Pseudomonas aeruginosa isolation from dog grooming products used by private owners or by professional pet grooming salons: prevalence and risk factors.

BACKGROUND: Pseudomonas aeruginosa is the most commonly isolated bacterium from skin lesions of dogs with post-grooming furunculosis (PGF). It is frequently found in human hair and skin care products, and may pose a health risk to consumers. Information regarding the prevalence of P. aeruginosa contamination of dog grooming products is lacking.
OBJECTIVES: To investigate the prevalence of P. aeruginosa contamination in nonmedicated dog grooming products after either home or professional use in pet grooming salons, and to identify risk factors that may be associated with contamination.
MATERIALS AND METHODS: Of 117 bottles of grooming products sampled for bacterial culture, 97 were used by pet grooming salons and 20 were used by private individuals. The following suspected risk factors were recorded: bottle size, relative remaining volume, content dilution, expiration date and ingredient list.
RESULTS: Pseudomonas aeruginosa was isolated from 14 of 117 samples [11.97%, 95% confidence interval (CI) 6.97-19.3%]. Diluted products were contaminated significantly more often compared to undiluted products (odds ratio = 15.5, 95%CI 2.05-117.23; P < 0.01). None of the other variables was significantly associated with P. aeruginosa contamination. CONCLUSIONS AND CLINICAL RELEVANCE: Pseudomonas aeruginosa contamination of dog grooming shampoos and conditioners was significantly associated with product dilution. Contaminated grooming products may predispose dogs to severe bacterial skin infections such as PGF.

INTRODUCTION

Pseudomonas aeruginosa is a pathogenic, Gram‐negative bacterium, ubiquitously found in the environment. It is frequently found in human hair and skin care products. , These contaminated products may pose a health risk to consumers. , Skin infections caused by P. aeruginosa also have been reported in humans exposed to contaminated water.

Post‐grooming furunculosis (PGF) is a distinctive type of deep pyoderma described in dogs. Furunculosis is believed to be a sequel to follicular trauma caused by vigorous manipulation of the skin and coat (e.g. hand‐stripping or traumatic brushing), followed by bathing with a contaminated product. Pseudomonas aeruginosa is the most commonly isolated bacteria from skin lesions of dogs affected with PGF. , The source of bacterial contamination often is unknown. Shampoos contaminated with P. aeruginosa are suspected to play an important role in the pathogenesis of PGF in dogs, although cultures from bottles of dog grooming products are rarely performed. , , Bacterial culture from skin lesions of a single dog diagnosed with PGF yielded P. aeruginosa with an identical genetic fingerprint to the P. aeruginosa isolated from the shampoo bottle used before disease onset.

The purpose of this study was to investigate the prevalence of P. aeruginosa contamination in nonmedicated dog grooming products, after either home or professional use at pet grooming salons, and to examine potential risk factors associated with contamination.

MATERIALS AND METHODS

Sixteen pet grooming salons and 18 pet owners (veterinary students) were enrolled in the study. Samples were collected by two investigators. Contact with the pet grooming salon operator was made by the investigators 2–48 h before visiting the facility. Verbal consent for participation in the study was obtained from all grooming salon operators. All the shampoo and conditioner bottles used on the day the investigator visited the facilities were sampled. In addition, 20 products used for home grooming by 18 veterinary students were brought directly to the main investigators for sampling. All of the home‐use products were used for a single dog at least once during the month before sampling.

Samples were obtained using a sterile swab with transport media for bacterial culture (invasive sterile Eurotube collection swab with Stuart transport medium; Deltalab). Immediately before sampling, a small amount of the grooming product (approximately 0.5 ml) was squeezed through the opening of the bottle and discarded. A sterile swab then was placed at the opening of the bottles, gently rotated, left for a few seconds to moisten and then carefully withdrawn. All swabs were inserted directly into transport tubes and the lids were secured tightly. Within 2 h of collection the samples were stored at 4°C until processing the following day.

The following information was recorded for each bottle of grooming product sampled: (a) type of grooming product (shampoo or conditioner); (b) type of use (home use by dog owner or professional use at grooming salon); (c) bottle size (more or less than 1 L); (d) relative remaining volume in the bottle (a quarter or less, between a quarter and one half, between one half and three quarters, three quarters or more); (e) whether the contents were diluted with water or not; (f) expiration date printed on the bottle; and (g) list of ingredients.

