In vitro antimicrobial activity of miconazole and polymyxin B against canine meticillin-resistant Staphylococcus aureus and meticillin-resistant Staphylococcus pseudintermedius isolates

Background – Meticillin‐resistant Staphylococcus aureus (MRSA) and meticillin‐resistant Staphylococcus pseudintermedius (MRSP) infections are increasingly reported in dogs, and these bacteria may be isolated from ear infections. Hypothesis/Objectives – The main aim of the present study was to investigate the in vitro antimicrobial activity of miconazole, polymyxin B and a combination of both against 24 canine MRSA and 50 canine MRSP isolates. The minimal inhibitory concentration (MIC) values of 12 other antimicrobial agents were also determined. Methods – All MIC values were determined according to a broth microdilution assay. Results – Acquired resistance was found to all tested agents, except for linezolid, miconazole and polymyxin B. The MIC values for miconazole and polymyxin B against MRSA were in the range of 4–8 and 8–64 μg/mL, respectively, while the MIC values for miconazole and polymyxin B against MRSP were in the range of 1–2 and 0.25–4 μg/mL, respectively. Using a combination of miconazole and polymyxin B, there was no evidence for enhanced in vitro activity of the combination (i.e. synergy) of both products. Nevertheless, MIC₉₀ values of the combination of these antimicrobial agents and of a commercial product containing both agents were at least 1000 times lower than the concentration present in the commercial product. Conclusions and clinical importance – These results indicate that the topical use of a combination of miconazole and polymyxin B in a 43.5:1 ratio may have potential for the treatment of MRSA‐mediated and MRSP‐associated otitis externa in dogs.     

Prophylactic and metaphylactic antimicrobial use in Belgian fattening pig herds

The monitoring of antimicrobial use is an essential step to control the selection and spread of antimicrobial resistance. Between January and October 2010 data on prophylactic and metaphylactic antimicrobial use were collected retrospectively on 50 closed or semi-closed pig herds. Ninety-three percent of the group treatments were prophylactic whereas only 7% were methaphylactic. The most frequently used antimicrobials orally applied at group level were colistin (30.7%), amoxicillin (30.0%), trimethoprim-sulfonamides (13.1%), doxycycline (9.9%) and tylosin (8.1%). The most frequently applied injectable antimicrobials were tulathromycin (45.0%), long acting ceftiofur (40.1%) and long acting amoxicillin (8.4%). The treatment incidences (TI) based on the used daily dose pig (UDD(pig) or the actually administered dose per day per kg pig of a drug) for all oral and injectable antimicrobial drugs was on average 200.7 per 1000 pigs at risk per day (min=0, max=699.0), while the TI based on the animal daily dose pig (ADD(pig) or the national defined average maintenance dose per day per kg pig of a drug used for its main indication) was slightly higher (average=235.8, min=0, max=1322.1). This indicates that in reality fewer pigs were treated with the same amount of antimicrobials than theoretically possible. Injectable products were generally overdosed (79.5%), whereas oral treatments were often underdosed (47.3%). In conclusion, this study shows that prophylactic group treatment was applied in 98% of the visited herds and often includes the use of critically important and broad-spectrum antimicrobials. In Belgium, the guidelines for prudent use of antimicrobials are not yet implemented.     

Effects of N-methyl-D,L-aspartate on LH,GH, and testosterone secretion in goat bucks maintained under long or short photoperiods

