Aeromonas sobria: Introduction, Morphology, Pathogenicity, Lab

Introduction

Table of Contents

Aeromonas sobria is a species of Gram-negative bacteria that belongs to the Aeromonas genus. It is a rod-shaped, facultative anaerobic bacterium that is commonly found in aquatic environments, such as freshwater and brackish water.

A. sobria can cause a range of infections in humans, including skin and soft tissue infections, sepsis, gastroenteritis, and wound infections. It can also cause infections in fish and other aquatic animals.

A. sobria is known to produce a variety of virulence factors, such as hemolysins, proteases, and lipases, which contribute to its pathogenicity. It can also form biofilms, which makes it more resistant to antibiotics and disinfectants.

Morphology

Aeromonas sobria is a Gram-negative, rod-shaped bacterium. The cells are typically around 1-3 micrometers in length and 0.5-1.0 micrometers in diameter. They are motile, possessing a single polar flagellum. The cell wall of it contains lipopolysaccharides, which contribute to its pathogenicity. The bacteria can grow both aerobically and anaerobically, but require oxygen for optimal growth. On agar plates, its colonies typically appear as gray or white, smooth, and slightly raised. The bacterium is also known to produce a distinctive sweet or fruity odor.

Biochemical Tests

The following are some commonly used biochemical tests to identify A. sobria:

Oxidase test: Aeromonas sobria is oxidase-positive, meaning that it produces the enzyme cytochrome c oxidase, which can be detected using a test strip or reagent.
Catalase test: It is catalase-positive, meaning that it produces the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen.
Indole test: The bacterium is indole-negative, meaning that it does not produce the enzyme tryptophanase, which breaks down tryptophan to produce indole.
Methyl Red (MR) test: A. sobria is MR-positive, meaning that it produces acids from glucose metabolism that lower the pH of the medium and can be detected by adding the MR reagent.
Voges-Proskauer (VP) test: It is VP-negative, meaning that it does not produce the enzyme acetoin from glucose metabolism, which can be detected by adding the VP reagents.
Citrate utilization test: A. sobria is citrate-negative, meaning that it does not utilize citrate as a carbon source, which can be detected by adding a citrate utilization medium and observing for growth.
Urea hydrolysis test: It is urea-negative, meaning that it does not produce the enzyme urease, which can be detected by adding a urea hydrolysis medium and observing for the production of ammonia.

Pathogenicity

Aeromonas sobria is known to be a pathogenic bacterium that can cause a range of infections in humans and animals. Some of the ways that A. sobria can cause disease include:

Wound infections: Aeromonas sobria can cause wound infections, especially in people who are exposed to contaminated water or soil, or who have weakened immune systems.
Gastroenteritis: It can cause diarrhea, abdominal cramps, and other symptoms of gastroenteritis. The bacterium is often associated with contaminated food or water.
Septicemia: A. sobria can cause sepsis, a life-threatening infection that occurs when the bacteria enter the bloodstream. This can occur through contaminated medical equipment or intravenous lines.
Skin and soft tissue infections: It can cause infections of the skin and soft tissues, such as cellulitis, necrotizing fasciitis, and myonecrosis. These infections can occur after exposure to contaminated water or soil.

Aeromonas sobria is able to cause disease through the production of various virulence factors, including hemolysins, proteases, and lipases. It is also able to form biofilms, which can make it more resistant to antibiotics and disinfectants.

