Raoultella terrigena’s epidemiology as a human pathogen is limited compared to other species in the genus Raoultella. However, data from case reports and retrospective investigations provide some insight into its incidence, sources of infection, risk factors, and antibiotic resistance patterns.
R. terrigena was concluded as the third most prevalent Raoultella species causing human infections in a 10-year retrospective investigation conducted in a tertiary-care hospital in Hungary, after R. planticola & R. ornithinolytica. The investigation found 11 cases of R. terrigena infection from 2007 to 2016, accounting for barely 0.01% of all clinical isolates. Urine (5 instances), blood (3 cases), & the respiratory tract (2 cases) were the most common sources of infection. Notably, most infected patients had underlying medical conditions, including diabetes, cancer, or chronic kidney disease. The mortality rate from R. terrigena infection was found to be 18.2%.
Case reports worldwide emphasize the clinical significance of R. terrigena infections in distinct patient populations. For example, a case report from Taiwan described a patient with liver cirrhosis who developed R. terrigena bacteremia following endoscopic retrograde cholangiopancreatography (ERCP). The patient’s excellent treatment with ceftriaxone and complete recovery shows a possible link between R. terrigena and ERCP-related infections.
Another case report from China described a patient with urinary tract abnormalities who were infected with R. terrigena via a carbapenem-resistant isolate containing the blaKPC-2 & blaSHV-12 genes. The necessity of antibiotic susceptibility testing and infection control strategies is emphasized in this paper, which highlights the evolution of antimicrobial resistance in R. terrigena strains.
A case report from Poland identified R. terrigena as a respiratory tract pathogen in a patient suffering from a pulmonary disorder who was admitted to the hospital for pneumonia. The patient’s effective treatment with meropenem & levofloxacin demonstrates that R. terrigena can cause respiratory infections in people with underlying lung problems.
Furthermore, a case report from Ukraine detailed a traumatic injury patient who acquired an R. terrigena wound infection after being admitted to the intensive care unit. After receiving prompt treatment with ceftriaxone & gentamicin, the patient recovered without complications, highlighting R. terrigena’s potential involvement as a wound pathogen in trauma patients.
Kingdom: Bacteria
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Enterobacterales
Family: Enterobacteriaceae
Genus: Raoultella
Species: Raoultella terrigena
Raoultella terrigena comprises a Gram-negative bacterium with a rod-shaped morphology (elongated & cylindrical cells). The bacteria are non-motile; it lacks flagella or other features that allow it to move independently.
R. terrigena cells can be 0.5 to 1.5 μm long and 0.3 to 0.7 μm wide.
Cells of R. terrigena may have a capsule, which is a slimy covering of polysaccharides or proteins that envelopes the bacterial cell wall.
The bacterium may also have pili or fimbriae, characterized by hair-like appendages on the bacterial surface that aid in adhesion to other surfaces.
Clinical manifestations:
Although the clinical symptoms of Raoultella terrigena diseases are not well-documented, there have been cases published in the medical literature. The bacterium has been linked to various diseases, particularly in patients with underlying health disorders or risk factors for infection.
Bacteremia, a bloodstream infection, is a common clinical symptom of R. terrigena infection. Bacteremia produced by this bacterium is common in people with impaired immune systems, like those with liver cirrhosis, diabetes, cancer, or immunosuppressive medication. In certain situations, the bacterium may enter the bloodstream from a localized infection site and propagate throughout the body, causing systemic symptoms & potentially severe problems.
Another significant symptom is urinary tract infection (UTI), common in individuals with indwelling catheters or urinary tract abnormalities. R. terrigena can enter the urinary tract through the catheter or take advantage of urinary tract anomalies, causing localized symptoms such as discomfort and burning during urination, repeated urination, and hematuria (blood in the urine).
Raoultella terrigena has also been linked to respiratory tract infections in people suffering from chronic obstructive pulmonary disorder (COPD) or cystic fibrosis. These people may get pneumonia or other respiratory infections, exhibiting symptoms such as coughing, shortness of breath, & fever.
Wound infections are seen in patients who have had traumatic injuries or have undergone surgical treatments. R. terrigena can colonize the wound site in these situations, causing local inflammation, redness, & pain.
R. terrigena has been related to ocular infections in rare cases, particularly in people who wear contact lenses or have had ocular trauma. This bacterium’s eye infections can produce symptoms such as redness, discomfort, discharge, & blurred vision.
Raoultella terrigena is a Gram-negative, rod-shaped bacterium with diverse characteristics contributing to its pathogenic potential. One study conducted by Izard in 1981 proposed a serotyping scheme for R. terrigena based on the O (somatic) and K (capsular) antigens. They identified 12 O antigens and 8 K antigens among 50 strains of R. terrigena isolated from soil and water samples. Interestingly, some of the O antigens were found to be shared with other Klebsiella species, such as Klebsiella pneumoniae and Klebsiella oxytoca. It suggests a possible cross-reactivity between Raoultella terrigena and other related bacteria.
