Infection Control & Hospital Epidemiology
The transmission of pathogens is reduced with gloves compared to bare hands, but it is not eliminated. Improper use of gloves, such as failure to remove gloves after performing aseptic proce- dures, is associated with poor hand hygiene compliance.19,20 An observational study found the rate of improper glove use to be as high as 64.4% among HCP, resulting in possible microbial transmission almost 20% of the time.21 One of the most common pathogens causing HAI, Staphylo-
coccus aureus, and has been shown to be incorporated in >50% of ICU DSB samples obtained from hospitals in Australia and Great Britain.9 The transmission rate of planktonic S. aureus varies between glove types22 and was least with nitrile gloves when compared to vinyl and latex gloves. In this study, we used our model of DSB23 to determine whether biofilm cells can be transferred from one surface to another and whether glove composition affects transmission rate.
Materials and Methods Test gloves
We used 3 types of gloves to determine the transmission rate of biofilm bacteria: (1) Nitrile gloves, which are latex-free, single-use, examination gloves (Promed, Tanawha, Australia), (2) 100% latex gloves (Thermo Fisher Scientific, Scoresby, Australia), and (3) sterile surgical, nonlatex, neoprene (synthetic rubber) gloves (Ansell Gammex PF DermaPrene Glove, Richmond, Australia). The nonsterile nitrile and latex gloves were sanitized by rub-
bing with 70% w/v ethanol until dry. To confirm sterility, both the gloved thumb and fore finger were pressed onto the surface of a blood agar plate (Edwards Group, Narellan, New South Wales, Australia) and incubated at 37°C overnight. The hydrophobicity of each glove material was determined 3
times using contact angle measurements. Briefly, a 10-µL drop of water was placed on each glove and photographed using a side- mounted camera. The contact angle was then measured using, Microsoft Visio professional software (2013, Microsoft, Redmond, WA).
Preparation of Staphylococcus aureus dry surface biofilm
Staphylococcus aureus ATCC 29352 DSB was grown on poly- carbonate and glass coupons in the Centers for Disease Control
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biofilm reactor (BioSurface Technologies, Bozeman, MT) over a period of 12 days as previously described by Almatroudi et al.23 In brief, biofilm was grown for 48 hours in 5% tryptone soya broth. Biofilm bacteria were then adapted to low water availability by an initial 48 hours of dehydration followed by 3 cycles of 6 hours of hydration interspersed with dehydration periods between 42 and 66 hours long. The resulting biofilm contained ~107 colony- forming units (CFU) and mimicked hospital DSB particularly, with very thick EPS.23 Quantitative polymerase chain reaction (qPCR) measuring the number of culturable and nonculturable bacteria in DSB and have found 106–107 CFU/cm2 contaminating hospital surfaces in Australia and Saudi Arabia.9,24 The biofilm- covered coupons were washed 3 times with PBS, while still in the rods to remove planktonic and loosely attached bacteria.
DSB transfer test protocol
The test coupon was lightly gripped between gloved thumb and index finger tip and the rod was elevated to a height of 30cm and returned to the start position (Fig. 1). The same operator or investigator performed the grip action and all of the serial presses for all experiments to consistently replicate the amount of pres- sure. The contaminated finger and thumb tips were then serially pressed, up to 19 times, onto the surface of sterile horse blood agar (HBA) plates. The plates incubated aerobically for 48 hours. We tested DSB transfer for 12 coupons per glove type.
Effect of wetting DSB with neutral detergent on the transfer of bacteria
We tested the effect of neutral detergent on the transmissibility of DSB by wetting biofilm covered coupons for 5 seconds with neutral detergent containing 10% ethoxylated Nonylphenol (Lemax, Whiteley Medical, Tomago, Australia). This was thought to mimic general wetting of surfaces during routine cleaning in the healthcare environment. Excess detergent was drained before the test procedure
detailed above was repeated (12 tests per glove type).
Statistical analysis
The number of bacterial cells transferred was determined by counting CFU directly from HBA plates. Contact/agar plates have
Fig. 1. Diagramatic representation of the experimental procedure of testing dry-surface biofilm (DSB) transmission.
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