Microbial barrier properties of healthcare professional uniforms

Abstract

In this study, the microbial barrier properties of textiles for two bacterial endospores were investigated. The reusable hospital textiles (PET/cotton and Tencel®) most commonly recommended for the manufacture of healthcare professional uniforms were tested for microorganism permeability. The three-layer textile laminate PET/PU/PET, which meets the European standards for surgical drapes EN 13795, was used as the reference material in this study. The microbial barrier properties of PET/cotton, Tencel®, PET/PU/PET, and corresponding seams were tested after 1, 10, 20, 30 and 50 washing-and-sterilization cycles. Washing and sterilization were performed by hospital laundry services under strict and controlled conditions. The testing of dry textile materials was conducted under newly developed methods. The most resistant forms of microorganisms of apathogenic bacterial endospores of the Bacillus genus Geobacillus stearothermophilus and Bacillus atrophaeus were used for investigating the microbial barrier permeability of textiles. This research is the first to investigate the permeability of these microorganisms in dry conditions. Additionally, the microbial barrier properties of the seams of these textiles were investigated. Regression analyses were performed and the effects of the seams on microorganism permeability were determined. It can be concluded that the two most commonly used seam types for the manufacture of healthcare uniforms do not have a significant influence on microbial barrier efficacy; however, the seam type 1.01.05/504.504.301 is more suitable for the manufacture of healthcare professional uniforms.

Keywords

microbial barrier healthcare professional uniforms seam sterilization

Healthcare workers (HCW) are exposed to numerous microorganisms when working directly with patients in a hospital setting. This exposure can lead to the transmission of disease from patient to healthcare professional, from patient to patient, as well as from healthcare professional to healthcare professional. Understanding the properties of textile permeability and the permeability of the seams of these textiles, in dry conditions, is critical to developing protective attire for healthcare professionals. The characteristics of the seams of healthcare professionals’ uniforms determines the overall product performance as a barrier to the spread of microorganisms. The seam provides a barrier against particulate, liquid, and gas/vapor, as well as potential chemical resistance and a biological barrier.^2–5 Conventional sewing techniques of interlacing or the interloping of threads by needles can leave holes in the fabric. Liquid penetration through these holes may result in functional failure of garments like gloves, lifejackets, inflatable boats, inflatable arm bands, wet-weather clothing, chemical protective clothing, footwear, and hospital staff uniforms.⁶ The aim of this work is to determine how the seam affects microorganism permeability. Additionally, the effects of the number of washings upon the microbial barrier were investigated.⁴

Due to the problems caused by disposable medical textiles, hospitals prefer reusable hospital textiles, which are reused after washing and sterilization. Ecological and financial problems imposed by the special waste management methods of single-use materials are thus significantly reduced. However, reusable hospital textiles may cause problems related to microorganism control. These textiles are in constant contact with microorganisms^3,4,7 and are recognized as a vehicle supporting cross-contamination, and microbial survival, but not necessarily growth. Since they retain moisture, reusable hospital textiles can be a source of contamination.^8,9 In order to survive, microorganisms require an environment full of nutritive substances (humid air or wet textile products), and they feed on skin cells.¹⁰ Fiber additives, such as lubricants and antistatic agents, in addition to other contaminants such as dirt, may act as nutrients for microorganisms. Textiles are a common material in healthcare facilities; therefore it is important that they are not a vehicle for the transfer of pathogens between healthcare professionals and patients, as well as between healthcare professionals.^11,12 Natural fibers are more prone to the influence of microorganisms.¹³ Due to their porous hydrophilic structure, which retains water, oxygen, and nutrients, cellulosic fibers such as cotton are suitable for the proliferation of microorganisms.¹⁴ During a microbiological attack, enzymes influence the release of sugars from cellulose, which can be used as a source of carbon needed for microbial growth.¹³ Cellulosic fibers are more prone to the growth of fungi compared to protein fibers, which are more susceptible to the growth of bacteria. Most synthetic fibers are microbiologically more resistant due to high levels of hydrophobicity.¹⁵

