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07 Jan 2024, 15:38
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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 revealed the clonal population structure of Lm and the global spread of clonal complex 1, known as Lm-CC1 (originally named epidemic clone ECI). Defined by multilocus sequence typing (MLST), this widespread clonal group was first identified in an Italian soldier suffering from meningitis during World War I (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.
Which of the following best describes the primary purpose of the first paragraph of the passage?
A. To provide a historical background on the discovery of Lm-CC1 during World War I.
B. To introduce the reader to the molecular characteristics of Lm-CC1.
C. To highlight the global prevalence of Lm-CC1 and its significance in clinical cases.
D. To discuss the lineage and ancestry of Lm-CC1.
E. To explain the methods of multilocus sequence typing (MLST).
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.
Which of the following best describes the primary purpose of the first paragraph of the passage?
A. To provide a historical background on the discovery of Lm-CC1 during World War I.
B. To introduce the reader to the molecular characteristics of Lm-CC1.
C. To highlight the global prevalence of Lm-CC1 and its significance in clinical cases.
D. To discuss the lineage and ancestry of Lm-CC1.
E. To explain the methods of multilocus sequence typing (MLST).
07 Jan 2024, 15:38
Kudos
Bookmarks
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 revealed the clonal population structure of Lm and the global spread of clonal complex 1, known as Lm-CC1 (originally named epidemic clone ECI). Defined by multilocus sequence typing (MLST), this widespread clonal group was first identified in an Italian soldier suffering from meningitis during World War I (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.
Which of the following best describes the primary purpose of the first paragraph of the passage?
A. To provide a historical background on the discovery of Lm-CC1 during World War I.
B. To introduce the reader to the molecular characteristics of Lm-CC1.
C. To highlight the global prevalence of Lm-CC1 and its significance in clinical cases.
D. To discuss the lineage and ancestry of Lm-CC1.
E. To explain the methods of multilocus sequence typing (MLST).
(A) Incorrect. The paragraph does mention WWI as an interesting historical detail, but that alone is not the paragraph’s main function. History is more of a side detail rather than the primary focus.
(B) Incorrect. Choice B can be eliminated by 2 indicators/aspects:
1. Choice B is too narrow in scope. While B mentions molecular characteristics in passing, It does not just introduces the reader to the molecular characteristics of Lm-CC1 (it goes way beyond it before and after that segment)
2. Choice B also does not really do a good job of introducing the molecular characteristics of Lm-CC1. The first paragraph text lacks any details of molecular characteristics... I would have assumed that would entail some long scientific text.
Can we rework choice B to make it work? Yes, we can. Choice B would be more spot on if it said "Introduce reader to the Lm-CC1" - I think that would be a better description than with the phrase "molecular characteristics". Because it does not do that. Tip: You should always check the first and the last sentences of a paragraph on the GMAT. They will always have more importance than the middle sentences and that can give you a feel for where the paragraph is leaning when you have a few choices that look appealing and you can't make up your mind.
(C) Correct Answer: The first paragraph focuses on the prevalence of Lm-CC1, noting its widespread distribution and its status as the most prevalent clinical clonal complex in several countries. This aligns with choice C, which accurately captures the paragraph's emphasis on the global prevalence and clinical significance of Lm-CC1.
(D) Incorrect. The very last sentence of the paragraph indeed contains the ancestry and lineage words but that is just a mention in passing. The paragraph does not actually discuss, again the emphasis on the word DISCUSS, just mentions it in passing (there are no details, elements or anything like that in addition to the mention). Imagine you were introducing Tim Cook and you said Tim is from the family with last name Cook and his family came from the east coast. Would that constitute a discussion of his lineage and ancestry? Only 13 words excluding articles and prepositions do not define the entire paragraph nor can there be a discussion in 13 words. Instead, the first paragraph mostly talks about the history and overall introduction to what Lm-CC1 is. The singular most important topic is not lineage and ancestry, which are just tangentially mentioned.
(E) Incorrect. Methods of sequence typing are not discussed in the first paragraph
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 revealed the clonal population structure of Lm and the global spread of clonal complex 1, known as Lm-CC1 (originally named epidemic clone ECI). Defined by multilocus sequence typing (MLST), this widespread clonal group was first identified in an Italian soldier suffering from meningitis during World War I (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.
Which of the following best describes the primary purpose of the first paragraph of the passage?
A. To provide a historical background on the discovery of Lm-CC1 during World War I.
B. To introduce the reader to the molecular characteristics of Lm-CC1.
C. To highlight the global prevalence of Lm-CC1 and its significance in clinical cases.
D. To discuss the lineage and ancestry of Lm-CC1.
E. To explain the methods of multilocus sequence typing (MLST).
(A) Incorrect. The paragraph does mention WWI as an interesting historical detail, but that alone is not the paragraph’s main function. History is more of a side detail rather than the primary focus.
(B) Incorrect. Choice B can be eliminated by 2 indicators/aspects:
1. Choice B is too narrow in scope. While B mentions molecular characteristics in passing, It does not just introduces the reader to the molecular characteristics of Lm-CC1 (it goes way beyond it before and after that segment)
2. Choice B also does not really do a good job of introducing the molecular characteristics of Lm-CC1. The first paragraph text lacks any details of molecular characteristics... I would have assumed that would entail some long scientific text.
Can we rework choice B to make it work? Yes, we can. Choice B would be more spot on if it said "Introduce reader to the Lm-CC1" - I think that would be a better description than with the phrase "molecular characteristics". Because it does not do that. Tip: You should always check the first and the last sentences of a paragraph on the GMAT. They will always have more importance than the middle sentences and that can give you a feel for where the paragraph is leaning when you have a few choices that look appealing and you can't make up your mind.
(C) Correct Answer: The first paragraph focuses on the prevalence of Lm-CC1, noting its widespread distribution and its status as the most prevalent clinical clonal complex in several countries. This aligns with choice C, which accurately captures the paragraph's emphasis on the global prevalence and clinical significance of Lm-CC1.
(D) Incorrect. The very last sentence of the paragraph indeed contains the ancestry and lineage words but that is just a mention in passing. The paragraph does not actually discuss, again the emphasis on the word DISCUSS, just mentions it in passing (there are no details, elements or anything like that in addition to the mention). Imagine you were introducing Tim Cook and you said Tim is from the family with last name Cook and his family came from the east coast. Would that constitute a discussion of his lineage and ancestry? Only 13 words excluding articles and prepositions do not define the entire paragraph nor can there be a discussion in 13 words. Instead, the first paragraph mostly talks about the history and overall introduction to what Lm-CC1 is. The singular most important topic is not lineage and ancestry, which are just tangentially mentioned.
(E) Incorrect. Methods of sequence typing are not discussed in the first paragraph
Answer: C
