An observational cohort study on antimicrobial usage on dairy farms in Quebec, Canada

Quantification of antimicrobial usage (AMU) is crucial to measure the effect of intervention programs, to determine associations between usage and resistance, to compare populations, and for benchmarking purposes. The primary objective of the study was to describe quantitatively the AMU on Quebec dairy farms over 1 yr: (1) the total AMU, (2) the AMU per administration route (intramammary, injectable, oral, intrauterine), and (3) the AMU per antimicrobial class and according to the categorizations of Health Canada and the World Health Organization. The secondary objective was to assess the effect of several characteristics (herd size, level of milk production, and incidence rate of common infectious diseases) on AMU rate. The AMU data were obtained for 101 dairy farms randomly selected in 3 important Quebec dairy regions by collecting and recording all empty drug packaging and invoices for medicated feed (spring 2017 to spring 2018). The AMU rate was reported in number of Canadian defined course doses for cattle per 100 cow-years. The average herd size was 67 cows per farm, and 2/101 farms were certified organic. Overall, an estimated mean of 537 Canadian defined course doses for cattle/100 cow-years was observed. The intramammary route during lactation was the most frequently observed, followed, in decreasing order of usage, by oral route in the feed, intramammary route at drying-off, and injectable route. Oral (other than in animal feed) and intrauterine formulations were infrequently collected from the garbage cans. The 5 most frequently observed antimicrobial classes were, by decreasing order of usage, ionophores, penicillins, aminocoumarins, aminoglycosides, and polymyxins. Highest priority critically important antimicrobials as defined by the World Health Organization were mainly collected from intramammary formulations during lactation followed by injectable and drying-off intramammary formulations. The herd size was positively associated with the total AMU rate but not with the usage rate of highest priority critically important antimicrobials. Incidence of diseases along with preventive use of antimicrobials (drying-off and medicated feed with antimicrobials) explained 48% of the variance in total AMU rate.

A Multidisciplinary Basic Airway Skills Boot Camp for Novice Trainees

INTRODUCTION

Otolaryngology and anesthesiology residents may be the first responders to airway emergencies, even in the first weeks of training. These residents may be unfamiliar with the armamentarium of airway maneuvers, the most basic of which may be lifesaving. Boot camp education has been demonstrated to be effective in multiple disciplines. In this study, we examine whether an immersive, multidisciplinary boot camp style simulation course leads to an improvement in novice airway provider confidence.

METHODS

Novice otolaryngology and anesthesiology residents participated in an annual (2013-2018) multidisciplinary boot camp simulation course. Residents completed an anonymous pre- and post-test self-assessment tool reporting their confidence for airway skills and concepts from the curriculum. Responses were on a Likert scale from 1 to 5 (1=no familiarity, 5=extremely comfortable). We analyzed pre- and post-course participant self-reported comfort level with the airway management skills and concepts addressed in the course. Frequencies and percentages were reported. Fisher's exact test was used to assess statistical significance at level 0.05.

RESULTS

A total of 62 residents, including 50 anesthesiology residents and 12 otolaryngology residents, completed a post-test self-assessment tool. For all topics covered in the course, there was a statistically significant change in the percentage of residents who reported familiarity with the topic (p<0.001). This corresponded to an increase in self-reported comfort level and a decrease in non-familiarity or discomfort with the airway topics covered in the course. The greatest increase in percentage of residents reporting feeling comfortable or extremely comfortable with the task after completion of the simulation boot camp were all moderately advanced airway maneuvers (laryngeal mask airway [LMA] placement, flexible fiberoptic intubation, glidescope intubation, endotracheal intubation, and two-person mask ventilation). The greatest decrease in non-familiarity or discomfort was seen in moderately complex to advanced airway topics (fiberoptic intubation, glidescope intubation, intubating LMA, rigid bronchoscopy, cricothyroidotomy, tracheostomy, and laryngectomy).

CONCLUSIONS

Our data support the use of immersive surgical boot camp experiences to enhance resident familiarity and comfort and decrease unfamiliarity and discomfort with a wide variety of airway topics and maneuvers.

