Antibiotics

  • Bacitracin
  • Chloramphenicol
  • Erythromycin
  • Kanamycin
  • Nalidixic Acid
  • Nitrofurantoin
  • Novobiocin
  • Optochin
  • Penicillin
  • Streptomycin
  • Sulfamethoxazole
  • Tetracycline

Biochemical tests

  • Acid from glucose
  • Adonitol fermentation test
  • Antibiotic susceptibility tests
  • Arabinose fermentation test
  • Arabitol fermentation test
  • Arginine dihydrolase test
  • Bacitracin susceptibility test
  • Catalase test
  • Cellobiose fermentation test
  • Citrate utilization test
  • Coagulase test
  • Deoxyribonuclease (DNase) test
  • Dulcitol fermentation test
  • Esculin hydrolysis test
  • Fructose fermentation test
  • Galactose fermentation test
  • Gas from glucose
  • Gelatin hydrolysis test
  • Glucose fermentation
  • Glycerol fermentation test
  • Growth in KCN (potassium cyanide)
  • Growth on 6.5% NaCl
  • Growth on 7.5% NaCl
  • Growth on bile salts test
  • Hemolysis on blood agar
  • Hydrogen sulfide (H2S) production test
  • Indole production test
  • Inositol fermentation
  • Lactose fermentation test
  • Lipase test (using corn oil)
  • Lysine decarboxylase test
  • Malonate utilization test
  • Maltose fermentation test
  • Mannitol fermentation test
  • Mannose fermentation test
  • Melezitose fermentation test
  • Melibiose fermentation test
  • Methyl red test
  • Motility test
  • myo-Inositol fermentation test
  • Nitrate reductase test
  • Novobiocin susceptibility test
  • OF glucose test
  • Optochin susceptibility test
  • Ornithine decarboxylase test
  • Oxidase test
  • Phenylalanine deaminase test
  • Raffinose fermentation test
  • Rhamnose fermentation test
  • Ribose fermentation test
  • Salicin fermentation test
  • Sorbitol fermentation test
  • Starch hydrolysis test
  • Sucrose fermentation test
  • Trehalose fermentation test
  • Urea hydrolysis test (Christiansen’s)
  • Voges-Proskauer test
  • Xylitol fermentation test
  • Xylose fermentation test

Gram negative enteric bacilli

  • Buttiauxella agrestis
  • Cedecea davisae
  • Cedecea lapagei
  • Cedecea neteri
  • Citrobacter amalonaticus
  • Citrobacter amalonaticus biogroup 1
  • Citrobacter freundii
  • Citrobacter koseri
  • Cronobacter sakazakii
  • Edwardsiella hoshinae
  • Edwardsiella ictaluri
  • Edwardsiella tarda (wild type)
  • Edwardsiella tarda biogroup 1
  • Enterobacter aerogenes
  • Enterobacter amnigenus biogroup 1
  • Enterobacter amnigenus biogroup 2
  • Enterobacter cancerogenus
  • Enterobacter cloacae
  • Enterobacter gergoviae
  • Escherichia coli
  • Escherichia fergusonii
  • Escherichia hermannii
  • Escherichia vulneris
  • Ewingella americana
  • Hafnia alvei
  • Klebsiella oxytoca
  • Klebsiella pneumoniae subspecies ozaenae
  • Klebsiella pneumoniae subspecies pneumoniae
  • Klebsiella pneumoniae subspecies rhinoscleromatis
  • Kluyvera ascorbata
  • Kluyvera intermedia
  • Leclercia adecarboxylata
  • Mollerella wisconsinsis
  • Morganella morganii subspecies morganii
  • Morganella morganii subspecies sibonii
  • Proteus mirabilis
  • Proteus myxofaciens
  • Proteus penneri
  • Proteus vulgaris
  • Providencia alcalifaciens
  • Providencia rettgeri
  • Providencia rustigianii
  • Providencia stuartii
  • Rahnella aquatilis
  • Raoultella ornithinolytica
  • Raoultella terrigena
  • Salmonella bongori
  • Salmonella enterica
  • Salmonella enterica subspecies arizonae
  • Salmonella enterica subspecies enterica
  • Salmonella enterica subspecies houtenae
  • Salmonella enterica subspecies paratyphi
  • Salmonella enterica subspecies salamae
  • Salmonella typhi
  • Serratia ficaria
  • Serratia fonticola
  • Serratia marcescens
  • Serratia odorifera biogroup 1
  • Serratia plymuthica
  • Serratia proteamaculans subspecies proteamaculans
  • Serratia rubidaea
  • Shigella dysenteriae
  • Shigella flexneri
  • Shigella sonnei
  • Shimwellia blattae
  • Tatumella ptyseos
  • Yersinia enterocolitica
  • Yersinia frederiksenii
  • Yersinia kristensenii
  • Yersinia pestis
  • Yersinia pseudotuberculosis

