Evaluation of Bacterial Contamination of Clipper Blades in Small Animal Private Practice

Introduction

It is expected that bacteria will be present in any hospital environment, however environmental contamination may be a reservoir for nosocomial pathogens.¹ Staphylococcus spp. and Pseudomonas spp. have been shown to survive for up to 16 months on inanimate objects.^1,2 In veterinary medicine, 8–36% of small animals admitted to the hospital will experience a nosocomial event during hospitalization.^3,4 Due to the increasing awareness of hospital-acquired infections in both human and veterinary hospitals, identifying potential fomites is critical to reduce the risk of pathogen transmission between patients. Proper hand hygiene, environmental decontamination, and equipment cleaning and disinfection are all vital to minimizing infectious microorganisms in the hospital environment.^2,5,6

Numerous surveillance studies evaluating the presence of bacteria in hospital environments, on hospital personnel, and on hospital equipment have been performed in both veterinary and human medicine. Computer keyboards, cellular telephones, hospital floors, and door handles have all been found to be contaminated with various bacterial pathogens, including both antimicrobial-susceptible and antimicrobial-resistant Staphylococcus spp., Enterococcus spp., Escherichia coli, and Salmonella spp.^1,5–9 In addition, inanimate objects that are in contact with patients, including stethoscopes, beds, cages, and otoscope cones, have been found to have bacterial contamination.^8,10–14

In veterinary medicine, shaving of hair is necessary prior to many procedures, including surgery, wound repair, ultrasounds, intravenous catheter placement, and intradermal allergy testing. Clipper blades can cause skin trauma, and using improperly maintained or dirty clipper blades creates the potential for transmission of pathogenic organisms.¹⁴ Contaminated clipper blades have been cited as potential fomites, and exposure to these blades has been shown to be a risk factor for the transmission of dermatophytes in veterinary medicine and human immunodeficiency virus and bacteria in human patients.^15–17 No studies evaluating bacterial contamination or cleaning protocols for clipper blades in veterinary hospitals were discovered. The primary goal of this study was to evaluate bacterial contamination on clipper blades in small animal specialty and general private practices and identify the types of bacteria found. A secondary goal was to assess whether there was an association between bacterial contamination of clipper blades and clipper blade cleaning solutions, clipper blade cleaning protocols, clipper blade storage, and type of practice.

Materials and Methods

Statistical Analysis

All statistical analyses were performed using R 2.15.2 software. Significance level was set at P < 0.05.

Cultures were classified as contaminated if any bacterial growth was present.

Cleaning solutions were classified into three categories: (1) commercially formulated disinfectants made for use on clipper blades (CD, clipper disinfectants), (2) non-specific disinfectants and antiseptics (D, disinfectants), and (3) clipper cleaners or lubricants containing no disinfectants (CC, clipper cleaner). Individual active ingredients were also evaluated (Table 1).

Table 1 Cleaning Solutions by Category

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Four cleaning protocols were reported: cleaning after every patient, daily, weekly, and as needed when visibly contaminated. Blade storage was classified as exposed to treatment area (on counters or treatment tables) or not exposed to treatment area (in drawers or cabinets). Samples collected from four practice types (dermatology, surgery, emergency, and general practice) were evaluated.

Logistic regression was used to evaluate the association between cleaning solutions, frequency of cleaning, clipper blade storage, and type of practice with the presence of bacteria on the clipper blades. Significant associations were analyzed using independent pairwise contrast.

Results

Fifty-one percent (31/60) of clipper blades sampled were contaminated with bacteria. Table 2 outlines information about the contaminated blades, including cleaning frequency, cleaning solutions, bacteria isolated, and type of practice.

Table 2 Summary of Contaminated Clipper Blade Culture Results and Cleaning Protocols

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No significant association was found between the number of contaminated clipper blades and cleaning frequency (χ² = 3.01, Df = 4, P = 0.55), storage location (χ² = 4.05, Df = 3, P = 0.26), or practice type (χ² = 7.48 Df = 3, P = 0.06).

There was a significant association between the number of contaminated clipper blades and category of cleaning solution (χ² = 8.11 Df = 2, P < 0.02), but no individual ingredient had any significant association with the presence of bacterial contamination (χ² = 9.64, Df = 12, P = 0.65). There were 7/21 blades cleaned with clipper disinfectants, 10/13 blades cleaned with clipper cleaners, and 13/26 blades cleaned with disinfectants that were positive for bacterial contamination. Pairwise contrasts showed significantly fewer clipper blades were contaminated when cleaned with clipper disinfectants compared to clipper cleaners (z = 2.6, P < 0.001). There was no significant difference in the number of contaminated blades cleaned with disinfectants or clipper cleaners (z = 1.4 P = 0.17).

Twenty-six clipper blades were stored in locations that were not exposed to the treatment area, while thirty-four clipper blades were exposed to the treatment area. Although not statistically significant, 42% (11/26) of the clipper blades that were not exposed to the treatment area and 58% (20/34) of the clipper blades exposed to the treatment area were contaminated.

Dermatology practices had fewer contaminated blades (2/15) than surgical practices (10/15), emergency practices (8/15), and general practices (11/15); however, this observation was not statistically significant (χ² = 7.48 Df = 3, P = 0.06).

