Beth Joiner is Manager of TechnicalSales and Services for the Georgia

Laboratory of North AmericanScience Associates, Inc. (NAMSA). She

is responsible for advising clientson technical matters, preparation of

routine and non-routine costestimates and proposals and

providing technical education,training and orientation to clients.

Ms Joiner has 24 years ofexperience in the field of

microbiology – four years withCustom Biologics and the Murray

State University Diagnostic andResearch Center and 20 years with

NAMSA. She is a member of theAssociation for the Standard Testing

of Materials (ASTM) and theAmerican Association of Textile

Chemists and Colorists (AATCC) RA31Antimicrobial Test Methods

committee and the American Societyof Microbiology (ASM). Ms Joiner isa registered microbiologist with theNational Registry of Microbiologistsin the area of consumer products

and quality assurance microbiology,pharmaceutical/medical devices/cosmetics. She has published an

article on determining antimicrobialefficacy in Nonwovens Industry

Magazine and wrote a chapter,“Determining Antimicrobial Efficacy

and Biocompatibility of TreatedArticles Using Standard Test

Methods”, in the American ChemicalSociety (ACS) Symposium Series 792

Bioactive Fibers and Polymers. MsJoiner holds a BSc Degree in

Biological Sciences from MurrayState University.

a report by

B e t h J o i n e r

Manager, Technical Sales and Services,

Georgia Laboratory of North American Science Associates, Inc. (NAMSA)

The purpose of this article is to determine which floorcovering performed the best when challenged withmultiple bacteria, mould and yeast. Antimicrobialefficacy testing was performed on four floor-coveringsamples: homogeneous polyvinyl chloride (PVC)sheet; medical-grade soft surface floor; linoleum sheetmaterial with two coats of acrylic floor sealer and twocoats of acrylic floor finish; and linoleum sheetmaterial with factory finish.

The American Association of Textile Chemists andColorists (AATCC) test method 100 was the testmethod used to determine antimicrobial efficacy ofthese floor coverings. This method provided aquantitative procedure to evaluate the antimicrobialactivity and provided bactericidal data. The standardtest method normally uses two test organisms,Staphylococcus aureus and Klebsiella pneumoniae.However, for the purpose of this study, the followingorganisms were used as challenge organisms: fivebacteria, Staphylococcus aureus American Type CultureCollection (ATCC) 6538, Klebsiella pneumoniae ATCC4352, Pseudomonas aeruginosa ATCC 9027, Salmonellacholeraesuis ATCC 10708 and Bacillus cereus ATCC11778, both vegetative and spores; two fungi,Aspergillus niger ATCC 16404 and Stachybotrys chartarumATCC 9182; and one yeast, Saccharomyces cerevisiaeATCC 9763. A sample size of 48mm disc was cut foreach test organism and sample type. The test samplewas inoculated with a population of (1-2) x 105

colony-forming units per 0.1ml. The inoculum wascovered with a piece of sterile film to allow intimatecontact of the flooring surface with the test organism.One container with each floor type and each testorganism was incubated for 24 hours. The bacteriawere incubated at 37ºC±2ºC and the mould and yeastat 28ºC±1ºC. Duplicate containers of each floor typeand each organism were tested to determine thepopulation at zero time. Population at zero time wasdetermined by adding a neutraliser solution to eachcontainer and plating serial dilutions. The serial dilu-tion plates were incubated at 37ºC±2ºC for 48 hoursfor bacteria and 28ºC±1ºC for the mould and yeast.

The test containers that were incubated for 24hours were removed from their respectiveincubators and the population of any remaining

viable organisms was determined by adding aneutraliser solution to each container and platingserial dilutions. The serial dilution plates wereincubated at 37ºC±2ºC for 48 hours for bacteriaand 28ºC±1ºC for the mould and yeast.

All plates, both zero exposure time and 24-hourexposure time, were counted using a Quebec® ColonyCounter. The per cent reduction of bacteria, fungi andyeast for each test sample was calculated by taking theaverage of the zero time count plus the count of theinoculum concentration and divided by two. Next, thecount of each bacteria, fungi and yeast per sample fromthe 24-hour plates is subtracted from that average andthat number is divided by the average and multipliedby 100 to get per cent kill. The test results show thateach of the test samples mentioned, with the exceptionof the homogeneous PVC sheet, showed greater than99% reduction against non-spore-forming bacteria.One exception, other than the homogeneous PVCsheet, was the medical-grade soft surface floor thatdemonstrated a poor reduction against the gram-negative Pseudomonas aeruginosa. The spore-formingBacillus cereus showed good reduction in the vegetativestate for all samples except the homogeneous PVCsheet. The spore state of Bacillus cereus showed goodreduction for all samples except the homogeneousPVC sheet and moderate reduction for the linoleumsheet material with two coats of acrylic floor sealer andtwo coats of acrylic floor finish. The fungal results,specifically looking at the fungal count after 24 hours,compare very closely for all samples except thehomogeneous PVC sheet. The test results for the yeastalso compare very closely for all samples except thehomogeneous PVC sheet when looking specifically atthe yeast count after 24-hour contact.

In summary, the homogeneous PVC sheet was theonly test sample that consistently showed noeffectiveness against any of the challenge organisms.The medical-grade soft surface floor showedconsistent results against bacteria but was not aseffective in the kill of yeast and fungi. However, theother linoleum sheet material samples presented verycomparable results and show that they prevent thegrowth of bacteria, both vegetative and spore-formers, as well as yeast and mould. ■

Ant imic rob ia l E f f i cacy Compar i son o f F loor Cover ings

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Infection Control & Sterilisation FLOORING

B U S I N E S S B R I E F I N G : H O S P I T A L E N G I N E E R I N G & F A C I L I T I E S M A N A G E M E N T 2 0 0 4

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