Morganella: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynotes

Introduction

Morganella is a genus of bacteria belonging to the family Enterobacteriaceae. The genus was named after the bacteriologist John Morgan. Morganella species are gram-negative, rod-shaped bacteria that are commonly found in the environment, including soil, water, and sewage.

One species of particular interest is Morganella morganii, which is known to cause opportunistic infections in humans. While it is normally found in the gastrointestinal tract, it can also be found in the urinary tract, respiratory tract, wounds, and bloodstream. Infections caused by M. morganii are often associated with underlying conditions such as urinary tract abnormalities, catheterization, or immunosuppression.

Its infections can present as urinary tract infections, respiratory tract infections, or wound infections. Symptoms may vary depending on the site of infection but can include fever, pain, inflammation, and purulent discharge. Treatment typically involves antibiotic therapy targeted against the specific strain of M. morganii involved, taking into account the local antimicrobial resistance patterns.

Morphology


The morphology of Morganella bacteria, specifically M. morganii, is as follows:

  1. Shape: Morganella bacteria are gram-negative rods, which means they have a rod-like shape. They are elongated and cylindrical in appearance.
  2. Size: The size of Morganella can vary, but they are typically around 2-5 micrometers in length and 0.5-1 micrometer in width.
  3. Arrangement: They are usually found as single cells or in pairs (diplobacilli). They do not form long chains or clusters like some other bacteria.
  4. Flagella: M. morganii is motile, meaning it possesses flagella, which are whip-like structures that allow the bacteria to move. These flagella enable Morganella morganii to exhibit a characteristic darting or swarming motility on agar plates.
  5. Capsule: Some strains of M. morganii can produce a polysaccharide capsule, which is a slimy outer layer that surrounds the bacterial cell. The presence of a capsule can provide protection against the host immune system and enhance the bacteria’s ability to cause infections.
Morganella morganii Colony Morphology on CLED agar of Urine Culture
Fig. Morganella morganii Colony Morphology on CLED agar of Urine Culture

It’s important to note that the morphology of bacteria can vary slightly depending on the strain and growth conditions. The information provided above describes the general characteristics of Morganella bacteria, but there may be some variation within the genus.

Pathogenicity

M. morganii, the most clinically relevant species within the Morganella genus, can be pathogenic and cause various infections in humans. Here are some key aspects of its pathogenicity:

  1. Opportunistic Pathogen: M. morganii is considered an opportunistic pathogen, meaning it usually infects individuals with compromised immune systems or underlying conditions that make them more susceptible to infection. These conditions can include urinary tract abnormalities, catheterization, immunosuppression, diabetes mellitus, or recent surgical procedures.
  2. Infection Sites: It can infect various sites in the body, including the urinary tract, respiratory tract, wounds, bloodstream, and gastrointestinal tract. The most common infections associated with M. morganii are urinary tract infections (UTIs) and hospital-acquired infections.
  3. Urinary Tract Infections: It is frequently isolated from urinary tract infections, especially in individuals with urinary catheters or urinary tract abnormalities. It can ascend the urinary tract, causing symptoms such as frequent urination, urgency, pain or burning during urination, and cloudy or bloody urine.
  4. Bacteremia and Septicemia: In severe cases, M. morganii can enter the bloodstream and cause bacteremia or septicemia, which are bloodstream infections. This can occur as a result of untreated or poorly managed urinary tract infections or from other sources of infection.
  5. Respiratory and Wound Infections: Morganella morganii can also cause respiratory tract infections, such as pneumonia, particularly in individuals with underlying lung diseases or compromised immune systems. Additionally, it can infect wounds, leading to wound infections and delayed wound healing.
  6. Virulence Factors: Morganella morganii possesses various virulence factors that contribute to its pathogenicity. These include fimbriae and pili for adherence to host tissues, flagella for motility and colonization, secretion systems for toxin delivery, and enzymes that facilitate tissue damage and evasion of host immune responses.
  7. Antibiotic Resistance: It has shown a propensity for developing antibiotic resistance, including extended-spectrum beta-lactamase (ESBL) production, which can limit treatment options and complicate the management of infections caused by this bacterium.

