Are multiple-use bottles of chlorhexidine solutions at risk of contamination in joint replacement surgery?

Abstract

Introduction

Chlorhexidine gluconate 2% w/v in isopropanol 70% solutions in multiple-use bottles is commonly used in surgery as a cost-effective method for skin disinfection. However, multiple-use bottles risk contamination. This study aims to test whether bacterial contamination of multiple-use bottles or their solutions occurs once open and on use between different patients.

Methods

Consecutive samples were taken each time a chlorhexidine bottle was used over a 7-day study period. Samples were tested using blood culture, agar plate and mass spectrometry.

Results

No growth was observed in 52 samples taken from 18 bottles inoculated into blood culture bottles. Four growths on agar plate culture were determined to be contaminants from the sampling process.

Conclusions

This study supports the use of multiple-use bottled chlorhexidine solutions as safe and cost-effective in surgical practice.

Introduction

Joint replacement is an effective surgical intervention that can dramatically improve a patient’s life by restoring mobility and reducing pain. As a result, it is commonly performed worldwide with increasing demand;¹ however, this exposes patients to the risk of developing a prosthetic joint infection (PJI) in approximately 1% of cases.² PJI is a devastating complication, causing significant morbidity.³ Its treatment requires invasive surgery to debride tissues and exchange implant components, followed by long inpatient stays for intravenous antibiotics.³ In addition to the human impact, PJIs are very costly to healthcare providers.^4,5 Therefore, every reasonable measure should be taken to reduce the risk.

Antimicrobial solutions are used throughout joint replacement procedures to reduce the risk of bacterial contamination. One commonly used solution is chlorhexidine gluconate 2% in isopropanol 70%. This is often used to clean the skin before incision and prior to closure.⁶ However, it is common practice to use chlorhexidine solutions stored in multiple-use bottles, which once open, are used for several patients. Typically, the recommended period of use may be up to 7 days before the bottle is discarded. Reuse of these bottles reduces cost and plastic waste compared with single-use devices. However, multiple-use may expose bottles to the risk of contamination.

This study aims to test the safety of multi-use chlorhexidine solutions by determining whether bacterial contamination of these bottles or their solutions occurs once open and on use between different patients.

Methods

Sample collection

This study was conducted in a high-volume UK arthroplasty unit between 3 and 12 July 2019. Standard practice at our institution is to store ECOLAB® chlorhexidine gluconate 2% w/v in isopropanol 70% bottles in the theatre preparation rooms. When required, the bottles are opened, and the solution is decanted into a sterile plastic pot for use in theatre. The bottle cap is then replaced and left ready for the next case. Bottles are labelled with the dates of opening and for discarding (7 days later). The bottles are handled by theatre staff wearing standard theatre clothing and nonsterile hats, masks and gloves.

To test for contamination, theatre staff were asked to continue with their standard practice with the addition of pouring the chlorhexidine solution into an additional sterile plastic pot. The first pot of chlorhexidine solution poured (pot 1) was used for testing because the initial pour will most likely capture any contaminants on the bottle rim. The second pot poured (pot 2) was taken to the operating room for clinical use. Pot 1 was then placed on a clean surface in the preparation room by a scrub practitioner or nurse wearing full sterile gown and gloves and nonsterile face mask and surgical hood for testing. A study operator then tested pot 1. A sterile 5-ml syringe and drawing-up needle was used to extract 3ml of the chlorhexidine solution for testing. A single drop was placed onto the surface of a Columbia blood agar (CBA) plate for direct cultures. With care taken not to contaminate the needle, the remaining test solution within the syringe was inoculated into a BD BACTEC™ PEDS Plus™/F plastic blood culture bottle for enrichment cultures. The bung of the blood culture bottle was cleaned with a single-use sterile 2% chlorhexidine and 70% alcohol disinfectant wipe before inoculation. The drop of test solution was then spread across the CBA plate using a sterile plastic inoculation loop by streaking it using a four-quadrant technique. The blood culture bottles and CBA plates were labelled with the chlorhexidine bottle number and the time and date the sample was taken. Steps were taken to ensure there was no cross-contamination during the sampling, including using an aseptic technique when handling the equipment. This process was repeated consecutively on each chlorhexidine bottle every time the solution was required in theatre until the bottle was emptied.

Microbiological methods

All blood culture bottles were incubated for 5 days at 35–37°C in a BD BACTEC™ automated system as per our institution’s laboratory standard operating procedure (SOP). Any positive growth indicated by the automated system was processed as per SOP, including an initial Gram stain followed by subculture onto solid agar plates. The CBA plates were incubated at 35–37°C and 5% CO₂ for 18–24 hours after which time they were observed for bacterial growth. Any positive growth underwent further identification of bacterial species by using matrix-assisted laser desorption ionisation-time of flight mass spectrometry.

