Sarocladium kiliense is a soil saprophytic mold with a global distribution, and it sporadically infects humans and other mammals. Initially, it was named Acremonium kiliense by Grutz in 1925. However, in 1971, Walter Gams retained the name A. kiliense to describe fungi frequently found in soil associated with skin infections. The first documented case of human infection by S. kiliense dates back to 1925 when a German soldier developed a mycetoma in his foot after a wound sustained in East Africa.
Since then, numerous cases of S. kiliense infection have been reported from various regions worldwide, including Africa, Asia, Europe, North America, and South America. S. kiliense has been primarily recognized as a human opportunistic pathogen, with infections more prevalent in tropical countries. However, in immunocompetent individuals, the pathogenicity of S. kiliense is very low.
In epidemiological studies, S. kiliense accounted for a small percentage of fungal isolates. For instance, from 1999 to 2008, it represented 0.4% of all fungal isolates and 2.7% of all Acremonium-like isolates. Another study conducted in India from 2004 to 2013 found that S. kiliense accounted for 0.6% of all fungal isolates and 4.4% of all Acremonium-like isolates. Notably, a multinational outbreak of S. kiliense bloodstream infections (BSI) occurred in 2013–2014.
This outbreak was associated with the receipt of contaminated antinausea medication among oncology patients in Colombia and Chile. It involved 18 patients and 7 medication vials and was traced to a single-point source using whole-genome sequence typing. These findings illustrate the sporadic nature of S. kiliense infections and highlight the need for vigilance in healthcare settings, particularly regarding medication safety and contamination control.
Classification and Structure:
Kingdom: Fungi
Phylum: Ascomycota
Class: Sordariomycetes
Order: Hypocreales
Genus: Sarocladium
Species:S. kiliense
The structure of Sarocladium kiliense is characterized by specific microscopic features:
Phialides: These are slender, slightly tapering structures that emerge from hyphae or conidiophores. Phialides of S. kiliense are long and straight and arise as side branches on hyphae, measuring 20-65 x 1.4-2.5 μm.
Conidiophores: Conidiophores are the structures from which conidia (asexual spores) are produced. In S. kiliense, they are long and straight with slightly tapering phialides, arising as side branches on hyphae.
Conidia: The conidia of S. kiliense are grouped in slimy heads, appearing cylindrical or ellipsoidal, measuring 3.3-5.5 x 0.9-1.8 μm. They are hyaline and accumulate at the ends of the phialides in ball-like clusters of ellipsoidal shape, measuring 3-6 x 1.5 mm.
Chlamydospores: Chlamydospores of S. kiliense are oval, uncolored structures with chromophilic walls. They measure approximately 4-8 μm in diameter and are formed either on the ends of hyphae or interspersed within filaments.
Sarocladium kiliense exhibits a range of intriguing characteristics that are worth noting. Firstly, it can produce antigens that are recognized by the host’s antibodies, including mannan and galactomannan, which can be valuable for diagnosing infections caused by this fungus. Furthermore, S. kiliense is known to produce toxins with diverse properties.
Saroclazines A-C, for instance, are cytotoxic toxins capable of exerting cell-killing effects on various cancer cell lines. Another toxin, Sarocladiumin, displays neurotoxic activity and can induce paralysis in experimental mice, underscoring its potential impact on the nervous system.
Additionally, this fungus is equipped with a repertoire of enzymes with distinct functions. L-asparaginase is an enzyme produced by S. kiliense, capable of breaking down the amino acid L-asparagine, which is crucial for the growth of certain cancer cells. The fungus also generates alkaline protease and amylase enzymes, which can efficiently break down proteins and starches, respectively, and find applications in various industrial processes.
Notably, Sarocladium kiliense possesses manganese oxidase, anenzyme that can oxidize manganese in the soil, affecting the availability of nutrients and metals for plants and microorganisms. This enzyme’s role in soil ecology can be significant.Moreover, S. kiliense was previously classified within the genus Acremonium and has been observed to have the capacity to degrade different polysaccharides.