During the washing and sterilization practices for reusable hospital textiles, antimicrobial treatments have to be effective enough to kill the causative agents.¹⁶ Textile materials are not resistant to microorganism survival, which is why various antibacterial finishes and disinfectants have been developed. Unfortunately, strong antimicrobial substances can be hazardous to the environment. Moreover, they can also have a negative effect on the properties of textile fibers and textile products, shortening their life-span. For this reason, reusable hospital textiles have to be replaced frequently.⁹ Healthcare professional uniforms are a potential source for transferring microorganisms and should have well-tested microbial barrier properties in both wet and dry conditions. That is, they should provide protection against microorganisms penetrating through the material and seams. As early as 1950, Beck recognized that the materials used for surgical drapes do not have an efficient microbial barrier, however it was not until 1975 that the textile industry started to develop effective anti-microbial materials for surgical drapes and covers.^17–19 Healthcare professional uniforms are a potential source for transferring microorganisms from patient to healthcare professional and vice versa, and from one patient to another. Wiener-Well et al.²⁰ conducted a study investigating the bacterial contamination of doctors’ and nurses’ uniforms. This research found that over 60% of samples taken from the abdominal area, end of sleeves, and pockets of the uniforms of these healthcare workers tested positive for potentially dangerous bacteria. Several studies have found that the bacterial contamination of healthcare professional uniforms occurs during patient treatment, which can lead to cross-contamination. Furthermore, it was shown that the maximum contamination occurs at the pocket area where there is continuous contact of washed hands with the uniform, potentially contaminating washed hands.^21–25 Textile materials can transfer not only natural flora, but also pathogenic microorganisms.^26,27 Bacteria can move through the air from one person to another or from object to object and then transferred during contact. Some areas of the surgical space that are not frequently touched, such as curtains, are not cleaned frequently, and a recent study found that 40% of these areas harbored pathogenic bacteria.⁸ Another study found that 20% of infections occurring after surgical treatment are caused by microorganisms existing in surgical drapes.²⁸

The exposure of healthcare workers to pathogenic bacteria can also result from contact with an infected person, contaminated object, or inappropriate care.²⁹ Maximizing prevention of hospital infections is the best approach to patient and healthcare worker protection. For this reason, the barrier properties of healthcare worker uniforms in both wet³⁰ and dry conditions^31–33 have been investigated.

Methods and materials

Textiles used

Reusable hospital textiles, Polyethylene terephthalate (PET)/cotton, and Tencel®, intended for manufacturing healthcare professionals’ uniforms were tested for microorganism permeability. A three-layer textile laminate, PET/Polyurethane (PU)/PET, used for surgical drapes, was also investigated. Microbial barrier properties of these textile materials and their seams were tested after 1, 10, 20, 30, and 50 washing-and-sterilization cycles. In today’s operating rooms the use of 100% cotton material is avoided since it creates dust.^34–36 The constructional parameters of fabrics were tested according to the following standards: ISO 2060 (yarn count), ISO 7211-2 (fabric density), and ISO 3801 (fabric mass) (see Table 1).^37–39

Table 1.

Properties of the textiles used

Sample	Linen	Composition (%)	Weave		Mass per area (g/m²)	Yarn count (tex)		Density (threads/cm)
Sample	Linen	Composition (%)	Weave		Mass per area (g/m²)	Warp	Weft	Warp	Weft
I	PET/cotton	50/50	Plain weave	Mean	178.6	28.6	42.3	34	25
				SD (%)	2.1	0.4	0.7	0	0
				CV (%)	1.2	1.3	1.6	0	0
II	Tencel®	100	Bluette 2/1	Mean	193.7	22.8	31.3	50	27
				SD (%)	1.5	0.5	0.4	0.4	0
				CV (%)	0.8	2.3	1.4	0.9	0
III	PET/PU/PET	Three-layer textile laminate		Mean	216.0
				SD (%)	0.4
				CV (%)	0

PET: Polyethylene terephthalate; PU: Polyurethane; SD: standard deviation; CV: coefficient variation (%).

A three-layer textile laminate was used as a reference material as it meets European standards for surgical textiles EN 13795 and also meets dry and wet microbiological tests.

Sewing conditions

For testing microorganism permeability through seams, the samples were stitched with seam type 1.01.05/504.504.301 and seam type 1.01.02/301.504 (ISO 4916). The test field was round, and the seam was placed along the diameter (Figure 1).⁴⁰

Figure 1.