Results

In total, 52 samples were collected from 18 different chlorhexidine solution bottles. The mean number of days chlorhexidine solution bottles were open was 2.3 (range 1–7 days) and the mean number of samples taken per bottle was 2.7 (range 1–5 samples). All samples underwent testing on both CBA plate and blood culture bottle. Of the 52 blood culture bottles incubated, all were negative for bacterial contamination. Four of 52 CBA plates tested were positive for bacterial growth (Table 1). Each of the four positive cultures came from different chlorhexidine solution bottles and grew a different species of bacteria. The four bacteria isolated were Staphylococcus epidermidis, Kocuria varians, Rothia dentocariosa and Staphylococcus hominis. Three of four positive cultures were followed by a negative direct culture on CBA plates on the next sample taken from the same bottle, and one was from the last sample taken from a bottle. All corresponding enrichment cultures collected in blood culture bottles to the positive agar plates also tested negative for bacterial growth.

Table 1 .

Presence of bacterial growth on each agar plate cultured

	Presence of bacteria
Bottle number	Sample 1	Sample 2	Sample 3	Sample 4	Sample 5	Sample 6
1	Positive	Negative	Negative	Negative
2	Negative	Negative	Negative
3	Negative	Negative	Negative	Negative	Negative
4	Negative	Positive	Negative	Negative	Negative	Negative
5	Negative
6	Negative	Negative
7	Negative	Negative
8	Negative
9	Negative	Negative	Negative	Negative
10	Negative	Negative
11	Negative
12	Negative	Negative	Negative	Negative	Positive	Negative
13	Negative	Negative
14	Negative	Negative	Negative	Positive
15	Negative
16	Negative	Negative
17	Negative	Negative
18	Negative	Negative	Negative	Negative	Negative

Every bottle of chlorhexidine was used a different number of times before being discarded, therefore the number of samples taken from each bottle was different. The blank cells indicate that no further samples were taken from the bottle of that row.

Discussion

This study aimed to identify whether multiple-use chlorhexidine and isopropanol solutions for skin disinfection are at risk of contamination and therefore pose potential risk for contamination and infection including PJI. Results suggest that the direct cultures on CBA plates were more likely due to contamination during study sampling or storage of agar plates than contamination of the test solution itself. This was confirmed by negative enrichment cultures of the respective samples as well as by negative subsequent direct cultures. This study therefore found no evidence that contamination was introduced to chlorhexidine bottles, or their solutions in a high-volume UK arthroplasty centre using modern microbiology testing protocols.

This study is limited by a small sampling period and relatively small sample size and, therefore, rare instances of contamination, if they occur, may have been missed. Because of the small study window, only a select number of theatre practitioners' techniques for decanting chlorhexidine solutions will have been tested for evidence of contamination. Chlorhexidine solutions are recognised as an effective antibacterial agent; however, there is evidence that antimicrobial resistance to chlorhexidine is increasing and that resistant bacteria are more commonly found in hospitals where there is selective pressure for their emergence.^7,8 Further research should be conducted to monitor for emergence of chlorhexidine-resistant bacteria in surgical practice. It is also limited by the relatively high contamination rate (7.69%) of the agar cultures. This could be evidence of a flawed study design which could have allowed contamination to occur more frequently or of errors in the sampling and processing of the cultures. The study does not provide any evidence as to when these contaminations may have occurred, but it is most likely when the samples were added to the agar plates because they are exposed to the open air for a short time. Although an aseptic technique was used, the sampler was not wearing sterile gown or gloves and the technique was not performed under the lamina flow of the operating room. The agar plates could potentially be exposed to bacteria from the skin, hair or clothes of the sampler. The preparation room was also susceptible to high traffic where staff would frequently enter and exit the room to gather and prepare equipment for theatre. This may increase the risk of contamination from the staff themselves and from the disrupted and turbulent air flow caused by their movements and the opening of doors. If this were the case, the environment of the preparation room might be a potential source of contamination and subsequent PJI in patients treated in this arthroplasty unit. Further study comparing infection rates of chlorhexidine solutions prepared using the current method with solutions opened in theatre, under lamina flow, just prior to use could be helpful in identifying whether preparing the solutions in the preparation room increases the risk of contamination of the chlorhexidine solution.

Conclusion

In conclusion, this study is in keeping with the literature and supports the continuing use of multiple-use bottles of chlorhexidine and isopropanol solutions as a safe and cost-effective antiseptic to reduce the risk of PJI.⁹ This study is applicable to the UK National Health Service practice at high-volume arthroplasty units. On the grounds of risk of contamination, this study does not support more expensive single-use chlorhexidine solutions over multiple-use bottled chlorhexidine solutions in surgical practice.