A culture of Staphylococcus of unknown density is diluted as follows (letters represent each step): • 60 mL of a bacterial culture is diluted by adding 440 mL of water • 1000 microliters from (A) is added to 9 mL of water • Dilution (B) is used to prepare a 103 dilution in water • 100 uL from dilution (C) is plated to nutrient agar and incubated at 37°C Following incubation, colonies are uniformly distributed on the agar, and 102 colonies are counted on one half of the plate. 1. Express the total CFU/mL of the original culture in scientific notation. 2. If 10 uL is plated from dilution (C), how many colonies should grow on the plate?

MSA (Mannitol Salt Agar) Match the description to the correct Bacterium A= growth, agar is yellow B= Growth, agar is not yellow C= no growth

Describe characteristics of Streptococcus Agalactiae in the Agar: (How does colonies look like (color) and explain does it grow on that agar. (Don't have to write the incubation period) ~ Only describe how would it look like on the Agar:  Blood Agar (Aerobic) MacConkey EMB PEA Mannitol Salt Agar Chocolate Agar Nutrient Agar

Listen Which of the following methods of microbial control is used most often with surgical equipment? a) autoclave b) sugar and salting c) dessication d) lyophilization

In performing the Kirby-Bauer procedure in a clinical laboratory setting, why must the agar be a certain depth? Why must the absorbance of the inoculum be standardized?

Why should bacterial culture plates be incubated inverted (bottom up)?

50 g of food is homogenized in 450 mL of water. From this, 1 mL is added to 29 mL of water, and then a 1:90 dilution is made from this, and then 1 mL from this is added to 99 mL of water, and then 100 uL of this last dilution is plated and after incubation 164 colonies are counted.a) What was the overall dilution factor?b) What was the total CFU/g of the original sample?

A lab technician is working with a bacterium in pure culture (in 5 ml of liquid media in a test tube). The bacterium is a mesophile that can infect humans. Which of the following is NOT true (with regards to temperature conditions for this bacterial culture)?     Lowering the temperature to -10 deg C for at least an hour will likely kill all the bacteria.     Placing the tube at 37 deg C will likely facilitate rapid growth of the bacteria.     Raising the temperature to 90 deg C for at least an hour will likely kill all the bacteria.     Placing the tube at 4 deg C will likely slow or halt growth of the bacteria.

Human error is a factor in the Kirby-Bauer procedure that often contributes to variation in zone size. Circle the effect on the zone size if the following occurred: ● ● Overinoculating the agar with bacteria: Waiting too long to place disks after inoculation: Using a culture that is less than 0.5 MacFarland: False increase False increase False increase False decrease False decrease False decrease

After an antimicrobial drugs test, the following results were obtained from a disk-diffusion test against a bacterium.   Antiboitic A= 6mm Antibiotic B= 18mm Antibiotic C= 11mm Antibiotic D= 19mm which drug should be used to treat an infect caused by this bacterium (assuming everything else is equal about these antibiotics)?