Schematic overview of the seam types used. (a) Seam type 1.01.05/504.504.301; (b) seam type 1.01.02/301.504.

A universal sewing machine (Brother Industries, Ltd., Japan, label S-7200B-403) was used for sewing the test samples. The machine sews with a lockstitch, stitch type 301 (ISO 4915). The parameters set on the machine were: stitch density, 5 stitch/cm; stitch sewing speed, 5000 min⁻¹; needle size, 90 Nm. Polyester (100%) thread size 2 × 22 tex was used for sewing the samples. Seam type 1.01.05/504.504.301 was ironed in all directions, while seam type 1.01.02/301.504 was ironed in only one direction.

The diameter of the hole left in the fabric from the passing of the needle marked 90 Nm (needle thickness 0.9 mm) is diminished due to the diameter of the thread being smaller than the diameter of the needle. The reason for the diminished hole is the release of the needle from the material, the return of the spaced threads, and the smaller diameter of the thread in the material than the diameter of the needle (Figure 2).

Figure 2.

Picture of the hole left from the passing of the needle. (a) Microscopic view of stitches with scale in mm; (b) Size of the openings between stitches.

Washing conditions

The samples were washed in a washing machine specifically built for hospital linens, a continuous assembly Jensen washing machine (Jensen-Group Belgium). Samples were then dried in a drum dryer. The sterilization of samples was performed in a Selectomat PL MMM steam sterilizer (Münchener Medizin Mechanik, Deutschland) for five minutes at 134℃. Washing and sterilization were performed in hospital laundry services under strict and controlled conditions (see Table 2). Sterilization was performed after each washing cycle at 134℃ for 5 min.

Table 2.

Washing parameters

Sample	Linen	Pre-washing	Washing	T (min)	Disinfecting agent	Neutralization	T (℃)	BR
I	PET/cotton	5 g/kg C^a 1.5 g/kg C^b 1 g/kg C^c	2.1 g/kg C^a 0.5 g/kg C^c	12	6 g/kg C^d	1.5 g/kg C^e	70	1:5
II	Tencel®	3 g/kg C^a 5 g/kg C^b 0.5 g/kg C^c	4 g/kg C^a 0.5 g/kg C^c	6	6 g/kg C^f	1.0 g/kg C^e	85	1:3
III	PET/PU/PET		4 g/kg C^c 2.5 g/kg C^a		–	0.7 g/kg C^e	60	1:5

Commercial names of all products are left out due to secrecy of the participant laundry and impartiality of the research. C^a – polycarboxylate (<5%), sodium hydroxide (10–20%); C^b – sodium carbonate (30–50%), sodium silicate (10–20%), etoxylated fat alcohol >5EO (2–5%), phosphonate (1–2%), citric acid (0.5–1%); C^c – etoxylated fat alcohol < C15 & <5EO (25–30%), solvent, 2-propanol, methanol (0.1–0.25%), amphoteric surfactants (1–2%), additives (0.1–0.25%); C^d – hydrogen peroxide (20–25%), acetic acid (10–20%), peracetic acid (5–10%); C^e – formic acid (50–100%); C^f – hydrogen peroxide (30–50%), acetic acid (2–5%), peracetic acid (2–5%); BR – liquor ratio.

Microorganisms used

Bacterial spores of the Bacillus genus Geobacillus stearothermophilus 105 (ATCC 12980, DSM 22) and Bacillus atrophaeus 106 (ATCC 49337, DSM 7264) were used as their primary purpose is to serve as a biological sterilization control.

This work was specific because of the use of spores, which can survive in a dry environment, while suspensions of various types of microorganisms were used in similar evaluations (Figure 3). The use of a suspension moistens the fabric and the permeability is changed. With the use of spores, we were able to keep the fabric dry and test the properties in conditions similar to those in the storage of sterile equipment.

Figure 3.

(a) Biological indicators (MesaLabs, Inc. USA). (b) Bacterial spores: Geobacillus stearothermophilus and Bacillus atrophaeus recorded with SEM at a magnification of 30,000×.

Microbial barrier properties

Figure 4 shows the newly developed method for testing dry textile material; this method is explained in detail in the cited literature.^31–33

Figure 4.

