Surgical site infections (SSIs) are an emerging cause of increased morbidity, mortality, and treatment cost, in veterinary medicine. Medical records were searched to evaluate for associations that could increase the risk of developing SSIs. Logistic regression was used to analyze the risk factors statistically, to determine their influence on SSI risk. An SSI incidence rate of 3.0% was found in this study for all small animal surgical procedures performed from September 2010 to July 2011, with implants, hypotension and surgical classification associated with increased likelihood of SSI. Active surveillance is crucial for the development of methods to prevent SSI’s. Biofilms contribute to the antimicrobial resistance properties commonly found in bacteria such as methicillin-resistant Staphylococcus pseudintermedius, which is found in canines. An enzyme known as DispersinB was studied to assess its effect on biofilm formation and degradation. DispersinB prevented the formation and eradicated biofilm in vitro. In vivo testing is required to further assess the effects of DispersinB. / Ontario Veterinary College Pet Trust, Canadian Institutes of Health Research, Kane Biotchech

Expression of the mexCD-oprJ multidrug efflux operon is enhanced by the presence of membrane damaging agents [e.g., the biocide chlorhexidine (Chx)] or mutations in the nfxB gene encoding a repressor of efflux gene expression, both dependent on the AlgU envelope stress response sigma factor. Details of mexCD-oprJ regulation are, however, lacking. In examining the mexCD-oprJ locus, a gene, PA4596, encoding a homologue of NfxB (61% identity) was identified downstream of oprJ, a location conserved in all sequenced Pseudomonas aeruginosa isolates and in Pseudomonas putida. Opposite to mexCD-oprJ, PA4596 expression was reduced by Chx exposure, as assessed using RT-PCR; although like mexCD-oprJ, this was AlgU-dependent (i.e., lost in a ΔalgU strain). Deletion of PA4596 had no impact on Chx resistance indicating that it is not required for Chx-inducible mexCD-oprJ expression/ MexCD-OprJ-dependent Chx resistance. In contrast, mexCD-oprJ expression and the attendant multidrug resistance of nfxB deletion mutants were compromised upon deletion of PA4596, indicating that PA4596 plays a positive role in mexCD-oprJ expression in such mutants. Consistent with this, PA4596 expression increased in nfxB deletion and missense mutants in parallel with mexCD-oprJ. Intriguingly, mexCD-oprJ expression and multidrug resistance were observed in a mutant lacking an nfxB mutation (demonstrating an NfxB-like phenotype) and in an nfxB missense mutant and these were not compromised upon deletion of PA4596. Thus, mexCD-oprJ hyperexpression can be both PA4596-dependent and -independent. A bacterial 2-hybrid assay revealed a PA4596-PA4596 interaction, consistent with the protein forming dimers as NfxB has been shown to do. Two-hybrid assays also demonstrated that NfxB and PA4596 interact. While the functional significance of this remains to be elucidated, it is consistent with their common role in regulating mexCD-oprJ expression and is suggestive of a complex and possibly novel regulatory mechanism. These data highlight the complexity of mexCD-oprJ regulation and the apparently multiple pathways to efflux gene expression, suggestive of multiple roles for this efflux system in P. aeruginosa independent of antimicrobial efflux. / Thesis (Master, Microbiology & Immunology) -- Queen's University, 2009-08-18 14:25:18.107

Pseudomonas aeruginosa is a common soil organism as well as an opportunistic human pathogen. Treatment of P. aeruginosa infections is often complicated by innate resistance to a variety of antimicrobials mediated by multidrug efflux systems. The MexAB-OprM efflux system is constitutively expressed in wildtype strains and contributes to innate antimicrobial resistance, while hyperexpression of the system results in acquired high levels of resistance. MexAB-OprM is hyperexpressed in nalC mutants containing mutations in the gene encoding NalC, a repressor of a two-gene operon, PA3720-armR. armR encodes a protein modulator of MexR, a repressor of mexAB-oprM expression. Previous reports showed that genes encoding the MexAB-OprM efflux system are upregulated in response to pentachlorophenol (PCP), a phenolic compound that is a common environmental contaminant. Induction of mexAB-oprM and PA3720-armR by PCP was confirmed using RT-PCR, and MexAB-OprM was shown to be involved in PCP resistance. An electromobility shift assay (EMSA) showed that PCP interacts with NalC, interfering with its binding to the PA3720-armR promoter region and thereby promoting PA3720-armR expression. Nonetheless, the increase in ArmR did not drive mexAB-oprM expression suggesting that PCP induction of this efflux operon occurred via a different mechanism. A direct PCP-MexR interaction could not be demonstrated using an EMSA. PCP exposure did, however, reduce expression of nalD, encoding a second repressor of mexAB-oprM, which might explain the PCP-promoted increase in mexAB-oprM expression. PCP is unlikely to be the intended inducer(s)/substrate(s) for this system but probably resembles these. Several compounds related to PCP were tested for an interaction with NalC but all were negative in EMSAs. Plants produce a variety of phenolic compounds, which are often antimicrobial and, so, root extracts of various plants were tested for an ability to interact with NalC and interfere with promoter binding. Extracts from Boehmeria tricuspis, Uncaria tomentosa and Ixiolirion tataricum were shown to interact with NalC, suggesting that plant compounds may be the intended inducers/substrates for NalC/MexAB-OprM. / Thesis (Master, Microbiology & Immunology) -- Queen's University, 2010-09-10 10:35:16.271

No description available.