Laboratory Diagnosis

The laboratory diagnosis of Aeromonas sobria can be done using a combination of culture and biochemical tests. Here are the steps involved:

Sample collection: A clinical sample such as wound swab, stool, blood or urine is collected from the patient and transported to the laboratory in appropriate transport media.
Culture: The sample is cultured on appropriate media such as MacConkey agar or blood agar. The colonies of A. sobria appear as gray-white, smooth and slightly raised. It is also known to produce a sweet or fruity odor.
Gram staining: The colonies are subjected to Gram staining, which reveals that A. sobria is a Gram-negative rod-shaped bacterium.
Biochemical tests: A series of biochemical tests such as oxidase, catalase, indole, MR-VP, citrate utilization, and urea hydrolysis tests are performed to confirm the identification of Aeromonas sobria. The bacteria is oxidase-positive, catalase-positive, indole-negative, MR-positive, VP-negative, citrate-negative and urea-negative.
Antibiotic susceptibility testing: An antibiotic susceptibility test is performed to determine the sensitivity of the bacterium to different antibiotics.
Molecular testing: Molecular tests such as PCR (Polymerase Chain Reaction) or DNA sequencing may be used for confirmation of the identification of the bacterium.

Gram Negative rods of Aeromonas sobria in Gram staining of culture — Fig. Gram Negative rods of *Aeromonas sobria* in Gram staining of culture

It is important to note that clinical symptoms, medical history and patient information should be considered in addition to laboratory results for a correct diagnosis of A. sobria infection.

Fig. Aeromonas sobria in wet mount of broth culture microscopy

Treatment

The treatment of Aeromonas sobria infections usually involves the use of antibiotics. The choice of antibiotics depends on the severity of the infection, the site of infection and the antibiotic susceptibility pattern of the bacterium. In some cases, combination therapy may be needed.

Some antibiotics that are commonly used to treat A. sobria infections include:

Ciprofloxacin
Levofloxacin
Tetracycline
Trimethoprim-sulfamethoxazole
Third-generation cephalosporins
Aminoglycosides

In severe cases of infection, hospitalization and intravenous administration of antibiotics may be required. Additionally, supportive care such as hydration, pain management, and wound care may be necessary.

Prevention

Prevention of A. sobria infections involves taking measures to reduce exposure to the bacterium. Here are some steps that can be taken to prevent infection:

Practice good hygiene: Regular hand washing with soap and water is important in preventing the spread of Aeromonas sobria. Hand sanitizers can also be used when hand washing facilities are not available.
Safe food handling: Avoid eating raw or undercooked seafood or other foods that may be contaminated with A. sobria. Proper storage and cooking of food is important to reduce the risk of infection.
Water safety: Avoid exposure to contaminated water sources such as swimming pools, lakes, and rivers. If exposure to contaminated water is unavoidable, avoid swallowing the water.
Wound care: Proper wound care is important to prevent A. sobria infections. Clean wounds thoroughly with soap and water and seek medical attention for any signs of infection.
Antibiotic stewardship: Overuse and misuse of antibiotics can contribute to the development of antibiotic-resistant strains of A. sobria. Therefore, it is important to use antibiotics only when prescribed by a healthcare professional and to complete the full course of treatment.
Environmental control: Adequate sanitation and hygiene practices in clinical settings, including hospitals, can help prevent the spread of A. sobria and other healthcare-associated infections.

Overall, prevention of Aeromonas sobria infections involves a combination of personal hygiene practices, safe food handling, environmental control, and appropriate use of antibiotics.

Keynotes

Aeromonas sobria is a Gram-negative, rod-shaped bacterium that is widely distributed in aquatic environments.
It is an opportunistic pathogen that can cause a range of infections in humans, including skin and soft tissue infections, gastroenteritis, and septicemia.
The bacterium produces a number of virulence factors that contribute to its pathogenicity, including hemolysins, enterotoxins, and proteases.
Diagnosis of Aeromonas sobria infections involves a combination of culture and biochemical tests. Antibiotic susceptibility testing and molecular testing may also be performed.
Treatment of A. sobria infections usually involves the use of antibiotics. The choice of antibiotics depends on the severity of the infection and the antibiotic susceptibility pattern of the bacterium.
Prevention of A. sobria infections involves practicing good hygiene, safe food handling, water safety, wound care, antibiotic stewardship, and environmental control.
With increasing antibiotic resistance, there is a growing concern about the need for alternative treatment options and prevention strategies for Aeromonas sobria infections.

Aeromonas sobria: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynotes