Minimum Inhibitory Concentration and Postantibiotic Effect of Amikacin for Equine Isolates of Methicillin-Resistant Staphylococcus aureus In Vitro

Objective— To report the minimum inhibitory concentration (MIC) of amikacin sulfate for equine clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and characterize the initial kill and duration of the postantibiotic effect (PAE) for selected strains.
Study Design— Experimental study.
Methods— Isolates of MRSA (n=35) had their amikacin MIC determined using the E-test agar diffusion method. Two isolates with MICs>256 μg/mL limit were further characterized using broth macrodilution. Six distinct isolates with amikacin MICs of 32, 48, 128 (2 isolates) and 500 (2 isolates) μg/mL had PAE determinations made over a range of amikacin concentrations from 31.25–1000 μg/mL using standard culture-based techniques.
Results— Median MIC of the 35 isolates was 32 μg/mL (range 2 to >256 μg/mL). Mean PAE of selected MRSA strains had an overall mean (all amikacin doses) of 3.43 hours (range 0.10–9.57 hours). PAE for MRSA exposed to amikacin at 1000 μg/mL was 6.18 hours (range 3.30–9.57 hours), significantly longer than that for all other concentrations ( P <.0001). There was no statistically significant effect of isolate MIC on PAE.
Conclusions— Isolates had a wide range of MIC; however, growth of all 6 selected strains were inhibited within the range of concentrations tested, including 2 strains with MICs of 500 μg/mL. PAE duration was not influenced by the MIC of amikacin but was significantly longer with treatment at 1000 μg/mL than at lower concentrations.
Clinical Relevance— Clinical isolates of MRSA are susceptible to amikacin at concentrations achieved by regional perfusion: however, the modest duration of PAE observed suggest that further laboratory and in vivo evaluation be conducted before recommending the technique for clinical use.     

Clinical Evaluation of Canine Acetabular Fractures Stabilized with an Acetabular Plate

A retrospective study of 14 dogs with one or more acetabular fractures stabilized with an acetabular plate was conducted. Twelve of the 14 dogs had additional orthopedic injuries. Follow-up was longer than 6 months. Eleven dogs were evaluated by assessment of radiographs, lameness, mid-thigh circumference, coxofemoral joint range of motion, crepitus, and pain. Varying degrees of osteoarthrosis were noted radiographically at follow-up. Ten of 12 dogs examined had occasional or no clinical lameness. In 10 of 12 dogs, mid-thigh circumference was less on the limb that sustained the acetabular fracture. Nonunion was diagnosed in one plated acetabulum in which two screws had broken. A return to normal or nearly normal function was observed when there were no more than two orthopedic injuries.     

Magnetic Motor Evoked Potentials for Assessing Spinal Cord Integrity in Dogs with Intervertebral Disc Disease

Magnetically elicited transcranial motor evoked potentials (MEPs) were studied in 37 dogs with type 1 intervertebral disc (IVD) disease. The waveforms were recorded from both cranial tibial muscles before and after surgery. The latencies and amplitudes obtained were compared to those of a control population (n = 14). MEPs were recordable in all dogs with mild or no neurologic deficits, but they were recordable in only 50% of ambulatory dogs that were severely ataxic. MEPs could not be elicited from nonambulatory dogs. There was a significant attenuation of the amplitudes in all clinical cases, even if the dogs demonstrated back pain alone. Significantly prolonged latencies were associated with neurologic deficits. MEPs were not good predictors of neurologic recovery. The responses obtained from the side where the disc material was found were not different from those recorded from the opposite side. MEPs were very sensitive to lesions of the spinal cord, as indicated by the significant changes in the waves in patients with mild or no neurologic deficits and in the loss of response in dogs that still demonstrated purposeful movement. Neurologic exams provided more accurate diagnoses and prognoses than did MEPs in dogs with IVD disease.     

Arteriovenous Fistulas as an Aid in Blood Collection from Canine Blood Donors

To facilitate blood collection from blood donor dogs, arteriovenous fistulas were established between the common carotid arteries and external jugular veins in five adult dogs. Twelve to 16 mm, side-to-side anastomoses were created using simple interrupted 6–0 polypropylene sutures. Starting 1 month after the surgical procedure, 500 ml of blood was collected from each dog as required. Electrocardiography, thoracic radiography, and cardiac output and rate were used to monitor cardiac changes. Blood flow characteristics, and proliferative and dystrophic cellular changes occurring in the vessels were documented in one dog.
The mean blood collection times were 2 minutes and 45 seconds from the fistula site and 9.0 minutes from the opposite jugular vein. Ventricular hypertrophy and myocardial changes were observed on electrocardiogram in two dogs, and radiographic evidence of pulmonary hypertension was noted in three dogs. Reversed blood flow was documented in the common carotid artery and external jugular vein distal to the arteriovenous fistula. Four dogs were still in use as blood donors 1 to 1 1/2 years after establishment of the fistulas. Clinical signs of congestive heart failure were not observed.     

