09-02-2013, 02:30 PM
Classification, nomenclature, taxonomy,identification
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Classification is arrangement of bacteria into groups ( the same organisms can be classified differently according to the view: serotype classification, antimicrobial resistance classification…)
Nomenclature is naming, the mean of communicating - it is binominal
Taxonomy - science of classification, identification, nomenclature and making a system
Identification is practical use of classification criteria to distinguish certain organism from others
Graduating
subspecies: serotyping Haemophilus influenzae type b
featurspecies - distinct organism with certain characteristic es, similar organism within genus Salmonella typhi
genera:Streptococcus, Salmonella,
families: Micrococaceae, Enterobacteriacae
orders
Approaches to taxonomy
Numerical, phylogenetic, genome size, Guanin+cytosine content, DNA relatedness,thermal stavility of DNA sequences, DNA relatedness under supraoptimal conditions…….
In practice - polyphasic approch - depending on importnace and purpose of nomenclature
Staphylococcus
Pathogens of man
Divided in 2 groups on plasmacoagulase production - artificial PC negative - common comensales of human skin and animals, some cause infections in some circumstances (Staphyoloc. epidermidis, warneri, haemolyticus, saprophyticus, hyicus) PC positive - Staphylococcus aureus, St. intermedius
Staphylococcus aureus G+coccus
colonizes nasal passage and axillae
able to grow on salt medium (10%), catalase +, grows in clusters, PC positive - distinguishing factor
Structure: capsule, peptidoglycan,protein A, teichooic acid, clumping factor, cytoplasmic membrane
Toxins: alfa, beta, delta, gama, leukocidin, exfoliating,toxic shock syndrome TSST,enterotoxin
Enzymes: coagulase, catalase, hyaluronidase, staphylokinase, lipases, fibrinolysin, nuclease, penicilinase
Virulence factor and patogenesis
Multifactorial
adherence - surface proteins (att.to fibronectin), fibrinogen/fibrin binding protein (att. to clots and traumatised cell, the most important part of slime on biomaterial of indwelling devices), fibronectin
avoidance of host defence - capsule polysaccharide, protein A - bind IgG - disruption of opsonisation, leukocidin - toxic for PMNL
damage of host tissue - toxins - alfa - membrane damaging, necrosis, beta - sfingomyelinase, delta - detergen like action, leucocidin - dermonecrosis, exfoliatin - epidermolytic toxin