Effects of pig hemoglobin binding on some physical and biological properties of Actinobacillus pleuropneumoniae lipopolysaccharides

Binding of pig hemoglobin (Hb) to Actinobacillus pleuropneumoniae lipopolysaccharide (LPS), either extracted or present at the surface of whole cells, was studied. After a short incubation period, pig Hb seemed to cover the bacterial cell surface and enhanced the cells' contrast when examined by transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy analysis showed that the amount of elemental iron detected was increased when cells of A. pleuropneumoniae were incubated with pig Hb. Coating with pig Hb, however, did not interfere with the accessibility of O- and capsular antigens to antibodies on the bacterial cell surface. Binding of pig Hb and polymyxin B to lipid A of A. pleuropneumoniae was confirmed with a fluorescent probe (dansylcadaverine) displacement assay. The binding of pig Hb to extracted LPS resulted in a disaggregation of LPS as observed by TEM after negative staining. Additional evidence for a direct physical interaction between pig Hb and A. pleuropneumoniae LPS was demonstrated by a shift in the sedimentation velocity of LPS-Hb complexes determined by sucrose gradient centrifugation. Pig Hb binding to extracted LPS or to bacterial cells resulted in a significant decrease of chromogenic Limulus amebocyte lysate activation. Finally, the capacity of extracted LPS to induce NO2-in the presence of pig Hb was tested by using cell line J774 and determined by the Greiss' reaction. LPS alone induced, as expected, NO2- production, whereas the presence of pig Hb significantly reduced NO2-production by murine macrophages. Taken together, our results indicate that binding of pig Hb affected some physical and biological properties of A. pleuropneumoniae LPS.

Methicillin-resistant Staphylococcus Aureus in Horses at a Veterinary Teaching Hospital: Frequency, Characterization, and Association with Clinical Disease

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging equine pathogen. To attempt to control nosocomial and zoonotic transmission, an MRSA screening program was established for all horses admitted to the Ontario Veterinary College Veterinary Teaching Hospital, whereby nasal screening swabs were collected at admission, weekly during hospitalization, and at discharge. MRSA was isolated from 120 (5.3%) of 2,283 horses: 61 (50.8%) at the time of admission, 53 (44.2%) during hospitalization, and 6 from which the origin was unclear because an admission swab had not been collected. Clinical infections attributable to MRSA were present or developed in 14 (11.7%) of 120 horses. The overall rate of community-associated colonization was 27 per 1,000 admissions. Horses colonized at admission were more likely to develop clinical MRSA infection than those not colonized at admission (OR 38.9, 95% CI 9.49 160, P < 0.0001). The overall nosocomial MRSA colonization incidence rate was 23 per 1,000 admissions. The incidence rate of nosocomial MRSA infection was at the rate of 1.8 per 1,000 admissions, with an incidence density of 0.88 per 1,000 patient days. Administration of ceftiofur or aminoglycosides during hospitalization was the only risk factor associated with nosocomial MRSA colonization. MRSA screening of horses admitted to a veterinary hospital was useful for identification of community-associated and nosocomial colonization and infection, and for monitoring of infection control practices.

Methicillin-resistant Staphylococcus aureus in horses and horse personnel, 2000-2002

Methicillin-resistant Staphylococcus aureus was isolated from horses and horse personnel in a pattern suggestive of interspecies transmission of a human-origin clone.

Methicillin-resistant Staphylococcus aureus (MRSA) infection was identified in 2 horses treated at a veterinary hospital in 2000, prompting a study of colonization rates of horses and associated persons. Seventy-nine horses and 27 persons colonized or infected with MRSA were identified from October 2000 to November 2002; most isolations occurred in a 3-month period in 2002. Twenty-seven (34%) of the equine isolates were from the veterinary hospital, while 41 (51%) were from 1 thoroughbred farm in Ontario. Seventeen (63%) of 27 human isolates were from the veterinary hospital, and 8 (30%) were from the thoroughbred farm. Thirteen (16%) horses and 1 (4%) person were clinically infected. Ninety-six percent of equine and 93% of human isolates were subtypes of Canadian epidemic MRSA-5, spa type 7 and possessed SCCmecIV. All tested isolates from clinical infections were negative for the Panton-Valentine leukocidin genes. Equine MRSA infection may be an important emerging zoonotic and veterinary disease.

