Anaplasma phagocytophilum and A. marginale are the etiologic agents of bovine anaplasmosis and human granulocytic anaplasmosis, respectively. As obligate intracellular pathogens, binding and entry of host cells is a prerequisite for survival. The molecular events associated with these processes are poorly understood. Identifying the adhesins mediating binding, delineating their key functional domains, and determining the molecular determinants to which they bind not only benefits better understanding of Anaplasma spp. pathobiology, but could also benefit the development of novel approaches for protecting against infection. We previously demonstrated that A. phagocytophilum outer membrane protein A (ApOmpA) is critical for bacterial binding and entry host through recognition of α2,3-sialic acid and α1,3-fucose of its receptors, including 6-sulfo-sLex. In this study, we determined that two amino acids, G61 and K64, within its binding domain (ApOmpA59-74), are essential for ApOmpA function. We also confirmed the ability of ApOmpA to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. We next extended our studies to A. marginale as it also expresses OmpA (AmOmpA) and its role in infection has not been studied. Molecular models of ApOmpA and AmOmpA were nearly identical, especially in the ApOmpA binding domain and its counterpart in AmOmpA. Antisera raised against AmOmpA or its putative binding domain inhibit A. marginale infection. AmOmpA G55 and K58 are contributory and K59 is essential for AmOmpA to bind to host cells. AmOmpA binding is dependent on α2,3-sialic acid and α1,3-fucose. Coating inert beads with AmOmpA conferred the ability to bind to and be taken up by host cells, confirming that it acts as an adhesin and invasin. 6-sulfo-sLex is dispensable for AmOmpA binding and A. marginale infection. ApOmpA works cooperatively with Asp14 (14-kDa A. phagocytophilum surface protein) to promote optimal infection of host cells. We found that Asp14 is conserved across A. phagocytophilum strains and in A. marginale and confirmed the ability of Asp14 to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. Collectively, this work advances our understanding of A. phagocytophilum and A. marginale adhesion and invasion of host cells.

The anti-pneumococcal function of native C-reactive protein (CRP) involves its binding to phosphocholine molecules present on Streptococcus pneumoniae and subsequent activation of the complement system. However, when pneumococci recruit complement inhibitory protein factor H on their surface, they escape complement attack. Non-native forms of CRP have been shown to bind immobilized factor H. Accordingly, we hypothesized that modified CRP would bind to factor H on pneumococci, masking its complement inhibitory activity, allowing native CRP to exert its anti-pneumococcal function. As reported previously, native CRP protected mice from lethal pneumococcal infection when injected 30 minutes before infection but not when injected 24 hours after infection. However, a combination of native and mutant CRP was found to protect mice even when administered 24 hours after infection. Therefore, it is concluded that while native CRP is protective only against early-stage infection, a combination of native and mutant CRP offers protection against late-stage infection.

The obligate intracellular bacterium, Chlamydia trachomatis, and Herpes Simplex Virus Type-2 (HSV-2) are the leading sexually transmitted pathogens in the world. These infections are usually asymptomatic and clinically mild, but complications can be severe. Reports of dual detection of Chlamydia and HSV within the genital tracts of humans led our laboratory to develop an in vitro Chlamydia/HSV co-infection model. Little is known regarding the specific pathogenesis of Chlamydia and HSV co-infections, but HSV-super-infection of Chlamydia-infected cells caused the chlamydiae to deviate from their normal developmental cycle into a non-replicative state termed persistence, or the chlamydial stress response. Interactions between HSV envelope protein, gD with host cell junction protein, nectin-1, were enough to stimulate the departure from normal chlamydial development. Additional data also suggested that there might be differences between single infection and co-infection outcomes in vivo. Thus, two diverging hypotheses were investigated here: i) that host nectin-1 is required for normal chlamydial development; and ii) that pathogen shedding and/or disease progression in Chlamydia and HSV-2 co-infected animals will differ from that observed in singly-infected animals. Chlamydial infection of nectin-1 knockdown cell lines revealed no inhibition of chlamydial entry, but significant reductions in inclusion size and production of infectious chlamydiae. Additionally, nectin-1 knockout mice shed fewer Chlamydia compared to wild type mice. In other studies, we developed a novel in vivo Chlamydia and HSV-2 intravaginal super-infection model in BALB/c mice. Infection with Chlamydia muridarum, followed up to 9 days later by HSV-2 super-infection, both reduced HSV shedding and protected mice from HSV-induced fatal neurologic disease compared to HSV singly-infected animals. Protection is lost when: i) infected animals are no longer shedding C. muridarum; ii) when mice are inoculated with UV-inactivated C. muridarum; or iii) when viable chlamydiae are eliminated from the genital tract using antibiotics prior to HSV-2 super-infection. Altogether, we have determined that host nectin-1 is required for chlamydial development both in vitro and in vivo, and that chlamydial pre-infection protects mice from subsequent HSV infection. We predict that these observations may lead to novel approaches to prevent human infection by these two common sexually transmitted pathogens.