This includes the degradation of polysaccharides like pectin, carboxymethyl cellulose, and xylans, with a particular emphasis on starch degradation for S. kiliense. Notably, A xylanolytic and cellulolytic strain CTGxxyl isolated from the gut of a termite- Reticulitermes santonensis, is documented.
Sarocladium kiliense primarily enters the human body through traumatic inoculation into the skin or subcutaneous tissues, which often results in mycetoma or onychomycosis. This traumatic entry can disrupt local immune defenses, making it easier for the fungus to establish infection. Infection typically occurs through penetrating injuries or open wounds exposed to the fungus.
Notably, S. kiliense‘s ability to undergo melanogenesis, a process that results in the production of melanin, plays a role in infections, particularly mycetoma.In immunocompetent individuals, S. kiliense infections tend to be less severe. However, in immunocompromised patients, severe systemicinfections may develop, potentially leading to conditions like peritonitis.
Studies have observed S. kiliense invading the lungs, evidenced by narrow septate hyphae, cylindrical conidia, and other characteristic features. This fungus can also affect the upper respiratory tract mucosa, sinuses, and conjunctiva.S. kiliense stands out among Sarocladium species due to its ability to produce melanin, a dark pigment that protects against environmental stress and host immune responses.
Melanin production enhances the fungus’s adhesion and invasion into host tissues and modulates inflammatory and oxidative reactions. This attribute has been associated with increased virulence and resistance to antifungal drugs. S. kiliense exhibits variable susceptibility to different antifungal agents, with some isolates showing resistance to commonly used drugs like amphotericin B, itraconazole, and caspofungin.
Human host defenses against Sarocladium kiliense infection primarily involve innate and adaptive immune responses. Phagocytes, including neutrophils, macrophages, and dendritic cells, play a crucial role in engulfing and eliminating the fungus through mechanisms such as oxidative and non-oxidative killing, autophagy, and the formation of extracellular traps.
These defense mechanisms not only combat the pathogen but also recruit other immune cells to the infection site via the production of cytokines & chemokines.In addition to phagocytes, T cells, including Th2, Th17, and Treg cells, contribute to the host’s defense. Th2 cells produce interleukin-4, interleukin-5, and interleukin-13, stimulating antibody production and the activation of eosinophils and mast cells.
Th17 cells, on the other hand, produce interleukin-17, interleukin-21, and interleukin-22, leading to the expression of antimicrobial peptides & the recruitment of neutrophils and monocytes. Treg cells, which produce interleukin-10 and transforming growth factor-beta, act to suppress inflammatory and immune responses, maintaining immune balance.
Furthermore, other immune cells, such as eosinophils, mast cells, basophils, gamma-delta T cells, NKT cells, and B-1 cells, also contribute to the defense against Sarocladium kiliense by producing various mediators and interacting with other immune cells. This intricate network of immune responses collectively combats the fungal infection and maintains host health.
Sarocladium kiliense is associated with a spectrum of clinical manifestations, each stemming from different modes of infection and affecting various parts of the body:
Mycetoma: One of the most common presentations of Sarocladium kiliense infection is mycetoma. This chronic granulomatous infection predominantly affects the skin and subcutaneous tissues. It is characterized by distinctive features such as swelling, the presence of draining sinuses, and the formation of fungal grains. Mycetoma typically occurs following the traumatic inoculation of the fungus into the skin.
Onychomycosis:Sarocladium kiliense can also cause onychomycosis, a fungal infection of the nails. This condition results in visible symptoms like nail discoloration, thickening, and brittleness. Onychomycosis may extend to the surrounding skin, leading to pain and inflammation in the affected area.
Keratomycosis: In some cases, Sarocladium kiliense can lead to keratomycosis, a fungal infection of the cornea, the transparent layer of the eye. This condition is characterized by symptoms such as eye redness, pain, blurred vision, and the development of ulcers on the cornea. Keratomycosis may occur through direct contact of the eye with the fungus, often linked to contaminated contact lenses or eye trauma.