Schematic of microbial barrier permeability testing.

Textile samples were prepared by fixing them on an O-ring device and then placed in transparent packaging. The packaged samples were subsequently exposed to sterilization at 134℃ for 5 min, after which the packaging was opened in a sterile environment to prevent contamination. In aseptic conditions, the spores were rubbed in equal motions on the front side of the tested samples, as well as on the seam placed across the diameter of the sample (test field 78 cm², 90 samples). The procedure was then repeated in the same order with the biological indicator stick reversed. A print was taken using a CT3P agar print plate (bioMérieux SA, Marcy I’Etoile, France), first from the back side, and then the front side, with a new plate. Agar plates were incubated for 72 h at 35℃, after which colony forming units (CFUs) were counted. This procedure was repeated following each washing and sterilization cycle.³¹

When testing the resistance of textiles to the permeability of microorganisms in their dry state, according to EN ISO 22612, contaminated talc is applied to the test material and pressed by a weight.⁴² Mechanical vibration distributes the talc uniformly. The talc falls onto the nutritive cultural sample pad. Permeability of the bacteria is determined by counting the number of bacterial colonies on the agar plate. This newly developed method of testing microbial barrier permeability in dry conditions involves directly rubbing the microorganisms onto the sterilized samples.³¹

Air permeability

The rate of air flow through a specified area of fabric is measured as the pressure difference across the fabric test area over a given time period. The measurement of air permeability is conducted according to ISO 9237 (Determination of the permeability of fabrics to air), and testing was carried out using a SDL (Shirley Development Laboratories) Atlas MO21S, with a pressure of 100 Pa and sample area of 5 cm². Ten different measurements of each sample were carried out and mean values were calculated. Air permeability R (mm/s) was calculated using equation (1)

R = \frac{\bar{q_{V}}}{A} \cdot 167

(1)

where

\bar{q_{V}}

is the arithmetic average of the air flow rate (dm³/min); A is the fabric area subjected to the test (cm³); 167 is the volume conversion factor for the transition (dm³/(min × cm²), mm/s).

Results and discussion

The results of testing microbial barrier permeability of HCW uniforms (PET/cotton 50%/50%, 100% Tencel® and the three-layer textile laminate PET/PU/PET) after extreme contamination by bacterial spores Geobacillus stearothermophilus 10⁵ and Bacillus atrophaeus 10⁶ are shown in Table 3 and Figure 5 –7.

Table 3.

Results of microbial barrier permeability for the tested medical textiles after extreme contamination with bacterial spores Geobacillus stearothermophilus and Bacillus atrophaeus (n = 270)

Samples	Washing and sterilization	Number of isolates	Colonies/plate Mean ± SD (range)
Samples	Washing and sterilization	Number of isolates	Without seam	1.01.05/504.504.301	1.01.02/301.504
PET/cotton	1 W+S	18	11 ± 6.1 (4–18)	5 ± 2.9 (1–9)	2 ± 2.9 (1–9)
	10 W+S	18	14 ± 6.6 (6–21)	4 ± 2.4 (1–7)	2 ± 2.4 (1–7)
	20 W+S	18	9 ± 3.6 (4–15)	3 ± 2.4 (1–7)	8 ± 3.6 (1–12)
	30 W+S	18	7 ± 6.3 (0–15)	4 ± 3.2 (1–9)	10 ± 5.4 (1–17)
	50 W+S	18	2 ± 1.5 (0–4)	4 ± 1.9 (1–6)	10 ± 4.3 (1–15)
Tencel®	1 W+S	18	7 ± 4.6 (1–12)	0	0
	10 W + S	18	8 ± 4.7 (2–13)	0	0
	20 W+S	18	2 ± 2.2 (0–6)	0	1 ± 2.3 (0–6))
	30 W+S	18	3 ± 2.4 (0–6)	0	6 ± 4.1 (0–10)
	50 W+S	18	2 ± 2.7 (0–7)	0	6 ± 5.5 (1–13)
Laminate PET/PU/PET	1 W+S	18	0	0	0
	10 W+S	18	0	0	0
	20 W+S	18	0	0	0
	30 W+S	18	0	0	0
	50 W+S	18	0	0	0

Figure 5.

