Abstract
Objectives
Inhalation chambers are commonly used for the delivery of aerosol drugs to cats with respiratory disease. The aim of the study was to identify successful cleaning methods for inhalation devices after standardised bacterial contamination.
Methods
Spacer devices of two different manufacturers were used: RC Chamber (Cegla Medizintechnik) and Aerokat (Trudell Medical International). The bacterial contamination was performed using Pseudomonas aeruginosa. Previously marked areas of the chamber were contaminated with 50 μl of bacterial solution, containing between 2.2 ×105 and 2.1 ×108 colony-forming units/ml each. After cleaning the devices as recommended by each manufacturer (RC Chamber: special microwave cleaning bag [n = 5] or boiling water with liquid dish detergent for 15 mins [n = 5]; Aerokat: rinsing in a solution of lukewarm water and liquid dish detergent for 15 mins), chambers were air-dried for 24 h and samples for bacterial culture were taken from three defined areas. Sample material was applied on Müller–Hinton agar plates and subsequently incubated for 24 h at 37°C.
Results
Bacterial contamination was not detected in any of the examined inhalation devices using the recommended cleaning methods.
Conclusions and relevance
If inhalation chambers are cleaned following the manufacturers’ recommendations, successful bacterial decontamination can be expected.
Introduction
In human medicine, several studies have been performed to investigate bacterial contamination of nebulisers used by cystic fibrosis patients.1,2 These studies revealed that nebulisers used by patients at home were frequently contaminated, and bacteria, including Pseudomonas aeruginosa, Staphylococcus aureus and Klebsiella pneumoniae, were detected in up to 65% of examined devices. 2 It is known that contaminated nebulisers increase the risk for infections of the lower airways in affected human patients. 3 The degree of contamination could be significantly reduced by regular replacement of the nebulisers, as well as employment of proper cleaning methods. 4
In veterinary medicine, spacer devices are commonly used for the treatment of dogs and cats with chronic airway disease. 5 Two common indications in cats are feline asthma and feline chronic bronchitis, diseases that are frequently treated with inhalative glucocorticoids to avoid systemic use and subsequent side effects associated with systemic glucocorticoids.6,7 Although nebulisers and inhalation chambers for metered dose inhalers cannot be directly compared with each other, because of their different functionality, studies investigating the contamination of nebulisers and concluding risks emphasise the importance of hygiene and disinfection in inhalation devices. 8 As long-term therapy is necessary in most patients with chronic airway diseases, spacer devices are commonly permanently in use. 9 To date, several inhalation devices specifically designed for use in pet cats are available on the veterinary market. Manufacturers of such spacer devices recommend different cleaning procedures for decontamination. Inhalation chambers should be cleaned on a regular basis and replacement once a year is advised.10,11 Thus far, in veterinary medicine no studies have been performed to evaluate the influence of different cleaning techniques on bacterial decontamination of inhalation devices.
Therefore, the purpose of the study was to evaluate the effectiveness of different cleaning protocols for feline spacer devices after standardised bacterial contamination. For that purpose, three different cleaning techniques were employed in accordance with instructions of the manufacturers of two commercially available feline inhalation chambers.
Materials and methods
Two different spacer devices were used in this prospective study: RC Chamber (RC) (Cegla Medical Technology) and Aerokat (AK) (Trudell Medical International). There is one recommendation of the manufacturer for cleaning the AK. 10 Four AK devices were contaminated, while one was used as a negative control. However, for the RC there are two different cleaning methods recommended by the manufacturer. 11 Therefore, 10 RC devices were used in the test series, five for each cleaning method, with 1/5 serving as a negative control. The contamination was performed using P aeruginosa as an indicator bacterium.
Before contaminating the spacer devices, all were sampled in a standardised fashion to ensure they were originally culture-negative. Every chamber was new and in its original packaging before usage. Samples were collected from each device component (mask, adapter, chamber) using sterile swabs (sterilised cotton-tipped applicators [Henry Schein]). Afterwards, samples were applied on three different agar plates: colistin–nalidixin–acid agar, Bordet–Gengou agar (a special agar for detection of Bordetella species) and sheep-blood agar. The agar plates were incubated for 3 days at 37°C before evaluation.
Before contamination of the devices, a dilution series was performed for the indicator bacterium, P aeruginosa, in order to determine the colony-forming units (CFU) per ml in the initial suspension used for contamination. The suspensions contained between 2.2 ×105 and 2.1 ×108 CFU/ml, depending on the dilution series carried out several times for the different sets of chambers. Each part of the device (mask, adapter, chamber) was contaminated in two previously marked areas. Every time 50 μl of the suspension was used. In addition, a third area was marked and contaminated in the chamber part of the spacer device, serving as positive control for a successful contamination, as shown in Figure 1.
Marked areas for contamination of the single chamber parts. Each part of the device (mask, adapter, chamber) was contaminated in two previously marked areas. Additionally, the chamber part was contaminated in a third area, which served as a positive control and was sampled prior to cleaning the device to ensure a successful contamination; 50 μl of the bacterial suspension was used for contamination every time
The devices were then air-dried for 24 h. After that, a sample from the contamination control area in the chamber was collected using a sterile swab, applied on Müller–Hinton agar, and incubated for 24 h at 37°C.
