62
been previously used for environmental sampling in numerous scientific studies (as reviewed by Galvin et al25). This method provides a reasonable estimate of bacterial numbers and is comparable in accuracy to swab techniques.25 Initial control CFU/cm2 of dry surface biofilm and total CFU/cm2 transferred via each glove type separately were used to calculate the transfer rate26 according to the following formula: TR=100 × CFU blood agar/CFU on the coupon. Data were analyzed using Microsoft Excel (2013, Microsoft,
Redmond WA) and SPSS statistical software (IBM, Armonk, NY). One-way analysis of variance (ANOVA) was performed on the data obtained, followed by post hoc Tukey test for comparison within 2 main groups: detergent treated and untreated. The data were then split into both detergents treated and untreated group subsets to assess the transfer by each glove type.
Results
The readings obtained for contact angles of the 3 types of gloves tested for hydrophobicity are presented in Table 1. The greater the contact angle, the more hydrophobic the material is. Hence, latex gloves were the most hydrophobic, followed by nitrile gloves, and surgical gloves were the least hydrophobic.
Transfer rate of S. aureus dry surface biofilm bacteria to microbiological media using 3 types of disposable gloves
Touching DSB once and up to 19 consecutive times was sufficient contact to transfer the biofilm bacteria from the coupon to the glove and then to microbiological media by all 3 types of gloves tested (Fig. 2). Latex gloves transferred significantly less bacteria than nitrile gloves, which transferred significantly less bacteria than surgical gloves (P<.01) (Table 2). The “number” of touches were a significant factor affecting bacterial transfer (P<.01). Significantly less bacteria were transferred per touch as the number of times the fingers touched the agar plate increased (P<.01) (Fig. 3). For nitrile gloves, and to a lesser extent for surgical gloves, a very high number of bacteria were transferred during the first 5 touches (Figs. 3 and 4).
Effect of wetting with neutral detergent on transmission
Wetting the DSB-covered coupon with 5% detergent for 5 sec- onds significantly increased the number of bacteria transferred by 3 times on latex gloves, by 5 times on nitrile gloves, and by 7 times on surgical gloves (P<.01) (Fig. 2). Latex gloves transferred significantly less bacteria from detergent-treated DSB than either nitrile or surgical gloves (P<.01) (Table 2 and Fig. 4). In contrast to results obtained with untreated DSB, nitrile and surgical gloves transferred similar numbers of bacteria. Significantly more bac- teria were initially transferred per touch, but as the “number” of times the fingers were touched on the agar plate increased, less bacteria were transferred per touch (P<.01). After the tenth touch, the average bacterial cell count transferred dropped dras- tically with all glove types (Fig. 4).
Discussion
Older scientific studies suggested that the hospital environment contributed negligibly to the acquisition of HAI.27,28 This resulted in the frequency of hospital environmental sampling to decline
Fig. 2. Mean number of colony-forming units (CFU) of S. aureus dry-surface biofilm (DSB) cells transmitted via nitrile, latex and surgical gloves before (untreated) and after treatment (treated) with 5% neutral detergent for 5 seconds. Starting number of biofilm bacteria 107 S. aureus per coupon.
and eventually becoming restricted to endemic outbreaks.29 However, over the past 20 years, the role of contaminated hos- pital surfaces in spreading HAIs has been reassessed.7 The existence of DSB containing viable, multidrug-resistant
(55%–89%)20,33 by HCPs.8,34,35 Pathogens from hospital surfaces surrounding infected patient, such as bed rails, trolleys’ and bed surfaces, are potential source of HAI.36,37 Hayden et al38 observed that 52% of HCPs entering with sterile hands contaminated them after touching the environment of VRE-infected patients. Our current study confirms that viable bacterial cells
and -sensitive organisms on high-touch surfaces in the healthcare environment has been confirmed.9,30 Biofilms on dry hospital surfaces are composed of multiple species, and more than 50% contain S. aureus, one of the most common pathogens causing HAI.9 Extensive literature shows that traditional hydrated biofilm is more tolerant to biocidal action, including disinfection (see Otter et al31 for a recent review). We have also shown that DSB is even more tolerant to biocidal action.32 A number of scientific studies indicate poor hand compliance
from DSB are easily transferred to other surfaces via gloved hands with 1 touch up to 19 touches. The estimated infective dose for S. aureus is 15 cells per square centimeter (1.18 logs/cm2) and is thought to be sufficient to cause infections in lesions.39 The minimum number of bacterial cells transferred by each touch is far more than the minimum infective dose required for initiating HAI for all 3 types of gloves. Wetting the DSB with neutral detergent increased the transfer rate by 3- to 7-fold. The adhesive forces between bacterial cells and contact surfaces mainly determine the bacterial transmission where
Shamaila Tahir et al
Table 1. Contact Angles for 3 Types of Gloves With a Mean of 3 Replicates Contact Angle
Type of Glove Latex Nitrile
Surgical Note. SD, standard deviation. Mean
111.01 88.81 75.43
SD
9.64 7.02 2.65
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