Proceedings of the 18th Annual Meeting of the. Italian Association of Equine Veterinarians SIVE

Transcription

1 Close this window to return to IVIS Proceedings of the 18th Annual Meeting of the Italian Association of Equine Veterinarians SIVE Feb. 3-5, Bologna, Italy Next SIVE Meeting: Feb. 1-3, 2013 Arezzo, Italy Reprinted in the IVIS website with the permission of the Italian Association of Equine Veterinarians SIVE

2 Antibiotic Use in Equine Reproduction: Local Versus Systemic Therapy Michelle M. LeBlanc DVM, Dipl ACT Rood and Riddle Equine Hospital, Lexington, KY Antibiotics are used to treat many infections of the equine reproductive tract including infectious endometritis, placentitis, metritis or retained placenta. Antibiotics may be infused locally, administered parentally or added to semen extenders. Evidence-based guidelines for the decision on treatment length, the most efficacious route of administration, or the use of intrauterine antibiotics after breeding are limited to non existent. Consequently, recommendations are based on clinical experience and tradition. Veterinarians have a responsibility to use antibacterial agents with due care and with appropriate recognition of the wider implications of resistance. Inappropriate course and dose are often the major instigating factor for antibiotic resistance. GENERAL GUIDELINES Various factors must be considered in the selection of antimicrobials for treating reproductive conditions including susceptibility of the microorganism, local versus systemic treatment, concentration of drug attainable at site of infection and the effect of the drug on immediate and future fertility (LeBlanc et al. 2003). Antimicrobial selection should be based on culture and sensitivity results. Unfortunately, in vitro and in vivo efficacy may not always be equivalent. For example, Streptococcus equi subsp zooepidemicus shows in vitro sensitivity to trimethoprim-sulfonamide combinations but rarely does the drug effect a clinical cure ((Ensink et al. 2005; Ensink et al. 2003). INTRAUTERINE ANTIBIOTIC THERAPY Intrauterine infusions need to be administered with sterile equipment and proper aseptic preparation of the mare. Catheters should be passed through the cervix and into the uterine lumen via a speculum or manually to ensure maximal cleanliness. Uterine size, determined by palpation and ultrasonographic examination, can be used to estimate the volume of antibiotic solution to be instilled (Neeley et al. 1983). The objective is to use sufficient volume to achieve uniform distribution in the uterus without excessive backflow through the cervix. Total infusion volumes of 30 to 200 ml have been recommended (Bedford and Hinrichs 1994; LeBlanc et al. 2003). Volume of infusion may affect rate of drug absorption. Decreasing the volume of beta-lactam antibiotic solutions to 100 ml increases the amount and rate of absorption; therefore, to maintain concentrations in the uterus for longer periods, larger diluted volumes of these antibiotics should be infused (Allen 1978; Spensley et al. 1986; Van Camp et al. 2000). The frequency of intrauterine antimicrobial therapy is usually based on convenience (Bennett 1986; Bretzlaff 1986; Threlfall and Carleton 1986). Mares may be treated for three to five days during estrus, every other day during estrus or for one to three days after ovulation. Intrauterine therapy has been preferred over systemic treatment because bacteria reside within the uterine lumen and antibiotic concentrations tend to be higher in endometrial tissues after intrauterine treatment than after systemic treatment. 62