Gram positive cocci

  • Dermacoccus nishinomiyaensis
  • Enterococcus avium
  • Enterococcus faecalis
  • Enterococcus faecium
  • Enterococcus gallinarum
  • Kocuria kristinae
  • Kocuria rosea
  • Kocuria varians
  • Kytococcus sedentarius
  • Lactococcus lactis
  • Lactococcus raffinolactis
  • Macrococcus caseolyticus
  • Micrococcus luteus
  • Micrococcus lylae
  • Nesterenkonia halobia
  • Rothia mucilaginosa
  • Staphylococcus aureus
  • Staphylococcus auricularis
  • Staphylococcus capitis
  • Staphylococcus caprae
  • Staphylococcus carnosus
  • Staphylococcus chromogenes
  • Staphylococcus cohnii ssp. cohnii
  • Staphylococcus cohnii ssp. urealyticum
  • Staphylococcus epidermidis
  • Staphylococcus gallinarum
  • Staphylococcus haemolyticus
  • Staphylococcus hominis
  • Staphylococcus hyicus
  • Staphylococcus intermedius
  • Staphylococcus lentus
  • Staphylococcus saccharolyticus
  • Staphylococcus saprophyticus
  • Staphylococcus sciuri
  • Staphylococcus simulans
  • Staphylococcus warneri
  • Staphylococcus xylosus
  • Streptococcus acidominimus
  • Streptococcus agalactiae
  • Streptococcus bovis
  • Streptococcus criceti
  • Streptococcus equi
  • Streptococcus equinus
  • Streptococcus ferus
  • Streptococcus iniae
  • Streptococcus mutans
  • Streptococcus pneumoniae
  • Streptococcus pyogenes
  • Streptococcus ratti
  • Streptococcus salivarius
  • Streptococcus sanguinis
  • Streptococcus sobrinus
  • Streptococcus uberis

Media

  • 6.5% NaCl broth
  • Arginine dihydrolase broth
  • Bile esculin agar slant
  • Blood agar
  • Christiansen’s urea broth
  • DNase agar with methyl green plate
  • Lysine decarboxylase broth
  • Malonate broth
  • Mannitol salt agar
  • MRVP broth
  • Nitrate broth with Durham tube
  • Nutrient agar plate
  • Nutrient broth
  • Nutrient gelatin
  • OF glucose broth
  • Ornithine decarboxylase broth
  • Phenol red adonitol broth
  • Phenol red arabinose broth
  • Phenol red arabitol broth
  • Phenol red cellobiose broth
  • Phenol red dulcitol broth
  • Phenol red fructose (levulose) broth
  • Phenol red galactose broth
  • Phenol red glucose (dextrose) broth with Durham tube
  • Phenol red glycerol broth
  • Phenol red inositol broth
  • Phenol red lactose broth
  • Phenol red maltose broth
  • Phenol red mannitol broth
  • Phenol red mannose broth
  • Phenol red melezitose broth
  • Phenol red melibiose broth
  • Phenol red raffinose broth
  • Phenol red rhamnose broth
  • Phenol red ribose broth
  • Phenol red salicin broth
  • Phenol red sorbitol broth
  • Phenol red sucrose (saccharose) broth
  • Phenol red trehalose broth
  • Phenol red xylitol broth
  • Phenol red xylose broth
  • Phenylalanine agar slant
  • Potassium cyanide (KCN) broth
  • Rabbit plasma
  • Simmons’ citrate agar slant
  • Spirit blue agar plate
  • Starch agar
  • Triple sugar iron agar slant
  • Tryptone broth

