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Listeria monocytogenes (Lm) is a foodborne bacterial zoonotic pathogen that can cause listeriosis, a severe infection with a high case fatality rate in immunocompromised individuals. Molecular studies have shown the clonal population structure of Lm and the worldwide distribution of clonal complex 1 (Lm-CC1, initially called epidemic clone ECI), a cosmopolitan clonal group defined by multilocus sequence typing (MLST), which was first isolated from an Italian soldier with meningitis during the first world war (WWI). Notably, Lm-CC1 is the most prevalent clinical clonal complex in several countries and actually corresponds to 20% of all of Lm clinical isolates deposited at the National Center for Biotechnology Information (NCBI) . Lm-CC1 belongs to Lm major lineage I and evolved from a subgroup of serotype 4b ancestry.
While there is no proven interhuman horizontal transmission of listeriosis, it was only in 1983 that the foodborne transmission of human listeriosis was formally established. Since then, Lm-CC1 has been reported in different food matrices, which constitute a major source of human listeriosis, including heavily contaminated dairy products. Previous studies have also demonstrated the hypervirulence of Lm-CC1, and its higher efficiency in gut colonization and fecal shedding, compared to hypovirulent Lm clones. Moreover, increasing evidence shows that bovines, which are frequent Lm asymptomatic carriers and contribute to Lm enrichment in soils, are the main source of disease and constitute a reservoir for Lm-CC1. In addition to Lm subclinical infections that may contaminate milk, the long-term persistence of Lm in cattle manure–amended soils also poses serious risks of transmission to fresh produce.
Understanding the global evolution of Lm-CC1, which is now spread over all continents, as well as its emergence and dissemination across different spatial levels is critical to understand Lm population dynamics and to develop better control strategies, particularly in countries with aging and/or immunosuppressed populations who are most at risk for severe infection. However, the complex movement of livestock and food products associated with asymptomatic intestinal colonization complicates traditional epidemiological investigations aiming at deciphering Lm epidemiology by linking isolates in space and time. Here, we took a population biology approach to fill this knowledge gap and conducted the largest genomic Lm-CC1 study to date, combining genomic and evolutionary approaches to decipher its evolutionary history and pattern of emergence and spread.
The author of the passage mentions that Lm-CC1 is the most prevalent clinical clonal complex in several countries in order to:
A. Emphasize the historical significance of Lm-CC1.
B. Argue that Lm-CC1 is harmless to humans.
C. Highlight the importance of studying its global distribution.
D. Suggest that Lm-CC1 is a recent development.
E. Downplay the significance of foodborne transmission.
While there is no proven interhuman horizontal transmission of listeriosis, it was only in 1983 that the foodborne transmission of human listeriosis was formally established. Since then, Lm-CC1 has been reported in different food matrices, which constitute a major source of human listeriosis, including heavily contaminated dairy products. Previous studies have also demonstrated the hypervirulence of Lm-CC1, and its higher efficiency in gut colonization and fecal shedding, compared to hypovirulent Lm clones. Moreover, increasing evidence shows that bovines, which are frequent Lm asymptomatic carriers and contribute to Lm enrichment in soils, are the main source of disease and constitute a reservoir for Lm-CC1. In addition to Lm subclinical infections that may contaminate milk, the long-term persistence of Lm in cattle manure–amended soils also poses serious risks of transmission to fresh produce.
Understanding the global evolution of Lm-CC1, which is now spread over all continents, as well as its emergence and dissemination across different spatial levels is critical to understand Lm population dynamics and to develop better control strategies, particularly in countries with aging and/or immunosuppressed populations who are most at risk for severe infection. However, the complex movement of livestock and food products associated with asymptomatic intestinal colonization complicates traditional epidemiological investigations aiming at deciphering Lm epidemiology by linking isolates in space and time. Here, we took a population biology approach to fill this knowledge gap and conducted the largest genomic Lm-CC1 study to date, combining genomic and evolutionary approaches to decipher its evolutionary history and pattern of emergence and spread.
