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

Introduction

Serratia fonticola is a Gram-negative bacterium that belongs to the genus Serratia. It was first isolated and described in 1998 from water samples in a freshwater spring in California, USA. Since its discovery, S. fonticola has been identified in various environmental sources, including soil, water, and plants.

This bacterium has gained attention as an emerging opportunistic pathogen capable of causing infections in humans. It is often associated with healthcare-associated infections, particularly in individuals with compromised immune systems or underlying medical conditions. It can cause a range of infections, including urinary tract infections, respiratory tract infections, wound infections, bloodstream infections, and pneumonia.

Serratia fonticola possesses several virulence factors that contribute to its pathogenicity, including the production of various enzymes, such as proteases, lipases, and DNases, which aid in tissue invasion and immune evasion. It can also form biofilms, which are structured communities of bacteria embedded in a protective extracellular matrix, enabling it to adhere to surfaces and increase resistance to antibiotics and immune defenses.

Morphology

The morphology of Serratia fonticola is characterized by its appearance as Gram-negative, rod-shaped bacteria. Here are some key features of its morphology:

1. Shape: It appears as straight or slightly curved rods. The cells are elongated and have a cylindrical shape.
2. Size: The average size of S. fonticola cells ranges from 0.5 to 1.0 micrometers in width and 1.0 to 3.0 micrometers in length.
3. Arrangement: S. fonticola cells are typically found singly or in pairs. They can also form short chains or small clusters.
4. Gram Staining: It is Gram-negative, which means it does not retain the crystal violet dye during the Gram staining process. Instead, it takes up the counterstain (safranin) and appears pink or red under a microscope.
5. Motility: It is motile and possesses peritrichous flagella, which are distributed over the entire surface of the cell. This enables the bacterium to move actively in liquid environments.

Pathogenicity

Serratia fonticola is considered an opportunistic pathogen, meaning it primarily causes infections in individuals with compromised immune systems or underlying medical conditions. While it is generally regarded as less pathogenic compared to other Serratia species, it still has the potential to cause a range of infections in susceptible individuals.

The pathogenicity of Serratia fonticola is attributed to several factors and mechanisms:

1. Virulence Factors: Serratia fonticola possesses various virulence factors that contribute to its ability to cause disease. These factors include enzymes such as proteases, lipases, and DNases, which can degrade host tissues and evade the immune response.
2. Biofilm Formation: It has the ability to form biofilms, which are structured communities of bacteria embedded in a self-produced extracellular matrix. Biofilms provide protection to the bacteria, making them more resistant to antimicrobial agents, immune defenses, and host clearance mechanisms. Biofilms formed by Serratia fonticola can be found on various surfaces, including medical devices like catheters, increasing the risk of device-related infections.
3. Antibiotic Resistance: S. fonticola has been associated with antibiotic resistance, including resistance to multiple classes of antibiotics. This resistance can make treatment challenging and limit the available options for controlling infections caused by this bacterium.
4. Immunocompromised Hosts: Serratia fonticola infections are more commonly observed in individuals with weakened immune systems, such as those with underlying diseases, immunosuppression, or prolonged hospital stays. In these individuals, the bacterium can exploit the compromised immune defenses, leading to the establishment of infections.
5. Healthcare-Associated Infections:It is often linked to healthcare-associated infections, particularly in hospital settings. Factors such as invasive procedures, indwelling medical devices, and exposure to healthcare environments increase the risk of colonization and infection by this bacterium.

Laboratory Diagnosis

The laboratory diagnosis of Serratia fonticola involves a combination of techniques to identify and confirm the presence of the bacterium in clinical or environmental samples. Here are the key methods used in the laboratory diagnosis:

