Proteus mirabilis is one really cool organism. It’s named after the Greek god Proteus who was able to change shape into anything to avoid being questioned. In the same way, Proteus mirabilis is able to change it’s shape. Although I’m sure it would answer your questions, it seems like a lovely bacterium.
See, this is what happens. When you grow Proteus mirabilis on agar plates, it uses a superpower called quorum sensing to synchronize with the entire colony and all at once they will change from a vegetative resting form to a motile form. They all swim a little bit, and then all at once change back into the vegetative form. This wacky movement pattern creates what look like tree rings on agar plates. We call this swarming motility.
Proteus mirabilis is a really motile organism because of this swarming motility, but it also creates a biofilm, and has multiple flagella, and has a uniquely large number of adhesion factors that all help to make it one sticky bug. This makes it especially sticky to plastic surfaces like those of catheters.
Proteus mirabilis also has urease which helps it survive in the acid environment of the urine causing urinary tract infections. The urease cleaves urea into ammonia so much that it makes the urine more basic, and smell like ammonia.
If a patient is chronically infected, or isn’t treated adequately, a long-term infection could cause the formation of stones made of ammonia-magnesium-phosphate or struvite stones. As these stones build up, they could cause renal obstruction and/or renal failure. They can even progress to form staghorn calculus which is a large structure that looks like deer antlers on imaging.
One very rare complication of a chronic Proteus mirabilis infection is the formation of granulomas within the kidney, called xanthogranulomatous pyelonephritis. Patients will present with chronic flank pain and abdominal pain. The longer this infection goes without treatment the more likely that the kidney will have to be removed.
Whopping cough is caused by Bordatella pertussis. This is a Gram-negative bacillus that is relatively prevalent in the population and can infect adults causing a mild flu-like illness, but in infants under 6 months of age it can be deadly.
Pertussis is transmitted through contaminated respiratory droplets and infects the epithelial cells of the nasopharynx. It binds to these epithelial cells by using a filamentous hemaglutinin and fimbrae that it uses to attach. The first stage of infection is called the catarrhal stage which is like a mild cold, but is when transmission to a new host occurs. The second stage is called the paroxysmal stage and is characterized by prolonged, uncontrollable coughing episodes that prevent the patient from inhaling. Sometimes this causes the patient to vomit after an episode, and sometimes they breath in so intensely that it causes an inspiratory stridor or whoop to occur. The third stage is the convalesce stage and is characterized by a gradual recovery with a chronic cough that can last months.
This bacterium creates the Pertussis Toxin which disables the inhibitory component of G proteins, increasing the intracellular cAMP causing massive cellular signaling confusion. This paralyzes the action of the epithelial cilia which helps the bacteria evade the flushing defense mechanism. The toxin is also believed to deeply affect diapedesis causing white blood cells to accumulate in the bloodstream, unable to enter the tissues, which would present as lymphocytosis. This also causes the release of insulin which can cause a patient to become hypoglycemic, which can be deadly in infants.
The Tracheal Cytotoxin is also created which destroys white blood cells and ciliated epithelial cells. The loss of the ciliated epithelial cells is why the convalesce stage can last so long, you’re actually waiting for those epithelial cells to regrow, and until that occurs the patient is relying on the cough mechanism only for mechanical defense.
The DTap and TDaP are regularly scheduled vaccines that contain different molecular components of Bordatella pertussis like the filamentous hemaglutinin, fimbrae, along with other molecules. Immunity with this vaccination does wane overtime, which isn’t a problem for the adult population, remember it’s just a mild cold to them. It becomes a problem when an infant less than 6 months old arrives. This is why pregnant women receive the vaccination within their third trimester and it’s recommended that every adult who will be caring for the child also receive a booster shot. We’re trying to surround the baby in herd immunity.
Pertussis can be diagnosed by culturing the organism from sputum samples, but this organism is very picky about it’s growing conditions. It will grow on Bordet-Gengou agar which contains potato extract, glycerol, and blood; which is kind of creepy when you think about how happy this organism is in your nose…Once diagnosed, patients can be treated with azithromycin effectively.
A 66-year-old male presents in the hospital three days after an exploratory laprotomy where a foley catheter was placed. The patient is now presenting with a 102F, and pain in the right lower back. Physical examination is normal. Laboratory studies reveal serum leukocytosis. Examination of the urine output is cloudy, and tinged red. A urinanalysis is preformed and is positive for bacteria, leukocyte esterase, and blood. Urine cultures grow an organism that is a urease-positive, Gram-negative, bacillus, that does not ferment lactose. The organism is producing ever enlarging concentric rings on the agar plates. Which of the following is the risk factor most associated with acquiring this infection?