3 Exudate in the uterine lumen may inactivate or dilute an infused antibiotic to a subtherapeutic concentration. Uterine lavage before the infusion of antibiotics is therefore a useful method of increasing the efficacy by removing inflammatory by-products and increasing contact of therapeutic agents with the endometrial surface. Intra-uterine infusion of antibiotics should be limited to estrus when the cervix is dilated. In experimental models of endometritis, progesterone treated mares that received an uterine inoculation of bacteria followed by infusion of intrauterine antibiotics developed either fungal or antibiotic resistant bacterial infections (Hinrichs et al. 1992; Mc- Donnell and Watson 1992). An inability to clear fluids through the cervix and hormonally induced immunological changes likely contributed to the infection after antibiotic administration. In the author s experience, mares with inadequate cervical dilation at breeding, mares that are manipulated repeatedly to recover embryos on day seven of diestrus and old maiden mares that have received progesterone for long periods are also more prone to develop bacterial or fungal infections. Complications may arise with intrauterine antibiotic treatment. Mares may develop secondary bacterial or fungal infections, exhibit severe endometrial irritation or may fail to resolve an infection. Treatment for one pathogen may result in the proliferation of another that often is more difficult to manage than the original. An example is treatment of a streptococcal infection that, after treatment with the appropriate antibiotic, is followed by development of a yeast or Pseudomonas infection. In these cases, a mixed infection may have existed initially and antibiotic use merely allowed proliferation of the other organism. In other cases, a second organism may be introduced accidentally during the course of treatment for the primary infection. FUNGAL ENDOMETRITIS Development of fungal endometritis is a frequent consequence of repeated intra-uterine antibiotic treatments (Dascanio 2007; Hinrichs et al. 1992). Many of these cases resolve spontaneously if the mare has normal perineal Table 1. Guidelines for administration of intrauterine antibiotics Dose per Drug infusion Comments Amikacin 2 gm a Buffer with bicarbonate or large volume of saline (200 ml); Excellent gram negative coverage Ampicillin 2 gm b Use only the soluble product; Susceptible Gram- positive & E coli Ceftiofur sodium 1gm Broad spectrum; save for resistant organisms Gentamicin 1-2 g a Buffer with bicarbonate or large volume of saline (200 ml); Some S. zooepidemicus; Enterobacter spp., E.coli, Klebsiella spp., Proteus spp., Serratia spp, P. aeruginosa, S. aureus Penicillin 5 million U S. zooepidemicus (potassium) Neomycin 4 gm Gram-negative organisms; Some E.coli & some Klebsiella spp.) Ticarcillin 6 gm Anti-pseudomonad penicillin; Gram-positive organisms; Infuse with a minimum of 200 ml of saline Ticarcillin 3-6 gm Beta-lactamase inhibitor confers greater activity against Enterobacter; S. aureus, clavulanic acid B. fragilis; Infuse with a minimum of 200 ml of saline a Buffered with equal volume of 7.5% bicarbonate and diluted in saline b Use at high dilutions because it can be irritating 63

4 anatomy and adequate uterine clearance. If the infection does not resolve in one to two estrous cycles, the uterus should be irrigated with a disinfectant for five to seven days. Disinfectant solutions used for fungal infections include 3% (v/v) hydrogen peroxide solution (30 ml hydrogen peroxide in 1 L of 0.9% saline), 2% (v/v) acetic acid (white vinegar-20 ml of vinegar in 1 L of 0.9% saline), % (v/v) povidone-iodine solution, or 20% DM- SO (Dascanio 2007; Ricketts 1999). If fungi are isolated after uterine irrigation with a disinfectant for 3 to 5 days, a uterine culture should be submitted for antibiotic sensitivity. Recalcitrant fungal infections require prolonged therapy which is costly and relapses are common. Both local and systemic treatments have been advocated and in some cases, mares are treated with both. Breaches in anatomical barriers must be repaired. Unfortunately, the most difficult fungal infections to resolve, in the author s opinion, are those in mares with a fibrotic cervix and inadequate uterine clearance and in mares with insulin resistance or Cushings Disease. In humans, a minimum of 10 to 14 days of treatment is recommended. In horses, intra-uterine treatment is usually limited to the duration of estrus or five to seven days. Mares may require two to three treatment sessions conducted during consecutive estrus periods to resolve an infection. The interval between treatments can be shortened by administration of prostaglandin. Two to three weeks after the second treatment session the uterus should be re-cultured. If fungi are isolated, the reproductive tract Table 2. Antibiotics for systemic treatment of bacterial infections of the equine reproductive tract Drug Dosage Route Interval Comments Amikacin sulfate 10 mg/kg IV or IM 24 h Excellent gram negative coverage Ampicillin sodium 29 mg/kg Iv or IM h Susceptible gram positive organisms & E. coli Ceftiofur 2.5 mg/kg IM h Broad spectrum Gram positive & some gram negative organisms Doxycycline 10 mg/kg PO 12 h Leptospirosis Gentamicin 6.6 mg/kg IV 24 h Slow intravenous infusion; Enterobacter spp., E. coli, Klebsiella spp., Proteus spp., Serratia spp, P. aeruginosa, S. aureus Enrofloxacin a 5.5 mg/kg IV 24 h Slow intravenous infusion; Gram negative 7.5 mg/kg PO infections caused by susceptible bacteria resistant to alternative, 1 st -choice drugs: DO NOT infuse into uterus Oxytetracycline 6.6 mg/kg IV b 12 h Leptospirosis Penicillin G 25,000 IU/kg IV 6 h Synergistic with aminoglycosides; Do not store (potassium) mixed in syringe for more than 12 hr; Do not mix in syringe with gentamicin; S. zooepidemicus, Leptospirosis Penicillin 25,000 IU/kg IM 12 h As for above (procaine) Trimethoprim- 30 mg/kg PO 12 h S. aureus, E. coli, Klebsiella spp Proteus; sulfonamide (combined) some Nocardia spp Metronidazole mg/kg PO 12 h Bacteroides fragilis c metritis a Should not be used in pregnant mares or in young growing horses because of the risk of arthropathy. b Dilute and give slowly IV. c Clostridium difficile and C perfringens diarrhea and death have been reported after use of Metronidazole in western US. 64