Laboratory Diagnosis

The laboratory diagnosis of Morganella, specifically M. morganii, typically involves the following methods:

  1. Specimen Collection: A suitable clinical specimen needs to be collected from the suspected site of infection. This could include urine for urinary tract infections, sputum for respiratory tract infections, wound swabs for wound infections, or blood cultures for bloodstream infections.
  2. Gram Stain: The first step in the laboratory diagnosis is usually the Gram stain. A Gram stain of the specimen allows for the initial identification of the bacteria based on their Gram reaction, morphology, and cellular arrangement. Morganella morganii appears as Gram-negative rods.
  3. Culture and Isolation: The next step is to culture the specimen on appropriate media. M. morganii can be grown on commonly used culture media such as blood agar, MacConkey agar, or cystine-lactose-electrolyte-deficient (CLED) agar. The agar plates are then incubated at the optimal temperature for Morganella growth, which is usually around 37 degrees Celsius.
  4. Colony Characteristics: After incubation, colonies of M. morganii on agar plates typically exhibit certain characteristics. They are usually non-lactose fermenting, appear as large, grayish or pinkish colonies, and may exhibit a characteristic swarming motility.
  5. Biochemical Tests: Several biochemical tests are performed to further confirm the identification of Morganella morganii. These tests include oxidase test, catalase test, indole production, citrate utilization, urease production, and other specific tests to differentiate it from other bacteria in the Enterobacteriaceae family.
  6. Antimicrobial Susceptibility Testing: Once the identification of M. morganii is confirmed, antimicrobial susceptibility testing is performed to determine the appropriate antibiotics for treatment. This testing helps guide the selection of antibiotics by assessing the susceptibility or resistance of the bacteria to different antimicrobial agents.
Morganella morganii bacilli in Wet Mount of Culture Microscopy
Fig. Morganella morganii bacilli in Wet Mount of Culture Microscopy
Biochemical Reactions of Morganella morganii in TSI, SIM, Citrate, Urea agar
Fig. Biochemical Reactions of Morganella morganii in TSI, SIM, Citrate, Urea agar

It’s important to note that the above steps are general guidelines for the laboratory diagnosis of M. morganii. The specific protocols and methods may vary depending on the laboratory’s procedures and available resources. Additionally, in some cases, advanced molecular techniques like polymerase chain reaction (PCR) or matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) may be used for rapid and accurate identification of the bacteria.

Treatment

The treatment of Morganella infections, particularly those caused by Morganella morganii, involves the use of appropriate antibiotics. The choice of antibiotic depends on the specific strain of Morganella and its susceptibility profile, which can vary geographically and over time. It is important to perform antimicrobial susceptibility testing to guide treatment decisions. Here are some general considerations:

  1. Antibiotic Therapy: Infections caused by Morganella morganii are often treated with broad-spectrum antibiotics initially, pending susceptibility results. Commonly used antibiotics include:
    • Third-generation cephalosporins: Ceftriaxone, cefotaxime, or ceftazidime.
    • Carbapenems: Imipenem, meropenem, or doripenem.
    • Fluoroquinolones: Ciprofloxacin or levofloxacin.
    • Aminoglycosides: Gentamicin or amikacin.
    • Trimethoprim/sulfamethoxazole (TMP/SMX): Particularly effective for urinary tract infections when susceptible.
  2. Combination Therapy: In severe infections or when Morganella morganii strains are resistant to multiple antibiotics, combination therapy with two or more antibiotics may be necessary. This approach can enhance the coverage of different antibiotic classes and improve treatment outcomes.
  3. Duration of Treatment: The duration of antibiotic therapy depends on the site and severity of the infection. In uncomplicated urinary tract infections, a 7 to 10-day course of antibiotics is typically sufficient. For more severe or complicated infections, longer treatment durations may be necessary, and the duration should be determined on a case-by-case basis.
  4. Antibiotic Resistance: It has demonstrated increasing resistance to multiple antibiotics, including extended-spectrum beta-lactamase (ESBL) production. If the isolate shows resistance to commonly used antibiotics, consultation with an infectious disease specialist is recommended to determine the most appropriate alternative therapy.
  5. Monitoring and Follow-up: During treatment, it is important to monitor the patient’s response to therapy, including resolution of symptoms and normalization of relevant laboratory parameters. Follow-up cultures may be required to ensure eradication of the infection.
AST of Morganella morganii
Fig. AST of Morganella morganii

Prevention

Preventing Morganella infections, particularly those caused by M. morganii, involves various measures aimed at reducing the risk of exposure and transmission. Here are some key prevention strategies:

