ARTHROBACTER: CHARACTERISTICS, TAXONOMY, MORPHOLOGY, SYMPTOMS - BIOLOGY - 2024

Arthrobacter is a genus of obligate aerobic bacteria, very common in different types of soils. Species in this group of microbes are Gram positive, although during exponential growth they are Gram negative.

All species of the genus are chemoorganotrophic, that is, they use organic compounds as a source of electrons in their metabolic reactions. They also have the particularity that they vary their shape during development, forming rods or cocci depending on the growth phase in which they are found.

Arthrobacter sp. Taken and edited from www.sciencesource.com

These bacteria can be very resistant to desiccation and lack of nutrients. Some species of the genus Arthrobacter have been isolated in immunocompromised patients, but most of them are not pathogenic.

General characteristics

They are extremely numerous bacteria on a wide variety of substrates, especially soils. They are aerobic, do not form spores and do not have fermentation metabolism.

The cell wall contains L-lysine and branched-type cellular fatty acids. The optimum temperature for the development of Arthrobacter species is between 20-30 ° C and they grow best in a medium with a neutral to slightly alkaline pH.

They are rod-shaped and are Gram negative during the exponential growth phase. During the stationary phase of growth, however, they are shaped like cocci and are Gram positive.

Taxonomy

The genus Arthrobacter was proposed by Conn & Dimmick in 1974, with Arthrobacter globiform as the type species. Later, the name of this species was modified to Arthrobacter globiformis.

These microorganisms belong to Phyllum and Class Actinobacteria, Order Actinomycetales, Suboroden Micrococcineae and Family Micrococcaceae. The genus Arthrobacter has at least 69 species valid for science.

Recently, some taxonomists have proposed that the genus Arthrobacter contains two "groups of species", the A. globiformis / A. citreus group and the A. nicotianae group. Both groups differ from each other in their lipid composition, peptidoglycan structure, and teichoic acid content.

Morphology

Arthrobacter have a color that varies from white to yellow, most of the species form colonies of approximately 2 mm in diameter, they do not form spores.

During the exponential growth phase they are shaped like rods, while in the stationary phase they are shaped like cocci. Sometimes they are in the form of large spherical bodies of 1 to 2 micrometers called cystites (cystites in English).

The change from rod to coconut occurs thanks to a micronutrient (Vitamin) called Biotin. The coconut form is highly resistant to desiccation and starvation.

The genre is distinguished by presenting a break zone or “Snapping Division”. This consists of a transverse septum in the inner layer of the cell wall. When the bacteria increases in dimension, tension is produced in the outer layer that ends up breaking, producing a sound in the form of a clicking sound.

Arthrobacter crystallopoites. Taken and edited from

Medical interest

From the end of the last century to the beginning of this, strains of Arthobacter have been recognized as opportunistic pathogens in humans.

Species such as A. cumminsii, A. woluwensis, A. creatinolyticus, A. oxydans, A. luteolus, and A. albus have been isolated from wounds, blood, urine, skin infections, blood cultures, and endophthalmitis.

Although they have been isolated from humans and other animals, bacteria of the genus Arthrobacter are considered rare or rare in clinical samples.

On the other hand, A. cumminsii is the most commonly found species in humans. This species has been found in samples from the cervix, vagina, middle ear, amniotic fluid, calcaneal osteomyelitis, deep tissue cellulitis, blood, and wounds.

Symptoms

The symptoms of Arthobacter infection will depend not only on the species involved in the infection, but also on the affected area.

Subacute infective endocarditis

Caused by bacterial penetration (in this case Arthrobacter woluwensis) into the circulatory system. Bacteria reach and stick to heart valves (sometimes injured).

The disease progresses gradually and subtly, over a period that can last from a few weeks to several months. This disease can be fatal.

The symptoms of this infection can be: tiredness, fever of 37.2 ° C to 38.3 ° C, cardiac arrhythmia, sweating, weight loss and anemia. These symptoms will be latent until endocarditis causes a blockage of an artery or damages the heart valves.

Other symptoms of subacute bacterial endocarditis can be: chills, joint pain, paleness, subcutaneous nodules and confusion.

Bacteremia

Caused by Arthrobacter woluwensis, bacteremia does not cause clear symptoms. In some situations it can cause fever, but it can be complicated by septicemia. Septicemia is a life-threatening complication of infection.

Its symptoms include: very high body temperature (greater than 38.3 ° C) or low (less than 36 ° C), more than 90 heart beats per minute, more than 20 breaths per minute. If complicated, chills, sensory disturbances, hypotension, abdominal pain, nausea, vomiting and diarrhea may appear.

Postoperative endophthalmitis

It is a disease that affects the eyeball, in the postoperative case it implies that the infection occurred due to surgery.

The symptoms of this infection caused by Arthrobacter sp. Are: eye pain, loss of visual acuity, presence of leukocytes and fibrin in the anterior chamber of the eye (Hypopyon).

Whipple's disease

It is a condition that attacks the digestive tract, especially the small intestine. The symptoms of this disease, caused by microbes of the genus Arthrobacter, are: fever, asymmetric polyarthritis, aphthous mouth ulcerations and loss of visual acuity.

Bacterial phlebitis

One of the detected agents that cause this condition is Arthrobacter albus. Bacterial phlebitis is very rare. It consists of the inflammation of a vein due to contamination of the circulatory system due to poor handling or hygiene of catheters.

The symptoms of this disease can vary depending on whether it is superficial or deep phlebitis.

Superficial phlebitis: redness of the skin, swelling in the vein area, pain to the touch, warmth in the vein area.

Deep phlebitis: extensive swelling, affected area with pale or cyanotic coloration, decreased pulse, severe pain, tachycardia, fever and sometimes venous gangrene may occur.

Treatments

Subacute infective endocarditis

This infection is treated with antibiotics (for approximately 8 weeks) almost always from the hospital care center and the treatment can be completed later at home.

Sometimes antibiotics are not enough and surgery will be required to replace damaged valves or drain abscesses.

Bacteremia

It is necessary to remove the source of the bacteremia such as catheters and treat with antibiotics.

Postoperative endophthalmitis

For endophthalmitis caused by Arthrobacter, treatment according to clinical studies is four weeks of intravitreal injections, and topical treatment of vancomycin and gentamicin, followed by oral amoxicillin.

Whipple's disease

The treatment for this disease, caused specifically by Arthrobacter, is the oral administration of sulfamethoxazole and trimethoprim (SMZ-TMP) together and rifampin.

Bacterial phlebitis

The treatment of this disease is adjusted to the type of disease, that is, there is a treatment for superficial phlebitis and another for deep phlebitis.

Superficial: anti-inflammatory, antiseptic ointments with zinc oxide and with heparinoids. Application of cold compresses. Elevate the affected limb.

Deep: administration of anti-inflammatory drugs, antibiotics, analgesics, heparin among others according to medical indications. When medication is not enough, treatment includes placing a filter in the vena cava or having it removed by surgery.

References

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