The objective of this research was to use Bacillus subtilis-based probiotics alone or combined with various additional antibiotic alternatives (yeast-derived prebiotics and zinc supplementation) to maintain gut health and improve growth performance of antibioticree broilers. Three consecutive studies have been conducted to evaluate dietary effects on intestinal morphology, digestive organ development, microbiota, and growth performance of commercial broilers under different coccidia-challenge circumstances. In the first study, broilers were raised under commercial conditions, without coccidia-challenge (Chapter III). Broilers fed diets supplemented with antibiotics exhibited the highest body weight gain (BWG) from d 15 to 27. Broilers fed diets supplemented with B. subtilis or prebiotics + B. subtilis exhibited higher BWG from d 28 to 41 and higher BWG from d 0 to 41 as compared to birds fed control diets. In the second study, broilers were exposed to a clinical coccidia-challenge (Chapters IV and V). Interaction and main effects of the dietary supplement and coccidial vaccination were studied. Diets supplemented with Prebiotics + B. subtilis facilitated broilers to reach a similar feed conversion ratio (FCR) as to the antibiotic control group from d 0 to 56. Feeding diets supplemented with B. subtilis to coccidial vaccinated broilers reduced microbiota diversity by increasing the proportion of an antibiotic-resistant bacterium, Rikenella microfusus. In the third study, interaction and main effects of the subclinical coccidia-challenge and the dietary supplement were studied (Chapters VI and VII). The dietary anticoccidial supplementation increased feed intake and BWG and decreased FCR of broilers from d 15 to 28. However, dietary B. subtilis supplementation did not improve any growth performance of broilers. The combined use of zinc and B. subtilis lowered the high mortality of broilers fed diet supplemented with B. subtilis or zinc alone. Additionally, the dietary supplementation of zinc lowered the proportion of Clostridium in cecal contents of broilers. In conclusion, different nutrition strategies should be considered when broiler chickens are under different health circumstances. Bacillus subtilis-based probiotics have potential to replace the antibiotics, but not anticoccidial feed additives.

As the international poultry industry searches for antibiotic alternatives, dietary probiotic supplementation has exhibited the ability to decrease FCR, increase live weight gain, and regulate inflammatory responses within the gut of broiler chickens. The in ovo (or in egg) supplementation of probiotics has the potential for promoting early colonization of probiotic bacteria in the gastrointestinal tract and providing enhanced protection against pathogens in the hatchery and grow-out facilities. In the present studies, the in ovo injection of either L. animalis + E. faecium combination or L. animalis + B. licheniformis combination on d 18 of incubation does not negatively affect the chick’s ability to hatch out of the egg. These combinations also influence post-hatch performance, where FCR, gastrointestinal tissue weights, and immune-physiological parameters were impacted under non-challenged and coccidiosis-challenged grow-out conditions. These results indicate the physiological and immunomodulatory role that beneficial bacteria may have on a developing chick.

Many important antibiotics have become nearly obsolete due to the rise of antibiotic resistant pathogens. Rhodococcus, an actinomycete related to the prolific antibiotic producing genus Streptomyces, harbors over 30 genes for secondary metabolism that could be involved in antibiotic production. Several antibiotics have already been reported for Rhodococcus, suggesting the genus may be a good source for new inhibitory compounds. Fifty four soil bacteria were isolated using enrichment culture techniques (including 37 Rhodococcus) and screened for antibiotic producers. BTHX2, a species of Bacillus was found to have activity against Micrococcus luteus and Rhodococcus erythropolis. BTHX2 has a 16S rDNA sequence 97% homologous to Bacillus licheniformis, and may be a new strain of B. licheniformis. The inhibitory substance produced by BTHX2 was and found to have a spectrum of activity against a broad Gram-positive bacteria and some fungus, and may have cytolytic activity.

Control of antibiotic resistance in bacteria is based on the concept that resistance incurs a fitness cost in non-selective conditions. Fitness costs were assessed for low- and high-level mupirocin resistance in locally-derived Staphylococcus aureus and S. epidermidis. Costs of resistance were assessed in pure cultures by comparing growth curve characteristics and in mixed culture as the proportion of resistant cells surviving. Costs were not present in comparisons of growth rates among groups of naturally-occurring isolates from the different resistance categories. However, in S. aureus, growth rates within resistance categories differed by approximately 30 – 90%. Among near-isogenic pairs of strains, fitness costs ≥10% were present in three of eleven pairs under pure culture and in six of eleven pairs under competition in mixed culture. Differences in intrinsic growth rates could easily mask fitness costs of the magnitudes observed. Thus, clinical outcomes also depend on whether there is a mixed infection and if so, on the growth rates of strains present.

No description available.

