Quantitative bacteriology of experimentally incised skin wounds in horses

Effect of Presurgical Iodine-Based Disinfection on Bacterial Colonization of the Equine Peripodal Region

OBJECTIVE

To compare bacterial colonization after diluted iodine tincture or povidone iodine solution for presurgical disinfection of the equine peripodal region.

STUDY DESIGN

Complete block design.

ANIMALS

Five horses.

METHODS

Disinfection protocols using iodine tincture or povidone iodine solutions were tested on 5 pairs (n = 10) equine front feet. Iodine tincture was applied to the left feet and povidone iodine to the right feet. Fixed surfaces of the sole, frog, hoof wall, and peripodal skin were swabbed pre-preparation (T0), after a standard pre-disinfection step (T1), after short disinfection with a 4-minute application of 0.5% iodine tincture or povidone iodine (T2), and after long disinfection with 12-hour soaking in 0.25% iodine tincture or povidone iodine (T3). Quantitative bacteriology was performed on each swab.

RESULTS

The frog and sole were the most contaminated sites compared to hoof wall and skin at T0. Bacterial counts were significantly decreased at T2 for both solutions. Bacterial counts did not change significantly with iodine tincture at T3 but increased with povidone iodine compared to T2. Skin abrasions were detected on almost all feet but were subjectively more severe on iodine tincture-treated feet.

CONCLUSION

Soaking for 12 hours with either iodine tincture or povidone iodine is not recommended as these solutions damaged the skin and bacterial recolonization was noted with povidone iodine. Four-minute disinfection using either iodine tincture or povidone iodine (0.5% available iodine) is appropriate for presurgical preparation of the equine peripodal region.

Presurgical hand antisepsis: concepts and current habits of veterinary surgeons

OBJECTIVE

To assess current habits for surgical hand preparation among veterinary surgical specialists and to compare data with current guidelines for hand asepsis techniques.

STUDY DESIGN

Survey of veterinary surgical specialists.

SAMPLE POPULATION

Diplomates of the American (ACVS) and European Colleges of Veterinary Surgeons (ECVS).

METHODS

An internet-based survey of hand preparation methods before surgical procedures was conducted of 1300 listed ACVS and ECVS Diplomates.

RESULTS

A 42.6% response rate was obtained. Approximately, 80% of respondents use disinfecting soaps as a primary method for hand antisepsis. Of those, 81% use chlorhexidine-based scrubs and 7% use a neutral soap followed by a hydroalcoholic solution.

CONCLUSIONS

Contrary to current recommendations of the World Health Organization and scientific evidence supporting use of hydro-alcoholic rubs for presurgical hand preparation, veterinary surgical specialists still use surgical scrub solutions containing disinfecting soaps.

Comparison of two methods for presurgical disinfection of the equine hoof

OBJECTIVES

To determine for equine hooves the normal resident aerobic bacterial population and the efficacy of 2 methods of disinfection. Study Design-Measurement of total bacterial, gram-positive bacterial, and gram-negative bacterial surface populations from the frog, sole, and hoof wall after each step of 2 different preoperative surgical disinfection techniques.

ANIMALS

Six adult horses.

METHODS

Hoof wall, sole, and frog samples were collected for quantitative bacteriology before, during, and after 2 multistep antiseptic preparation techniques: Method A-6-minute scrub with povidone-iodine soap, followed by 24-hour submersion in povidone-iodine solution-soaked cotton; and Method B-initial removal of superficial layer of hoof capsule before completing Method A disinfection procedures.

RESULTS

Removal of the superficial hoof layer, application of the povidone iodine scrub, and completion of the povidone-iodine soak all significantly (P < .0008) decreased total bacterial numbers. Method B had significantly lower bacterial counts than method A at each consecutive step. Final total bacterial counts remained greater than 10(5) bacteria per gram of tissue regardless of preparation method.

