Serratia ficaria: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment,Prevention, and Keynotes

Serratia ficaria: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment,Prevention, and Keynotes


Serratia ficaria is a bacterial species belonging to the genus Serratia, which is a part of the family Enterobacteriaceae. It is commonly known as Serratia marcescens or Serratia liquefaciens. This species is Gram-negative and facultatively anaerobic, meaning it can survive in both aerobic (with oxygen) and anaerobic (without oxygen) environments.

It is known for its ability to produce a red pigment called prodigiosin, which gives the bacterium a distinctive red or pink coloration. This pigment has led to its nickname “the red bacteria.” However, it’s important to note that S. ficaria can also exhibit other pigments, including orange, yellow, and white.

In terms of its habitat, S.  ficaria can be found in various environments, including soil, water, and plants. It is also known to colonize the human body, particularly in the respiratory and urinary tracts, as well as in wounds and medical devices such as catheters.

While Serratia ficaria is generally considered to be an opportunistic pathogen, it can cause infections in immunocompromised individuals, newborns, and the elderly. It has been associated with various infections, including urinary tract infections, respiratory tract infections, bacteremia (bacterial bloodstream infections), wound infections, and endocarditis (inflammation of the inner lining of the heart). It can also be involved in nosocomial (hospital-acquired) infections.

It  possesses a range of virulence factors that contribute to its pathogenicity. These factors include the production of various enzymes, such as lipases and proteases, as well as the ability to form biofilms, which enhance its resistance to antibiotics and the immune system.

In the laboratory, S. ficaria can grow on standard culture media, including nutrient agar and MacConkey agar. It is motile due to the presence of flagella and can ferment sugars, producing acid and gas. It is also able to utilize citrate as a carbon source.


The morphology of Serratia ficaria is typical of Gram-negative bacteria. Here are some key features of its morphology:

  1. Shape: Serratia ficaria bacteria are generally rod-shaped (bacilli). They appear as elongated cells with straight or slightly curved edges.
  2. Size: The average size of Serratia ficaria cells ranges from 0.5 to 1.0 micrometers in width and 1.0 to 3.0 micrometers in length. However, the size can vary depending on growth conditions.
  3. Cell Arrangement: S. ficaria cells typically occur singly or in pairs, but they can also form short chains or clusters.
  4. Gram Staining: Serratia ficaria is classified as a Gram-negative bacterium. When subjected to Gram staining, its cell wall does not retain the crystal violet stain, but instead takes up the counterstain (safranin or fuchsin), causing it to appear red or pink under a microscope.
  5. Motility: Serratia ficaria is usually motile due to the presence of peritrichous flagella. These flagella are distributed over the entire surface of the cell, allowing the bacterium to move actively in liquid environments.
  6. Capsule: Some strains of Serratia ficaria may produce a slimy capsule around the bacterial cell. The capsule provides protection and can contribute to the bacterium’s virulence.
  7. Pigmentation: Serratia ficaria is known for its ability to produce pigments. The most common pigment is prodigiosin, which imparts a red or pink color to the bacteria. However, other strains may produce different pigments, resulting in colors such as orange, yellow, or white.


Serratia ficaria is an enterobacterium involved in the fig tree ecosystem, has been isolated from human clinical samples in rare instances, and its role as a pathogen is unclear. However it has been found in  patient with septicemia and  biliary infections.

Lab Diagnosis

The laboratory diagnosis of Serratia fonticola typically involves a combination of microbiological techniques. Here are the common methods used for the identification and diagnosis of Serratia ficaria :

  1. Gram Staining: A Gram stain can provide initial information about the bacterial morphology and Gram reaction of the isolate. S. ficaria  will appear as Gram-negative rods.
  2. Culture and Isolation: S. ficaria  can be cultured from clinical specimens, such as urine, sputum, wound swabs, or blood. Specimens are streaked onto appropriate culture media, such as MacConkey agar or blood agar, and incubated at a suitable temperature (typically 35-37°C) for 24-48 hours. Serratia ficaria colonies may appear as smooth, round, and slightly raised colonies with potential red or yellow or orange pigmentation.
  3. Biochemical Tests: Various biochemical tests can be performed to further identify S. fonticola. These may include testing for the presence of catalase (positive), oxidase (negative), and the ability to ferment sugar like glucose and  but lactose. Additionally,
  4. API Systems: The API 20E system or similar commercially available identification systems may be used to confirm the identification of S.  ficaria . These systems utilize a panel of biochemical tests to identify the bacterial species based on specific reactions.
  5. Molecular Methods: Polymerase chain reaction (PCR) assays or other molecular techniques can be employed to detect and identify Serratia ficaria more accurately. These methods target specific genes or sequences unique to S.  ficaria for definitive identification.
  6. Antibiotic Susceptibility Testing: Determining the antibiotic susceptibility pattern of the isolated Serratia fonticola strain is crucial for guiding appropriate treatment. The Kirby-Bauer disk diffusion method or automated systems, such as the Vitek or MicroScan systems, can be used to test the susceptibility of the isolate to various antibiotics.