Endophthalmitis and Pneumonia: In more severe instances, Sarocladium kiliense can give rise to endophthalmitis, a severe infection of the inner eye involving the vitreous humor and the retina. This condition manifests with symptoms including vision loss, eye pain, swelling, and discharge. Endophthalmitis may develop as a complication of keratomycosis or through the hematogenous spread of the fungus from other sites of infection.
Furthermore, S. kiliense can lead to pneumonia, a lung infection causing inflammation, and the accumulation of fluid in the air sacs. Pneumonia is marked by symptoms like cough, fever, chest pain, and difficulty breathing and can occur through inhalation of the fungus or dissemination from other sites of infection.
Culture test: This is the most definitive diagnostic method, involving the growth of the fungus on various media like glucose peptone agar, sabouraud dextrose agar (SDA), or oatmeal agar. Characteristics such as colony morphology, color, and microscopic features are observed. For instance, on glucose peptone agar, S. kiliense colonies can reach up to 50 mm in diameter and have a flat, grey-to-orange coloration. On SDA, colonies are initially white and later turn pink. Oatmeal agar may produce colonies with poorly differentiated phialides and single-celled, thick-walled chlamydospores. Additionally, culture allows for antifungal susceptibility testing to guide treatment.
Microscopy: Microscopy is a rapid diagnostic test used to detect the presence of S. kiliense in tissue samples or fungal grains. Stains like potassium hydroxide (KOH), periodic acid-Schiff (PAS), or Grocott-Gomori methenamine silver (GMS) are employed to visualize typical conidiophores, conidia, and chlamydospores.
Molecular Methods: Molecular techniques, such as polymerase chain reaction, are sensitive & specific tests that identify S. kiliense by amplifying and detecting its DNA or RNA in clinical specimens like blood, tissue, or joint fluid. These methods are not only used for identification but can also perform genotyping or whole-genome sequencing to determine the strain or source of the infection.
Individuals should avoid or minimize contact with soil or contaminated materials that may harbor the fungus, particularly if they have a history of trauma, immunosuppression, or chronic diseases.
In healthcare settings, using sterile or disposable medical devices, such as catheters, needles, syringes, and implants, is crucial. Following proper infection control practices is necessary to prevent nosocomial infections.
Regular surveillance and screening of clinical specimens and environmental samples for S. kiliense using culture, microscopy, or molecular methods can aid in the early detection and monitoring of the fungus’s presence.
Performing antifungal susceptibility testing for S. kiliense isolates is crucial. This allows healthcare professionals to choose the most effective and safe antifungal regimen based on individualized results, improving treatment outcomes.
Sarocladium kiliense is a soil saprophytic mold with a global distribution, and it sporadically infects humans and other mammals. Initially, it was named Acremonium kiliense by Grutz in 1925. However, in 1971, Walter Gams retained the name A. kiliense to describe fungi frequently found in soil associated with skin infections. The first documented case of human infection by S. kiliense dates back to 1925 when a German soldier developed a mycetoma in his foot after a wound sustained in East Africa.
Since then, numerous cases of S. kiliense infection have been reported from various regions worldwide, including Africa, Asia, Europe, North America, and South America. S. kiliense has been primarily recognized as a human opportunistic pathogen, with infections more prevalent in tropical countries. However, in immunocompetent individuals, the pathogenicity of S. kiliense is very low.
In epidemiological studies, S. kiliense accounted for a small percentage of fungal isolates. For instance, from 1999 to 2008, it represented 0.4% of all fungal isolates and 2.7% of all Acremonium-like isolates. Another study conducted in India from 2004 to 2013 found that S. kiliense accounted for 0.6% of all fungal isolates and 4.4% of all Acremonium-like isolates. Notably, a multinational outbreak of S. kiliense bloodstream infections (BSI) occurred in 2013–2014.