CONCLUSIONS

The hoof surface hosts a broad spectrum of aerobic gram-positive and -negative bacteria, many of which are potential pathogens. Bacterial numbers can be significantly reduced by removal of the superficial hoof surface, by application of a povidone-iodine scrub, and by use of a 24-hour povidone-iodine soak. However, bacterial populations >10(5) g per tissue persist after these disinfection procedures.

CLINICAL RELEVANCE

Regardless of the preparation methods used in this study, bacterial populations capable of inducing wound infection remain on the hoof capsule.

Bacterial culturing of ventral median celiotomies for prediction of postoperative incisional complications in horses

OBJECTIVE

The purpose of this study was to determine whether detection of bacterial contamination of ventral midline incisions was predictive of postoperative incisional complications in horses undergoing exploratory celiotomy for colic.

STUDY DESIGN

Prospective study.

ANIMAL OR SAMPLE POPULATION

Horses that had ventral median celiotomies for colic at Colorado State University between May 1, 1991 and April 30, 1993 were studied prospectively. Complete information was obtained on 66 horses.

METHODS

Bacterial cultures were obtained from ventral midline incisions at surgery. Information regarding the type of surgery performed (celiotomy vs celiotomy plus enterotomy or enterectomy), preoperative total nucleated cells and presence of a left shift, postoperative fever (> 38.5 degrees C), incisional drainage, incisional herniation, and outcome were obtained from medical records. Additional information concerning incisional drainage, herniation, and survival was obtained at a minimum of 18 months after surgery.

RESULTS

Examination of odds ratio (ORs) and confidence intervals (CIs) revealed that a celiotomy plus enterotomy or enterectomy was positively, but not significantly, associated (OR > 1) with positive culture results, presence of incisional drainage and incisional herniation. A significant association between incisional drainage and hernia formation was found; odds of incisional herniation were 62.5 times greater in horses that had incisional drainage. Incisional drainage and herniation were negatively associated with patient survival. The later association was significant (OR = 0.18, P = .04).

CONCLUSIONS

This study indicated that detection of bacterial contamination at incisional closure by the swab culture technique was not beneficial in the prediction of postoperative incisional problems in horses undergoing colic surgery. Incisional drainage or infection appeared to be associated with hernia formation.

CLINICAL RELEVANCE

Immediate treatment of incisional drainage or method to prevent incisional infections may decrease hernia formation.

Principles of wound healing

Wound healing can be divided into immediate (zero to 1 hour), early (1 to 24 hours), intermediate (1 to 7 days), and late (greater than 7 days) stages. Many physical and physiologic events occur simultaneously and sequentially during these stages to produce the final wound scar. The processes of skin retraction, scab formation, would debridement, wound contraction, epithelial migration and proliferation, fibroplasia, and collagen maturation all must occur for healing to be successful. Many factors affect the size and shape of the resulting scar, including anatomic location and skin tension forces, systemic condition of the patient, blood supply to the wound, nutritional factors, environmental temperature, the presence of systemic drugs, wound infection, motion, wound oxygen gradient, wound moisture, and bandaging. Ideally, each of the factors would occur at a level compatible with optimal healing, but, in many clinical cases, one or more factors compromise normal, rapid healing. When we intervene with therapy, we probably adversely affect another factor in healing, while trying to correct the factor that is out of balance. In these decisions, the effects of our treatment on wound healing should be considered. The trade-off should be weighed and the treatment pursued only as long as necessary to allow healing to progress; then it should be discontinued or changed. With these considerations, it is hoped that we can attain healing at the most rapid physiologic rate.

Second-intention healing

Second-intention healing (contraction and epithelization) is most appropriate for heavily traumatized, contaminated wounds that may have a prolonged debridement phase. Therapy during healing can promote rapid debridement and faster healing. Healing of lower limb wounds by second intention may be protracted, owing to poorer wound contraction and excessive granulation tissue production as compared with body wounds.