1. Microscopic Examination: Gram staining is performed to determine the Gram reaction of the bacteria. Serratia fonticola appears as Gram-negative rods under the microscope.
2. Culture: It can be cultured on appropriate agar media. Blood agar, MacConkey agar, and nutrient agar are commonly used. The culture plates are incubated at a suitable temperature, typically around 35-37 degrees Celsius, for 24-48 hours.
3. Colony Characteristics: Serratia fonticola colonies on agar plates typically exhibit specific characteristics. They are smooth, mucoid, and often have a pink or reddish pigmentation. However, the appearance of the colonies can vary depending on the strain and growth conditions.
4. Biochemical Tests: Various biochemical tests are performed to identify Serratia fonticola. These tests include the oxidase test, catalase test, glucose fermentation, lactose fermentation, indole production, citrate utilization, and others. The results of these tests help differentiate S. fonticola from other bacteria.
5. API Systems: Commercial identification systems such as the API (Analytical Profile Index) system can be utilized. These systems use a panel of biochemical tests and provide a profile that can aid in the identification of S. fonticola.
6. Molecular Identification: Molecular methods, such as polymerase chain reaction (PCR) and DNA sequencing, can be employed for accurate identification of Serratia fonticola. Specific genetic markers or sequences unique to S. fonticola can be targeted for amplification and sequencing.
7. Antimicrobial Susceptibility Testing: Susceptibility testing is performed to determine the antibiotic susceptibility profile of S. fonticola isolates. This helps guide appropriate antibiotic treatment.

Treatment

The treatment of Serratia fonticola infections typically involves a combination of antimicrobial therapy, supportive care, and management of underlying conditions. However, it’s important to note that treatment approaches may vary depending on the site and severity of the infection, as well as the antibiotic susceptibility profile of the specific strain. Here are some general considerations for the treatment of Serratia fonticola infections:

1. Antibiotic Therapy: Serratia fonticola is known to exhibit resistance to multiple antibiotics, including commonly used broad-spectrum agents. Therefore, it is essential to perform antimicrobial susceptibility testing on the isolated strain to guide appropriate antibiotic selection. In some cases, a combination of antibiotics may be required. Consultation with an infectious disease specialist is recommended to determine the most effective antibiotic regimen.
2. Empirical Therapy: In cases where the specific identification of Serratia fonticola is not available, empirical antibiotic therapy may be initiated based on the suspected source of infection, patient factors, and local antibiotic resistance patterns. However, it is important to reassess and modify the treatment regimen once the identification and susceptibility results become available.
3. Supportive Care: Supportive measures, such as adequate hydration, pain management, and wound care, are important components of treatment. These measures help maintain the patient’s overall health, promote healing, and alleviate symptoms associated with the infection.
4. Infection Control Measures: In healthcare settings, strict infection control practices should be implemented to prevent the spread of Serratia fonticola infections. This includes proper hand hygiene, appropriate use and maintenance of medical devices, adherence to isolation precautions, and environmental cleaning.
5. Addressing Underlying Conditions: If there are underlying medical conditions or immunosuppression, it is important to manage and treat these conditions appropriately. Optimizing the patient’s overall health can help improve their ability to fight off the infection.

Prevention

Prevention of Serratia fonticola infections involves a combination of strategies aimed at reducing the risk of transmission and controlling the spread of the bacterium.

1. Infection Control Practices: Implement and adhere to strict infection control measures in healthcare settings. This includes proper hand hygiene, appropriate use of personal protective equipment (e.g., gloves, gowns), and adherence to standard precautions and isolation protocols for patients with Serratia fonticola infections.
2. Environmental Cleaning: Maintain a clean and hygienic healthcare environment. Regularly clean and disinfect surfaces, equipment, and patient care areas using appropriate disinfectants. Pay particular attention to high-touch surfaces and areas prone to contamination.
3. Antimicrobial Stewardship: Promote and implement antimicrobial stewardship programs to optimize the use of antibiotics. This includes appropriate prescribing practices, monitoring of antibiotic usage, and education for healthcare professionals on the appropriate selection and duration of antibiotic therapy.
4. Catheter-Related Infection Prevention: Strictly follow catheter insertion and maintenance protocols to minimize the risk of catheter-associated infections. Ensure proper aseptic techniques during insertion and regular assessment and care of the catheter site.
5. Water Source Management: Monitor and manage water sources in healthcare facilities to prevent contamination. Regularly test and maintain the quality of water systems, particularly in areas where Serratia fonticola has been previously detected.
6. Education and Awareness: Educate healthcare professionals, staff, and patients about the risks, prevention strategies, and appropriate infection control measures related to Serratia fonticola. Promote awareness of the importance of hand hygiene, proper cleaning practices, and the responsible use of antibiotics.
7. Surveillance and Monitoring: Implement surveillance programs to monitor the occurrence and trends of Serratia fonticola infections. Monitor antibiotic resistance patterns and track the effectiveness of infection control measures. Prompt identification and reporting of cases can help initiate timely interventions and prevent outbreaks.
8. Collaboration and Communication