Further studies analyzing the O antigen types using commercial antisera revealed that 14 belonged to O1, 3 to O2, 2 to O5, and 1 to O8 among the tested strains. Additionally, a PCR-based typing method detected K-antigen-encoding genes in the strains. Specifically, 11 strains carried the k2A gene, 4 carried the k2B gene, and 5 lacked K-antigen genes. This genetic diversity of K antigens may contribute to the bacterium’s pathogenicity and ability to evade the host’s immune response.
Raoultella terrigena has been shown to produce haemagglutinins like type 1 fimbriae & mannose-resistant haemagglutinin (MRHA). These virulence factors aid in colonizing and invading many bodily locations, including the urinary tract, respiratory tract, and blood vessels. Its propensity to cling to host tissues increases its ability to infect susceptible individuals, particularly those with underlying health disorders or impaired immune systems.
Another critical aspect of Raoultella terrigena’s pathogenicity is its ability to produce various beta-lactamases, including TEM-57, CTX-M-15, SHV-12, KPC-2, and NDM-1. Some beta-lactamases are classified as extended-spectrum beta-lactamases (ESBLs) or carbapenemases, which can efficiently degrade a wide range of beta-lactam antibiotics. This ability to produce antibiotic-resistance enzymes contributes to the challenge of treating infections caused by drug-resistant strains of R. terrigena, posing significant concerns for public health.
Several strains of Raoultella terrigena have been reported in the literature, each with unique characteristics and potential for pathogenicity. For example, the multidrug-resistant strain R. terrigena GODA, isolated from the blood of a patient with septic shock in Taiwan, carries the blaTEM-57 gene and multiple transporters related to drug efflux. Additionally, strains like R. terrigena NCTC 13098, R. terrigena NCTC 13097, and R. terrigena DSM 7331 have been isolated from different clinical and environmental sources, highlighting this bacterium’s diverse origins and potential virulence.
Raoultella terrigena pathogenesis entails its capacity to enter the human body via numerous routes and avoid the host’s immune system, resulting in colonization, invasion, & eventual tissue damage & inflammation. The bacterium may enter the body through skin or mucous membrane tears caused by traumatic injuries, catheterization, surgical procedures, or endoscopic interventions. It can also be consumed or inhaled from polluted sources such as soil, water, or food.
Once inside the host, R. terrigena uses a variety of virulence factors to attach to and infiltrate host cells or tissues. Surface proteins, including haemagglutinins, fimbriae, & pili, let the bacterium adhere to specific receptors on host cells, allowing it to colonize. This colonization can develop in various locations, including the urinary system, respiratory tract, blood arteries, and other susceptible areas.
R. terrigena employs protective factors, such as capsular polysaccharides, lipopolysaccharide, and siderophores, to evade the host immune system. These factors can hinder phagocytosis, complement-mediated killing, and iron deprivation by the host, helping the bacterium to survive and persist in the host’s tissues.
R. terrigena may release toxins, enzymes, or inflammatory mediators during infection, leading to tissue damage and inflammation. These virulence factors can cause tissue necrosis and abscess formation and activate the host’s immune response, leading to systemic inflammatory reactions. In severe cases, this could result in septic shock or systemic inflammatory response syndrome, posing a significant risk to the patient’s health.
To combat Raoultella terrigena infections, the immune system deploys several defense mechanisms. One crucial component is the complement system, a set of proteins that can be triggered through several pathways (classical, alternative, or lectin) to increase the immune response against the bacterium. R. terrigena is recognized by the complement system by attaching to its surface components, like lipopolysaccharide (LPS) or capsular polysaccharide (CPS). Complement components can also interact with antibodies specific to R. terrigena antigens, assisting in pathogen detection. Activation of the complement system causes opsonization, which promotes phagocyte attachment to the bacterium, inflammation to attract immune cells, and R. terrigena lysis.
Phagocytosis has significance in the elimination of R. terrigena from the body. This process is aided by specialized cells such as neutrophils, macrophages, & dendritic cells. Opsonins, such as antibodies or complement components, coat R. terrigena, making it easier for phagocytes to recognize it. Once engulfed, phagocytes can destroy the bacterium within the phagolysosome utilizing reactive oxygen species (ROS), reactive nitrogen species (RNS), & antimicrobial peptides, thereby neutralizing the pathogen.
B and T cells coordinate the adaptive immune response. B cells generate antibodies that attach to R. terrigena antigens, resulting in various results. Antibodies can neutralize the bacterium, stopping it from causing harm. They can also opsonize R. terrigena, making it more susceptible to immune cell phagocytosis. Antibodies can also stimulate the complement system, increasing the immunological response to R. terrigena. Furthermore, antibodies can engage additional immune cells to target and kill R. terrigena via a process known as antibody-dependent cellular cytotoxicity (ADCC).
