Annette Petersen

Frequency of isolation and antimicrobial susceptibility patterns of Staphylococcus intermedius and Pseudomonas aeruginosa isolates from canine skin and ear samples over a 6-year period (1992-1997)

Staphylococcus intermedius (S. intermedius) was isolated from 88.6% and 49.4% of skin and ear samples, respectively, during the years 1992 through 1997, and frequency of isolation remained unchanged. More than 95% of all S. intermedius isolates were susceptible to cephalothin and oxacillin, providing support for empirical treatment of canine skin and ear infections with cephalexin. Pseudomonas aeruginosa (P. aeruginosa) was isolated from 7.5% and 27.8% of skin and ear samples, respectively. The frequency of isolation from skin samples increased over the study period. Because of multidrug-resistant profiles for P. aeruginosa isolates, especially for ear isolates, empirical treatment of P. aeruginosa infections is not advisable.

Multi-drug and methicillin resistance of staphylococci from canine patients at a veterinary teaching hospital (2006-2011).

Background: Over the past 10 years, an increase in methicillin and multi-drug resistant staphylococcal species has been identified worldwide and anecdotally reported within our veterinary teaching hospital. Objective: To determine the methicillin resistance (MR) and multi-drug resistance (MDR) patterns of staphylococcal species isolated from canine patients between 2006 and 2011. Animals and Methods: Staphylococcal isolates (n = 1069) were cultured from the canine patient population of the veterinary teaching hospital. The susceptibility reports of Staphylococcus pseudintermedius, S. aureus, S. schleiferi v. coagulans, S. schleiferi v. schleiferi, and other coagulase-negative staphylococci (CoNS) were assessed. Isolates were organized into five site categories. Isolates were scored on a 0–10 scale based on resistance to antimicrobial classes, with MDR classified as an isolate scoring a value ≥3. Statistical analysis included χ2, Fishers exact test, and ANOVA with mean square and post hoc analysis; p < 0.05 was significant. Results: S. pseudintermedius (76.6%), S. aureus (15.5%), S. schleiferi v. coagulans (5.7%), S. schleiferi v. schleiferi (1.2%), and CoNS (0.9%) isolation was observed. MR occurred in 11.4% of all combined isolates, with no difference between sites and years. Of the S. pseudintermedius isolates, 4.5% were methicillin resistant. Of all the isolates, 27.5% were MDR. The mean resistance score of S. pseudintermedius isolates increased significantly comparing 2006 and 2008 (p = 0.0006) and 2006 and 2009 (p = 0.0009). The mean score of all combined isolates increased significantly comparing 2006 and 2008 (p = 0.001). Conclusion: MR staphylococci isolation is similar when compared to other studies. However, increased MDR isolation is of greater concern and high-scoring MDR staphylococci will limit our future antimicrobial choices.

Investigation on the effects of ciclosporin (Atopica) on intradermal test reactivity and allergen-specific immunoglobulin (IgE) serology in atopic dogs

The ability to use ciclosporin (Atopica®: Novartis Animal Health, Greensboro, NC, USA) prior to intradermal testing (IDT) would help avoid exacerbation of clinical disease that can be associated with drug withdrawal. This study evaluated the effects of 30 days of administration of ciclosporin at a dose of 5 mg/kg once daily on IDT reactivity (immediate phase reactions) in a group of dogs with atopic dermatitis (AD) with initial positive IDT reactions. 16 dogs diagnosed with AD were included in the study. Eight dogs (group A) were treated with ciclosporin orally at 5 mg/kg once daily for 30 days. Eight dogs (group P) were treated with a placebo orally once daily for 30 days. IDT was performed at day 0 and day 30 on all dogs enrolled using a standardized panel of 45 aqueous allergens (Greer Laboratories, Lenoir, NC, USA) appropriate to our geographical region. IDT reactivity was assessed by both subjective and objective methods at 15 min post-intradermal injection. Serum for allergen-specific immunoglobulin (IgE) serology was obtained at day 0 and day 30. The study was designed as a double-blinded, placebo-controlled, cross-over study. Data were analysed using a split-plot analysis of variance with the grouping factor of treatment and the repeat factor of time (SAS System for Windows). At week 4, ciclosporin did not have a statistically significant effect on IDT reactivity or serology results. It therefore appears that, no withdrawal is recommended to evaluate immediate phase reactions.