This outbreak was associated with the receipt of contaminated antinausea medication among oncology patients in Colombia and Chile. It involved 18 patients and 7 medication vials and was traced to a single-point source using whole-genome sequence typing. These findings illustrate the sporadic nature of S. kiliense infections and highlight the need for vigilance in healthcare settings, particularly regarding medication safety and contamination control.
Classification and Structure:
Kingdom: Fungi
Phylum: Ascomycota
Class: Sordariomycetes
Order: Hypocreales
Genus: Sarocladium
Species:S. kiliense
The structure of Sarocladium kiliense is characterized by specific microscopic features:
Phialides: These are slender, slightly tapering structures that emerge from hyphae or conidiophores. Phialides of S. kiliense are long and straight and arise as side branches on hyphae, measuring 20-65 x 1.4-2.5 μm.
Conidiophores: Conidiophores are the structures from which conidia (asexual spores) are produced. In S. kiliense, they are long and straight with slightly tapering phialides, arising as side branches on hyphae.
Conidia: The conidia of S. kiliense are grouped in slimy heads, appearing cylindrical or ellipsoidal, measuring 3.3-5.5 x 0.9-1.8 μm. They are hyaline and accumulate at the ends of the phialides in ball-like clusters of ellipsoidal shape, measuring 3-6 x 1.5 mm.
Chlamydospores: Chlamydospores of S. kiliense are oval, uncolored structures with chromophilic walls. They measure approximately 4-8 μm in diameter and are formed either on the ends of hyphae or interspersed within filaments.
Sarocladium kiliense exhibits a range of intriguing characteristics that are worth noting. Firstly, it can produce antigens that are recognized by the host’s antibodies, including mannan and galactomannan, which can be valuable for diagnosing infections caused by this fungus. Furthermore, S. kiliense is known to produce toxins with diverse properties.
Saroclazines A-C, for instance, are cytotoxic toxins capable of exerting cell-killing effects on various cancer cell lines. Another toxin, Sarocladiumin, displays neurotoxic activity and can induce paralysis in experimental mice, underscoring its potential impact on the nervous system.
Additionally, this fungus is equipped with a repertoire of enzymes with distinct functions. L-asparaginase is an enzyme produced by S. kiliense, capable of breaking down the amino acid L-asparagine, which is crucial for the growth of certain cancer cells. The fungus also generates alkaline protease and amylase enzymes, which can efficiently break down proteins and starches, respectively, and find applications in various industrial processes.
Notably, Sarocladium kiliense possesses manganese oxidase, anenzyme that can oxidize manganese in the soil, affecting the availability of nutrients and metals for plants and microorganisms. This enzyme’s role in soil ecology can be significant.Moreover, S. kiliense was previously classified within the genus Acremonium and has been observed to have the capacity to degrade different polysaccharides.
This includes the degradation of polysaccharides like pectin, carboxymethyl cellulose, and xylans, with a particular emphasis on starch degradation for S. kiliense. Notably, A xylanolytic and cellulolytic strain CTGxxyl isolated from the gut of a termite- Reticulitermes santonensis, is documented.
Sarocladium kiliense primarily enters the human body through traumatic inoculation into the skin or subcutaneous tissues, which often results in mycetoma or onychomycosis. This traumatic entry can disrupt local immune defenses, making it easier for the fungus to establish infection. Infection typically occurs through penetrating injuries or open wounds exposed to the fungus.
Notably, S. kiliense‘s ability to undergo melanogenesis, a process that results in the production of melanin, plays a role in infections, particularly mycetoma.In immunocompetent individuals, S. kiliense infections tend to be less severe. However, in immunocompromised patients, severe systemicinfections may develop, potentially leading to conditions like peritonitis.
Studies have observed S. kiliense invading the lungs, evidenced by narrow septate hyphae, cylindrical conidia, and other characteristic features. This fungus can also affect the upper respiratory tract mucosa, sinuses, and conjunctiva.S. kiliense stands out among Sarocladium species due to its ability to produce melanin, a dark pigment that protects against environmental stress and host immune responses.
