Primary Plating Media
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SBA
1) 4+ white 2) 4+ large gray mucoid
The white pigmented colony is probably a staph and the large gray mucoid is an enteric gram negative rod, which usually grow larger than the staphs or the streps.
SBA
Beta hemolysis SBA
4+ translucent beta (S. pyogenes)
Large zones of hemolysis. Clearing of the RBC all the way through the plate.
Beta hemolysis SBA
Smoky Beta hemolysis SBA
3+ translucent beta (S. agalactiae)
Smokey zones of hemolysis where clearing is not complete.
Smoky Beta hemolysis SBA
Alpha hemolysis SBA
4+ alpha (S. pneumoniae)
Green pigment surrounding colinies is due to break down of hemoglobin into met hemoglobin.
Alpha hemolysis SBA
PEA
1) 4+ white, 2) 4+ pinpoint
The white colony is a Gram pos cocci and the pinpoint colony is an enteric GNR. If you were to compare the PEA to the SBA, the white colony would look about the same on both plates. The pinpoint colony would appear as a large gray mucoid on the SBA. Note that a PEA plate is equal to a CNA plate except that the GNR would not grow at all.
PEA
MAC Lac. pos. Bile ptt.
2+ Lac pos, bile ppt (E. coli)
Note the bile ppt red haze coming from quad 1 and 2. This organism is capable of breaking down the lactose very quickly, causing a sharp drop in the pH, resulting in the bile salts falling out of solution and forming a red precipitate.
MAC Lac. pos. Bile ptt.
MAC Lac. pos.
2+ Lac pos (Enterobacter)
The lactose reaction should only be interpreted in the areas of the plate where the organism is isolated, such as in Quad 2 and 3. In this photo, there are areas where there is a high concentration of organism, such as Quad 1 and 2, where all of the lactose has been utilized, giving the appearance of lac neg organism. The yellow colonies in this concentrated area are due to the depletion of lactose and then the utilization of the peptones in the media, which raises the pH.
MAC Lac. pos.
MAC @ 48hrs.
4+ Lac pos, bile ppt @ 48 hrs
Note the yellow color that is forming after incubation for 48 hrs., just to the upper left center of the plate. This is due to the media drying out, which turns the neutral red dye yellow from the rise in pH. MAC plates should be interpreted at 24 hrs.
MAC @ 48hrs.
Choc
3+ white (Neisseria gonorrhoeae)
This fastidious pathogen will not grow on SBA.
Choc
MSA
Man positive. (S. aureus)
Note the individual yellow colonies in Quad 2.
MSA
MSA Neg/Pos
Man neg on left and Man pos on right @ 48 hrs
This is a bi-plate with two organisms Man neg is S. epidermidis and the Man pos is S. aureus.
MSA Neg/Pos
HEA Lac/suc pos non-pathogen
2+ lac/suc pos
The salmon colored colonies indicates non-pathogen
HEA Lac/suc pos non-pathogen
HEA Lac/suc neg possible pathogen
1+ lac/suc neg
The green colored colonies indicates a possible pathogen. Also note the salmon colored colonies from the lac/suc pos non-pathogenic GNR enteric flora.
HEA Lac/suc neg possible pathogen
HEA Lac/suc neg possible pathogen
2+ lac/suc neg
The black colored colonies indicates a possible pathogen, perhaps Salmonella. Also note the salmon colored colonies from the lac/suc pos non-pathogenic GNR enteric flora. Note: there are also other non-pathogenic organisms that can produce black colonies on HEA, such as Citrobacter and Proteus.