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To evaluate the efficacy of all-purpose cleaners with inactivating a surrogate virus for COVID-19 on a hard surface without agitation.
Pour Plate Method - MS2 Bacteriophage
Six hours prior to one run (26 plates), E.coli 15597 was subcultured into three milliliters of tryptic soy broth (TSB) screw-cap tubes and incubated at 37°C (98.6°F). Four glass Petri dishes, each containing one stainless steel coupon, along with 27 screw-cap tubes filled with 10ml of 0.5X tryptic soy agar (TSA) were autoclaved. The biosafety cabinet (BSC) was sprayed with 70% v/v isopropyl alcohol using a paper towel before spraying any items going into the BSC. Once autoclaving was complete, the TSA tubes were placed into a 45°C (113°F) D.I. water bath inside the biosafety cabinet (BSC). The four glass Petri dishes were marked using a black sharpie to designate the positive (P+), negative (N-), Test 1 (T1), and Test 2 (T2). Ten microliters of the organism were pipetted onto the P+, T1, and T2 stainless steel coupons and air-dried for 15 minutes. A motorized pipette with 10ml tips was used to pipet 15 ml of Dey-Engley (D/E) neutralizing broth into four separate 50ml conical tubes labeled P+, N-, T1, and T2. Once the MS2 bacteriophage dried on the coupons, the P+ coupon was placed into the conical tube. The N-, T1, and T2 were pipetted with 1000μl of the cleaning solution onto each coupon for one minute before immediately placing them in the conical tube with an autoclaved forceps. The conical tubes were then placed on the shaker for 10 minutes. During this time, using the 1000ml pipette, 900ml of 1x phosphate-buffered saline (PBS) was pipetted into nine autoclaved dilution tubes, and serial dilutions were made for P+, T1, and T2 up to 10-4 using 100μl of the shaken D/E broth. Once the six-hour sub-time was complete, the E. coli 15597 subculture was removed from the incubator for use. For each variable (N-, P+, T1, and T2), 100μl of the stock and serial dilutions of MS2 bacteriophage, and 100μl of the E.coli 15597 subculture were combined into an empty dilution tube. A screwcap tube of 0.5X TSA was removed from the water bath, wiped with a paper towel to remove moisture, and poured into the dilution tube. The mixture was immediately poured into a sterile polystyrene petri dish; swirled to cover the entire plate surface, and then air-dried before covering. Dried Petri dishes were placed into a clean labeled zip lock bag that was partially closed and incubated at 37°C overnight. Plates were counted the following day based on the clear lysis zones in the bacterial lawn of growth (1 plate forming unit) to calculate log reduction and percent removal.
|Product Name||New/ Old Bottle||Log Reduction||% Reduction|
|Castille Lavender Soap||Old||0.97||89.0877|
|Annie’s Pure and Simple||Old||1.3897||94.0945|
|Annie’s Pure and Simple||New||TBD||TBD|
|Mrs. Myers Clean Day||New||TBD||TBD|
Products in the results labeled "old" were at least two years old since purchase and or opening. Products were considered "new" if they were purchased and or opened within a year. The cleaning products were all ready-to-use (RTU) except the Castille Lavender Soap which used Dr. Bronner's All-Purpose Cleaner dilution of ¼ cup of soap in a quart of water in a spray bottle. Annie's Pure and Simple "old" product was not shaken first before using for this test.
The 409 Multi-Surface cleaner contains quaternary ammonium compounds and is meant for disinfection whereas the all-purpose cleaners were designed without the intention of disinfecting.
Success Rating:Results successful using TACT (time, agitation, concentration, and temperature, as well as rinsing and drying) and/or other cleaning chemistries examined.
409 Multi-Surface and ThreeMain Multi-Surface were the two effective all-purpose cleaners that had a 100% reduction of MS2 bacteriophage after one-minute contact on stainless steel. All of the other all-purpose cleaners performed between 0-1 Log reduction.