Melanin production enhances the fungus’s adhesion and invasion into host tissues and modulates inflammatory and oxidative reactions. This attribute has been associated with increased virulence and resistance to antifungal drugs. S. kiliense exhibits variable susceptibility to different antifungal agents, with some isolates showing resistance to commonly used drugs like amphotericin B, itraconazole, and caspofungin.
Human host defenses against Sarocladium kiliense infection primarily involve innate and adaptive immune responses. Phagocytes, including neutrophils, macrophages, and dendritic cells, play a crucial role in engulfing and eliminating the fungus through mechanisms such as oxidative and non-oxidative killing, autophagy, and the formation of extracellular traps.
These defense mechanisms not only combat the pathogen but also recruit other immune cells to the infection site via the production of cytokines & chemokines.In addition to phagocytes, T cells, including Th2, Th17, and Treg cells, contribute to the host’s defense. Th2 cells produce interleukin-4, interleukin-5, and interleukin-13, stimulating antibody production and the activation of eosinophils and mast cells.
Th17 cells, on the other hand, produce interleukin-17, interleukin-21, and interleukin-22, leading to the expression of antimicrobial peptides & the recruitment of neutrophils and monocytes. Treg cells, which produce interleukin-10 and transforming growth factor-beta, act to suppress inflammatory and immune responses, maintaining immune balance.
Furthermore, other immune cells, such as eosinophils, mast cells, basophils, gamma-delta T cells, NKT cells, and B-1 cells, also contribute to the defense against Sarocladium kiliense by producing various mediators and interacting with other immune cells. This intricate network of immune responses collectively combats the fungal infection and maintains host health.
Sarocladium kiliense is associated with a spectrum of clinical manifestations, each stemming from different modes of infection and affecting various parts of the body:
Mycetoma: One of the most common presentations of Sarocladium kiliense infection is mycetoma. This chronic granulomatous infection predominantly affects the skin and subcutaneous tissues. It is characterized by distinctive features such as swelling, the presence of draining sinuses, and the formation of fungal grains. Mycetoma typically occurs following the traumatic inoculation of the fungus into the skin.
Onychomycosis:Sarocladium kiliense can also cause onychomycosis, a fungal infection of the nails. This condition results in visible symptoms like nail discoloration, thickening, and brittleness. Onychomycosis may extend to the surrounding skin, leading to pain and inflammation in the affected area.
Keratomycosis: In some cases, Sarocladium kiliense can lead to keratomycosis, a fungal infection of the cornea, the transparent layer of the eye. This condition is characterized by symptoms such as eye redness, pain, blurred vision, and the development of ulcers on the cornea. Keratomycosis may occur through direct contact of the eye with the fungus, often linked to contaminated contact lenses or eye trauma.
Endophthalmitis and Pneumonia: In more severe instances, Sarocladium kiliense can give rise to endophthalmitis, a severe infection of the inner eye involving the vitreous humor and the retina. This condition manifests with symptoms including vision loss, eye pain, swelling, and discharge. Endophthalmitis may develop as a complication of keratomycosis or through the hematogenous spread of the fungus from other sites of infection.
Furthermore, S. kiliense can lead to pneumonia, a lung infection causing inflammation, and the accumulation of fluid in the air sacs. Pneumonia is marked by symptoms like cough, fever, chest pain, and difficulty breathing and can occur through inhalation of the fungus or dissemination from other sites of infection.
Culture test: This is the most definitive diagnostic method, involving the growth of the fungus on various media like glucose peptone agar, sabouraud dextrose agar (SDA), or oatmeal agar. Characteristics such as colony morphology, color, and microscopic features are observed. For instance, on glucose peptone agar, S. kiliense colonies can reach up to 50 mm in diameter and have a flat, grey-to-orange coloration. On SDA, colonies are initially white and later turn pink. Oatmeal agar may produce colonies with poorly differentiated phialides and single-celled, thick-walled chlamydospores. Additionally, culture allows for antifungal susceptibility testing to guide treatment.
