General Bacteriology Flashcards
cell wall of gram positive
peptidoglycan, teichoic acid, Carbohydrates Proteins Lipids waxes
Cell wall of gram negative
Peptidoglycans
LPS
porins
Cytoplasmic membrane
2/3 protein 1/3 lipids no sterols phospholipids energy prodution, invaginations
Nuclear material
single chromosome 1-2mm, superhelix
haploid ring
Capsule, components
Polysaccharide, hyaluronic acid polypeptide in order of commonness glycocalyx
How do you examin unstained live bacteria?
Hanging drop or wet chamber
Why can’t you examine a bacteria unstained?
They have no cell material thus no contrast material, except ribosomes
What is simple staining
Staining which reacts with all microbes in an identical fashion, increases contrast
Differential staining methods
Gram - blue or pink
Ziehl neelson - red or blue mycobacterium
Koster - red brucella
Stamp - chlamydia chlamydophila
Gram staining
Nacl Crystal violet - 3-5 lugol 1-2 96% alcohol 5-6 drops fuchsin 0.5-1min
Ziehl Neelsen
Strong carbol fuchsin heat three times wash sulphuric 5% alcohol 96% wash methylene blue 1-2min wash red is positive blue negative
Components of a bacteria
85-90% water
2-15% proteins or minerals
2-40% waxes/lipids
upto 50% carbs, higher in gram negative
Things that help move materials across bacterial membranes
Porin protiens
permease
extracellular enzymes
Autotrophic bacteria
Utilize INORGANIC C&N
all saprophytes
Phototropic - chloroplasts, upper layer of fresh/salt water
Chemotropic - Oxidates inorganic material, make nitrogen usable for plants, nitrobacter, or found in deep water.
Heterotrop bacteria
Majority saprophytes but all pathogenic bacteria are heterotropic
ORGANIC Carbon demand
INORGANIC N, amino acids or proteins
What are paratropic bacteria
Cannot be cultured on artificial media need unknown addatives
Addatives some bacteria need
NAD, haemophilus/actinocacillus - Vfactor
Haem, haemophillus - Xfactor
Mycobactin, mycobacterium avium ssp. PTB
DNA hydrolisate, Mycoplasm
Products of nitrogen metabolism
Amines - histamine, cadaverine, putrescene
Keto- acids
Acids - lactic, acetic, butyric and valeric
NH3, CO2, H2O, H2,H2S idole
Detection f nitrate metabolism
Nitrate reduction - illosvay reagent
Urease production - carbamide
Phenylalanine deaminase - phenyl pyruvic acid
H2S production
Indole production - kovacs reagent tryptophan to indole
lysine decarboxylase
Aims of culturing
Diagnostic - isolation
Vaccine production
industry - food fermentaion, antibiotics
How do you classify media
Aim - common, selective or differential
State - solid, semi solid or liquid
Origin - natural artificial or synthetic
What is the difference between selective and differential culture
Selective contains antibiotics or other material to inhibit the growth of unwanted bacteria
Differential is an indicator due to biochemical reactions on the media. often containing fermentable sugars and a PH indicator
Name some artificial cultures
Nutrient
Blood - differential 10% ox/ov blood, chocolate 80deg x 20min
MacConkeys - selective, bile salts and crystal violet
Lactose +
Salt Mannitol - 10% NaCl staphylococcus selective
Culture additives
C source - saccharides, glycosides, alcohols
N source - anorganic N like ammonium salts or nitrates, AA - peptone or triptone
Native protein
Viatmins - B1/2 lactobacilli
V/X factor haemophilus
Demands of a disinfectant
Low cost Broad spectrum Not toxic to host or env homogenous, odourless, soluable, stable good penetrance detergent effect not corrosive
Factors influencing the effectivity of a disinfectant
Temperature increases effectivity Duration of contact Concentration of dissinfectant Nature of surface PH Bacterial resistance Amount of bacteria
Characterisation of disinfectant activity
Side effects Species killed Species inactivated Speed Phenol coefficient
Groups of disinfectants
Halogens Aldehydes Oxidative alcohols detergents phenol compounds acids alkalies dyes sterilising gases
Principles of antibiotic therapy
Correct diagnosis Correct dosage duration Correct dose Usage of the most effective antibiotic Exceed ED in the infected tissue