Afterwards, the devices were cleaned following the manufacturers’ instructions. The three different cleaning protocols are described briefly. The AK device was cleaned disassembled into its component parts by soaking the parts in a mild solution of standard liquid dish detergent (‘Pril’; Henkel) and lukewarm clean water for 15 mins while moving the parts gently. 10 Afterwards, all parts were rinsed in clean water, shaken out to remove excess water and then air-dried in a vertical position. For the RC, two different cleaning methods were used.11,12 Before cleaning, all RC devices were also disassembled into their component parts. Then, all parts were soaked in the solution of liquid dish detergent and lukewarm water and rinsed under warm water as described earlier for the AK device. After that, five RC devices were placed in boiling clean water for 5 mins. The other five RC devices were disinfected in a special microwave bag after soaking and rinsing the parts as described above. The so called ‘RC-clean’ bag (Cegla Medizintechnik) was filled with water and placed in the microwave oven (Panasonic NN-5202BGPG; Panasonic) for 3 mins at 800 W. Afterwards, all parts were left to dry out, followed by sample collection to examine the effectiveness of decontamination. All samples were collected using a sterile swab for each device part using the same protocol as described above. The samples were applied on Müller–Hinton agar and incubated for 24 h at 37°C.
Results
All samples taken before contamination from every location on the newly unwrapped spacer devices were negative on all three culture plates.
After contamination, samples taken from the previously marked areas for contamination control from all 12 spacers were positive for bacterial growth of P aeruginosa.
After cleaning the devices following each of the manufacturer’s instructions, sampling and incubating the samples, no microbial contamination could be detected in any part of the 15 devices from all three groups.
Discussion
In this study, the success of manufacturer-recommended cleaning methods for feline inhalation chambers was investigated. Inhalation chambers are commonly used for aerosol treatment of cats with chronic respiratory disease. It is assumed that cats with chronic inflammatory bronchial disease can develop secondary bacterial infections as a complication. 9 Whether bacterial contamination of inhalation devices can be a risk factor for respiratory infections is so far unknown. While studies have been performed in human medicine investigating contamination of nebulisers used by patients with cystic fibrosis, to our knowledge this is the first study to examine the cleaning protocols for inhalation chambers in veterinary medicine.8,13 In a human study investigating the contamination of 30 respiratory devices, including nebulisers used by 23 patients, bacteria could be cultured from 28/30 devices. A cleaning procedure including soaking the different parts of the device in hot clean water and standard dishwashing detergent for 10 mins, rinsing with water and air drying resulted in a complete decontamination in 50% of the samples, partial decontamination in 30% and failure in four samples. 14
The results of the present study demonstrate the effectiveness of several cleaning methods in two commercially available chambers and show that adequate decontamination can be achieved with little effort. Both devices can easily be cleaned without any special equipment. According to the manufacturer’s cleaning manual, the RC spacer device can also be put in the dishwasher. 11 Unfortunately, this cleaning method could not be investigated in the laboratory setting this study was performed in. The ‘RC-clean’ bag, which can be purchased for cleaning the RC device using a microwave, can be used up to 20 times according to the manufacturer; however, the effectiveness of this cleaning method if repeated several times using the same bag could also not be evaluated in this study. 12
Studies have shown that contaminated nebulisers are a potential source for susceptible humans to develop respiratory infections.15,16 However, nebulisers and metered-dose inhaler spacers exhibit significant differences in use and maintenance of the devices. Nebulisers are used with aerosol liquids, which are delivered over a longer time period, while inhalation spacers and are only used for 15–20 s at a time.17–19 The feline inhalation chambers contain a special low-resistant valve that is supposed to release the medication inside the chamber only during inspiration and prevents the exhaled air from flowing back into the chamber.17,18 As nebulisers do not have such a valve, contamination with patient-associated bacteria is more likely, because exhaled air can flow back into the circuit.
The results of this prospective contamination study might, however, not be transferable to clinical practice. As the devices used in this study were contaminated with only one type of indicator bacterium and cleaned only once, statements about long-term effects of decontamination or cleaning effect after contamination with different types of microbes, as well as effectiveness of cleaning the devices after longer use, cannot be made based on the results of this study. Prospective studies are warranted to investigate these questions in feline inhalation chambers in long-term use with regard to cleaning protocol and health status of the cats.
Conclusions
The results of this study confirm that an adequate decontamination of spacer devices is possible, if cleaning is performed in accordance with the manufacturer’s recommendations. Instructing cat owners properly appears crucial to minimise the amount of bacterial contamination of spacer devices and prevent airway infections potentially resulting from contaminated spacer devices.
Footnotes
Acknowledgements
The authors thank the laboratory assistants at the Institute for Infectious Diseases and Zoonoses, LMU University of Munich for their support throughout the experiments.
Conflict of interest
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
This study was partly funded by the ‘VetResearch’ programme of the veterinary faculty of the LMU-University of Munich. All 10 RC chamber inhalation devices were provided by R Cegla GmbH & Co. KG.
Ethical approval
This work did not involve the use of animals and therefore ethical approval was not required.
Informed consent
This work did not involve the use of animals and therefore informed consent was not required. This work did not involve the use of animals and therefore informed consent for publication was not required.