Microscopy: Microscopy is a rapid diagnostic test used to detect the presence of S. kiliense in tissue samples or fungal grains. Stains like potassium hydroxide (KOH), periodic acid-Schiff (PAS), or Grocott-Gomori methenamine silver (GMS) are employed to visualize typical conidiophores, conidia, and chlamydospores.
Molecular Methods: Molecular techniques, such as polymerase chain reaction, are sensitive & specific tests that identify S. kiliense by amplifying and detecting its DNA or RNA in clinical specimens like blood, tissue, or joint fluid. These methods are not only used for identification but can also perform genotyping or whole-genome sequencing to determine the strain or source of the infection.
Individuals should avoid or minimize contact with soil or contaminated materials that may harbor the fungus, particularly if they have a history of trauma, immunosuppression, or chronic diseases.
In healthcare settings, using sterile or disposable medical devices, such as catheters, needles, syringes, and implants, is crucial. Following proper infection control practices is necessary to prevent nosocomial infections.
Regular surveillance and screening of clinical specimens and environmental samples for S. kiliense using culture, microscopy, or molecular methods can aid in the early detection and monitoring of the fungus’s presence.
Performing antifungal susceptibility testing for S. kiliense isolates is crucial. This allows healthcare professionals to choose the most effective and safe antifungal regimen based on individualized results, improving treatment outcomes.
Sarocladium kiliense is a soil saprophytic mold with a global distribution, and it sporadically infects humans and other mammals. Initially, it was named Acremonium kiliense by Grutz in 1925. However, in 1971, Walter Gams retained the name A. kiliense to describe fungi frequently found in soil associated with skin infections. The first documented case of human infection by S. kiliense dates back to 1925 when a German soldier developed a mycetoma in his foot after a wound sustained in East Africa.
Since then, numerous cases of S. kiliense infection have been reported from various regions worldwide, including Africa, Asia, Europe, North America, and South America. S. kiliense has been primarily recognized as a human opportunistic pathogen, with infections more prevalent in tropical countries. However, in immunocompetent individuals, the pathogenicity of S. kiliense is very low.
In epidemiological studies, S. kiliense accounted for a small percentage of fungal isolates. For instance, from 1999 to 2008, it represented 0.4% of all fungal isolates and 2.7% of all Acremonium-like isolates. Another study conducted in India from 2004 to 2013 found that S. kiliense accounted for 0.6% of all fungal isolates and 4.4% of all Acremonium-like isolates. Notably, a multinational outbreak of S. kiliense bloodstream infections (BSI) occurred in 2013–2014.
This outbreak was associated with the receipt of contaminated antinausea medication among oncology patients in Colombia and Chile. It involved 18 patients and 7 medication vials and was traced to a single-point source using whole-genome sequence typing. These findings illustrate the sporadic nature of S. kiliense infections and highlight the need for vigilance in healthcare settings, particularly regarding medication safety and contamination control.
Classification and Structure:
Kingdom: Fungi
Phylum: Ascomycota
Class: Sordariomycetes
Order: Hypocreales
Genus: Sarocladium
Species:S. kiliense
The structure of Sarocladium kiliense is characterized by specific microscopic features:
Phialides: These are slender, slightly tapering structures that emerge from hyphae or conidiophores. Phialides of S. kiliense are long and straight and arise as side branches on hyphae, measuring 20-65 x 1.4-2.5 μm.
Conidiophores: Conidiophores are the structures from which conidia (asexual spores) are produced. In S. kiliense, they are long and straight with slightly tapering phialides, arising as side branches on hyphae.
Conidia: The conidia of S. kiliense are grouped in slimy heads, appearing cylindrical or ellipsoidal, measuring 3.3-5.5 x 0.9-1.8 μm. They are hyaline and accumulate at the ends of the phialides in ball-like clusters of ellipsoidal shape, measuring 3-6 x 1.5 mm.
Chlamydospores: Chlamydospores of S. kiliense are oval, uncolored structures with chromophilic walls. They measure approximately 4-8 μm in diameter and are formed either on the ends of hyphae or interspersed within filaments.