Studies of the route of administration and role of conditioning with radiation on unrelated allogeneic mismatched mesenchymal stem cell engraftment in a nonhuman primate model

OBJECTIVE

The aim of this study was to examine the effects of the route of administration [intrabone marrow (IBM) vs intravenous (IV)] and the role of conditioning with irradiation in optimizing mesenchymal stem cell (MSC) transplantation.

MATERIALS AND METHODS

To determine if irradiation resulted in depletion of colony-forming unit fibroblasts (CFU-F), which might favor the engraftment of donor MSC, the number of CFU-Fs was assayed from animals receiving either hemibody irradiation (HBI) or total body irradiation (TBI).

RESULTS

TBI resulted in a marked reduction of CFU-F numbers that spontaneously resolved, whereas animals receiving HBI did not experience depletion of CFU-F. Animals receiving MSC grafts by the IV route had higher numbers of marrow CFU-F. MSC were transduced using retroviral vectors encoding the neomycin resistance gene (Neo(R)) and a second gene encoding either the human soluble tumor necrosis factor receptor (hsTNFRII) or beta-galactosidase (beta-Gal). MSCs were administered by either the IV or IBM route to animals receiving HBI. The Neo(R) transgene was detectable in hematopoietic tissues of all animals and nonhematopoietic tissues in a single animal. Evidence of transgene expression was documented by detection of beta-Gal(+) cells in BM smears and transiently elevated serum levels of hsTNFRII.

CONCLUSION

These studies indicate that 1) MSC possess the ability to engraft and persist in an unrelated mismatched allogeneic hosts; 2) 250-cGy HBI did not favor engraftment of MSC; 3) the IBM route was not more effective than the IV route in delivering MSC grafts; and 4) transplanted MSC preferentially localized to the marrow rather than nonhematopoietic tissues.

Investigation of allogeneic mesenchymal stem cell-based alveolar bone formation: preliminary findings

This study was designed to evaluate mesenchymal stem cell (MSC)-based alveolar bone regeneration in a canine alveolar saddle defect model. MSCs were loaded onto hydroxyapatite/tricalcium phosphate (HA/TCP) matrices. Scanning electron microscopic (SEM) evaluation demonstrated greater than 75% MSC coverage of the HA/TCP porous surface prior to placement regardless of MSC donor. Matrices, 6 mm x 6 mm x 20 mm, with and without cells, were implanted for 4 and 9 weeks, then removed for histological evaluation of bone formation. Cell-free control matrices were compared with MSC-loaded matrices post implantation. Histomorphometrical analysis showed that equivalent amounts of new bone were formed within the pores of the matrices loaded with autologous MSCs or MSCs from an unrelated donor. Bone formation in the cell-free HA/TCP matrices was less extensive. There was no histologic evidence of an immunological response to autologous MSCs. Surprisingly, allogeneic MSC implantation also failed to provoke an immune response. Analysis of circulating antibody levels against MSCs supported the hypothesis that neither autologous nor allogeneic MSCs induced a systemic response by the host. Analysis of dye-labelled MSCs in histological sections confirmed that the MSCs persisted in the implants throughout the course of the experiment. At 9 weeks, labelled cells were present within the lacunae of newly formed bone. We conclude that autologous and allogeneic MSCs have the capacity to regenerate bone within craniofacial defects.

Mesenchymal stem cells combined with biphasic calcium phosphate ceramics promote bone regeneration

The reconstruction and repair of large bone defects, resulting from trauma, cancer or metabolic disorders, is a major clinical challenge in orthopaedics. Clinically available biological and synthetic grafts have clear limitations that necessitate the development of new graft materials and/or strategies. Human mesenchymal stem cells (MSCs), obtained from the adult bone marrow, are multipotent cells capable of differentiating into various mesenchymal tissues. Of particular interest is the ability of these cells to differentiate into osteoblasts, or bone-forming cells. At Osiris, we have extensively characterized MSCs and have demonstrated MSCs can induce bone repair when implanted in vivo in combination with a biphasic calcium phosphate, specifically hydroxyapatite/tricalcium phosphate. This article reviews previous and current studies utilizing mesenchymal stem cells and biphasic calcium phosphates in bone repair.