Discussion

Bacteria was isolated from 51% (31/60) of clipper blades sampled, indicating that clipper blades should be considered a potential fomite for bacterial transmission. Cutaneous pathogens, including Staphylococcus aureus, Staphylococcus schleiferi, Staphylococcus pseudintermedius, Pseudomonas spp., and Actinomyces spp., were isolated from 14/60 (23%) clipper blades. Since clipper blades can create superficial trauma to the skin, cutaneous infection could result from clipping with contaminated clipper blades. Enteric bacteria, including Escherichia coli and Enterococcus spp., were cultured from four blades. These bacteria are unlikely to cause cutaneous infections, but their presence may indicate that blades are not being cleaned adequately after fecal contamination. E. coli, Enterococcus spp., and several of the Staphylococcus spp., including S. aureus, S. capitis, S. warneri, and S. auricularis, cultured from blades in this study are potential human pathogens, which may indicate contamination from hospital personnel.^8,19–21 This finding suggests that clipper blades could pose a risk of pathogen transmission to both animals and hospital personnel. Finally, several of the organisms cultured, including Acinetobacter spp. and several coagulase negative Staphylococcus spp., have been cited as potential pathogens in human and large animal species, but the clinical relevance in small animals is unknown.^12,22

In this study, cleaning with clipper disinfectants was significantly associated with fewer contaminated clipper blades than cleaning with clipper cleaners. The results of this study indicated that cleaning with clipper cleaners was significantly associated with higher number of contaminated clipper blades compared to clipper disinfectants. Thirty-three percent (7/21) of blades cleaned with a commercially formulated clipper disinfectants were positive for bacterial contamination compared to 77% (10/13) of blades cleaned with cleaners containing no disinfectant and 50% (13/26) of blades cleaned with non-specific chemical disinfectants. In vitro studies evaluating the efficacy of a cleaning agent typically utilize a known, controlled baseline level of contamination, while in vivo studies often use serial cultures collected before and after cleaning to prove a reduction in contamination level.^23,24 An inherent limitation of this observational study was that only a single sample without a known baseline contamination level was collected from each hospital; therefore, efficacy of the cleaning agents could not be assessed. Since efficacy of cleaning agents could not be evaluated, the authors are unable to make recommendations on the ideal cleaning protocol for disinfection of contaminated clipper blades. However, Pseudomonas species have been found to be resistant to many quaternary ammonium derivatives, including benzalkonium chloride.²⁵ In addition, quaternary ammonium cleaners have been found to be contaminated with Pseudomonas species, making them an overall poor choice for environmental disinfection.^4,23,25

A study performed in human medicine concluded that clipper blades used repeatedly without cleaning had high levels of bacterial contamination.²⁰ Current infectious disease protocols recommend that blades should be sterilized routinely, especially after use on any patient with a potentially infectious pathogen or when blades are in contact with feces, urine, blood, or other bodily fluid.^9,26 This study reported four cleaning protocols: cleaning after every patient, daily, weekly, or as needed when visibly contaminated. Although it would be expected that more frequent cleaning would decrease bacterial contamination of clipper blades, no significant association was noted between the cleaning frequencies in this study. This result may relate to the cleaning agent used or inaccurate reporting of cleaning frequency on the questionnaires. An innate flaw of gathering information via surveys is that study outcomes could be skewed by inaccurate reporting by the individual completing the questionnaire.²⁷

Although not statistically significant, clipper blades from dermatology practices had the fewest contaminated blades (2/15) compared to surgical practices (10/15), emergency practices (8/15), and general practices (11/15). The increasing prevalence of methicillin-resistant Staphylococcus spp. pyoderma may have created an increased awareness in dermatology practices of the need for infectious disease control and effective disinfection of equipment.^21,28,29

Bacterial contamination of clipper blades may also be affected by other factors not investigated in this study. The frequency of clipper use may impact bacterial contamination. Another factor that could have impacted the results of this study is the possibility that residual antiseptic activity on the blades may have prevented or decreased bacterial growth in cultures.²⁴ Since baseline levels of contamination at each practice were unknown, it is possible that low or absent bacterial growth on culture resulted solely from low levels of baseline contamination. Finally, certain metals, such as copper and silver, can have antibacterial effects and could decrease the level of bacterial growth independent of the cleaning agent used.^30,31,32 In this study, the blades sampled were made of either high-carbon stainless steel or ceramic. Future studies may evaluate the effect of these factors on bacterial contamination.

The information in this study may serve as a basis for future studies. A prospective, controlled study evaluating cleaning protocols is necessary to determine cleaning recommendations for minimizing fomite potential of clipper blades. Evaluation of the clinical relevance of contaminated clipper blades and rates of bacterial transfer between clipper blades and patients could be investigated in future studies. Finally, with the growing awareness of methicillin-resistant infection, future studies may test for the presence of methicillin-resistant bacteria on contaminated clipper blades.

Conclusion

This study documented bacterial contamination of clipper blades in veterinary practices. These contaminated blades may serve as a potential source of bacterial transmission. Proper cleaning and disinfection of blades is likely important in reducing this potential risk to animals and hospital personnel. Further studies are necessary to determine ideal cleaning and disinfection protocols.