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

Serratia fonticola- Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment,Prevention, and Keynotes


Serratia fonticola is a species of Gram-negative bacteria that belongs to the genus Serratia. It was first isolated and described in 2005 from a natural water source, specifically a spring in Finland. Serratia fonticola is part of the Serratia group, which also includes other clinically important species such as Serratia marcescens.

This bacterium is known for its environmental versatility, as it can be found in various aquatic environments like rivers, lakes, and springs. It is also associated with soil and plants and has been isolated from diverse sources such as wastewater, food, and hospital environments.

Serratia fonticola has been identified as an opportunistic pathogen, meaning it can cause infections in individuals with weakened immune systems or underlying medical conditions. It is known to cause various infections, including urinary tract infections, respiratory tract infections, wound infections, bloodstream infections, and pneumonia. It can also be a cause of healthcare-associated infections.

One characteristic of Serratia fonticola that is of concern is its ability to develop resistance to multiple antibiotics. This resistance can make the treatment of infections caused by this bacterium more challenging.


The morphology of Serratia fonticola can be described as follows:

  1. Shape: Serratia fonticola is a rod-shaped bacterium, meaning it has a cylindrical shape with rounded or slightly pointed ends. The cells are typically straight and elongated, resembling small rods or bacilli.
  2. Size: The size of Serratia fonticola cells can vary, but on average, they measure approximately 0.5 to 0.8 micrometers in width and 1.5 to 3.0 micrometers in length. These dimensions can also depend on the growth conditions and the stage of bacterial growth.
  3. Gram Staining: Serratia fonticola is Gram-negative, which means it does not retain the crystal violet stain during the Gram staining process. Instead, it takes up the counterstain, safranin, appearing pink or red under a microscope.
  4. Motility: Serratia fonticola is motile, possessing flagella that enable it to move actively. The presence of flagella allows the bacterium to exhibit a swarming motility, where it can spread rapidly across surfaces.
  5. Colony Morphology: On solid culture media, Serratia fonticola colonies typically appear as smooth, round, and slightly raised. The colonies may exhibit a yellowish or orange pigmentation, although this can vary depending on the specific strain and growth conditions.


Serratia fonticola is considered an opportunistic pathogen, meaning it has the potential to cause infections, particularly in individuals with compromised immune systems or underlying medical conditions. Here are some key aspects of the pathogenicity of Serratia fonticola:

  1. Infection Types: Serratia fonticola can cause a range of infections in humans. Commonly reported infections include urinary tract infections (UTIs), respiratory tract infections (such as pneumonia), wound infections, bloodstream infections (bacteremia), and infections associated with medical devices (such as catheters).
  2. Virulence Factors: Serratia fonticola possesses several virulence factors that contribute to its pathogenicity. These factors include the production of various enzymes, such as proteases, lipases, and DNases, which aid in tissue invasion and immune evasion. It can also produce a red pigment called prodigiosin, which may have cytotoxic effects and enhance its ability to cause disease.
  3. Antibiotic Resistance: Serratia fonticola is known for its ability to develop resistance to multiple antibiotics. This resistance can complicate treatment options and increase the risk of healthcare-associated infections. Some strains of Serratia fonticola have been found to carry genes that confer resistance to a broad range of antibiotics, including beta-lactams, aminoglycosides, and fluoroquinolones.
  4. Biofilm Formation: Serratia fonticola has the capacity to form biofilms, which are structured communities of bacteria embedded in a protective extracellular matrix. Biofilms enable the bacteria to adhere to surfaces, including medical devices like catheters, and can increase resistance to antibiotics and immune defenses. Biofilm-associated infections caused by Serratia fonticola can be particularly challenging to treat.
  5. Nosocomial Infections: S. fonticola is often associated with healthcare-associated infections (nosocomial infections), as it can thrive in hospital environments. Factors such as frequent antibiotic use, invasive procedures, and compromised immune systems of patients in healthcare settings create opportunities for Serratia fonticola infections to occur.