Emergence of Salmonella typhimurium definitive type 104 (DT104) as an important cause of salmonellosis in horses in Ontario

Salmonella Typhimurium definitive type 104 (DT104) has emerged as a common cause of salmonellosis in humans and cattle, yet previous reports involving horses are sparse. This study reports the emergence of DT104 as an important pathogen in horses in Ontario. The first clinical case of DT104 infection at the Ontario Veterinary College was identified in 1997. Seventeen cases of DT104-associated salmonellosis were identified between 1997 and 2000. In 2000, 12 of 13 cases of salmonellosis were due to DT104. Salmonellosis in horses due to DT104 is of concern, since the organism is multiresistant to antibiotics and poses increased zoonotic risk. Phage type distribution of Salmonella isolates should be monitored to determine whether DT104 will remain a prevalent equine pathogen.

Inhibition of adherence of Actinobacillus pleuropneumoniae to porcine respiratory tract cells by monoclonal antibodies directed against LPS and partial characterization of the LPS receptors

Actinobacillus pleuropneumoniae is the causative agent of porcine fibrinohemorrhagic necrotizing pleuropneumonia. We have previously identified the lipopolysaccharides (LPS) as the major adhesin of A. pleuropneumoniae involved in adherence to porcine respiratory tract cells. In the present study, adherence of A. pleuropneumoniae to porcine tracheal frozen sections was inhibited by homologous monovalent Fab fragments produced from monoclonal antibodies 5.1 G8F10 and 102-G02 directed, respectively, against the A. pleuropneumoniae serotype 1 or serotype 2 O-antigens. These results confirm the important role played by LPS in adherence of A. pleuropneumoniae and suggest that these adhesins might represent good vaccine candidates. We also investigated the presence of A. pleuropneumoniae receptors in tracheal cell preparations from piglets of four different breeds. Using Far-Western binding assays, we identified proteins recognized by whole cells of A. pleuropneumoniae reference strains for serotype 1 and 2, and local isolates belonging to the same serotypes, and also recognized by extracted LPS from both reference strains. We confirmed the proteinaceous nature of these LPS-binding molecules by their staining with Coomassie brilliant blue, sensitivity to proteinase K digestion, resistance to sodium m-periodate oxidation, and their inability to stain with glycoprotein-specific reagents. Four low-molecular-mass bands (14-17 kDa) seemed to correspond to histones. We also identified proteins at Mr 38,500 that could represent putative receptors for A. pleuropneumoniae LPS in swine respiratory tract cells.

Evaluation of the hemoglobin-binding activity of Actinobacillus pleuropneumoniae using fluorescein-labeled pig hemoglobin and flow cytometry

In the present study, the hemoglobin (Hb)-binding activity of Actinobacillus pleuropneumoniae was examined using fluorescein-labeled pig Hb and flow cytometry. Comparison of the Hb-binding activity of A. pleuropneumoniae serotype 1 strain 4074 grown under iron-restricted conditions with cells grown under iron-sufficient conditions indicated that iron-restriction in A. pleuropneumoniae promotes the expression of Hb receptors, and that Hb-binding activity is, at least in part, iron-repressible. Hb-binding activity was also observed in representative strains of A. pleuropneumoniae belonging to serotypes 1 and 2. In addition, A. pleuropneumoniae serotype 1 LPS or capsule isogenic mutants were tested in flow cytometry in order to understand the influence of surface polysaccharides on Hb-binding activity. Experiments with an acapsulated mutant indicated that surface molecules with Hb-binding activity are more exposed at the cell surface in the absence of capsular polysaccharides. However, the Hb-binding activity of LPS mutants analyzed in this study was unchanged compared to the parent strain. The outer membrane proteins profile of A. pleuropneumoniae serotype 1 grown under iron-restricted or iron-sufficient conditions was also evaluated by polyacrylamide gel electrophoresis. Iron-regulated outer membrane proteins were observed under iron-restricted growth conditions which suggests that one or more of these outer membrane proteins may play a role in the Hb-binding activity detected by flow cytometry.