No description available.

Although nanocrystalline silver is used commercially to treat burns and wounds, the mechanisms of action (MOA) for its activity are not clear. The purposes of this work were to determine if nanocrystalline silver has anti-inflammatory activity, determine physicochemical properties critical for its MOA, and develop nanocrystalline silver-derived solutions for use in the treatment of lung diseases, including ARDS and pneumonia. In a porcine contact dermatitis model, nanocrystalline silver had anti-inflammatory activity independent of antimicrobial activity, with increased apoptosis induction in inflammatory cells, but not keratinocytes; decreased expression of TNF-, TGF-, IL-8, and MMPs; and increased expression of IL-4, EGF, KGF, and KGF-2. Treatment with AgNO3 (Ag+) increased inflammation, and caused apoptosis induction in keratinocytes. Thus, nanocrystalline silver releases additional species, perhaps Ag^(0)-containing clusters, resulting in anti-inflammatory activity. SIMS analysis showed significant deposition of Ag-clusters after nanocrystalline silver, but not AgNO3, treatment. Nanocrystalline silver had a systemic effect, despite SIMS analysis showing minimal skin penetration by silver, suggesting that nanocrystalline silver interacts with cells near tissue surfaces that release signals altering the inflammatory cascade. Relative to various Ag+-releasing dressings, nanocrystalline silver had significantly enhanced antimicrobial activity, Ag+-resistant bacteria kill, and was not prone to development of resistant bacteria, indicating that nanocrystalline silver releases antimicrobial species additional to Ag+, and has multiple bactericidal MOA. Single silver nanocrystals are inactive, and heat treatment of nanocrystalline silver resulting in crystallites over ~30 nm caused loss of antimicrobial activity, soluble silver, silver oxide, and oxygen. This indicates a poly-nanocrystalline silver structure is necessary for optimal antimicrobial activity, as is having silver oxide to pin the nanostructure, preventing its growth. While oxygen is necessary during sputtering to produce silver oxide, too much oxygen reduces antimicrobial activity, as silver oxide is predominantly deposited. Sufficient total silver, modifiable with current and time, is also important for activity. Nanocrystalline silver-derived solution properties vary significantly with dissolution conditions. Solutions generated at pH 4-6 have stronger antimicrobial activity, and solutions generated at pH 9 have stronger anti-inflammatory activity. Overall, nanocrystalline silver-derived solutions have biological properties similar to nanocrystalline silver, indicating that they may be useful in a variety of medical applications.

Despite their beneficial effects, concerns have been raised about the role of antimicrobial growth promoters (AGP) in the emergence of antibiotic resistant bacteria. This study evaluated the effects of approved AGP on the emergence of antibiotic resistance in commensal E. coli and foodborne pathogen Salmonella. A survey of antibiotic resistance levels in commercial broiler chicken farms in the Fraser Valley (B.C.) and an experimental feeding trial were conducted from May 2004 to February 2005 and May to November 2005, respectively. The latter examined the effects of ten AGP formulations (bambermycin, penicillin, salinomycin, bacitracin, combination of salinomycin and bacitracin, chlortetracycline, virginiamycin 11ppm, virginiamycin 22ppm, monensin and narasin) on bird performance as well. Multiple antibiotic resistant commensal E. coli and Salmonella carrying virulence genes were found at commercial broiler chicken farms and therefore may serve as reservoirs for these genes. There was no significant difference between feed formulations on the phenotypic or genotypic characteristics of the isolates, except for tetracycline resistance gene tet(B). In the experimental feeding trial, broiler chickens were fed a diet including or excluding AGP. Birds were sampled prior to and weekly during feeding of the control and the AGPP containing diets. Although not detected on day 0, E. coli increased after day 7 to more than 9.9 log10 CFU/g in ceca. Multi-drug resistant E. coli were isolated from birds fed the ten AGP containing diets as well as the control diet. Except for penicillin, none of the AGP containing diets significantly improved bird performance compared to the control diet (P>0.05). Good management practices can significantly improve broiler chickens performance and decrease the mortality rate.

Thesis (Ph.D.). / Written for the Dept. of Medicine, Division of Experimental Medicine. Title from title page of PDF (viewed 2008/05/08). Includes bibliographical references.