5 should be re-evaluated for anatomical defects and cervical incompetence and testing should be performed for Cushings Disease. Systemic therapy for a minimum of 21 days should be considered. Table 3 contains antifungal drugs and dosages for systemic and local infusion. SYSTEMIC ANTIBIOTIC THERAPY Persistent chronic endometritis, retained placenta and metritis are best treated with systemic antibiotics, uterine irrigation and ecbolics. Systemic administration of antibiotics results in higher minimal inhibitory concentrations (MIC) throughout the genital tract as compared to intrauterine therapy. In addition, there is less likelihood of super infections secondary to changes in vaginal flora, the antibiotics are not degraded by conditions in the uterine lumen and parental therapy does not irritate the endometrium (Causey 2007). The length of systemic treatment is not dictated by the estrous cycle and antibiotics may be given for 10 to 14 days if deemed necessary. Systemic therapy eliminates the need to invade the vestibule, vaginal canal and cervix. The vestibule and clitoral fossa harbor a vast array of bacteria, even in reproductively normal mares. These organisms might serve as a source of uterine inoculation when the hand or an instrument is passed through the vulva to cannulate the cervix during intrauterine infusion (Hinrichs et al. 1988). If metritis is present, systemic antibiotics are indicated because they more easily penetrate the myometrium. In chronic cases, the uterus should be evaluated on the last day of treatment to determine if therapy should be continued. If there is fluid within the uterine lumen or there is excessive uterine edema visualized ultrasonographically, intra-uterine treatment should be continued for 2 to 3 more days unless the mare has ovulated and the cervix is tightly closed. Treatment of mares during diestrus should be avoided as it has resulted in fungal endometritis (Hinrichs et al. 1992). The results of therapy should be monitored at the next estrus. Treatment failure Table 3. Usual dosages of systemic and topical antifungal agents for use in equine reproduction Drug Dosage Route Interval (h) Spectrum Systemic Amphotericin B 0.3 to 0.9 mg/kg IV* Broad spectrum Ketoconazole 20 mg/kg (in 0.2 N HCL) NGT a 12 Yeast c Fluconazole Loading dose 14 mg/kg PO, IV 24 Yeast 5 mg/kg Itraconazole 5 mg/kg PO b, IV Broad spectrum d Topical Clotrimazole mg IU 24h x 7d Broad spectrum Miconazole mg IU 24h x 7d Broad spectrum Nystatin million units e IU 24h x 7d Yeast Amphotericin B mg IU 24h x 7d Broad spectrum Fluconazole 100 mg IU 24h x 7d Yeast a Nasogastric intubation is require to avoid the irritant effect of HCL on the oral cavity and throat b The bioavailability of the oral suspension is superior to that of the capsules c Yeasts: Candida spp d Broad spectrum: yeasts, Aspergillus, dimorphic fungi * Diluted to 1 mg/ml in 5% dextrose and administered over 1-2 h e Must be diluted in sterile water (100 to 200 ml) as it precipitates in saline 65