Topically applied diacylglycerols increase pigmentation in guinea pig skin

Exposure of human and murine melanocytes in vitro to the diacylglycerol (DAG) 1-oleoyl-2-acetyl-sn-glycerol (OAG) markedly increases melanin production within 24 h. To determine whether OAG can increase melanin production in vivo, increasing concentrations of OAG (10-60 mg/ml) in propylene glycol were applied daily for 5 d to shaved guinea pigs. Dose-dependent increased pigmentation was visible first on days 17-22 and persisted for 10-14 weeks. Peak epidermal melanin content in OAG-treated sites was more than twice that of untreated or vehicle-treated sites, as assessed by computerized image analysis of Fontana-Masson stained biopsy cross sections. In another experiment to assess the mechanism of DAG-mediated pigmentation, guinea pigs received twice daily separate applications of OAG, dipalmitoylglycerol (diC16), dioctanoylglycerol (diC8), each 50 mg/ml, 20 microliters/application, and propylene glycol vehicle alone for 5 d. Increased pigmentation was visible after 10 d in the OAG and diC8 sites but not in diC16 or vehicle sites. These results correlate with the reported ability of these compounds to activate protein kinase C in vitro. In a final experiment, guinea pigs received OAG 25 mg/ml three times daily to one test site, and once daily ultraviolet B (70 mJ/cm2, equivalent to 0.6 minimal erythemal dose) radiation to another for 10 d. The OAG and ultraviolet B test sites developed comparable pigmentation by both clinical and histologic criteria. Our data demonstrate that topically applied DAGs can produce a long-lasting increase in epidermal pigmentation, presumably through protein kinase C activation, which clinically and histologically closely resembles ultraviolet-induced tanning.

Keratinocytes and fibroblasts in a human skin equivalent model enhance melanocyte survival and melanin synthesis after ultraviolet irradiation

To investigate paracrine effects of fibroblasts and keratinocytes on melanocyte behavior after ultraviolet (UV) irradiation, we compared an in vitro skin equivalent model with melanocyte cultures. Human melanocytes were maintained alone in monolayer cultures or on dermal equivalents with or without keratinocytes and were irradiated daily with solar-simulated light. After seven daily UV irradiations, monolayer melanocytes displayed dose-dependent increases in cellular damage. In contrast, melanocytes on dermal equivalents survived strikingly better. Moreover, UV-irradiated skin equivalent melanocytes became highly dendritic as compared with sham-irradiated cells, closely mimicking their morphology in UV-irradiated skin. In addition, in skin equivalents melanocytes migrated from the center to the periphery of the keratinocyte layer after UV irradiation. Melanin production per culture, as measured by 14C-dihydroxyphenylalanine incorporation, was consistently higher in skin equivalent melanocytes than in monolayer melanocytes from the same donor, and it was highest in melanocytes from skin equivalents containing both keratinocytes and fibroblasts. Our data strongly suggest that fibroblasts and keratinocytes modulate melanocyte function in skin. The skin equivalent is a valuable model for investigating paracrine effects on melanocytes after UV irradiation.

The trk family of receptors mediates nerve growth factor and neurotrophin-3 effects in melanocytes

We have recently shown that (a) human melanocytes express the p75 nerve growth factor (NGF) receptor in vitro; (b) that melanocyte dendricity and migration, among other behaviors, are regulated at least in part by NGF; and (c) that cultured human epidermal keratinocytes produce NGF. We now report that melanocyte stimulation with phorbol 12-tetra decanoate 13-acetate (TPA), previously reported to induce p75 NGF receptor, also induces trk in melanocytes, and TPA effect is further potentiated by the presence of keratinocytes in culture. Moreover, trk in melanocytes becomes phosphorylated within minutes after NGF stimulation. As well, cultures of dermal fibroblasts express neurotrophin-3 (NT-3) mRNA; NT-3 mRNA levels in cultured fibroblasts are modulated by mitogenic stimulation, UV irradiation, and exposure to melanocyte-conditioned medium. Moreover, melanocytes constitutively express low levels of trk-C, and its expression is downregulated after TPA stimulation. NT-3 supplementation to cultured melanocytes maintained in Medium 199 alone prevents cell death. These combined data suggest that melanocyte behavior in human skin may be influenced by neurotrophic factors, possibly of keratinocyte and fibroblast origin, which act through high affinity receptors.