Grows on bordet gengou agar potato infusion glycerol

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Grows on Bordet-Gengou agar (potato infusion, glycerol, peptone, salts,agar and 20-30% sheeps blood)of normal flora and one without incase this Bordatella is sensitiveGrowth is slow & it is hemolytic (but this may not been seen)ObservationsCulture: Bissected pearls (smooth rounded circular colonies) seen onB-G agarGram stain: Very small Gm (-) cocci similar to H. fluFlourescence test shows bright green bacteria under the microscopeAntibiotic Susceptibility Testing (Lab 6 & 7)Group A beta-hemolytic strep are uniformly sensitive to penicillinResistance to first line therapeutic agents have been found, therefore some clinical isolatesmust need sensitivity testing to determine optimal treatmentoDilution MethodSerial dilutions of an abx are prepared to find the lowest concentration ofantibiotic where growth is suppressed (Minimal inhibitory concentration)oDiffusion MethodBacteria is inoculated onto the surface of an agar and zone of inhibitiongives clues to sensitivityZone size is a function of amount of abx added, size of bacterialinnoculum, the speed of diffusion of the abx, rate of growth ofbacteria and depth of the agarKirby-Bauer technique uses a plot of zone diameter to determine the actualMIC. The larger the diameter around a single antibiotic, the moresusceptible. Plotting the zone vs the MIC you can get the sensitivity of theorganism
Characterizes an organism as clinically sensitive or clinicallyresistantE-Test: strip with a gradient of abx concentration allows visualization of theMIC fairly rapidly.Transfer of ResistanceoWidespread use in livestock & humans has fueled Abx resistance caused by1) Mutations in their own DNA2) Acquisition of new DNA (more common)1) Transformation (pick up new naked DNA)oCommon in Neisseria, Haemophilus, Helicobacter &pneumococci (SpNHH)2) Transduction (Phage mediated)3) Conjugation (Sex pili- most important mechanism)oPermits acquisition of large amount of genetic info withoutloss or alteration of intrinsic genesoDrug resistance plasmids are the main concern since they cantransmit multiple genes with multiple resistancesoRequires cell to cell contact (plasmids encode conjugationsystems)oMating can occur in both broth cultures and agar culturesoR100 PlasmidEncodes resistance to TCN, Cloramphenicol, Streptomycin, andsulfonamidesHost range is most enterobacteriaceaeSalmonella enteriditis is a recipient strain that contains resistanct to nalidixicacid (the first quinolone) through a Xsome mutation in DNA gyraseSalmonella that received the R100 was able to grow on agar platescontaining TCN+ nalidixic acid and Chloramphenicol + nalidixic acidindicating successful transfer.

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Term
Spring
Professor
staff
Tags
Bacteria, Gram stain, Blood Agar

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