Introduction to Microbial Pathogenesis PDF

Introduction to microbial pathogenesis Interaction between host and microbe SARS-Cov-2 host and microbe interaction via spike protein (ACE-2 receptors) Quiz content meanings: Microbe Mutualism Commensal Parasite Pathogen Microbial pathogenesis Virulence Virulence factors Avirulence In v...

Introduction to microbial pathogenesis Interaction between host and microbe SARS-Cov-2 host and microbe interaction via spike protein (ACE-2 receptors) Quiz content meanings: Microbe Mutualism Commensal Parasite Pathogen Microbial pathogenesis Virulence Virulence factors Avirulence In vitro In vivo episome Gut bacteria dominated by anaerobic bacteria More gut bacteria than host cells 10^13 vs 10^12 To demonstrate if a pathogen causes disease -> koch’s postulates, molecular kochs postulates Molecular interactions KOCH’S POSTULATES 1) Microbe found in diseased tissue but not in normal tissue 2) Microbe can be isolated from diseased tissue as pure culture 3) Microbe can cause disease when inoculated in animal or man 4) Microbe must then be reisolated in pure culture from animal or man  5) Therapeutic or preventaitve measuees eliminated disease MOLECULAR KOCHS POSTULATES (defining virulaence factors) 1) Virulence gene is associated with bacteria that cause disease but is absent or inactive in strains that fail to cause disease 2) Disrupt gene in virulent strian -> avirulence 3) Introduced cloned-gene into avirulent strain -> virulence 4) Gene is expressed during infection Up to date kochs postulates Metagenomics -> bullk sequencing Next generation sequencign (NGS) identifictaion Quantitative real time PCR COMPLICATED INFECTIOUS FORMS OF BACTERIA L-forms Cell wall deficient bacteria Biofilms ATTRIBUTES TO A SUCCESSFUL PATHOGEN 1) Colonise 2) Persist (to find a unique niche or to subvert host defences) 3) Disseminate 4) Cause disease Intracellular pathogens can persist by avoiding host defences ie. Laying dormant IDENTIFICATION OF VIRULENCE FACTORS 1) Secreted proteins and abundant surfaces 2) Highly antigenic proteins (serum antibodys act as probes) 3) Signature tagged mutagenesis (to identify genes required for the survival of the pathogen) also for identifying genes essential for growth in vivo 4) COMPLEMENTATION SCREENING To compare for gain of function phenotype for example e.coli does not usually enter epithelial cells but with the yersinia gene it does enter through epithelial cells. EPISOMAL EXPRESSION The genetic elements of some bacteria cells used to replicate independently is used to allow the expression of a foreign gene or the complementation of a mutation. PATHOGENICITY ISLANDS - Virulent genes clustered into a specific area of the genome - Virulent genes are normally found in pathogenicity islands or scattered around in the core genome.