Relationship of Femoral Intramedullary Pins to the Sciatic Nerve and Gluteal Muscles after Retrograde and Normograde Insertion

An anatomic analysis of retrograde and normograde intramedullary (IM) pinning of proximal, midshaft, and distal femoral fractures was performed in 28 canine cadavers. For all fracture locations, normograde pins were significantly more cranial in the middle gluteal muscle than retrograde pins (p less than 0.01). There was no significant difference between pinning techniques in craniocaudal position of the IM pin in the superficial gluteal muscle. In distal fractures, normograde pins were placed significantly more lateral than retrograde pins in the superficial gluteal muscle (p less than 0.01). One of 15 normograde pins and 9 of 13 retrograde pins were located in the medial half of the trochanteric fossa. Normograde pins were significantly more lateral in the trochanteric fossa than were retrograde pins in midshaft fractures (p less than 0.01). Normograde pins were significantly (p less than 0.01) farther from the sciatic nerve than retrograde pins when the hip was positioned at coxofemoral flexion angles of 85 degrees in midshaft and 110 degrees in distal fractures. Seven of 13 retrograde pins, but none of 15 normograde pins, contacted the sciatic nerve. Normograde pinning of the femur may be less likely to induce sciatic nerve injury, particularly in midshaft and distal fractures.     

Chlorhexidine Diacetate and Povidone-iodine Cytotoxicity to Canine Embryonic Fibroblasts and Staphylococcus aureus

Chlorhexidine diacetate and povidone-iodine were evaluated for fibroblast toxicity on a primary line of canine embryonic fibroblasts, and for bactericidal efficacy against Staphylococcus aureus. The cultured fibroblasts or S. aureus were exposed for 30 minutes to incremental dilutions of 0.5 and 0.0005% chlorhexidine diacetate, 5.0 to 0.05% povidone-iodine, or physiologic buffered saline as a control. To determine survival, fibroblasts were trypsinized and counted; S. aureus colonies were counted on brain-heart infusion agar. Survival for both groups was expressed by calculating the number of living cells in test dilutions as a percentage of the number in control cultures. Fibroblast survival occurred at chlorhexidine concentrations less than 0.013% and at povidone-iodine concentrations less than 0.5% (p less than 0.05). Significant S. aureus survival (p less than 0.05) was noted at chlorhexidine concentrations less than 0.05% and povidone-iodine concentrations less than 1.0%. These data showed that all bactericidal concentrations of chlorhexidine diacetate and povidone-iodine were lethal to canine embryonic fibroblasts in vitro, whereas non-lethal concentrations allowed significant bacterial survival.     

Crosspin Fixation of Fractures of the Proximal Tibia in Three Foals

Three foals, each less than 1 month of age, were presented with Salter Type II fractures of the proximal tibial physis. Reduction of the fractures was accomplished manually and maintained by crosspin fixation. Fracture healing in two of the foals was uncomplicated. The third foal developed an infection around the implants, which responded to periodic local antiseptic flushing and administration of penicillin and gentamicin. Follow-up information ranging from 11 to 22 months after surgery revealed satisfactory results in two of three foals; premature closure of the proximal tibial physis was found in the other foal, resulting in the development of an angular limb deformity.     

Total Ear Canal Ablation Combined with Lateral Bulla Osteotomy for End-Stage Otitis in Dogs Results in Thirty Dogs

Thirty dogs with end-stage otitis were treated by either unilateral or bilateral total ear canal ablation and lateral bulla osteotomy. Otitis was considered end stage when the horizontal ear canal was collapsed, stenotic, or occluded in conjunction with chronic infection of the external and middle ear. The dogs were evaluated clinically and radiographically for 4 to 63 months. The frequency of scratching, head shaking, aural drainage, and para-aural fistulation was significantly decreased. Abnormal ear carriage and head tilt were not changed. The results in 23 dogs were graded as excellent or improved. One dog died of intraoperative hemorrhage. Complications during the period from suture removal to follow-up included para-aural fistulation (3 dogs), facial nerve paralysis (5 dogs), and head tilt (3 dogs).     

Urethral Extension for Correction of Urovagina in Cattle A Review of 14 Cases

Urethral extension was performed in 14 cows with clinical urovagina and infertility. Urovagina was corrected in nine cows (64%) and was reduced in the others. Formation of fistulas at the cranial end of the extension site was the most frequent complication (4 cows). In one cow, the urethral extension was not extended far enough caudally. Eleven cows (79%) returned to fertility after surgery. Severity of urine pooling, cranial displacement of the urethral orifice, and severe preoperative vaginitis may explain the failure of the urethral extension in some cows.     

Surgical Wound Infection Rates in Dogs and Cats Data from a Teaching Hospital

Two thousand sixty-three surgical procedures were performed on 1992 patients (1715 dogs and 277 cats). In a retrospective analysis, the procedures were categorized according to the expected degree of wound contamination, and corresponding wound infection rates were determined. The number of procedures in each category and the percent that became infected were as follows: clean (1100, 2.5%), clean-contaminated (554, 4.5%), contaminated (172, 5.8%), and dirty (237, 18.1%). The administration of antibiotics significantly reduced the frequency of wound infection in clean surgical procedures performed by senior veterinary students (p less than 0.05), but not in clean elective procedures performed by faculty or resident surgeons that required 90 minutes or less to complete. There was a significant correlation between elevation of rectal temperature postoperatively and increased duration of the surgical procedure. However, the rectal temperature measured the day after surgery was not an accurate predictor of wound infection.