differentiates the pathogenic S aureus from the non-pathogenic S. epidermidis and S. aphrophyticus
-Plasma plus Specimen
Positive: visible clumping
Negative: no visible clumping
-Plasma plus specimen
Positive: visible clump or coagulum
Negative: no clot or water coagulum
Pathogenic S aureus (positive)
NP S epidermidis and S saphrophyticus (negative)
CATALASE test set-up
Catalase test uses 3% H202
The positive reaction is indicative of bubbling or effervescence
All staphylococcus spp.
All gram negative enteric bacilli except Shigella dysenteriae
All Streptococcus spp.
Bacteriologic analysis of water
Most probable number method (MPN) orMultiple tube technique
A set of tubes of Brillant Green Bile Lactose Broth (BGBLB) and water sample.
TUBE 1 with 10ml (double strength) BGBLB and 10 ml water sample
TUBE 2 with 10ml (single strength) BGBLB and 1.0 ml water sample
TUBE 3 with 10ml (single strength) BGBLB and 0.1 ml water sample
Small tube is called Durham’s fermentation tube
This test requires inoculation of the content of any positive BGBLB tube onto a plated EMB agar
This test requires inoculation of any positive EMB plate colonies into a BGBLB tube and nutrient agar slant. Colonies grown on the nutrient agar are gram stained and examined for presence of gram negative short bacilli or coccobacilli which are not sporeforming.
VP RGT. A
VP RGT. B
Reagents used in
Indole Production test
Methyl Red Test
Methyl Red VP medium
Simmon Citrate Agar
INDOLE test set up
-this liquid medium in the indole test w/c is used to identify GR. – enteric bacilli
-based on the ability of the organism to produce enzyme, tryptophanase
-Tryptophanase-enzyme decomposes this tryptone broth producing indole that subsequently forms a red colored complex upon the addition of the Kovac’s reagent or p-dimethyl benzaldehyde reagent
-a.k.a peptone glucose broth
-identify Gr – bacilli ability of org to ferment glucose to pyruvic acid by one of the two pathways:
MR TEST- acid fermentation pathway
Voges proskauer- Butylene glycol pathway
METHYL RED TEST SET-UP
If the org would ferment glucose via mixed acid fermentation pathway, more acids are produced like lactic, acetic, formic, succinic acids, w/c decreases the ph of the med to 4.4 or lower-hence, upon the addition of the indicator, methyl red broth becomes red in color.
If the org would not use this pathway, the Ph of hte med inc 5.5 or higher –hence, upon the addition of the indicator, mr the broth becomes yellow in color
VOGES PROSKAUER TEST
If the organism would ferment glucose via the butylene glycol pathway and intermediate product acetyl methyl carbinol or acetoine which is neutral is converted to diacetyl upon the addition of VP rgt. B 40% KOH with 0.3% creatine. In the presence of VP rgt. A 5% alpha naphthol in absolute methyl alcohol. Di acetyl is red in color negative is yellow in color
This liquid medium is used to identify gram negative enteric bacilli based on their ability to produce enzyme urease within 2-4 hours(rapid) or within 24 hours(late) of incubation.
pH indicator- phenol red
if the organism produces urease, this splits urea into ammonia carbon dioxide and water . Ammonia is then converted into an alkaline compound (ammonium carbonate) which changes the color of the medium to pink red.
*Rapid urease producers (positive within 2 to 4 hours of incubation)
*Late urease producers positive within 24 hours of incubation
SIMMONS CITRATE AGAR (SCA)
This tubed medium is used to identify the Gram negative enteric bacilli based on the ability of the organisms to utilize citrate as the sole source of carbon.(Citrate utilization test)
The organism which utilizes citrate as its source of carbon, degrades it to ammonia and then subsequently converts it to ammonium hydroxide. The pH of the medium is then increased and this is indicated by a change in color from green to blue.
pH indicator-bromthymol blue
source of carbon-sodium citrate
no carbohydrate nor protein component
SULFIDE INDOLE MOTILITY MEDIUM (SIM)
This semisolid medium is used to identify Gram negative enteric bacilli based on the following characteristics:
Hydrogen sulfide production-indicated by blackening of the medium
Indole production-indicated by red color of the medium
Motility-indicated by diffusion of growth away from the point of inoculation