found in the human intestinal tract and urinary tract and is known for its ability to produce urease, an enzyme that breaks down urea, which can lead to the formation of struvite crystals in the urinary tract and cause kidney stones. This bacteria can be identified in a urine culture, and the treatment of its infections involves antibiotics like trimethoprim-sulfamethoxazole, fluoroquinolones, and cephalosporins.


Copyright © 2023 Elsevier, except certain content provided by third parties

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.