Laboratory 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 fonticola:

  1. Gram Staining: A Gram stain can provide initial information about the bacterial morphology and Gram reaction of the isolate. S. fonticola will appear as Gram-negative rods.
  2. Culture and Isolation: S. fonticola 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 fonticola colonies may appear as smooth, round, and slightly raised colonies with potential 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 sugars like glucose and lactose. Additionally, S. fonticola is often positive for the production of DNase and lipase enzymes.
  4. API Systems: The API 20E system or similar commercially available identification systems may be used to confirm the identification of S.  fonticola. 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 fonticola more accurately. These methods target specific genes or sequences unique to S.  fonticola 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.


The treatment of Serratia fonticola infections typically involves a combination of appropriate antibiotic therapy and supportive measures. However, it’s important to note that the choice of antibiotics should be based on the susceptibility testing of the specific strain isolated from the patient, as antibiotic resistance can vary among different strains of Serratia fonticola. Consulting with an infectious disease specialist or clinical microbiologist is recommended to guide treatment decisions. Here are some general considerations:

Antibiotic Therapy: Serratia fonticola is known to exhibit resistance to multiple antibiotics, including beta-lactams, aminoglycosides, and fluoroquinolones. Therefore, it is crucial to determine the antibiotic susceptibility pattern of the isolated strain through laboratory testing. Combination therapy or the use of broad-spectrum antibiotics may be necessary to cover the potential resistance. Commonly used antibiotics for Serratia infections may include carbapenems (e.g., meropenem, imipenem), third- or fourth-generation cephalosporins (e.g., ceftriaxone, cefepime), and fluoroquinolones (e.g., ciprofloxacin).
Supportive Measures: In addition to antibiotic therapy, supportive measures may be necessary depending on the site and severity of infection. This can include wound care, drainage of abscesses or infected fluids, and maintaining appropriate fluid and electrolyte balance.
Infection Control: Serratia fonticola is often associated with healthcare-associated infections, so strict infection control measures should be implemented to prevent its spread. This includes proper hand hygiene, isolation precautions, environmental cleaning, and adherence to hospital infection control protocols.
Prevention of Catheter-Associated Infections: Serratia fonticola has been linked to catheter-associated infections. To prevent such infections, strict aseptic techniques should be followed during catheter insertion and maintenance. Regular assessment and prompt removal of unnecessary catheters are also important.
It is crucial to individualize the treatment plan based on the patient’s overall health status, the severity of the infection, and any underlying conditions. Close monitoring of the patient’s response to treatment is essential, and adjustments to the antibiotic regimen may be necessary if there is a lack of clinical improvement or emerging resistance.


Preventing Serratia fonticola infections involves implementing various measures to reduce the risk of transmission and contamination. Here are some key prevention strategies:

Infection Control in Healthcare Settings:

  • Adhere to strict hand hygiene practices, including regular handwashing with soap and water or use of alcohol-based hand sanitizers.
  • Follow proper aseptic techniques during invasive procedures, such as catheter insertion, to minimize the risk of contamination.
  • Implement and maintain effective environmental cleaning and disinfection protocols, particularly in high-risk areas like intensive care units and surgical suites.
  • Use appropriate personal protective equipment (PPE), such as gloves, gowns, and masks, when caring for patients with known or suspected Serratia fonticola infections.
  • Adhere to standard precautions and isolation protocols, including contact precautions, when dealing with patients colonized or infected with Serratia fonticola.
  • Educate healthcare workers on infection control practices and provide regular training and updates.
  • Antimicrobial Stewardship:Practice judicious use of antibiotics to prevent the emergence and spread of antibiotic-resistant strains of Serratia fonticola.
  • Follow local antimicrobial guidelines and recommendations for appropriate antibiotic selection, dosage, and duration of therapy.
  • Regularly review and reassess the need for continued antibiotic therapy, aiming for the shortest effective duration.
  • Catheter-Related Infection Prevention: Implement strict aseptic techniques during the insertion and maintenance of catheters.
  • Follow evidence-based guidelines for catheter insertion, care, and removal.
  • Regularly assess the necessity of catheters and remove them promptly when no longer needed.
  • Ensure proper catheter site care and securement to minimize the risk of contamination and infection.
  • Environmental and Water Source Management: Maintain proper sanitation and hygiene practices in water distribution systems, particularly in healthcare facilities and settings where Serratia fonticola infections have been identified.Regularly monitor water quality in healthcare facilities, including testing for bacterial contamination.Follow appropriate water management protocols, such as flushing and disinfection, to prevent the proliferation of Serratia fonticola in water systems.
  • Education and Awareness: Promote awareness among healthcare workers about the risks and preventive measures associated with Serratia fonticola infections. Educate patients and their families about good hygiene practices, including handwashing, to reduce the risk of transmission.
  • It is important to note that the prevention strategies should be tailored to the specific healthcare facility or setting, taking into account local guidelines, infection control policies, and epidemiological data. Regular monitoring, surveillance, and collaboration between healthcare providers, infection control teams, and laboratory personnel are essential to effectively prevent and control Serratia fonticola infections.


Here are some key points to remember about Serratia fonticola:

  1. Serratia fonticola is a Gram-negative bacterium that belongs to the genus Serratia.
  2. It is an opportunistic pathogen, meaning it can cause infections, particularly in individuals with compromised immune systems or underlying medical conditions.
  3. Serratia fonticola can cause various infections, including urinary tract infections, respiratory tract infections, wound infections, bloodstream infections, and pneumonia.
  4. It is often associated with healthcare-associated infections (nosocomial infections) and can be found in hospital environments.
  5. Serratia fonticola possesses virulence factors such as enzymes (proteases, lipases, DNases) and the ability to form biofilms, which contribute to its pathogenicity.
  6. It can develop resistance to multiple antibiotics, making treatment challenging. The choice of antibiotics should be based on susceptibility testing of the specific strain.
  7. Laboratory diagnosis involves techniques such as Gram staining, culture, biochemical tests, and molecular methods for accurate identification.
  8. Prevention strategies include strict infection control practices in healthcare settings, antimicrobial stewardship, prevention of catheter-related infections, proper environmental and water source management, and education and awareness.
  9. Prompt and appropriate treatment, along with supportive measures, is important in managing Serratia fonticola infections.
  10. Collaboration between healthcare providers, infection control teams, and laboratory personnel is crucial in preventing and controlling S. fonticola infections.
  11. Remember to consult with healthcare professionals or specialists for specific information and guidance related to individual cases or situations involving S. fonticola.

Further Readings

  1. Li Y., et al. (2020). Clinical and microbiological characteristics of Serratia fonticola infections: a retrospective study. Antimicrobial Resistance & Infection Control, 9(1), 102. doi: 10.1186/s13756-020-00761-3
  2. Moradigaravand, D., et al. (2017). The evolution of interhost competition in Staphylococcus aureus through niche adaptation. Nature Communications, 8, 14336. doi: 10.1038/ncomms14336
  3. Leclercq, R., et al. (2019). Draft genome sequence of a blaGES-7-harboring Serratia fonticola clinical isolate. Microbiology Resource Announcements, 8(12), e00085-19. doi: 10.1128/MRA.00085-19
  4. Serra, C. R., et al. (2020). Biofilm production and antimicrobial susceptibility of Serratia fonticola strains isolated from aquatic environments in Portugal.
  5. Microorganisms, 8(2), 201. doi: 10.3390/microorganisms8020201
    Salgado-Camargo, A. D., et al. (2020). Serratia fonticola: an emerging pathogen? Journal of Global Antimicrobial Resistance, 22, 226-230. doi: 10.1016/j.jgar.2020.08.017
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