Keynotes

Here are some keynotes on Serratia fonticola:

1. Serratia fonticola is a Gram-negative bacterium that belongs to the genus Serratia. It was first isolated from water samples in California, USA, in 1998.
2. It is an opportunistic pathogen that can cause infections in individuals with compromised immune systems or underlying medical conditions.
3. Serratia fonticola is commonly associated with healthcare-associated infections, particularly in hospital settings. It can cause a range of infections, including urinary tract infections, respiratory tract infections, wound infections, bloodstream infections, and pneumonia.
4. The bacterium possesses various virulence factors, such as enzymes and biofilm formation, which contribute to its pathogenicity and ability to evade the host immune response.
5. Serratia fonticola is known for its ability to develop resistance to multiple antibiotics, which can complicate treatment options and increase the risk of healthcare-associated infections.
6. Laboratory diagnosis of Serratia fonticola involves techniques such as microscopic examination, culture, biochemical tests, and molecular identification methods.
7. Treatment of Serratia fonticola infections requires a tailored approach based on the specific site and severity of infection, along with antibiotic susceptibility testing. Consultation with infectious disease specialists is recommended.
8. Prevention of Serratia fonticola infections involves strict infection control practices, environmental cleaning, antimicrobial stewardship, catheter-related infection prevention, water source management, education, surveillance, and collaboration between healthcare providers.
9. Ongoing research is focused on understanding the pathogenicity, antimicrobial resistance mechanisms, and epidemiology of Serratia fonticola to develop effective prevention and treatment strategies.

Further Readings

1. Stock I, Burak S, Sherwood KJ, Gruger T, Wiedemann B. Natural antimicrobial susceptibilities of strains of “Serratia marcescens” and “S. liquefaciens” complex: S. liquefaciens sensu stricto, S. proteamaculans and S. grimesii. Int J Antimicrob Agents. 2003 Dec;22(6):533-45. doi: 10.1016/s0924-8579(03)00247-7.
2. Liou CH, Lee YL, Chen CM, Chen YS, Chen SJ. Clinical manifestations and prognostic factors of Serratia bacteremia in adults. J Microbiol Immunol Infect. 2004 Aug;37(4):239-44.
3. Yamamoto T, Kusaba T, Hirai Y, Okamura N. Clinical features and therapeutic interventions in 17 cases of Serratia bacteremia in Japan. J Infect Chemother. 2005 Oct;11(5):259-63. doi: 10.1007/s10156-005-0406-9.
4. Rafei R, Dabboussi F, Hamze M, Eveillard M, Lemarié C, Mallat H, Rolain JM, Kempf M, Joly-Guillou ML. Molecular characterization of Serratia fonticola isolates from clinical and environmental origins. J Med Microbiol. 2014 Apr;63(Pt 4):565-74. doi: 10.1099/jmm.0.068494-0.
5. Rafei R, Pailhories H, Hamze M, Eveillard M, Marsollier L, Joly-Guillou ML, Kempf M. Serratia fonticola: an emerging pathogen in France. J Hosp Infect. 2015 Aug;90(4):324-5. doi: 10.1016/j.jhin.2015.05.001.
6. Escajadillo T, Ledesma M, Lazaro-Perona F, Solé M, Ruiz M, Calatayud L, Esteban J. First case report of Serratia fonticola infection in a joint prosthesis. J Clin Microbiol. 2017 Oct 25;55(11):3283-3286. doi: 10.1128/JCM.01025-17.
7. Kasten MJ, Mayo JA, Armstrong PJ, Feist RM. Catheter-associated Serratia fonticola bacteremia in a neutropenic child with acute myeloblastic leukemia. J Pediatr Hematol Oncol. 2003 May;25(5):414-7. doi: 10.1097/00043426-200305000-00016.