Photoperiod modulates reproduction in goats. We tested the hypothesis that the excitatory glutamatergic tone is reduced in the photoinhibited goat. The objectives of this study were to determine the effect of photoperiod and glutamatergic stimulation on LH, GH, and testosterone (T) secretion in goat bucks. Eight mature, intact bucks were used in two simultaneous 4 x 4 Latin square designs. Variables were two photoperiod regimens (short day; SD, 10 h light:14 h dark, n = 4; vs long day; LD, 16 h light:8 h dark, n = 4) and four doses of N-methyl-D-L-aspartate (NMA; 0, 1, 2 and 4 mg/kg BW, i.v.). Venous blood was obtained for 2 h before and after NMA injection, followed by GnRH injection and then a final 1 h of sampling. Injection of NMA increased (P < 0.002) LH secretion within 20 min. This increase was sustained for 120 min, but the response was most pronounced in LD goats. The increase in mean LH was associated with a concomitant dose-dependent increase in pulse frequency (P < 0.006). However, NMA treatment had no effect (P > 0.10) on LH pulse amplitude. The release of LH after injection of GnRH was not affected by photoperiod. Exposure of bucks to LD reduced T secretion relative to that of SD bucks (P < 0.01). However, GH secretion was enhanced in LD bucks (P< 0.001). The response of GH to NMA was dependent on photoperiod history. A highly significant immediate and sustained increase (P < 0.001) was observed in LD but not in SD bucks within 10 min. Overall, a dose-dependent increase (P < 0.01) in T secretion was stimulated by NMA in both LD and SD bucks. These results indicate that NMA receptors may be involved in the regulation of LH, GH, and testosterone secretion in the goat. Furthermore, length of day influences GH secretion in the goat and NMA receptor activation had divergent effects on the secretion of this hormone.     

Concentrations of leptin in serum and milk collected from lactating sows differing in body condition

Leptin concentrations in the circulation and milk were determined in sows that differed in body condition at farrowing, and in feed consumption during lactation. Serum concentrations of leptin at farrowing and weaning were highest in sows exhibiting the greatest amount of backfat. Leptin was detected in both skim and whole milk throughout lactation, but levels were not correlated with backfat thickness or circulating leptin concentrations. This report provides the first evidence for the presence of leptin in sow milk; its function in the physiology of suckling pigs remains to be determined.     

Effect of pasteurized egg yolk on the quality of cryopreserved boar semen

Egg yolk (EY, control) is an essential ingredient of diluents for boar semen cryopreservation. Pasteurized egg yolk (PEY) reduces hygienic risks in processing and is easier to standardize. The aim of this study was to evaluate the in vitro effect of PEY (treatment) on frozen-thawed boar semen. In a split-sample approach (n = 13 boars), it could be shown that there is neither an influence (p > .05) on post-thawing motility (PTM: 5, 30 and 120 min) nor on morphologically intact sperm, percentage of acrosome defects and membrane fluidity using a PEY extender compared to the control. Mitochondrial activity (p = .043), membrane integrity (p = .015) and PTM 300 min (p = .023) were slightly affected in the treatment group. Overall, sperm quality was at a high level in both experimental groups. Further studies are needed to determine the impact of PEY on the fertilizing capacity of boar ejaculates.     

Perfrin,a novel bacteriocin associated with netB positive Clostridium perfringens strains from broilers with necrotic enteritis

Necrotic enteritis in broiler chickens is associated with netB positive Clostridium perfringens type A strains. It is known that C. perfringens strains isolated from outbreaks of necrotic enteritis are more capable of secreting factors inhibiting growth of other C. perfringens strains than strains isolated from the gut of healthy chickens. This characteristic could lead to extensive and selective presence of a strain that contains the genetic make-up enabling to secrete toxins that cause gut lesions. This report describes the discovery, purification, characterization and recombinant expression of a novel bacteriocin, referred to as perfrin, produced by a necrotic enteritis-associated netB-positive C. perfringens strain. Perfrin is a 11.5 kDa C-terminal fragment of a 22.9 kDa protein and showed no sequence homology to any currently known bacteriocin. The 11.5 kDa fragment can be cloned into Escherichia coli, and expression yielded an active peptide. PCR detection of the gene showed its presence in 10 netB-positive C. perfringens strains of broiler origin, and not in other C. perfringens strains tested (isolated from broilers, cattle, sheep, pigs, and humans). Perfrin and NetB are not located on the same genetic element since NetB is plasmid-encoded and perfrin is not. The bacteriocin has bactericidal activity over a wide pH-range but is thermolabile and sensitive to proteolytic digestion (trypsin, proteinase K). C. perfringens bacteriocins, such as perfrin, can be considered as an additional factor involved in the pathogenesis of necrotic enteritis in broilers.     