Culture and species identification of samples

Samples were streaked onto MacConkey agar plates and incubated aerobically at 37°C overnight. Plates were examined for colonies resembling P. aeruginosa morphology, which then were isolated and identified to species level by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry with an Autoflex system (Bruker) using the direct protocol according to the manufacturer's instructions.

Statistical analysis

In order to test the association between categorical variables and a positive culture of P. aeruginosa, chi‐square or Fisher's exact test was used, as appropriate. A multivariable logistic regression included those associations found to be significant on chi‐square or Fisher's exact test, as well as the grooming establishment in order to adjust for clustering (more than one sample per establishment). Confidence intervals (95%) of proportions were calculated by Fisher's exact test (winpepi, DESCRIBE A, v3.18). Statistical significance was set at p < 0.05. Calculations were carried out using Spss v25 and 27 (IBM).

RESULTS

A total of 117 bottles of dog grooming products were sampled from 34 establishments. Twenty samples were obtained from 18 private owners (two owners provided two samples each) and 97 samples were obtained from 16 grooming salons (Table 1). Pseudomonas aeruginosa was isolated from 14 of 117 samples (11.97%, 95%CI 6.97%–19.3%). Of the 14 positive samples, 12 were collected from grooming products used in seven grooming salons and two samples were collected from shampoo bottles used by two private owners (one sample each; Table 2).

Table 1

The number of samples from each pet grooming salon and the number of positive samples by location

Commercial pet grooming salon	Number of samples	Number of positive samples
1	8	0
2	3	0
3	3	1
4	5	1
5	4	0
6	12	1
7	3	0
8	4	0
9	9	0
10	7	1
11	8	0
12	3	0
13	9	2
14	3	0
15	5	2
16	11	4

Table 2

Association between contamination of grooming products with Pseudomonas aeruginosa and suspected risk factors

Characteristics		Number of samples n (%)	Positive samples for P. aeruginosa n (%)
Type of grooming product	Shampoo	97 (82.9%)	10 (10.3%)
	Conditioner	20 (17.1%)	4 (20.0%)
Type of use	Professional use by pet grooming salon	97 (82.9%)	12 (12.4%)
	Private use by the dog owners	20 (17.1%)	2 (10.0%)
Size of grooming bottle product	>1 L	61 (47.9%)	5 (8.2%)
	<1 L	56 (52.1%)	9 (16.1%)
Relative amount remaining in the bottle	<¼	27 (23.1%)	3 (11.1%)
	¼–½	31 (26.5%)	5 (16.1%)
	½–¾	27 (23.1%)	2 (7.4%)
	>¾	32 (27.3%)	4 (12.5%)
Dilution	Diluted	18 (15.4%)	7 (38.9%)
	Not diluted	99 (86.6%)	7 (7.1%)
Expiration date	Expired	6 (5.1%)	2 (33.3%)
	In date	29 (24.8%)	3 (10.3%)
	No data	82 (70.1%)	9 (11.0%)

Contamination was significantly associated with diluted products compared to undiluted products [odds ratio (OR) = 15.5, 95%CI: 2.05–117.23; P < 0.01]. No statistically significant association was found between the isolation of P. aeruginosa and the type of grooming product (i.e. shampoo versus conditioner), the type of usage (i.e. private versus professional), the size of the bottle, the relative amount remaining in the bottle, or the expiration date.

Information regarding the ingredients was available for 103 of the 117 products sampled (Table 3). No significant association was found between any of the ingredients and the isolation of P. aeruginosa. This organism was not isolated from any of the bottles lacking an ingredient list.

Table 3

Association between contamination with Pseudomonas aeruginosa and ingredients of grooming products