Sarocladium kiliense exhibits a range of intriguing characteristics that are worth noting. Firstly, it can produce antigens that are recognized by the host’s antibodies, including mannan and galactomannan, which can be valuable for diagnosing infections caused by this fungus. Furthermore, S. kiliense is known to produce toxins with diverse properties.
Saroclazines A-C, for instance, are cytotoxic toxins capable of exerting cell-killing effects on various cancer cell lines. Another toxin, Sarocladiumin, displays neurotoxic activity and can induce paralysis in experimental mice, underscoring its potential impact on the nervous system.
Additionally, this fungus is equipped with a repertoire of enzymes with distinct functions. L-asparaginase is an enzyme produced by S. kiliense, capable of breaking down the amino acid L-asparagine, which is crucial for the growth of certain cancer cells. The fungus also generates alkaline protease and amylase enzymes, which can efficiently break down proteins and starches, respectively, and find applications in various industrial processes.
Notably, Sarocladium kiliense possesses manganese oxidase, anenzyme that can oxidize manganese in the soil, affecting the availability of nutrients and metals for plants and microorganisms. This enzyme’s role in soil ecology can be significant.Moreover, S. kiliense was previously classified within the genus Acremonium and has been observed to have the capacity to degrade different polysaccharides.
This includes the degradation of polysaccharides like pectin, carboxymethyl cellulose, and xylans, with a particular emphasis on starch degradation for S. kiliense. Notably, A xylanolytic and cellulolytic strain CTGxxyl isolated from the gut of a termite- Reticulitermes santonensis, is documented.
Sarocladium kiliense primarily enters the human body through traumatic inoculation into the skin or subcutaneous tissues, which often results in mycetoma or onychomycosis. This traumatic entry can disrupt local immune defenses, making it easier for the fungus to establish infection. Infection typically occurs through penetrating injuries or open wounds exposed to the fungus.
Notably, S. kiliense‘s ability to undergo melanogenesis, a process that results in the production of melanin, plays a role in infections, particularly mycetoma.In immunocompetent individuals, S. kiliense infections tend to be less severe. However, in immunocompromised patients, severe systemicinfections may develop, potentially leading to conditions like peritonitis.
Studies have observed S. kiliense invading the lungs, evidenced by narrow septate hyphae, cylindrical conidia, and other characteristic features. This fungus can also affect the upper respiratory tract mucosa, sinuses, and conjunctiva.S. kiliense stands out among Sarocladium species due to its ability to produce melanin, a dark pigment that protects against environmental stress and host immune responses.
Melanin production enhances the fungus’s adhesion and invasion into host tissues and modulates inflammatory and oxidative reactions. This attribute has been associated with increased virulence and resistance to antifungal drugs. S. kiliense exhibits variable susceptibility to different antifungal agents, with some isolates showing resistance to commonly used drugs like amphotericin B, itraconazole, and caspofungin.
Human host defenses against Sarocladium kiliense infection primarily involve innate and adaptive immune responses. Phagocytes, including neutrophils, macrophages, and dendritic cells, play a crucial role in engulfing and eliminating the fungus through mechanisms such as oxidative and non-oxidative killing, autophagy, and the formation of extracellular traps.
These defense mechanisms not only combat the pathogen but also recruit other immune cells to the infection site via the production of cytokines & chemokines.In addition to phagocytes, T cells, including Th2, Th17, and Treg cells, contribute to the host’s defense. Th2 cells produce interleukin-4, interleukin-5, and interleukin-13, stimulating antibody production and the activation of eosinophils and mast cells.
Th17 cells, on the other hand, produce interleukin-17, interleukin-21, and interleukin-22, leading to the expression of antimicrobial peptides & the recruitment of neutrophils and monocytes. Treg cells, which produce interleukin-10 and transforming growth factor-beta, act to suppress inflammatory and immune responses, maintaining immune balance.