Commonly used antibiotics for treating Serratia ficaria infections include:

  1. Cephalosporins: These antibiotics, such as ceftriaxone or cefotaxime, are often effective against S. ficaria. They work by disrupting the synthesis of the bacterial cell wall.
  2. Carbapenems: Drugs like imipenem or meropenem are broad-spectrum antibiotics that can be used to treat severe Serratia ficaria infections. They inhibit bacterial cell wall synthesis and are effective against many Gram-negative bacteria.
  3. Fluoroquinolones: Antibiotics like ciprofloxacin or levofloxacin are another option for treating Serratia ficaria infections. They interfere with the replication and DNA synthesis in bacteria.


Preventing Serratia ficaria infections involves implementing good hygiene practices and taking appropriate precautions, especially in healthcare settings where the bacterium can pose a greater risk. Here are some preventive measures:

  • Hand hygiene: Proper handwashing is crucial in preventing the spread of bacteria. Wash your hands thoroughly with soap and water for at least 20 seconds, especially before and after handling wounds or medical devices.
  • Infection control in healthcare settings: Healthcare facilities should follow strict infection control protocols, including regular cleaning and disinfection of surfaces and medical equipment. Proper sterilization and disinfection techniques should be employed for reusable medical devices.
  • Use of personal protective equipment (PPE): Healthcare workers should wear appropriate PPE, such as gloves, masks, gowns, and eye protection, when handling potentially contaminated materials or caring for patients with known or suspected Serratia ficaria infections.
  • Wound care: Maintain good wound hygiene and proper wound care techniques to minimize the risk of infection. Keep wounds clean, covered, and promptly seek medical attention for any signs of infection, such as increased redness, swelling, or discharge.
  • Antibiotic stewardship: Appropriate use of antibiotics helps prevent the emergence and spread of antibiotic-resistant bacteria. Use antibiotics only when necessary and as prescribed by healthcare professionals. Completing the full course of antibiotics as directed is important to ensure complete eradication of the bacteria.
  • Environmental hygiene: Maintain clean and hygienic environments, especially in healthcare settings. Regularly clean and disinfect surfaces and equipment to minimize the risk of bacterial contamination.
  • Patient isolation: In healthcare settings, appropriate isolation measures should be implemented for patients with known or suspected Serratia ficaria infections to prevent the spread of the bacterium to other patients.


Here are some keynotes on Serratia ficaria:

  1. Serratia ficaria is a Gram-negative bacterium that belongs to the Serratia genus. It is a part of the Enterobacteriaceae family.
  2. It is commonly found in the environment, including soil, water, and plants. It can also be present as a commensal bacterium in the gastrointestinal tract of humans and animals.
  3. Serratia ficaria is not considered a major human pathogen, but it can occasionally cause infections, particularly in individuals with weakened immune systems or those undergoing invasive medical procedures.
  4. Infections caused by Serratia ficaria are typically opportunistic and can include urinary tract infections, respiratory tract infections, bloodstream infections, and wound infections.
  5. The bacterium possesses several virulence factors that contribute to its pathogenicity, including the production of various enzymes and toxins.
  6. Serratia ficaria is typically resistant to multiple antibiotics, which can complicate treatment. Antibiotic susceptibility testing is important to guide appropriate treatment.
  7. In healthcare settings, Serratia ficaria can be a cause of healthcare-associated infections. Adequate infection control measures, such as hand hygiene, proper disinfection, and sterilization techniques, are crucial in preventing its spread.
  8. Proper wound care and maintenance of good hygiene practices can help reduce the risk of Serratia ficaria infections.
  9. The prevention and control of Serratia ficaria infections require a multidisciplinary approach involving healthcare professionals, infection control measures, and appropriate use of antibiotics.
  10. It is important to consult with a healthcare professional for an accurate diagnosis, appropriate treatment, and preventive strategies tailored to individual circumstances.
  11. Potatolike odor is the primary feature of S. ficaria.

Further Readings

  1. Coenye T, Vandamme P. Diversity and significance of Burkholderia species occupying diverse ecological niches. Environ Microbiol. 2003 Nov;5(11):719-29. doi: 10.1046/j.1462-2920.2003.00471.x.
  2. Grimont PAD, Grimont F. Genus XIV. Serratia Bizio 1823, 481 AL emend. Grimont and Grimont 1978, 79VP. In: Brenner DJ, Krieg NR, Staley JT, Garrity GM, editors. Bergey’s Manual of Systematic Bacteriology, Volume 2: The Proteobacteria, Part B: The Gammaproteobacteria. 2nd edition. New York: Springer; 2005. p. 855-876.
  3. Mahlen SD. Serratia infections: from military experiments to current practice. Clin Microbiol Rev. 2011 Oct;24(4):755-91. doi: 10.1128/CMR.00017-11.
  4. National Center for Biotechnology Information (NCBI) Serratia ficaria. Available online: (Accessed 8 June 2023).
  5. Peeters C, Cooper VS, Hatcher PJ, et al. Burkholderia isolates from cystic fibrosis patients: a genomovar assignment and comparative genomics study. BMC Genomics. 2017 Mar 14;18(1):159. doi: 10.1186/s12864-017-3558-0.


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