The influence of stress from transport and handling on hematologic and clinical chemistry blood parameters of racing pigeons (Columba livia domestica)

In the present study, the influence of stress from handling and transport on some frequently examined blood parameters of racing pigeons was evaluated. After 3 hr, there was a highly significant (P < 0.01) increase in the number as well as in the percentage of heterophils and decrease of lymphocytes. In clinical chemistries, increases of creatine kinase and glucose and a decrease of uric acid were observed. There was a mean decrease of the total white blood count of >15% that was less significant (P < 0.05). Changes in lactate dehydrogenase, basophils, and monocytes did not prove to be significant; eosinophils, aspartate aminotransferase, total protein, and the packed cell volume were not influenced by stress.     

Cytokines and acute phase proteins associated with acute swine influenza infection in pigs

This study set out to investigate the cytokines and acute phase proteins (APPs) associated with the acute stages of experimentally-induced swine influenza virus (SIV) infection in 3-week-old, colostrum-deprived, caesarean-derived piglets. The piglets were inoculated intratracheally with 10^7.5 50% egg infective dose [EID₅₀] Swine/Belgium/1/98 (H1N1) SIV and were euthanased at time-points between 0 and 120 h post-inoculation (PI). Broncho-alveolar lavage fluid (BALF), lung homogenates and sera were examined for inflammatory mediators by bioassay or ELISA. Interferon (IFN)-α, interleukin (IL)-6, IL-1 and tumour necrosis factor (TNF)-α peaked in BALF 24–30 h PI, when virus titres and the severity of clinical signs were maximal.Whereas IFN-γ and IL-12, but not IL-18, increased in tandem in BALF, serum cytokine concentrations were either undetectable or were up to 100-fold lower. The APP C-reactive protein (CRP) and haptoglobin peaked 24 h later than the cytokines and reached higher levels in serum than in BALF. In contrast, lipopolysaccharide (LPS)-binding protein (LBP) only increased in BALF. Lung virus titres tightly correlated with BALF IFN-α, IL-6, IL-1, TNF-α, IFN-γ and IL-12, as well as with serum IL-6, IFN-α and IFN-γ. Signs of disease correlated with the same cytokines in BALF and serum, as well as with BALF LBP and serum CRP. The findings suggest that IFN-γ and IL-12 play a role in the pathogenesis of SIV and that APPs are induced by cytokines. This influenza infection model may have value in assessing the therapeutic potential of cytokine antagonists.     

Qualitative Comparison of 0.27T, 1.5T,and 3T Magnetic Resonance Images of the Normal Equine Foot

Magnetic resonance (MR) imaging has become an important diagnostic tool in the investigation of foot pain in horses. The aim of this study was to qualitatively compare ex-vivo MR images of the same equine feet obtained at three magnetic field strengths: 0.27, 1.5, and 3 tesla (T). Ten cadaver feet were used. All feet were imaged with two high-field systems (3T, 1.5T) and with a low-field (LF) system at 0.27 T designed for standing horses. Images were acquired using similar pulse sequences in all 3 MR units. MR images were subjectively evaluated by three independent experienced image analysts for image quality and clarity of visualization of individual anatomical structures using a four-point grading scale. The images from all of the examinations were considered to be of diagnostic value except for the hoof capsule where substantial artifacts were present in LF images with distortion and loss of signal at the dorsal/distal aspect of the hoof capsule in LF images. Anatomical structure scoring values of images obtained at 3T and 1.5T were significantly greater than scores of images obtained at 0.27T. Scores for images obtained at 3T were significantly higher than those for images obtained at 1.5T. Mean score differences between 1.5T and 3T were higher for cartilage of the distal interphalangeal joint and for the ungular cartilages.