Question

1 Week 2-Discussion Activities Hospitals, nursing homes, and other patient care facilities require an effective cleaning and disinfection program to maintain aseptic conditions and prevent microbial contamination and infection control problems. The qualification of a chemical disinfectant to be used in these environments is extremely important Disinfectant qualifications require more planning, time and resources than many facilities realize. The patient care issues and difficulties that will occur if a disinfectant does not perform as it should is a major concern in any facility. You studied in Chapter 6 how microorganisms grow - their requirements such as temperature, pH, carbon, trace elements, and oxygen (or the lack of it). So, now you know some of the substances needed for microbial growth. Now, let's say you are working as a nurse in a hospital and the environmental services (housekeeping in the old days) wants to purchase and use a new disinfectant in the facility. ms, now we want to eliminate them from patient care areas. You have been assigned by the DON to become a member of a committee to evaluate the use of a new disinfectant The American Society for Microbiology (ASM) has established the following steps in the evaluation of effectiveness of a disinfectant. Step 1: Determine the Test Method Step 2: Determine the Challenge Organisms Step 3: Determine the Surface Types to be Tested Step 4: Determine Expiration of Disinfectants Step 5: Method Validation (Making sure your testing methods actually work)

Answer 1

Answer : disinfectant test are usually performed using 5x5 cm tiles of surface material ,referred to as test carriers ,contaminated with relevant micro organism

The disinfectant is applied at a strength used in practice ,leftvon the test carrier for an appropriate time ,dropped into a neutralizing solution ,and rinsed .

The micro organism in the rinsing solution are then investigated ,either by incubating the solition on agar plates or the filter obtained after membrane filtration is incubated on agar.

This is followed by enumeration procedure .

Example :

Step 1 : suspension method

Step 2 : bacillus subtilis , escherichia coli ,candida albicans ,aspergillus niger ,staphylococcus aureus .

Step 3 : sop for preparation of microbiological media.

Suspension method :

Objective :

To establish the test concentration and the contact Time a suspension test estimate the invitro bacterial activity of disinfectant under microbial strain

Procedure :

Prepare the culture suspension from the original culture as per SOP for preparation of microbiological culture media .

Select the dilusion which will yield 10 '5 to 10 '6 cells per ml.

Prepare 10 ml of test dilution to be tested with sterile distilled water.

Vortex the tube for 1 minute .

Add 0.1 ml of any one culture containing 10'5 to 10'6 cells per ml into the test disinfectant with the dicided concentration

The final concentration shall be 10'4 to 10'5 cells per the tube .consider preoaration for 0 minute .

Prepare like same above for other 3 different sets for 3 different time intervals .

Give contact time 0, 5 min,10 min,15 minutes .

After specified contact time ,filter the samples through 0.45 m membrane filter.

Give three washing of 100 ml each with sterile peptone water /sterile water.

After filtration place it in soybean casein digest agar.

Incubate bacterial culture at 20 _25 degree centigrade for 72 to 120 hours .

Afterincubation count the number of colonies present on membrane .

Note down number of colonies .

Select plates which have least to nil counts .

Proceed in the same manner taking all the cultures to be tested .

Contact time for the usage of disinfectant will be set on basis of the results ,which will have least counts .