T cells are classified as either helper T cells (Th) or cytotoxic T cells (Tc). Helper T cells generate cytokines that regulate the activation & differentiation of other immune cells, such as B cells & macrophages. This coordination aids in optimizing the immunological response to R. terrigena. Cytotoxic T cells specifically target and destroy R. terrigena-infected cells by producing perforin and granzymes, causing the infected cells to apoptose.
Culture method: Culture is the most popular and reliable approach for isolating and identifying the bacterium from diverse sources such as blood, urine, wound, respiratory tract, soil, or water samples for diagnosing Raoultella terrigena infections. Under aerobic conditions, R. terrigena can be cultivated on conventional mediums like Brain heart, blood, or MacConkey agar. R. terrigena, colonies on blood agar, are generally mucoid, smooth, convex, & cream-colored, but on MacConkey agar, they are lactose-fermenting & pink-colored.
Phenotypic identification: Another way to identify R. terrigena is to examine several aspects such as morphology, motility, Gram-staining, antigenic structure, or enzymatic activity. It can be accomplished by traditional tests like Gram staining, motility tests, oxidase testing, serotyping, or automated methods such as VITEK 2 or API 20E. However, because R. terrigena is like other Klebsiella species and Enterobacteriaceae, phenotypic identification may only sometimes be accurate or consistent.
Biochemical Tests: After isolation, various biochemical tests are performed to distinguish R. terrigena from other closely related Enterobacteriaceae. These tests include indole, ornithine decarboxylase, lysine decarboxylase, citrate utilization, oxidase, and other relevant tests that can help identify the bacterium based on its metabolic characteristics.
Housekeeping gene sequencing: It provides a more definitive and exact way of identifying and determining the phylogeny of R. terrigena. Housekeeping genes are necessary genes that participate in basic cellular activities and are conserved across species. Housekeeping genes for R. terrigena that are widely used for sequencing include rpoB (RNA polymerase beta subunit), gyrA (DNA gyrase subunit A), & parC (DNA topoisomerase IV subunit A). The identity of R. terrigena can be determined precisely by comparing the sequences of these housekeeping genes with reference sequences in databases.
Using excellent agricultural practices, food safety standards, water quality monitoring, management of waste, & disinfection technologies to reduce or eliminate R. terrigena sources and reservoirs in the environment, such as soil, water, or food.
To avoid R. terrigena transmission among patients and healthcare staff, stringent infection prevention and control measures should be used in hospital settings. Hand hygiene, using safety gear or PPE kits, proper disinfection of medical devices, and isolation precautions for infected or colonized patients.
Raoultella terrigena: Current state of knowledge, after two recently identified clinical cases in Eastern Europe – Lekhniuk – 2021 – Clinical Case Reports – Wiley Online Library
Raoultella terrigena’s epidemiology as a human pathogen is limited compared to other species in the genus Raoultella. However, data from case reports and retrospective investigations provide some insight into its incidence, sources of infection, risk factors, and antibiotic resistance patterns.
R. terrigena was concluded as the third most prevalent Raoultella species causing human infections in a 10-year retrospective investigation conducted in a tertiary-care hospital in Hungary, after R. planticola & R. ornithinolytica. The investigation found 11 cases of R. terrigena infection from 2007 to 2016, accounting for barely 0.01% of all clinical isolates. Urine (5 instances), blood (3 cases), & the respiratory tract (2 cases) were the most common sources of infection. Notably, most infected patients had underlying medical conditions, including diabetes, cancer, or chronic kidney disease. The mortality rate from R. terrigena infection was found to be 18.2%.
Case reports worldwide emphasize the clinical significance of R. terrigena infections in distinct patient populations. For example, a case report from Taiwan described a patient with liver cirrhosis who developed R. terrigena bacteremia following endoscopic retrograde cholangiopancreatography (ERCP). The patient’s excellent treatment with ceftriaxone and complete recovery shows a possible link between R. terrigena and ERCP-related infections.
Another case report from China described a patient with urinary tract abnormalities who were infected with R. terrigena via a carbapenem-resistant isolate containing the blaKPC-2 & blaSHV-12 genes. The necessity of antibiotic susceptibility testing and infection control strategies is emphasized in this paper, which highlights the evolution of antimicrobial resistance in R. terrigena strains.
A case report from Poland identified R. terrigena as a respiratory tract pathogen in a patient suffering from a pulmonary disorder who was admitted to the hospital for pneumonia. The patient’s effective treatment with meropenem & levofloxacin demonstrates that R. terrigena can cause respiratory infections in people with underlying lung problems.