Regression analysis of washing and sterilization effects on microbial permeability of HCW uniforms. CFU: number of colony forming units penetrating the back side.

Figure 6.

Regression analysis of the influence of washing and sterilization on microbial barrier permeability of HCW uniforms on the seam: seam type 1.01.05/504.504.301. CFU: number of colony forming units penetrating the back side.

Figure 7.

Regression analysis of the effect of washing and sterilization on microbial barrier permeability of HCW uniforms on the seam: seam type 1.01.02/301.504. CFU: number of colony forming units penetrating the back side.

The results of testing the microbial barrier permeability of medical textiles after extreme contamination by bacterial spores show that the sample of the three-layer textile laminate that was tested does not allow permeation of microorganisms in their dry state even after 50 washings and sterilizations. The Tencel® sample has better microbial barrier properties than the PET/cotton sample. It was also noted that the barrier property increases during washing and sterilization, since the density of the textile samples increases following washing and sterilization procedures (Figure 5).

Properties of the microbial barrier on seam type 1.01.05/504.504.301 are shown in Figure 6, while Figure 7 shows the properties of seam type 1.01.02/301.504.

Microorganism permeability on seam 1.01.05/504.504.301 was lower than directly on the fabric (no seam). This tendency can be explained by the seam type, since the number of layers increases, resulting in a double layer of the fabric. The results also showed that microorganism permeability at the seam occurred only with the PET/cotton sample, while in other samples the microorganisms did not penetrate the seam (Figure 6).

Regression analysis of the effects of washing and sterilization on microbial barrier permeability of HCW uniforms on seam type 1.01.02/301.504 showed the highest level of microbial permeability for the sample PET/cotton and Tencel® (Figure 7). These results could be explained by the fact that the fabric is damaged by the needle, and this damage spreads during washing. Another possibility could be that the seam was only ironed in one direction, leaving only one layer of fabric on one side of the seam and three layers of fabric on the other side. Three-layer textile laminate PET/PU/PET did not show signs of permeability across the seam.

The results of testing air permeability of HCW uniforms (PET/cotton 50%/50%, 100% Tencel® and three-layer textile laminate PET/PU/PET) are shown in Figure 8 and Table 4. The properties of airflow across the seam (seam type 1.01.05/504.504.301) are shown in Figure 9, while Figure 10 shows the properties of seam type 1.01.02/301.504.

Figure 8.

Regression analysis of the effect of washing and sterilization on air permeability of the HCW uniforms.

Table 4.

Air permeability of the tested medical textiles R (mm/s) according to EN ISO 9237:2003.⁴³

Samples	Washing and sterilization	Air permeability
		Without seam			1.01.05/504.504.301			1.01.02/301.504
		R (mm/s)	SD (%)	CV (%)	R (mm/s)	SD (%)	CV (%)	R (mm/s)	SD (%)	CV (%)
PET/cotton	10 W+S	184.0	15.1	16.4	113.6	4.9	7.1	230.5	10.6	9.2
	20 W+S	170.3	4.7	5.5	132.3	4.7	7.1	242.5	9.6	7.9
	30 W+S	135.3	3.5	5.2	148.3	2.2	3.0	238.5	8.2	6.9
	50 W+S	131.3	7.2	11.1	142.3	2.2	3.1	226.5	7.6	6.7
Tencel®	10 W+S	221.0	4.7	4.3	180.4	3.5	3.9	280.6	21.9	15.6
	20 W+S	202.4	5.2	5.1	180.4	5.0	5.6	278.6	14.3	10.3
	30 W+S	178.4	3.9	4.4	190.4	3.5	3.7	262.5	13.9	10.6
	50 W+S	168.3	4.6	5.5	168.3	4.2	5.0	246.5	6.7	5.5
Laminate PET/PU/PET	10 W+S	0	0	0	10.4	3.5	3.9	37.9	0.8	4.3
	20 W+S	0	0	0	9.6	5.0	5.6	35.9	1.5	8.4
	30 W+S	0	0	0	9.8	3.5	3.7	30.9	1.2	8.1
	50 W+S	0	0	0	9.4	4.2	5.0	31.9	2.3	14.4

W+S: washing and sterilization; R: (mm/s) average air permeability (n = 10).