Ingredients	Number of samples containing the ingredient (% of total sampled); n (%)	Number of samples positive for Pseudomonas aeruginosa (% of positive samples of total number containing the ingredient); n (%)
Aloe	9 (8.7%)	3 (33.3%)
Aloe vera	38 (36.9%)	5 (13.2%)
Aloe barbadenesis leaf juice	9 (8.7%)	3 (33.3%)
Cocamide DEA	19 (18.4%)	3 (15.8%)
Cocamidopropyl betaine	39 (37.9%)	6 (15.4%)
Coconut	21 (20.4%)	2 (9.5%)
Creatine	10 (9.7%)	2 (20.0%)
DMDM hydantoin	25 (24.3%)	3 (12.0%)
EDTA	15 (14.6%)	2 (13.3%)
Fragrance	57 (55.3%)	6 (10.5%)
Glycerin	23 (22.3%)	4 (17.4%)
Jojoba	24 (23.3%)	4 (16.7%)
Limonene	12 (11.7%)	3 (25.0%)
Panthenol	41 (39.8%)	8 (19.5%)
Phenoxyethanol	14 (13.6%)	3 (21.4%)
Purified water/deionised water	35 (34.0%)	3 (8.6%)
Sodium chloride	18 (17.5%)	2 (11.1%)
Sodium laureth sulfate	24 (23.3%)	3 (12.5%)
Tea tree oil	15 (14.6%)	3 (20.0%)
Vitamin A	20 (19.4%)	2 (10.0%)
Vitamin D	21 (20.4%)	2 (9.5%)
Vitamin E	47 (45.6%)	9 (19.1%)
Water	21 (20.4%)	4 (19.0%)

DISCUSSION

Nearly 12% of pet grooming products tested were contaminated with P. aeruginosa. This is consistent with previous culture of this organism from both dog and human shampoos. , , To the best of the authors' knowledge, this is the first publication examining the prevalence of P. aeruginosa contamination of grooming products on a larger scale.

Dilution of shampoo and conditioners with tap water is a common practice in pet grooming salons. In our study, all diluted products were diluted with tap water according to the manufacturer's instruction. Previous reports suggest that shampoos diluted with tap water may be a risk factor for contamination. The present study supports this assumption. The source of contamination may be the tap water itself, as outbreaks of P. aeruginosa associated with contaminated tap water have been reported.

In previous publications reporting the isolation of P. aeruginosa from grooming products, the expiration date of the grooming products was not mentioned. , In our study, of the 35 grooming products for which there was information regarding the expiration date, six were expired, and P. aeruginosa was isolated from two of those. Although not statistically significant, it is important to further investigate this issue as the use of expired grooming products is a potentially common practice.

There was no association between individual ingredients and P. aeruginosa contamination. Aloe vera, one of the most common ingredients in dog grooming products, has been found to have in vitro antibacterial activity against P. aeruginosa. Although aloe vera was present in over half of the products evaluated in this study, large variation in ingredient combinations and concentrations made it impossible to draw conclusions regarding any association between ingredients and P. aeruginosa contamination.

All pet grooming salons that participated in this study reported using the same bottle of shampoo for several dogs, while the private owners in this study used each shampoo bottle for one dog. The fact that no significant differences were found in the contamination rate between the products used in pet grooming salons and those used by the dog owners, suggests that the number of dogs for which the product was being used does not pose a greater risk of contamination with P. aeruginosa.

One study limitation is the advanced notice given to pet grooming salon operators before investigators arrived. Even though pet grooming salon operators stated they did not change the sampled bottles or take any disinfection measures before sampling, this possibility cannot be entirely excluded. Another limitation is the relatively small sample size that may contribute to the lack of statistical significance for some of the risk factors evaluated.

Overall, the prevalence of contamination of the grooming products in this study was surprisingly high. This contamination rate may expose dogs being groomed to contaminated products that increase the risk of developing bacterial skin infection. Furthermore, dilution of grooming products can increase the risk of contamination. Future studies are warranted to examine the prevalence of contamination of grooming products with other bacteria isolated from skin of dogs with PGF such as Staphylococcus pseudintermedius, Staphylococcus epidermidis, Enterobacter cloacae, Serratia marcescens, Staphylococcus hominis, Klebsiella oxytoca and Burkholderia cepacia. ,

CONFLICT OF INTEREST

No conflicts of interest have been declared.

AUTHOR CONTRIBUTIONS

Elad Perry: Conceptualization; data curation; investigation; methodology; project administration; visualization; writing – original draft; writing – review and editing. Gila Sutton: Formal analysis; methodology; writing – original draft; writing – review and editing. Lotem Haggag: Data curation; investigation; methodology; project administration; writing – review and editing. Marcelo Fleker: Methodology; resources; writing – review and editing. Shlomo Blum: Methodology; resources; writing – review and editing. Ronnie Kaufmann: Supervision; writing – review and editing.