Furthermore, a case report from Ukraine detailed a traumatic injury patient who acquired an R. terrigena wound infection after being admitted to the intensive care unit. After receiving prompt treatment with ceftriaxone & gentamicin, the patient recovered without complications, highlighting R. terrigena’s potential involvement as a wound pathogen in trauma patients.
Kingdom: Bacteria
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Enterobacterales
Family: Enterobacteriaceae
Genus: Raoultella
Species: Raoultella terrigena
Raoultella terrigena comprises a Gram-negative bacterium with a rod-shaped morphology (elongated & cylindrical cells). The bacteria are non-motile; it lacks flagella or other features that allow it to move independently.
R. terrigena cells can be 0.5 to 1.5 μm long and 0.3 to 0.7 μm wide.
Cells of R. terrigena may have a capsule, which is a slimy covering of polysaccharides or proteins that envelopes the bacterial cell wall.
The bacterium may also have pili or fimbriae, characterized by hair-like appendages on the bacterial surface that aid in adhesion to other surfaces.
Clinical manifestations:
Although the clinical symptoms of Raoultella terrigena diseases are not well-documented, there have been cases published in the medical literature. The bacterium has been linked to various diseases, particularly in patients with underlying health disorders or risk factors for infection.
Bacteremia, a bloodstream infection, is a common clinical symptom of R. terrigena infection. Bacteremia produced by this bacterium is common in people with impaired immune systems, like those with liver cirrhosis, diabetes, cancer, or immunosuppressive medication. In certain situations, the bacterium may enter the bloodstream from a localized infection site and propagate throughout the body, causing systemic symptoms & potentially severe problems.
Another significant symptom is urinary tract infection (UTI), common in individuals with indwelling catheters or urinary tract abnormalities. R. terrigena can enter the urinary tract through the catheter or take advantage of urinary tract anomalies, causing localized symptoms such as discomfort and burning during urination, repeated urination, and hematuria (blood in the urine).
Raoultella terrigena has also been linked to respiratory tract infections in people suffering from chronic obstructive pulmonary disorder (COPD) or cystic fibrosis. These people may get pneumonia or other respiratory infections, exhibiting symptoms such as coughing, shortness of breath, & fever.
Wound infections are seen in patients who have had traumatic injuries or have undergone surgical treatments. R. terrigena can colonize the wound site in these situations, causing local inflammation, redness, & pain.
R. terrigena has been related to ocular infections in rare cases, particularly in people who wear contact lenses or have had ocular trauma. This bacterium’s eye infections can produce symptoms such as redness, discomfort, discharge, & blurred vision.
Raoultella terrigena is a Gram-negative, rod-shaped bacterium with diverse characteristics contributing to its pathogenic potential. One study conducted by Izard in 1981 proposed a serotyping scheme for R. terrigena based on the O (somatic) and K (capsular) antigens. They identified 12 O antigens and 8 K antigens among 50 strains of R. terrigena isolated from soil and water samples. Interestingly, some of the O antigens were found to be shared with other Klebsiella species, such as Klebsiella pneumoniae and Klebsiella oxytoca. It suggests a possible cross-reactivity between Raoultella terrigena and other related bacteria.
Further studies analyzing the O antigen types using commercial antisera revealed that 14 belonged to O1, 3 to O2, 2 to O5, and 1 to O8 among the tested strains. Additionally, a PCR-based typing method detected K-antigen-encoding genes in the strains. Specifically, 11 strains carried the k2A gene, 4 carried the k2B gene, and 5 lacked K-antigen genes. This genetic diversity of K antigens may contribute to the bacterium’s pathogenicity and ability to evade the host’s immune response.
Raoultella terrigena has been shown to produce haemagglutinins like type 1 fimbriae & mannose-resistant haemagglutinin (MRHA). These virulence factors aid in colonizing and invading many bodily locations, including the urinary tract, respiratory tract, and blood vessels. Its propensity to cling to host tissues increases its ability to infect susceptible individuals, particularly those with underlying health disorders or impaired immune systems.
Another critical aspect of Raoultella terrigena’s pathogenicity is its ability to produce various beta-lactamases, including TEM-57, CTX-M-15, SHV-12, KPC-2, and NDM-1. Some beta-lactamases are classified as extended-spectrum beta-lactamases (ESBLs) or carbapenemases, which can efficiently degrade a wide range of beta-lactam antibiotics. This ability to produce antibiotic-resistance enzymes contributes to the challenge of treating infections caused by drug-resistant strains of R. terrigena, posing significant concerns for public health.
Several strains of Raoultella terrigena have been reported in the literature, each with unique characteristics and potential for pathogenicity. For example, the multidrug-resistant strain R. terrigena GODA, isolated from the blood of a patient with septic shock in Taiwan, carries the blaTEM-57 gene and multiple transporters related to drug efflux. Additionally, strains like R. terrigena NCTC 13098, R. terrigena NCTC 13097, and R. terrigena DSM 7331 have been isolated from different clinical and environmental sources, highlighting this bacterium’s diverse origins and potential virulence.