A. Elderly patient
B. Underwent an exploratory laprotomy
C. Smoker
D. Catheterization
First, diagnose the patient.
The patient is presenting in the hospital after surgery with new-onset fever and pain. Cloudy and bloody urine is suspicious, and the urinanalysis results confirm the suspicions. The dipstick was positive for bacteria, blood, and leukocyte esterase. Leukocyte esterase is an enzyme created by white blood cells and only secreted once their activated. Therefore this patient most likely has a complicated urinary tract infection, that might have progressed to pyelonephritis.
- Bacteria discoverd in the urine
- Causes dysuria
- It is complicated because the patient has a penis, and is catheterized
This complicated UTI might have already progressed to pyelonephritis
- fever, dysuria, flank pain
- Detected presence of WBC activity in the urine
- Often produces blood in the urine
- Often seen with WBC casts.
The most common cause of UTIs is Uropathogenic E. coli, but that organism does ferment lactose, so it isn’t the organism infecting our patient. Our organism also creates ever widening concentric rings on the agar plates which is a good description for the swarming motility seen in Proteus mirabilis.
A. Being elderly isn’t overly associated with Proteus spp. infection
B. Exploratory laprotomy is not associated with any particular UTI
C. Smoking does irritate the bladder, and increases the likely hood that the patient will have a UTI, but it’s not associated with a particular organism.
D. Catheterization is highly associated with Proteus mirabilis urinary tract infections.
Therefore,
A 3-month-old male presents to the clinic with anorexia, weight loss, and a persistent cough with nocturnal proxysms for the last four weeks. Vital signs are a temperature of 98F, and oxygen saturation of 96% on room air. Auscultation of the lungs revealed diffuse crackles and expiratory wheezes. He experienced episodes of violent coughing during the examination and one episode ended with emesis. Past medical history is significant for an incomplete vaccine record. Serum white blood cell numbers were extremely high. Chest radiography revealed heterogenous infiltrates of the inferior third of both lung fields. Tuberculin skin test was negative. What type of vaccine could have prevented this infection?
A. Inactivated vaccine
B. Attenuated vaccine
C. Conjugated vaccine
D. Toxoid vaccine
First, diagnose the patient.
This patient is presenting with a long-term cough, evidence of lung infiltration, severe leukocytosis. Mycobacterium tuberculosis would be a good guess, but the skin test was negative, so it’s less likely. The fact that this patient is a child less than 5 years old that has violent coughing that ends in emesis and has an incomplete vaccine record is highly suggestive of Whooping cough.
- Long-term violent coughing episodes that might end in vomiting
- Lack of rhinorrhea
- Severe lymphocytosis
- In children under 5 years old
The incidence of pertussis can be significantly lessened (not completely removed) by using the pertussis vaccine. This vaccine is an acellular vaccine that is just a mixture of disembodied antigenic molecules like the several different versions of the filamentous hemaglutinin and fimbrae.
A. An inactivated vaccine is when the infectious agent is grown and then destroyed in some way, usually by heat so that it won’t cause any replication in patients. This version is safer, but isn’t as effective as other types of vaccines. An example of this vaccine is the Rabies Virus vaccine.
B. An attenuated vaccine is when the infectious agent is grown in conditions that are slightly less than optimal, which creates a version of the agent that is slightly less virulent. This version of the vaccine creates the most effective immunity, but since it’s still “live” then it could rarely cause infections in patients. This can be very dangerous to patients who are immunocompromised. An example of this vaccine is the Rotavirus vaccine.
C. Acellular or conjugated or recombinate vaccines are usually recombinant proteins where the antigen from the infectious agent is literally attached to a more powerful antigen, often the diptheria toxin is used. You often need booster shots for these due to changing antigen sequences. An example of this vaccine is the Human Papillomavirus vaccine.
D. Toxoid vaccines are vaccines that are attempting to neutralize a particular toxin created by an infectious agent. These vaccines don’t technically prevent infection, but do prevent the effect of the toxin. Often, this is enough to allow the immune system to launch an effective response against the infectious agent. An example of this is the Diphtheria vaccine.
Therefore,
References:
https://microbewiki.kenyon.edu/index.php/Proteus_mirabilis
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4638163/
https://apic.org/Resource_/TinyMceFileManager/Resources/CAUTI_2015_with_answers_Final.pdf
The Bradley Lab 