An alarming problem has plagued both human and veterinary healthcare for decades: the ever-increasing presence of antibiotic resistant bacteria. Specifically, Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-resistant Staphylococcus pseudintermedius (MRSP) are of great concern. A new compound, aptly named, LavenGel has recently been developed and demonstrates treatment potential to effectively inhibit the growth of at least two Staphylococcus species: S. aureus and S. pseudintermedius. LavenGel has been previously shown in our lab to inhibit a variety of microbes, particularly S. aureus. However, the molecular pathway that LavenGel utilizes to inhibit S. aureus and whether this inhibition could be translated to other Staphylococcus species, particularly in animals, has yet to be investigated. The major aims of this study are to demonstrate and quantify the efficacy of LavenGel in preventing S. aureus and S. pseudintermedius growth and to understand the specific S. aureus cellular mechanisms that LavenGel impacts. In order to quantitatively represent the effectiveness of LavenGel for veterinary purposes, biofilms of S. pseudintermedius were treated at different phases of development. LavenGel inhibited both the attachment of cells to form biofilms, as well as the eradication of pre-existing biofilms. Minimum inhibitory concentrations and minimum bacterial concentrations were determind for S. pseudintermedius. To better understand the impact that LavenGel may have in human healthcare, a panel of genes expressed under LavenGel treatment were examined. LavenGel does not induce the typical SOS response in S. aureus that is seen when using other leading bactericidal treatments for Staphylococcus infections which have also been shown to induce resistance. LavenGel could potentially help solve the bacterial resistance issue by working against the bacterial cell membrane instead of inducing the typical SOS response. The threat of antibiotic resistant bacteria is a constant concern in the scientific and healthcare community. The implications of this study dictate LavenGel is a highly effective, all-natural, unique option for treating common Staphylococcus infections in both veterinary and human healthcare and shows promise as a treatment that, as of yet, does not induce bacterial resistance. LavenGel could prove to be a powerful tool in the future of medical management of bacterial infections.

No description available.

In this report, we describe a case of a 61-year-old male patient who had the bacterium growing in a blood culture. It was susceptible to ampicillin, ceftriaxone, levofloxacin, and vancomycin but was intermediately resistant to erythromycin. The patient did not have a negative outcome as a consequence of this bacterium, which retrospectively could have been predicted based on the epidemiological data within the patient's profile.

Antibiotic resistant infections are a growing health care concern, with many cases reported annually. Infections can cause irreversible bodily damage or death if they are not diagnosed in a timely matter. To rapidly diagnose antibiotic resistance in infections, it is important to be able to capture and isolate the DNA coding for the resistance genes. This is challenging because bacteria are present in blood in minute concentrations. To enrich the DNA to detectable levels, I modified magnetic microbeads with ssDNA sequences complementary to the target DNA to capture the DNA via hybridization. I compared DNA capture efficiency in three different methods: Co-flow, packed bead bed, and pre-hybridization. The pre-hybridized method worked better than the other two. Since pre-hybridization involved mixing, I chose to study mixing in a microfluidic device. The mixing chamber was a well carved out of PMMA placed between two electromagnets. To test the mixing well, beads and capture DNA were placed in it, and the electromagnets were subjected to different frequencies, including symmetric or asymmetric magnetic fields. For each condition the capture efficiency was determined by measuring the relative fluorescence units (RFU). A 100 Hz asymmetric magnetic field had the best capture efficiency out of all conditions. These results demonstrate a path for enriching low concentrations of DNA to detectable levels, and future work should be done to develop electromagnetic mixing in microfluidic devices.

The upper water column (<1 m depth) of freshwater lakes, which includes the surface microlayer (SML; <1 mm depth), is an important microbial habitat as well as an accumulation and dissemination site for chemical and microbial contaminants. This doctoral thesis reports novel insights into how the physical structure and functional capabilities of microbial communities can influence the presence of trace metals and health-relevant bacteria in the upper waters (SML and 0.5 m depth) of freshwater lakes. Two physically and geochemically contrasting lake environments, a remote sheltered boreal lake and a higher energy urban beach on Lake Ontario, were investigated to identify system-dependent physical and biogeochemical factors controlling contaminant-relevant microbial characteristics. The SML was identified as a major site for generation of contaminant-sequestering suspended flocs from a distinct biofilm-forming microbial community over diurnal timeframes via wind and sunlight exposure, with this process being enhanced at the higher energy beach site. More generally, upper waters including the SML were demonstrated to be inhabited by a diverse group of atypical facultative Fe(III)-reducing bacteria (IRB) that exhibited a SML- and lake-specific capacity for solid Fe(III) reduction directly related to floc and Fe(III) availability. Although IRB were hypothesized to be highly resistant to metals and antibiotics relative to other bacteria due to their ability to dissolve metal-rich Fe(III) minerals, this was not found to be the case. Nevertheless, IRB enriched from the SML demonstrated higher antibiotic resistance compared to those from 0.5 m depth and enriched Fe(III)-reducing communities from both depths harboured resistance-mobilizing genetic elements and included potentially pathogenic bacteria. Results of this thesis represent new knowledge concerning how microbial communities regulate the presence of contaminants in the upper waters of lakes. This has important implications for assessing the ecological and human health impacts of contaminants in freshwater systems. / Thesis / Doctor of Philosophy (PhD)