Raoultella terrigena pathogenesis entails its capacity to enter the human body via numerous routes and avoid the host’s immune system, resulting in colonization, invasion, & eventual tissue damage & inflammation. The bacterium may enter the body through skin or mucous membrane tears caused by traumatic injuries, catheterization, surgical procedures, or endoscopic interventions. It can also be consumed or inhaled from polluted sources such as soil, water, or food.
Once inside the host, R. terrigena uses a variety of virulence factors to attach to and infiltrate host cells or tissues. Surface proteins, including haemagglutinins, fimbriae, & pili, let the bacterium adhere to specific receptors on host cells, allowing it to colonize. This colonization can develop in various locations, including the urinary system, respiratory tract, blood arteries, and other susceptible areas.
R. terrigena employs protective factors, such as capsular polysaccharides, lipopolysaccharide, and siderophores, to evade the host immune system. These factors can hinder phagocytosis, complement-mediated killing, and iron deprivation by the host, helping the bacterium to survive and persist in the host’s tissues.
R. terrigena may release toxins, enzymes, or inflammatory mediators during infection, leading to tissue damage and inflammation. These virulence factors can cause tissue necrosis and abscess formation and activate the host’s immune response, leading to systemic inflammatory reactions. In severe cases, this could result in septic shock or systemic inflammatory response syndrome, posing a significant risk to the patient’s health.
To combat Raoultella terrigena infections, the immune system deploys several defense mechanisms. One crucial component is the complement system, a set of proteins that can be triggered through several pathways (classical, alternative, or lectin) to increase the immune response against the bacterium. R. terrigena is recognized by the complement system by attaching to its surface components, like lipopolysaccharide (LPS) or capsular polysaccharide (CPS). Complement components can also interact with antibodies specific to R. terrigena antigens, assisting in pathogen detection. Activation of the complement system causes opsonization, which promotes phagocyte attachment to the bacterium, inflammation to attract immune cells, and R. terrigena lysis.
Phagocytosis has significance in the elimination of R. terrigena from the body. This process is aided by specialized cells such as neutrophils, macrophages, & dendritic cells. Opsonins, such as antibodies or complement components, coat R. terrigena, making it easier for phagocytes to recognize it. Once engulfed, phagocytes can destroy the bacterium within the phagolysosome utilizing reactive oxygen species (ROS), reactive nitrogen species (RNS), & antimicrobial peptides, thereby neutralizing the pathogen.
B and T cells coordinate the adaptive immune response. B cells generate antibodies that attach to R. terrigena antigens, resulting in various results. Antibodies can neutralize the bacterium, stopping it from causing harm. They can also opsonize R. terrigena, making it more susceptible to immune cell phagocytosis. Antibodies can also stimulate the complement system, increasing the immunological response to R. terrigena. Furthermore, antibodies can engage additional immune cells to target and kill R. terrigena via a process known as antibody-dependent cellular cytotoxicity (ADCC).
T cells are classified as either helper T cells (Th) or cytotoxic T cells (Tc). Helper T cells generate cytokines that regulate the activation & differentiation of other immune cells, such as B cells & macrophages. This coordination aids in optimizing the immunological response to R. terrigena. Cytotoxic T cells specifically target and destroy R. terrigena-infected cells by producing perforin and granzymes, causing the infected cells to apoptose.
Culture method: Culture is the most popular and reliable approach for isolating and identifying the bacterium from diverse sources such as blood, urine, wound, respiratory tract, soil, or water samples for diagnosing Raoultella terrigena infections. Under aerobic conditions, R. terrigena can be cultivated on conventional mediums like Brain heart, blood, or MacConkey agar. R. terrigena, colonies on blood agar, are generally mucoid, smooth, convex, & cream-colored, but on MacConkey agar, they are lactose-fermenting & pink-colored.
Phenotypic identification: Another way to identify R. terrigena is to examine several aspects such as morphology, motility, Gram-staining, antigenic structure, or enzymatic activity. It can be accomplished by traditional tests like Gram staining, motility tests, oxidase testing, serotyping, or automated methods such as VITEK 2 or API 20E. However, because R. terrigena is like other Klebsiella species and Enterobacteriaceae, phenotypic identification may only sometimes be accurate or consistent.
Biochemical Tests: After isolation, various biochemical tests are performed to distinguish R. terrigena from other closely related Enterobacteriaceae. These tests include indole, ornithine decarboxylase, lysine decarboxylase, citrate utilization, oxidase, and other relevant tests that can help identify the bacterium based on its metabolic characteristics.
