Lab 28 Goals and Objectives:

Read results

Exercise 31: Lethal Effect of UV Light

Exercise 33: Effectiveness of Alcohol as an Antiseptic

Exercise 36: Effectiveness of Hand Scrubbing

Exercise 34: Antimicrobial Sensitivity Testing

Exercise 35: Evaluation of Antiseptics

Read results

Exercise 31: Lethal Effect of UV Light Score plates (+++, ++, +, -) for growth using control side of each plate

as +++ for comparison; record on class sheet

Cover half with paper card

UV Exposed side

Control (was covered)

Read results

Exercise 31: Lethal Effect of UV Light Score plates (+++, ++, +, -) for growth using control side of each plate

as +++ for comparison; record on class sheet

Exercise 33: Effectiveness of Alcohol as an AntisepticCalculate percent reduction for control, dip and swab

Colony count 1st press = 100%Colony count 1st press – Colony count 2nd press = reduced number of bacteria (Colony count 1st press – Colony count 2nd press)

Percent reduction = x 100 Colony count 1st press

Exercise 38: Effectiveness of Hand ScrubbingCalculate CFU/ml for each scrubbing round: don’t forget to multiply

by dilution factors:0.1ml → x 10 (0.1ml is 1/10 of 1ml)0.2ml → x 5 (0.2ml is 1/5 of 1ml)0.4 ml → x 2.5 (0.4ml is 2/5 of 1ml)

Exercise 34: Antimicrobial Sensitivity Testing

Figure 20.17

• Disk-Diffusion Test (Kirby-Bauer test) is used in determining what treatment of antibiotics should be used when treating an infection– to determine the inhibition of bacterial growth measured under standard conditions – a culture medium - the Mueller-Hinton agar– plate lawn of bacteria and place disks of known antimicrobials on the lawn – measure zones of inhibition (total diameter in mm)

• Record millimeter diameter on class data chart• compare to a standard table for that drug

– Sensitive– Intermediate– Resistant

• Determine if organism is resistant,

sensitive, or intermediate

Exercise 35: Evaluation of AntisepticsNote different effects Gram + vs Gram – for some agents