Comparison of hair follicle histology between horses with pituitary pars intermedia dysfunction and excessive hair growth and normal aged horses

BACKGROUND Pituitary pars intermedia dysfunction (PPID) in older equids is commonly recognized by a long hair coat that fails to shed. OBJECTIVE The aim of this study was to compare hair follicle stages in PPID-affected horses with excessively long hair coats with the stages of normal aged horses (controls) and to compare hair follicle stages in PPID-affected horses after 6 months of treatment with pergolide mesylate with those of control horses. ANIMALS Eight PPID-affected horses and four normal, age-matched, control horses. METHODS Skin biopsies were collected from the neck and rump of PPID-affected and control horses. A diagnosis of PPID was established based on hair coat changes and supportive overnight dexamethasone suppression test results. Skin biopsies were repeated after 6 months of treatment with pergolide. The number of hair follicles in anagen (A) or telogen (T) was counted for each skin biopsy using transverse sections. RESULTS Pretreatment biopsies had a greater percentage of A follicles (neck 96%, rump 95%) and a lower percentage of T follicles (neck 4%, rump 5%) in PPID-affected horses than in control horses (A, neck 15%, rump 25%; and T, neck 85%, rump 75%). After treatment with pergolide, all PPID-affected horses had improved shedding, and the percentages of A follicles (neck 69%, rump 70%) and T follicles (neck 31%, rump 30%) were not different from untreated control horses (A, neck 68%, rump 82%; and T, neck 32%, rump 18%). CONCLUSIONS These findings document that excessive hair growth (hypertrichosis) in PPID-affected horses is due to persistence of hair follicles in A. Furthermore, treatment with pergolide improved shedding and reduced the percentage of A follicles in PPID-affected horses.

Effects of dexamethasone and hydroxyzine treatment on intradermal testing and allergen-specific IgE serum testing results in horses

To determine whether dexamethasone or hydroxyzine affect intradermal testing (IDT) and allergen-specific IgE serum testing (ASIST) results in horses, these tests were performed serially in five horses without signs of atopic dermatitis before and after treatment with the drugs. IDT consisted of saline, histamine (1:100,000 w/v) and eight commercial extracts; results were evaluated as subjective scores by comparison to saline (0) and histamine (4) and as objective measurement of wheal diameter (mm). After baseline testing, dexamethasone (20 mg) was administered intramuscularly daily for 7 days. Testing was repeated 3-4 h, 7 days, and 14 days after the final dose of dexamethasone. Hydroxyzine (500 mg) was subsequently administered orally twice daily for 7 days. Testing was performed 3-4 h, 3 days, and 7 days after the final dose of hydroxyzine. No differences were found between pre- and post-treatment subjective IDT scores for either drug. However, wheal diameter for histamine and house dust, dust mite mix, and black ant extracts decreased (P < 0.05) at all times post-injection for IDT performed 3-4 h after the final dose of both medications. Wheal diameter returned to pre-treatment levels 14 days after discontinuation of dexamethasone and 7 days after discontinuation of hydroxyzine. No significant changes in ASIST results were found. In conclusion, treatment of horses with dexamethasone or hydroxyzine for 7 days had no effect on ASIST results but did decrease IDT wheal diameters. Based on findings of this study, withdrawal times of 14 and 7 days for dexamethasone and hydroxyzine, respectively, prior to IDT can be recommended.

Endolymphatic Sac Tumor in Two Dogs

Endolymphatic sac tumors (ELSTs) are rare neoplasms of the inner and middle ear described in humans. Diagnosis of such neoplasms is difficult and largely dependent on a combination of histologic, immunohistochemical, and clinical findings. Although the neoplastic cells lack cellular features of malignancy, these are clinically aggressive tumors that often invade the surrounding temporal bone. Here, we describe 2 dogs with middle ear masses that share morphologic, immunohistochemical, and clinical similarities with human ELSTs. Advanced imaging of the masses revealed evidence of aggressive behavior such as bony lysis of the temporal bone. Histologically, the neoplastic epithelial cells formed papillary structures, lacked mitotic figures, and had mild anisocytosis and anisokaryosis. The neoplastic cells were immunohistochemically positive for cytokeratin AE1/AE3 but were negative for chromogranin, synaptophysin, and thyroglobulin. Local invasion and bone destruction but no evidence of metastases suggest a clinical behavior similar to human ELSTs.