Housekeeping gene sequencing: It provides a more definitive and exact way of identifying and determining the phylogeny of R. terrigena. Housekeeping genes are necessary genes that participate in basic cellular activities and are conserved across species. Housekeeping genes for R. terrigena that are widely used for sequencing include rpoB (RNA polymerase beta subunit), gyrA (DNA gyrase subunit A), & parC (DNA topoisomerase IV subunit A). The identity of R. terrigena can be determined precisely by comparing the sequences of these housekeeping genes with reference sequences in databases.
Using excellent agricultural practices, food safety standards, water quality monitoring, management of waste, & disinfection technologies to reduce or eliminate R. terrigena sources and reservoirs in the environment, such as soil, water, or food.
To avoid R. terrigena transmission among patients and healthcare staff, stringent infection prevention and control measures should be used in hospital settings. Hand hygiene, using safety gear or PPE kits, proper disinfection of medical devices, and isolation precautions for infected or colonized patients.
Raoultella terrigena: Current state of knowledge, after two recently identified clinical cases in Eastern Europe – Lekhniuk – 2021 – Clinical Case Reports – Wiley Online Library
Raoultella terrigena’s epidemiology as a human pathogen is limited compared to other species in the genus Raoultella. However, data from case reports and retrospective investigations provide some insight into its incidence, sources of infection, risk factors, and antibiotic resistance patterns.
R. terrigena was concluded as the third most prevalent Raoultella species causing human infections in a 10-year retrospective investigation conducted in a tertiary-care hospital in Hungary, after R. planticola & R. ornithinolytica. The investigation found 11 cases of R. terrigena infection from 2007 to 2016, accounting for barely 0.01% of all clinical isolates. Urine (5 instances), blood (3 cases), & the respiratory tract (2 cases) were the most common sources of infection. Notably, most infected patients had underlying medical conditions, including diabetes, cancer, or chronic kidney disease. The mortality rate from R. terrigena infection was found to be 18.2%.
Case reports worldwide emphasize the clinical significance of R. terrigena infections in distinct patient populations. For example, a case report from Taiwan described a patient with liver cirrhosis who developed R. terrigena bacteremia following endoscopic retrograde cholangiopancreatography (ERCP). The patient’s excellent treatment with ceftriaxone and complete recovery shows a possible link between R. terrigena and ERCP-related infections.
Another case report from China described a patient with urinary tract abnormalities who were infected with R. terrigena via a carbapenem-resistant isolate containing the blaKPC-2 & blaSHV-12 genes. The necessity of antibiotic susceptibility testing and infection control strategies is emphasized in this paper, which highlights the evolution of antimicrobial resistance in R. terrigena strains.
A case report from Poland identified R. terrigena as a respiratory tract pathogen in a patient suffering from a pulmonary disorder who was admitted to the hospital for pneumonia. The patient’s effective treatment with meropenem & levofloxacin demonstrates that R. terrigena can cause respiratory infections in people with underlying lung problems.
Furthermore, a case report from Ukraine detailed a traumatic injury patient who acquired an R. terrigena wound infection after being admitted to the intensive care unit. After receiving prompt treatment with ceftriaxone & gentamicin, the patient recovered without complications, highlighting R. terrigena’s potential involvement as a wound pathogen in trauma patients.
Kingdom: Bacteria
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Enterobacterales
Family: Enterobacteriaceae
Genus: Raoultella
Species: Raoultella terrigena
Raoultella terrigena comprises a Gram-negative bacterium with a rod-shaped morphology (elongated & cylindrical cells). The bacteria are non-motile; it lacks flagella or other features that allow it to move independently.
R. terrigena cells can be 0.5 to 1.5 μm long and 0.3 to 0.7 μm wide.
Cells of R. terrigena may have a capsule, which is a slimy covering of polysaccharides or proteins that envelopes the bacterial cell wall.
The bacterium may also have pili or fimbriae, characterized by hair-like appendages on the bacterial surface that aid in adhesion to other surfaces.
Clinical manifestations:
Although the clinical symptoms of Raoultella terrigena diseases are not well-documented, there have been cases published in the medical literature. The bacterium has been linked to various diseases, particularly in patients with underlying health disorders or risk factors for infection.
Bacteremia, a bloodstream infection, is a common clinical symptom of R. terrigena infection. Bacteremia produced by this bacterium is common in people with impaired immune systems, like those with liver cirrhosis, diabetes, cancer, or immunosuppressive medication. In certain situations, the bacterium may enter the bloodstream from a localized infection site and propagate throughout the body, causing systemic symptoms & potentially severe problems.
Another significant symptom is urinary tract infection (UTI), common in individuals with indwelling catheters or urinary tract abnormalities. R. terrigena can enter the urinary tract through the catheter or take advantage of urinary tract anomalies, causing localized symptoms such as discomfort and burning during urination, repeated urination, and hematuria (blood in the urine).
