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home:pathogenesis:successive_infection [09.20.2011] – [Notes and comments] paulalberthome:pathogenesis:successive_infection [09.09.2012] – [Pea soup] paulalbert
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 Using high throughput sequencing, one research team found that of bacteria present on the hands of 51 undergraduate students leaving an exam room, there were 332,000 genetically distinct bacteria belonging to 4,742 different species. Each student carried on average 3,200 bacteria from 150 species on their hands. Only five species were found on all the students’ hands, while any two hands – even belonging to the same person – had only 13% of their bacterial species in common.(({{pubmed>long:19004758}})) According to the study's authors, each student’s bacterial “fingerprint” was totally unique.  Using high throughput sequencing, one research team found that of bacteria present on the hands of 51 undergraduate students leaving an exam room, there were 332,000 genetically distinct bacteria belonging to 4,742 different species. Each student carried on average 3,200 bacteria from 150 species on their hands. Only five species were found on all the students’ hands, while any two hands – even belonging to the same person – had only 13% of their bacterial species in common.(({{pubmed>long:19004758}})) According to the study's authors, each student’s bacterial “fingerprint” was totally unique. 
  
-However, variability in disease has more to do with how bacteria interact through processes like horizontal gene transfer than merely the sheer number of species present. Horizontal gene transfer is the process in which a bacterium inserts genetic material, usually circular strands of DNA called plasmids, into the genomes of other pathogens.+However, variability in disease has more to do with how bacteria interact through processes like horizontal gene transfer than merely the sheer number of species present. Horizontal gene transfer is the process by which a bacterium inserts genetic material, usually circular strands of DNA called plasmids, into the genomes of other pathogens.
  
 Given the frequency with which horizontal gene transfer occurs and the number of plasmids a given bacteria can contain – some bacteria have more than 20 plasmids – it is no surprise that the human microbiota is so diverse.  Given the frequency with which horizontal gene transfer occurs and the number of plasmids a given bacteria can contain – some bacteria have more than 20 plasmids – it is no surprise that the human microbiota is so diverse. 
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   * **Mice exposed to an airborne pathogen develop sub-chronic lung inflammation** – Repeated low dose aerosol exposures to //Bacillus thuringiensis// (a commercial pesticide) can induce sub-chronic lung inflammation in mice, which may be the first step in the development of chronic lung diseases.(("Sub-chronic lung inflammation after airway exposures to Bacillus thuringiensis biopesticides in mice" Look up on PubMed later.))   * **Mice exposed to an airborne pathogen develop sub-chronic lung inflammation** – Repeated low dose aerosol exposures to //Bacillus thuringiensis// (a commercial pesticide) can induce sub-chronic lung inflammation in mice, which may be the first step in the development of chronic lung diseases.(("Sub-chronic lung inflammation after airway exposures to Bacillus thuringiensis biopesticides in mice" Look up on PubMed later.))
   * **Bacterial infection causes stress-induced memory dysfunction in mice.** – Mice were infected with the non-invasive intestinal pathogen, //Citrobacter rodentium// in both C57BL/6 mice and "germ-free" Swiss-Webster mice, in the presence or absence of acute  stress.  No behavioural abnormalities were observed, either at the height of infection or following bacterial clearance. After infection clearance, however, when infected Swiss-Webster mice were exposed to acute stress, however, memory dysfunction was apparent. Conventionally reared, control Swiss-Webster mice with an intact intestinal microbiota did not develop memory problems.(({{pubmed>long:20966022}}))    * **Bacterial infection causes stress-induced memory dysfunction in mice.** – Mice were infected with the non-invasive intestinal pathogen, //Citrobacter rodentium// in both C57BL/6 mice and "germ-free" Swiss-Webster mice, in the presence or absence of acute  stress.  No behavioural abnormalities were observed, either at the height of infection or following bacterial clearance. After infection clearance, however, when infected Swiss-Webster mice were exposed to acute stress, however, memory dysfunction was apparent. Conventionally reared, control Swiss-Webster mice with an intact intestinal microbiota did not develop memory problems.(({{pubmed>long:20966022}})) 
- +  * **Bacterial vaginosis and HIV** – Bacterial vaginosis is associated with a greater than three-fold risk of female-to-male transmission of HIV.(({{pubmed>long:22745608}})) 
 +  * **Prenatal infection and autism** – A population-wide study from Denmark spanning two decades of births indicates that infection during pregnancy increases the risk of autism in the child. Hospitalization for a viral infection, like the flu, during the first trimester of pregnancy triples the odds. Bacterial infection, including of the urinary tract, during the second trimester increases chances by 40 percent.(({{pubmed>long:20414802}})) 
 +  * **Childhood infections and asthma** – Children who experience repeated rhinovirus-induced wheezing episodes in infancy have a significantly increased risk of developing asthma.(({{pubmed>long:22053589}})) Neonates colonized in the hypopharyngeal region with //S. pneumoniae, H. influenzae,// or //M. catarrhalis,// or with a combination of these organisms, are at increased risk for recurrent wheeze and asthma early in life.(({{pubmed>long:17928596}})) 
  
  
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 It is common practice to assign one group of patients participating in a controlled trial to be the "healthy control group." While researchers are apt to make a hard distinction between health and disease, this dichotomy is contrary to what we know about successive infection.  It is common practice to assign one group of patients participating in a controlled trial to be the "healthy control group." While researchers are apt to make a hard distinction between health and disease, this dichotomy is contrary to what we know about successive infection. 
  
-The process of successive infection does not just occur in sick people or people who are symptomatic. In healthy subjects, subclinical infection is not the exception, but the rule. For example, 30% of healthy people are carriers of the pathogen //Staphylococcus aureus//.(({{pubmed>long:21297670}})) From even before birth, every human is //constantly// acquiring new microbes as demonstrated in several studies(({{pubmed>long:20441597}})) by Rob Knight and Jeffrey Gordon's team. After sequencing the microbiome of two individuals at four body sites over 396 timepoints, the group essentially concluded that the notion of a "core microbiome" is overblown.+The process of successive infection does not just occur in sick people or people who are symptomatic. In healthy subjects, subclinical infection is not the exception, but the rule. For example: 
 +  * 30% of healthy people are carriers of the pathogen //Staphylococcus aureus//.(({{pubmed>long:21297670}}))  
 +  * A 2011 pyrosequencing study looked at 16S rDNA amplicons of eight culture-negative healthy female urine specimens.(({{pubmed>long:22047020}})) The study found a significant amount of sequences belonging to bacteria with a known pathogenic potential.  
 + 
 + 
 +From even before birth, every human is //constantly// acquiring new microbes as demonstrated in several studies(({{pubmed>long:20441597}})) by Rob Knight and Jeffrey Gordon's team. After sequencing the microbiome of two individuals at four body sites over 396 timepoints, the group essentially concluded that the notion of a "core microbiome" is overblown.
  
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home/pathogenesis/successive_infection.txt · Last modified: 09.14.2022 by 127.0.0.1
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