6 is most common when dealing with fungal or chronic gram negative bacterial infections. Failure may be associated with continual contamination of the uterus because of loss of anatomical barriers, inappropriate dosage regimen, drug resistance, inappropriate microenvironment, superinfection, or impaired host s defense mechanisms. When response to treatment is not as expected, the cause should be sought, and the problem corrected. CONCLUSION When choosing antibiotics for treatment of reproductive diseases, veterinarians should base their decisions on culture and antibiotic sensitivity testing. Although treatment length is frequently empirical, some studies indicate that three to five days of intra-uterine treatment may be adequate for resolving endometritis. As endometritis is frequently due to a break down in anatomical barriers and delayed uterine clearance, anatomical barriers should be repaired surgically and ecbolics given to improve uterine clearance. Uterine irrigation with saline or lactated ringers should precede intrauterine infusion of antibiotics because many drugs are inactivated by tissue or inflammatory debris. Systemic therapy should be considered in persistent uterine infections, retained placenta, metritis and genital infections of stallions. Antibiotics should be used judiciously as inappropriate course and dose are often the major instigating factor for antibiotic resistance. ACKNOWLEDGEMENTS Portions of this manuscript are taken from: LeBlanc, MM. The current status of antibiotic use in equine reproduction. EVE 2009: 21: REFERENCES Allen, W.E. (1978) Plasma concentrations of sodium benzyl penicillin after intrauterine infusion in pony mares. Equine Vet J 10, Bedford, S.J. and Hinrichs, K. (1994) The effect of insemination volume on pregnancy rates of pony mares. Theriogenology 42, Bennett, D.G. (1986) Therapy of endometritis in mares. J Am Vet Med Assoc 188, Bretzlaff, K.N. (1986) Factors of importance for the disposition of antibiotics in the female genital tract. In: Current Therapy in Theriogenology 2, Ed: D.A. Morrow, W.B. Saunders, Philadelphia. pp Causey, R.C. (2007) Uterine therapy for mares with bacterial infections. In: Current Therapy in Equine Reproduction, Eds: J.C. Samper, J.F. Pycock and A.O. McKinnon, Saunders-Elsevier, St Louis. pp Dascanio, J.J. (2007) Treatment of fungal endometritis. In: Current Therapy in Equine Reproduction, Eds: J.C. Samper, J.F. Pycock and A.O. McKinnon, Saunders-Elsevier, St Louis. pp Ensink, J.M., Bosch, G. and van Duijkeren, E. (2005) Clinical efficacy of prophylactic administration of trimethoprim/sulfadiazine in a Streptococcus equi subsp. zooepidemicus infection model in ponies. J Vet Pharmacol Ther 28, Ensink, J.M., Smit, J.A. and van Duijkeren, E. (2003) Clinical efficacy of trimethoprim/sulfadiazine and procaine penicillin G in a Streptococcus equi subsp. zooepidemicus infection model in ponies. J Vet Pharmacol Ther 26, Hinrichs, K., Cummings, M.R., Sertich, P.L. and Kenney, R.M. (1988) Clinical significance of aerobic bacterial flora of the uterus, vagina, vestibule, and clitoral fossa of clinically normal mares. J Am Vet Med Assoc 193, Hinrichs, K., Spensley, M. and McDonough, P. (1992) Evaluation of progesterone treatment to create a model for equine endometritis. Equine Veterinary Journal 24, LeBlanc, M.M., Lopate, C., Knottenbelt, D.C. and Pascoe, R. (2003) The mare. In: Equine Stud Farm Medicine and Surgery, Eds: D.C. Knottenbelt, M.M. LeBlanc, C. Lopate and R.R. Pascoe, Elsevier, London. pp McDonnell, A.M. and Watson, E.D. (1992) The effect of transcervical uterine manipulations on establishment of uterine infection in mares under the influence of progesterone. Theriogenology 38, Neeley, D.P., Liu, I.K.M. and Hillman, R.B. (1983) Evaluation and therapy of genital disease in the horse. In: Equine Reproduction, Ed: 6J.P. Hughes, Veterinary Learning Systems, Princeton Junction. pp Ricketts, S.W. (1999) The treatment of equine endometritis in studfarm practice. Pferdeheilkunde 15, Spensley, M.S., Baggot, J.D., Wilson, W.D., Hietala, S.D. and Mihalyi, J.E. (1986) Pharmacokinetics and endometrial tissue concentrations of ticarcillin given to the horse by intravenous and intrauterine routes. Am J Vet Res 47, Threlfall, W.R. and Carleton, C.L. (1986) Treatment of uterine infection in the mare. In: Current Therapy in Theriogenology 2, Ed: D.A. Morrow, Saunders, Philadelphia. pp Van Camp, S.D., Papich, M.G. and Whitacre, M.D. (2000) Administration of ticarcillin in combination with clavulanic acid intravenously and intrauterinely to clinically normal oestrous mares. J Vet Pharmacol Ther 23,