Poultry are vital to food security, with 60 billion chickens reared worldwide per annum and demand fast accelerating. For many years antibiotic growth promoters have been used to promote energy retention from the diet and control intestinal bacterial growth. Antibiotic use for prophylaxis or growth-promotion in farmed animals is prohibited under EU Directives due to human health concerns, but a pressing need exists to maintain the efficiency of animal production by finding alternatives. Antimicrobial peptides (AMPs), part of the innate immune system exist naturally in most species and could provide a vast array of potential therapeutics. Microbial resistance to AMPs is unlikely due to their relatively unspecific mode of action, their ability to target multiple sites within a cell and diverse immune-modulatory activities. The avian egg provides antimicrobial protection through many mechanisms including AMPs which are incorporated into the egg white by the hen. The ovodefensin family and ‘transiently expressed in neural precursors’ (TENP) have been identified as potential novel antimicrobials in egg white and therefore formed the basis of the peptide portfolio of this study. TENP was first identified as having a role in neurological development but has since been shown to be an important egg component constituting ~0.1-0.5% of the total protein. TENP is conserved across avian species being found in chicken, turkey, duck and zebra finch. Its homology with the bacterial permeability-increasing family of innate immune genes suggests it may contribute to antimicrobial function in the egg. This study confirmed that expression of TENP is confined to the albumen forming region of the oviduct in adult hens and is under gonadal steroid control, typical of an oviduct and egg specific gene. The ovodefensin family are β defensin related antimicrobial peptides thought to be restricted to the albumen producing region of the avian oviduct. This study identified twenty five novel ovodefensin members through genome analysis, expanding the ovodefensin family to include reptiles for the first time. Phylogenetic analysis showed a unique example of the evolution of a cysteine spacing motif alongside traditional sequence evolution. The expression of eight ovodefensins was shown to be oviduct specific supporting the hypothesis that ovodefensins evolved to protect the egg. Antimicrobial activity for three ovodefensins from chicken and duck was investigated against gram negative organisms E. coli and Salmonella including pathogenic strains as well as a gram positive organism, S. aureus, for the first time. The spectrum of activity varied greatly between peptides suggesting a link between structure and function. Inclusion of recombinant ovodefensin peptides in the feed of chickens showed beneficial effects on the gut microbiome, metabolite profile and most crucially an increase in mean body weight. This demonstrates the potential of antimicrobial peptides as alternatives to antibiotic growth promoters in poultry.

A pele humana é o maior e um dos mais importantes órgãos, esta é a principal barreira entre o corpo e o meio externo, sempre que há um desequilíbrio no mecanismo de defesa inata, o risco de uma infecção é proeminente. A queimadura é um quadro clínico em que a barreira epitelial é danificada, resultado em uma defesa imunológica deficitária e uma grande abundância de nutrientes, o que favorece a proliferação de micro-organismos. No presente estudo foi desenvolvido e caracterizado uma suspensão inovadora de nanocápsulas poliméricas de poli(ε-caprolactona) com triclosan e α-bisabol, revestida com quitosana (NCCQ) para aplicação tópica em feridas de queimadura, com intuito de reduzir a contaminação microbiana. Foram realizados ensaios de caracterização físico-química, microbiológica e cutânea. Os resultados obtidos para os ensaios de caracterização mostraram que a suspensão de nanocápsulas apresentou diâmetro de partícula adequado, ausência de cristais ou contaminação micrométrica, potencial zeta catiônico, pH levemente ácido, com uma alta eficiência de encapsulação e estável no período de trinta dias. Os ensaios microbiológicos foram realizados frente Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa e Candida albicans, através de microdiluição seriada e teste do desafio. O primeiro ensaio mostrou uma redução no valor da concentração inibitória mínima e melhores resultados para quase todas as cepas analisadas frente aos controles e dados da literatura, inclusive P. aeruginosa, a qual possui uma alta resistência ao triclosan. O teste do desafio serviu para comprovar que o efeito antimicrobiano da suspensão, se manteve ao longo de 28 dias, mesmo quando incorporada ao curativo de hemi-celulose. Os ensaios cutâneos de permeação/penetração e lavabilidade mostraram que a suspensão de nanocápsulas NCCQ teve uma retenção no estrato córneo, o que é desejável para uma formulação tópica. / The human skin is the largest and one of the most important organs, this is the main barrier between the body and the external environment, whenever there is an imbalance in innate defense mechanism, the risk of infection is prominent. Burn is a clinical condition in which the epithelial barrier is damaged, resulting in a deficient immune defense, also the abundance of nutrients favors to proliferation of microorganisms. In the present study it was developed and characterized a novel suspension of polymeric nanocapsules of poly (ε-caprolactone) with triclosan and α-bisabol coated with chitosan (NCCQ) for topical application in burn wounds, in order to reduce microbial contamination. Physical-chemical, microbiological and skin tests were performed in order to prove its applicability. The results obtained for the characterization tests showed that the suspension of nanocapsules had suitable particle diameter, no crystals or micrometric contamination cationic zeta potential, slightly acid pH with a high encapsulation efficiency and stable within thirty days. Microbiological tests were carried forward Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans, via serial microdilution and challenge test. The first experiment showed a reduction in the value of the minimum inhibitory concentration and best results for nearly all strains analyzed when compared with controls and data from the literature, including P. aeruginosa, which has a high resistance to triclosan. The challenge test was used to demonstrate that the antimicrobial effect of the suspension was maintained over 28 days even when incorporated into the dressing hemi-cellulose. The skin permeation/penetration and washability tests of NCCQ nanocapsule suspension showed that it had retention in the stratum corneum, which is desirable for a topical formulation.