  1. Hand Hygiene: Practicing proper hand hygiene is essential in preventing the spread of Morganella morganii and other infectious agents. Wash your hands thoroughly with soap and water for at least 20 seconds, especially before eating, after using the restroom, and after coming into contact with potentially contaminated surfaces or objects.
  2. Infection Control Measures: In healthcare settings, implementing stringent infection control measures is crucial to prevent the spread of M. morganii and other healthcare-associated infections. This includes proper disinfection and cleaning of surfaces, appropriate use of personal protective equipment (e.g., gloves, gowns), and adherence to proper sterilization techniques for medical equipment.
  3. Urinary Catheter Care: Since urinary tract infections (UTIs) are a common source of Morganella infections, appropriate care and maintenance of urinary catheters are vital. Avoid unnecessary use of urinary catheters, and when they are necessary, ensure sterile insertion, regular monitoring, and timely removal to minimize the risk of infection.
  4. Antimicrobial Stewardship: Promoting the appropriate use of antibiotics through antimicrobial stewardship programs can help prevent the emergence of antibiotic-resistant strains of Morganella morganii. This includes avoiding unnecessary or prolonged antibiotic use, choosing the right antibiotic based on susceptibility testing, and ensuring proper dosing and duration of therapy.
  5. Proper Wound Care: For wound infections, proper wound care is essential. Cleanse wounds with mild antiseptics or sterile saline, cover them with appropriate dressings, and ensure regular assessment and follow-up by healthcare professionals.
  6. Personal Hygiene: Maintaining good personal hygiene can reduce the risk of Morganella infections. This includes regular bathing, keeping wounds clean and covered, and avoiding the sharing of personal items like towels or razors.
  7. Education and Awareness: Education plays a critical role in preventing infections. Healthcare professionals and individuals should be educated about the risk factors, signs, and symptoms of Morganella infections, as well as preventive measures to minimize the spread of the bacteria.

Keynotes

Here are some keynotes on Morganella:

  1. Morganella is a genus of gram-negative bacteria belonging to the family Enterobacteriaceae.
  2. The most clinically relevant species within the genus is M. morganii.
  3. M. morganii is an opportunistic pathogen that can cause infections in humans, particularly in individuals with compromised immune systems or underlying conditions.
  4. Common infections associated with M. morganii include urinary tract infections (UTIs), respiratory tract infections, wound infections, and bloodstream infections.
  5. Morganella morganii can be identified through laboratory techniques such as Gram staining, culture, and biochemical tests.
  6. Treatment of Morganella infections involves the use of appropriate antibiotics based on antimicrobial susceptibility testing.
  7. It has shown a propensity for developing antibiotic resistance, including extended-spectrum beta-lactamase (ESBL) production, which can complicate treatment.
  8. Prevention of Morganella infections involves measures such as hand hygiene, infection control practices, proper urinary catheter care, antimicrobial stewardship, wound care, personal hygiene, and education.
  9. Monitoring the response to treatment and follow-up cultures may be necessary to ensure eradication of the infection.
  10. Consultation with healthcare professionals is essential for accurate diagnosis, appropriate treatment, and prevention strategies tailored to individual circumstances.

Further Readings

  1. Bacterial Genus: Morganella – MicrobeWiki: This resource provides an overview of Morganella, including its taxonomy, characteristics, pathogenicity, and clinical significance. You can find it at: https://microbewiki.kenyon.edu/index.php/Morganella
  2. Morganella morganii Infections: A Review of Clinical Outcomes and Antimicrobial Resistance: This review article discusses the clinical outcomes, epidemiology, antimicrobial resistance patterns, and treatment options for infections caused by Morganella morganii. It is available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6167323/
  3. Molecular Epidemiology and Antimicrobial Susceptibility of Morganella morganii Isolated from Clinical Samples: This study explores the molecular epidemiology and antimicrobial susceptibility patterns of Morganella morganii strains isolated from clinical samples. The article can be accessed at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451193/
  4. Morganella morganii: Clinical and Laboratory Characteristics of an Emerging Opportunistic Pathogen: This research article provides insights into the clinical and laboratory characteristics of Morganella morganii as an emerging opportunistic pathogen. It can be found at: https://pubmed.ncbi.nlm.nih.gov/25392245/
  5. Morganella morganii: An Overlooked Pathogen with Increasing Clinical Significance: This article discusses the clinical significance, pathogenesis, virulence factors, and antibiotic resistance mechanisms of Morganella morganii. You can access it at: https://www.sciencedirect.com/science/article/pii/S221371652030040X

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