Raoultella terrigena has also been linked to respiratory tract infections in people suffering from chronic obstructive pulmonary disorder (COPD) or cystic fibrosis. These people may get pneumonia or other respiratory infections, exhibiting symptoms such as coughing, shortness of breath, & fever.
Wound infections are seen in patients who have had traumatic injuries or have undergone surgical treatments. R. terrigena can colonize the wound site in these situations, causing local inflammation, redness, & pain.
R. terrigena has been related to ocular infections in rare cases, particularly in people who wear contact lenses or have had ocular trauma. This bacterium’s eye infections can produce symptoms such as redness, discomfort, discharge, & blurred vision.
Raoultella terrigena is a Gram-negative, rod-shaped bacterium with diverse characteristics contributing to its pathogenic potential. One study conducted by Izard in 1981 proposed a serotyping scheme for R. terrigena based on the O (somatic) and K (capsular) antigens. They identified 12 O antigens and 8 K antigens among 50 strains of R. terrigena isolated from soil and water samples. Interestingly, some of the O antigens were found to be shared with other Klebsiella species, such as Klebsiella pneumoniae and Klebsiella oxytoca. It suggests a possible cross-reactivity between Raoultella terrigena and other related bacteria.
Further studies analyzing the O antigen types using commercial antisera revealed that 14 belonged to O1, 3 to O2, 2 to O5, and 1 to O8 among the tested strains. Additionally, a PCR-based typing method detected K-antigen-encoding genes in the strains. Specifically, 11 strains carried the k2A gene, 4 carried the k2B gene, and 5 lacked K-antigen genes. This genetic diversity of K antigens may contribute to the bacterium’s pathogenicity and ability to evade the host’s immune response.
Raoultella terrigena has been shown to produce haemagglutinins like type 1 fimbriae & mannose-resistant haemagglutinin (MRHA). These virulence factors aid in colonizing and invading many bodily locations, including the urinary tract, respiratory tract, and blood vessels. Its propensity to cling to host tissues increases its ability to infect susceptible individuals, particularly those with underlying health disorders or impaired immune systems.
Another critical aspect of Raoultella terrigena’s pathogenicity is its ability to produce various beta-lactamases, including TEM-57, CTX-M-15, SHV-12, KPC-2, and NDM-1. Some beta-lactamases are classified as extended-spectrum beta-lactamases (ESBLs) or carbapenemases, which can efficiently degrade a wide range of beta-lactam antibiotics. This ability to produce antibiotic-resistance enzymes contributes to the challenge of treating infections caused by drug-resistant strains of R. terrigena, posing significant concerns for public health.
Several strains of Raoultella terrigena have been reported in the literature, each with unique characteristics and potential for pathogenicity. For example, the multidrug-resistant strain R. terrigena GODA, isolated from the blood of a patient with septic shock in Taiwan, carries the blaTEM-57 gene and multiple transporters related to drug efflux. Additionally, strains like R. terrigena NCTC 13098, R. terrigena NCTC 13097, and R. terrigena DSM 7331 have been isolated from different clinical and environmental sources, highlighting this bacterium’s diverse origins and potential virulence.
Raoultella terrigena pathogenesis entails its capacity to enter the human body via numerous routes and avoid the host’s immune system, resulting in colonization, invasion, & eventual tissue damage & inflammation. The bacterium may enter the body through skin or mucous membrane tears caused by traumatic injuries, catheterization, surgical procedures, or endoscopic interventions. It can also be consumed or inhaled from polluted sources such as soil, water, or food.
Once inside the host, R. terrigena uses a variety of virulence factors to attach to and infiltrate host cells or tissues. Surface proteins, including haemagglutinins, fimbriae, & pili, let the bacterium adhere to specific receptors on host cells, allowing it to colonize. This colonization can develop in various locations, including the urinary system, respiratory tract, blood arteries, and other susceptible areas.
R. terrigena employs protective factors, such as capsular polysaccharides, lipopolysaccharide, and siderophores, to evade the host immune system. These factors can hinder phagocytosis, complement-mediated killing, and iron deprivation by the host, helping the bacterium to survive and persist in the host’s tissues.
R. terrigena may release toxins, enzymes, or inflammatory mediators during infection, leading to tissue damage and inflammation. These virulence factors can cause tissue necrosis and abscess formation and activate the host’s immune response, leading to systemic inflammatory reactions. In severe cases, this could result in septic shock or systemic inflammatory response syndrome, posing a significant risk to the patient’s health.
To combat Raoultella terrigena infections, the immune system deploys several defense mechanisms. One crucial component is the complement system, a set of proteins that can be triggered through several pathways (classical, alternative, or lectin) to increase the immune response against the bacterium. R. terrigena is recognized by the complement system by attaching to its surface components, like lipopolysaccharide (LPS) or capsular polysaccharide (CPS). Complement components can also interact with antibodies specific to R. terrigena antigens, assisting in pathogen detection. Activation of the complement system causes opsonization, which promotes phagocyte attachment to the bacterium, inflammation to attract immune cells, and R. terrigena lysis.
