Prevotella intermedia/nigrescens group bacteria are Gram-negative, non-motile, anaerobic rods abundant in the subgingival microbiome of human periodontitis patients, and relatively sparse in persons with periodontal health. P. intermedia/nigrescens may be inadequately suppressed in periodontal pockets with conventional mechanical-surgical forms of periodontal therapy. Therefore, short-term systemic antibiotic therapy is often recommended in the treatment of recalcitrant (refractory) severe periodontitis patients where high numbers of P. intermedia/nigrescens persist in the subgingival microbiota. Limited available data suggests that the antibiotic sensitivity profile of periodontal P. intermedia/nigrescens has changed over time among severe periodontitis patients in the United States, with increasing levels of antibiotic resistance reported. These findings have potentially important clinical implications for dental professionals and their severe periodontitis patients which need further confirmation and clarification. To further expand knowledge on this clinically relevant issue, the purpose of the present study was to determine and compare over a 10-year period (2011 versus 2021) the prevalence of in vitro resistance of periodontal P. intermedia/nigrescens to the antibiotics amoxicillin, metronidazole, clindamycin, and doxycycline. / Oral Biology

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.

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.