Furthermore, other immune cells, such as eosinophils, mast cells, basophils, gamma-delta T cells, NKT cells, and B-1 cells, also contribute to the defense against Sarocladium kiliense by producing various mediators and interacting with other immune cells. This intricate network of immune responses collectively combats the fungal infection and maintains host health.
Sarocladium kiliense is associated with a spectrum of clinical manifestations, each stemming from different modes of infection and affecting various parts of the body:
Mycetoma: One of the most common presentations of Sarocladium kiliense infection is mycetoma. This chronic granulomatous infection predominantly affects the skin and subcutaneous tissues. It is characterized by distinctive features such as swelling, the presence of draining sinuses, and the formation of fungal grains. Mycetoma typically occurs following the traumatic inoculation of the fungus into the skin.
Onychomycosis:Sarocladium kiliense can also cause onychomycosis, a fungal infection of the nails. This condition results in visible symptoms like nail discoloration, thickening, and brittleness. Onychomycosis may extend to the surrounding skin, leading to pain and inflammation in the affected area.
Keratomycosis: In some cases, Sarocladium kiliense can lead to keratomycosis, a fungal infection of the cornea, the transparent layer of the eye. This condition is characterized by symptoms such as eye redness, pain, blurred vision, and the development of ulcers on the cornea. Keratomycosis may occur through direct contact of the eye with the fungus, often linked to contaminated contact lenses or eye trauma.
Endophthalmitis and Pneumonia: In more severe instances, Sarocladium kiliense can give rise to endophthalmitis, a severe infection of the inner eye involving the vitreous humor and the retina. This condition manifests with symptoms including vision loss, eye pain, swelling, and discharge. Endophthalmitis may develop as a complication of keratomycosis or through the hematogenous spread of the fungus from other sites of infection.
Furthermore, S. kiliense can lead to pneumonia, a lung infection causing inflammation, and the accumulation of fluid in the air sacs. Pneumonia is marked by symptoms like cough, fever, chest pain, and difficulty breathing and can occur through inhalation of the fungus or dissemination from other sites of infection.
Culture test: This is the most definitive diagnostic method, involving the growth of the fungus on various media like glucose peptone agar, sabouraud dextrose agar (SDA), or oatmeal agar. Characteristics such as colony morphology, color, and microscopic features are observed. For instance, on glucose peptone agar, S. kiliense colonies can reach up to 50 mm in diameter and have a flat, grey-to-orange coloration. On SDA, colonies are initially white and later turn pink. Oatmeal agar may produce colonies with poorly differentiated phialides and single-celled, thick-walled chlamydospores. Additionally, culture allows for antifungal susceptibility testing to guide treatment.
Microscopy: Microscopy is a rapid diagnostic test used to detect the presence of S. kiliense in tissue samples or fungal grains. Stains like potassium hydroxide (KOH), periodic acid-Schiff (PAS), or Grocott-Gomori methenamine silver (GMS) are employed to visualize typical conidiophores, conidia, and chlamydospores.
Molecular Methods: Molecular techniques, such as polymerase chain reaction, are sensitive & specific tests that identify S. kiliense by amplifying and detecting its DNA or RNA in clinical specimens like blood, tissue, or joint fluid. These methods are not only used for identification but can also perform genotyping or whole-genome sequencing to determine the strain or source of the infection.
Individuals should avoid or minimize contact with soil or contaminated materials that may harbor the fungus, particularly if they have a history of trauma, immunosuppression, or chronic diseases.
In healthcare settings, using sterile or disposable medical devices, such as catheters, needles, syringes, and implants, is crucial. Following proper infection control practices is necessary to prevent nosocomial infections.
Regular surveillance and screening of clinical specimens and environmental samples for S. kiliense using culture, microscopy, or molecular methods can aid in the early detection and monitoring of the fungus’s presence.
Performing antifungal susceptibility testing for S. kiliense isolates is crucial. This allows healthcare professionals to choose the most effective and safe antifungal regimen based on individualized results, improving treatment outcomes.
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