Reagents, Chemicals, Stains

  • Ammonium Sulfate (saturated)
  • Barritt’s A reagent
  • Barritt’s B reagent
  • Crystal Violet
  • Ferric chloride (10%) reagent
  • Gram’s Decolorizer
  • Gram’s Iodine
  • HCl 0.1N reagent
  • Hydrogen peroxide
  • Iodine reagent
  • Kovac’s reagent
  • Methyl red reagent
  • Nitrate A reagent
  • Nitrate B reagent
  • Oxidase reagent
  • Rabbit Plasma
  • Safranine
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  • Optochin susceptibility test

Optochin susceptibility test

About this test

What is the purpose of the test?  

Optochin is a chemical that is toxic to some bacteria but harmless to others. It is useful in the identification of Streptococcus pneumoniae , the alpha-hemolytic Streptococcus most commonly susceptible to this chemical. This test determines whether the bacterium is either sensitive (susceptible) to optochin or resistant to the chemical.

How is optochin susceptibility determined?  

Susceptibility to optochin is determined by placing an optochin-impregnated disk on a nutrient agar plate seeded with the microbe under investigation. As the microbe multiplies during incubation to produce a lawn of confluent growth, cells are exposed to the chemical diffusing into the agar from the paper disk. If the bacteria are susceptible to optochin, there will be a visible zone of inhibition forming around the disk, representing an area where the chemical concentration has prevented bacterial growth. Should the microbe be resistant, the lawn of cells will form visible growth up to the margin of the disk.  Note: Our version of the test is clearly “susceptibility” or “resistance”. In actuality, interpretation of this test requires measurement of the diameter of the zone of inhibition and comparison to standards to determine susceptibility or resistance.

What medium is used?  

The medium used for growing the bacterial lawn is typically either blood agar or a nutrient rich, general-purpose medium like nutrient agar . In VirtualUnknown:Microbiology™, we use nutrient agar .

How is the test performed?  

An inoculum from a pure culture is transferred aseptically to a sterile plate of nutrient agar, typically by use of cotton-tipped applicator (swab).  In a clinical setting, the applicator often contains other fibers than cotton to prevent any toxic residue found in cotton after processing from interfering with the growth of delicate pathogens. The inoculum is spread over the plate to distribute the bacteria as evenly and thoroughly as possible over the entire agar surface. A chemical-impregnated disk containing optochin is then aseptically placed in the center of the agar surface. The inoculated plate is incubated at 35-37 C for 24 hours and the results are determined. Growth of the lawn up to the margin of the disk indicates the bacterium is resistant to the chemical. An obvious clear zone around the disk, termed the zone of inhibition , indicates the bacterium to be susceptible to the chemical.

What reagents are needed?  

None. The disk is added before incubation. No additions are made following incubation.

Performing this test in the VUMIE Online lab

Inoculation of Medium

1. Select the nutrient agar plate medium.  

2. Complete the process of a tube-to-lawn aseptic transfer to inoculate the medium.

Addition of the Antibiotic Sensitivity Disk

3. Once the lawn has been created and BEFORE incubating the plate, add select a Optochin disk and place it on the lawn.

4. Replace the cap on the inoculum tube and the plate lid.

Incubation of the Inoculated Medium

5. Place the inoculated tube into the 35-37 C incubator.  

6. Press the New Day button to move forward 24 hours.

Determination of Test Results

7. Retrieve the incubated culture from the incubator.

8. Observe the growth on the surface of the plate, especially in the vicinity of the antibiotic disk. If there is a visible zone of inhibition surrounding the disk, an area where the lawn has not grown due to the antibiotic in the disk, the microbe is susceptible to the antibiotic. If no zone is present, the microbe is resistant to the antibiotic.

9. Record test result.


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Updated on June 12, 2022
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