Phagocytosis has significance in the elimination of R. terrigena from the body. This process is aided by specialized cells such as neutrophils, macrophages, & dendritic cells. Opsonins, such as antibodies or complement components, coat R. terrigena, making it easier for phagocytes to recognize it. Once engulfed, phagocytes can destroy the bacterium within the phagolysosome utilizing reactive oxygen species (ROS), reactive nitrogen species (RNS), & antimicrobial peptides, thereby neutralizing the pathogen.
B and T cells coordinate the adaptive immune response. B cells generate antibodies that attach to R. terrigena antigens, resulting in various results. Antibodies can neutralize the bacterium, stopping it from causing harm. They can also opsonize R. terrigena, making it more susceptible to immune cell phagocytosis. Antibodies can also stimulate the complement system, increasing the immunological response to R. terrigena. Furthermore, antibodies can engage additional immune cells to target and kill R. terrigena via a process known as antibody-dependent cellular cytotoxicity (ADCC).
T cells are classified as either helper T cells (Th) or cytotoxic T cells (Tc). Helper T cells generate cytokines that regulate the activation & differentiation of other immune cells, such as B cells & macrophages. This coordination aids in optimizing the immunological response to R. terrigena. Cytotoxic T cells specifically target and destroy R. terrigena-infected cells by producing perforin and granzymes, causing the infected cells to apoptose.
Culture method: Culture is the most popular and reliable approach for isolating and identifying the bacterium from diverse sources such as blood, urine, wound, respiratory tract, soil, or water samples for diagnosing Raoultella terrigena infections. Under aerobic conditions, R. terrigena can be cultivated on conventional mediums like Brain heart, blood, or MacConkey agar. R. terrigena, colonies on blood agar, are generally mucoid, smooth, convex, & cream-colored, but on MacConkey agar, they are lactose-fermenting & pink-colored.
Phenotypic identification: Another way to identify R. terrigena is to examine several aspects such as morphology, motility, Gram-staining, antigenic structure, or enzymatic activity. It can be accomplished by traditional tests like Gram staining, motility tests, oxidase testing, serotyping, or automated methods such as VITEK 2 or API 20E. However, because R. terrigena is like other Klebsiella species and Enterobacteriaceae, phenotypic identification may only sometimes be accurate or consistent.
Biochemical Tests: After isolation, various biochemical tests are performed to distinguish R. terrigena from other closely related Enterobacteriaceae. These tests include indole, ornithine decarboxylase, lysine decarboxylase, citrate utilization, oxidase, and other relevant tests that can help identify the bacterium based on its metabolic characteristics.
Housekeeping gene sequencing: It provides a more definitive and exact way of identifying and determining the phylogeny of R. terrigena. Housekeeping genes are necessary genes that participate in basic cellular activities and are conserved across species. Housekeeping genes for R. terrigena that are widely used for sequencing include rpoB (RNA polymerase beta subunit), gyrA (DNA gyrase subunit A), & parC (DNA topoisomerase IV subunit A). The identity of R. terrigena can be determined precisely by comparing the sequences of these housekeeping genes with reference sequences in databases.
Using excellent agricultural practices, food safety standards, water quality monitoring, management of waste, & disinfection technologies to reduce or eliminate R. terrigena sources and reservoirs in the environment, such as soil, water, or food.
To avoid R. terrigena transmission among patients and healthcare staff, stringent infection prevention and control measures should be used in hospital settings. Hand hygiene, using safety gear or PPE kits, proper disinfection of medical devices, and isolation precautions for infected or colonized patients.
Raoultella terrigena: Current state of knowledge, after two recently identified clinical cases in Eastern Europe – Lekhniuk – 2021 – Clinical Case Reports – Wiley Online Library
Raoultella – an overview | ScienceDirect Topics
Loading...
Free CME credits
Both our subscription plans include Free CME/CPD AMA PRA Category 1 credits.
Digital Certificate PDF
On course completion, you will receive a full-sized presentation quality digital certificate.
medtigo Simulation
A dynamic medical simulation platform designed to train healthcare professionals and students to effectively run code situations through an immersive hands-on experience in a live, interactive 3D environment.
medtigo Points
medtigo points is our unique point redemption system created to award users for interacting on our site. These points can be redeemed for special discounts on the medtigo marketplace as well as towards the membership cost itself.
Community Forum post/reply = 5 points
*Redemption of points can occur only through the medtigo marketplace, courses, or simulation system. Money will not be credited to your bank account. 10 points = $1.
All Your Certificates in One Place
When you have your licenses, certificates and CMEs in one place, it's easier to track your career growth. You can easily share these with hospitals as well, using your medtigo app.