Figure 9.

Regression analysis of the influence of washing and sterilization on air permeability of HCW uniforms on the seam: seam type 1.01.05/504.504.301.

Figure 10.

Regression analysis of the effect of washing and sterilization on air permeability of HCW uniforms on the seam: seam type 1.01.02/301.504.

It is assumed that air permeability increases at the seam after washing seam type 1.01.05/504.504.301 (Figure 1(a)), and that this is due to the openings between stitches increasing following repeated washing. The size of the openings depends on the distance between stitches. The seam 1.01.02/301.504 (Figure 1(b)) is not subject to this phenomenon since the fabric covers the seam.

The results for air permeability of the seamless textiles showed a decrease in permeability with the increasing number of washings and sterilization, while the laminate samples were not found to be permeable to air penetration (Figure 8).

Air permeability of seam 1.01.05/504.504.301 (Figure 9) was lower than for the fabric (without seams, Figure 8) and was lower than for seam 1.01.02/301.504 (Figure 10). The Tencel® sample had better air properties than the PET/cotton sample. Permeability increased in test samples that were stitched with seam type 1.01.02/301.504, compared to samples with no seam.

Understanding the permeability of HCW uniforms is of critical importance to the safety of HCW and patients, and the reduction of the spread of disease in the hospital setting. Although single-use textiles have repeatedly been shown to be most effective against microorganism transmission,^25,44 disposal, waste, and environmental factors limit the feasibility of single-use garments as a viable long-term solution for HCW uniforms. Research on the durability of reusable fabrics, including permeability of microorganisms through fabrics in both wet and dry conditions, is critical for determining the safety and efficacy of the fabric of HCW uniforms. In 2001, Perry found that 52% of nurse uniforms were contaminated with methycillin-resistant Staphylococcus aureas (MRSA) and vancomycin-resistant enteroccoci (VRE).²⁵ Several years later, Osawa also found that 79% of lab coats were contaminated with MRSA.² In a study by Wiener-Well and colleagues, 135 uniforms of both nurses and physicians were examined and over 60% of these were colonized with potentially pathogenic bacteria, in particular with resistant bacteria.²⁰ It has been well documented that moist fabric has a higher transfer of bacteria than dry fabric, and that contact/rubbing of fabrics increases transmission over five times.¹ However, to date there is little data on dry fabric permeability to bacteria.

Conclusions

This study examined the permeability of HCW uniform fabric, as well as the influence of the fabric seam on microbial barrier properties. The testing of dry textile materials were conducted under newly developed methods. The most resistant forms of microorganisms of apathogenic bacterial endospores of the Bacillus genus Geobacillus stearothermophilus and Bacillus atrophaeus were used for investigating the microbial barrier permeability of textiles. The effects of washing and sterilization were studied to see what impact these procedures had on the microbial barrier properties of fabric and their seams.

The results of this study found that the three-layer fabric laminate PET/PU/PET is most effecting against the permeability of the microorganisms studied, with no bacteria found to permeate the fabric samples even following 50 washing and sterilization cycles. When comparing Tencel® and PET/cotton, Tencel® was found to be more effective in preventing transmission of the microorganisms studied through the fabric, and that microbial permeability decreased over time as the density of the cellulose fabrics increased with washing and sterilization. Regression analysis of seam type found that seam type 1.01.05/504.504.301 was only found to be permeable in the PET/cotton samples, whereas seam type 1.01.02/301.504 showed greater permeability with both Tencel® and PET/cotton samples. It can be concluded that the two most commonly used seam types for manufacturing HCW uniforms do not have a significant effect on microbial barrier fabric efficacy. Seam type 1.01.05/504.504.301 (Figure 1(a)) may be more suitable for manufacturing HCW uniforms because of its lower risk for cross-contamination. This is likely due to the fact that three layers of fabric protect the seam from transmission of bacteria, whereas seam type 1.01.02/301.504 may be less resistant due to the fact that tension on the fabric at the seam can create openings between the fabric pieces and allow for the transmission of bacteria. Further research is needed to investigate the permeability of other bacteria, including MRSA and VRE, in this setting.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

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