Lab 23 Respiratory Microorganisms

Objectives Interpret hemolysis results Classify various Streptococcus species

Streptococci There are 19 groups (A-R) of Streptococci that are classified based on their characteristics – Some aggressively lyse RBC – Some hydrolyse esculin – Some are highly salt tolerant – Some are catalase positve

Sheep Blood Agar 5% Sheep whole blood added to TSA base – Hugely nutritious media – Complete or partial hemolysis ( α, β) – Some judgment calls Look for clearing

For today… No barfing – We want throat cultures, not tongue cultures – Beware the gag reflex 1 SBA Plate per pair – Wet sterile swab and go for the sides or back of the throat (carefully) – Inoculate the 1 st region and streak for isolation using the loop. – You need isolated colonies for use in the next 2 labs! – Incubate in candle jar, not aerobically

2 nd session Interpret hemolysis (look through the plate) – Yeast and other organisms can cause β hemolysis Gram stain 2-4 colonies (if possible choose a representative α and β ) If you have G+ cocci (you should) – Inoculate new SBA (Plus bacitracin disc) – Bile esculin slant – Salt tube

3 rd Session Measure zone of inhibition – Clearing doesn’t necessarily mean susceptibility Catalase and Oxidase test colonies off SBA or Bile Esculin slants. Compare with figure 23.1 (pg 190)