Distribution of bacteria within the layers of the integument of dogs has been described.1 Depending on the bacterial species, microflora can thrive or be inhibited by the presence of hair.2 Colonization of the skin after preparation with chlorhexidine has been evaluated in preterm infants.3 In that study,3 similar numbers of gram-negative bacteria were detected before and up to 48 hours after preparation with chlorhexidine, compared with the number of bacteria at those same times after bathing with water. In adults, daily scrubbing with chlorhexidine has been associated with a reduction of skin colonization by antimicrobial-resistant bacteria.4 However, no studies have been conducted in humans or veterinary patients to evaluate changes in skin flora immediately after clipping hair and 24 hours after surgical preparation (ie, surgical scrub). Furthermore, no studies have been conducted to investigate whether the length of hair after clipping influences the bacterial flora before scrubbing the skin or after recolonization. Although multiple variables have a role in development of surgical site infections, changes in the bacterial population of healthy skin after clipping could increase this risk by promoting a favorable environment for proliferation of certain types of bacteria.
With few exceptions, hair of veterinary patients is clipped before surgery to prevent it from interfering with the surgical site. This is in accordance with current preoperative guidelines recommended by the CDC and the World Health Organization to reduce the risk of surgical site infections. It is generally accepted that clipping the hair leads to fewer infections than shaving with a razor because razor blades result in microtrauma to the skin before surgery.5–7 In veterinary patients, inflammation caused by clipper-induced trauma has anecdotally been observed for several days after clipping of the hair, which indicates a potential for prolonged impairment of the skin's natural barriers. Inflammation leads to changes in lipid synthesis and aggregation on the skin, a higher pH, and disruption of differentiation and desquamation of the epidermis. In experimental settings, this barrier returns to normal within a few hours after the cause is removed.8
No standard has been established for the size of clipper blades used to remove hair before surgery. However, one of the most commonly used is a No. 40 blade, which leaves hair with a length of approximately 0.25 mm, depending on the brand of clipper blade. Another commonly used size is a No. 10 blade, which leaves hair with a length of approximately 1.5 mm, again depending on the brand of clipper blade. Thus, hair length after clipping with a No. 10 blade is 6 times the length of hair after clipping with a No. 40 blade. Both lengths of hair would minimally interfere with the surgical site.
Distribution of bacteria differs depending on the location within the integument and coat, including the hair, skin surface, and hair follicles. In humans and dogs, bacteria from the family Micrococcaceae represent the largest portion of the flora within the hair follicles. This family includes Staphylococcus spp and Micrococcus spp, various soil and water bacterial species, and airborne bacterial species. The pathogenic potential of Staphylococcus spp has been recognized, and investigation into ways to reduce bacterial load of staphylococci during recolonization of the skin is warranted.9
The objective of the study reported here was to evaluate at various time points the number of CFUs and types of microorganisms after clipping of the hair by use of a No. 10 blade and a No. 40 blade. Our hypothesis was that clipping hair closer to the skin would lead to increased irritation of the skin and bacterial dislodgement from the hair follicles, thereby increasing the bacterial load on the skin immediately after clipping and during the recolonization of the skin, compared with results for clipping that resulted in longer hair.
Supported by Sierra Veterinary Specialists and Emergency Center and Blue Pearl Science.
The authors declare there were no conflicts of interest related to this study.
The authors thank Dr. Erik Hofmeister for assistance with the statistical analysis.
Body condition score
Oster CryogenX, Oster, Boca Raton, Fla.
Microsoft Excel, version 2010, Microsoft Corp, Redmond, Wash.
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