The author of the passage mentions that Lm-CC1 is the most prevalent clinical clonal complex in several countries in order to:
A. Emphasize the historical significance of Lm-CC1.
B. Argue that Lm-CC1 is harmless to humans.
C. Highlight the importance of studying its global distribution.
D. Suggest that Lm-CC1 is a recent development.
E. Downplay the significance of foodborne transmission.
07 Jan 2024, 15:43
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Official Solution:
Listeria monocytogenes (Lm) is a foodborne bacterial zoonotic pathogen that can cause listeriosis, a severe infection with a high case fatality rate in immunocompromised individuals. Molecular studies have shown the clonal population structure of Lm and the worldwide distribution of clonal complex 1 (Lm-CC1, initially called epidemic clone ECI), a cosmopolitan clonal group defined by multilocus sequence typing (MLST), which was first isolated from an Italian soldier with meningitis during the first world war (WWI). Notably, Lm-CC1 is the most prevalent clinical clonal complex in several countries and actually corresponds to 20% of all of Lm clinical isolates deposited at the National Center for Biotechnology Information (NCBI) . Lm-CC1 belongs to Lm major lineage I and evolved from a subgroup of serotype 4b ancestry.
While there is no proven interhuman horizontal transmission of listeriosis, it was only in 1983 that the foodborne transmission of human listeriosis was formally established. Since then, Lm-CC1 has been reported in different food matrices, which constitute a major source of human listeriosis, including heavily contaminated dairy products. Previous studies have also demonstrated the hypervirulence of Lm-CC1, and its higher efficiency in gut colonization and fecal shedding, compared to hypovirulent Lm clones. Moreover, increasing evidence shows that bovines, which are frequent Lm asymptomatic carriers and contribute to Lm enrichment in soils, are the main source of disease and constitute a reservoir for Lm-CC1. In addition to Lm subclinical infections that may contaminate milk, the long-term persistence of Lm in cattle manure–amended soils also poses serious risks of transmission to fresh produce.
Understanding the global evolution of Lm-CC1, which is now spread over all continents, as well as its emergence and dissemination across different spatial levels is critical to understand Lm population dynamics and to develop better control strategies, particularly in countries with aging and/or immunosuppressed populations who are most at risk for severe infection. However, the complex movement of livestock and food products associated with asymptomatic intestinal colonization complicates traditional epidemiological investigations aiming at deciphering Lm epidemiology by linking isolates in space and time. Here, we took a population biology approach to fill this knowledge gap and conducted the largest genomic Lm-CC1 study to date, combining genomic and evolutionary approaches to decipher its evolutionary history and pattern of emergence and spread.
The author of the passage mentions that Lm-CC1 is the most prevalent clinical clonal complex in several countries in order to:
A. Emphasize the historical significance of Lm-CC1.
B. Argue that Lm-CC1 is harmless to humans.
C. Highlight the importance of studying its global distribution.
D. Suggest that Lm-CC1 is a recent development.
E. Downplay the significance of foodborne transmission.
The author of the passage mentions that Lm-CC1 is the most prevalent clinical clonal complex in several countries in order to:
C. Highlight the importance of studying its global distribution.
Correct. By stating that Lm-CC1 is the most prevalent clinical clonal complex in several countries, the author aims to emphasize the importance of understanding its distribution and impact on a global scale, aligning with choice C.
Here are the reasons why the other options are incorrect:
A. Emphasize the historical significance of Lm-CC1. This option is incorrect because the passage does not focus on the historical significance of Lm-CC1. While it mentions the first isolation of Lm-CC1 during WWI, the main emphasis is on its current prevalence and global distribution.
B. Argue that Lm-CC1 is harmless to humans. This option is incorrect because the passage clearly states that Lm-CC1 is a hypervirulent pathogen and a major source of human listeriosis, particularly in immunocompromised individuals, indicating it is harmful rather than harmless.
D. Suggest that Lm-CC1 is a recent development. This option is incorrect because the passage does not suggest that Lm-CC1 is a recent development. Instead, it mentions its historical isolation and current prevalence, focusing on its evolution and spread over time.
E. Downplay the significance of foodborne transmission. This option is incorrect because the passage highlights the significance of foodborne transmission, noting that Lm-CC1 has been reported in various food matrices and emphasizing its role in human listeriosis.
Answer: C
Listeria monocytogenes (Lm) is a foodborne bacterial zoonotic pathogen that can cause listeriosis, a severe infection with a high case fatality rate in immunocompromised individuals. Molecular studies have shown the clonal population structure of Lm and the worldwide distribution of clonal complex 1 (Lm-CC1, initially called epidemic clone ECI), a cosmopolitan clonal group defined by multilocus sequence typing (MLST), which was first isolated from an Italian soldier with meningitis during the first world war (WWI). Notably, Lm-CC1 is the most prevalent clinical clonal complex in several countries and actually corresponds to 20% of all of Lm clinical isolates deposited at the National Center for Biotechnology Information (NCBI) . Lm-CC1 belongs to Lm major lineage I and evolved from a subgroup of serotype 4b ancestry.
While there is no proven interhuman horizontal transmission of listeriosis, it was only in 1983 that the foodborne transmission of human listeriosis was formally established. Since then, Lm-CC1 has been reported in different food matrices, which constitute a major source of human listeriosis, including heavily contaminated dairy products. Previous studies have also demonstrated the hypervirulence of Lm-CC1, and its higher efficiency in gut colonization and fecal shedding, compared to hypovirulent Lm clones. Moreover, increasing evidence shows that bovines, which are frequent Lm asymptomatic carriers and contribute to Lm enrichment in soils, are the main source of disease and constitute a reservoir for Lm-CC1. In addition to Lm subclinical infections that may contaminate milk, the long-term persistence of Lm in cattle manure–amended soils also poses serious risks of transmission to fresh produce.
Understanding the global evolution of Lm-CC1, which is now spread over all continents, as well as its emergence and dissemination across different spatial levels is critical to understand Lm population dynamics and to develop better control strategies, particularly in countries with aging and/or immunosuppressed populations who are most at risk for severe infection. However, the complex movement of livestock and food products associated with asymptomatic intestinal colonization complicates traditional epidemiological investigations aiming at deciphering Lm epidemiology by linking isolates in space and time. Here, we took a population biology approach to fill this knowledge gap and conducted the largest genomic Lm-CC1 study to date, combining genomic and evolutionary approaches to decipher its evolutionary history and pattern of emergence and spread.
The author of the passage mentions that Lm-CC1 is the most prevalent clinical clonal complex in several countries in order to:
A. Emphasize the historical significance of Lm-CC1.
B. Argue that Lm-CC1 is harmless to humans.
C. Highlight the importance of studying its global distribution.
D. Suggest that Lm-CC1 is a recent development.
E. Downplay the significance of foodborne transmission.
The author of the passage mentions that Lm-CC1 is the most prevalent clinical clonal complex in several countries in order to:
C. Highlight the importance of studying its global distribution.
Correct. By stating that Lm-CC1 is the most prevalent clinical clonal complex in several countries, the author aims to emphasize the importance of understanding its distribution and impact on a global scale, aligning with choice C.
Here are the reasons why the other options are incorrect:
A. Emphasize the historical significance of Lm-CC1. This option is incorrect because the passage does not focus on the historical significance of Lm-CC1. While it mentions the first isolation of Lm-CC1 during WWI, the main emphasis is on its current prevalence and global distribution.
B. Argue that Lm-CC1 is harmless to humans. This option is incorrect because the passage clearly states that Lm-CC1 is a hypervirulent pathogen and a major source of human listeriosis, particularly in immunocompromised individuals, indicating it is harmful rather than harmless.
D. Suggest that Lm-CC1 is a recent development. This option is incorrect because the passage does not suggest that Lm-CC1 is a recent development. Instead, it mentions its historical isolation and current prevalence, focusing on its evolution and spread over time.
E. Downplay the significance of foodborne transmission. This option is incorrect because the passage highlights the significance of foodborne transmission, noting that Lm-CC1 has been reported in various food matrices and emphasizing its role in human listeriosis.
Answer: C
15 May 2024, 02:52
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