Growing resistance of bacteria towards antibiotics resulted in extensive research effort for development and application of new materials and techniques. Due to their unique properties, graphene quantum dots (GQDs) have attracted much attention and are a promising material with potential applications in many fields. One use of GQDs is as a photodynamic therapy agent that generates singlet oxygen. In this work, GQDs synthesized by focusing nanosecond laser pulses into a mixture of benzene and nickel(II) oxide were combined with methylene blue (MB) to eradicate Gram-negative Escherichia coli and Gram-positive Micrococcus luteus. Theoretical calculation of pressure evolution was calculated using the standard finite difference method. Detailed characterizations were performed with transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), UV-Visible (UV-Vis), and photoluminescence (PL) spectra. Furthermore, singlet oxygen generation from MB-GQD mixture was investigated by measuring the rate of 9,10-anthracenediyl-bis(methylene) dimalonic acid photobleaching at 400 nm. Combining MB with GQDs caused enhanced singlet oxygen generation, leading to improved bacterial deactivation rate. The (3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide) (MTT) assay was used to determine if GQDs in dark conditions caused human cellular side-effects and affected cancer and noncancer cellular viability. We found that even high concentrations of GQDs do not alter viability under dark conditions. These results suggest that the MB-GQD combination is a promising photodynamic therapy agent that may be useful when antibiotics resistance is present.

Lyme disease (LD) is the most prevalent vector borne disease is North America with 300,000-600,000 human cases each year. Preventative strategies for LD in humans are poorly developed and largely inadequate. While preventive vaccines for LD are widely used in veterinary medicine, there are no vaccines available for use in humans. The goal of this study was to develop a human vaccine that can elicit antibody responses that kill spirochetes in both the tick and mammalian environments. The approach applied in this study centered on the development of chimeric epitope proteins, referred to as chimeritopes. Chimeritopes consist of a series of epitopes derived from one or more proteins or protein variants. Three chimeritope proteins designated as Chv1, Chv2 and Chv3 were designed. These proteins harbor the same set of 18 linear epitopes derived from 9 different OspC type proteins. They differ in epitope arrangement or by the presence or absence of linkers between specific protein segments. The immunogenicity of each protein was assessed in multiple animal models including mice, rats, and purpose bred beagles. Immunoblot, ELISA, and IFA analyses using sera from immunized animals demonstrated that the Chv proteins elicit IgG responses that recognize a diverse array of OspC type proteins. Anti-Chv and anti-OspA antisera displayed complement dependent bactericidal activity. To assess protective efficacy, purpose bred beagles were immunized with each vaccine formulation and then challenged by infestation with infected ticks. Efficacy was assessed by monitoring seroconversion, cultivation of tissue biopsies, clinical presentation and histopathological analysis of joints and tissues. All dogs vaccinated with the Chv2-OspA combination were fully protected. All dogs in this group were seronegative for LD, biopsy culture negative and did not develop LD associated symptoms including lameness or lesions in tissues or joints. In light of market concerns centered on the use of full length OspA in a human vaccine, epitope mapping was performed to identify a linear epitope that could be employed in development of a possible OspC-OspA chimeritope. A linear epitope, designated as OspA221-240was identified. Antisera to KLH-OspA221-240displayed potent and broad bactericidal activity. Interestingly, the OspA221-240epitope has homology to residues 244 to 263 of OspB suggesting that OspB may also be a potential candidate for inclusion in a human vaccine. This study establishes proof of principle for the use of OspC chimeritopes in LD subunit vaccines and highlights the need to employ a multi-valent, multi-antigen vaccine approach in development of a human LD vaccine.

246 samples of bulk and packaged spices from retail stores in the western, southeastern, southern, midwestern, and northeastern areas of the U.S. were examined for the presence of Clostridium -perfringens. Isolates were checked for the presence of the lecithinase gene (cpa) and enterotoxin genes (cpe) by PCR. Enterotoxin formation during sporulation was investigated using the Oxoid Toxin Detection Kit. Forty-three confirmed isolates (from 17% of total samples) were cpa-positive. Of those, 27 were cpe-positive. Together, levels of C. perfringens spores ranged from 3.6-2400/gm. The amount of enterotoxin in cell extracts ranged from 2-16 ng/ml. Some of the SEM images of isolated spore (# 78) and one plasmid-borne ent control (FD-153) showed an organized surface structure termed “candy-wrapper”. This extracellular structure remained after treatment with 0.1 % SDS for 1 hr, suggesting it was not composed of membrane debris from the mother cell. The D values of spores ranged from 1.19- 3.31 min. The addition of lysozyme in the plating medium elevated the recovery rate of heat-treated spores. The growth rate of a cocktail of spores from spices (# 31, # 32, # 45) between 4 to 5 hr after inoculation was determined with a doubling time of 6.82 min in hamburger. A cocktail of spores of plasmid-borne ent control showed an optimum growth rate between 5 to 8 hr after inoculation with doubling time of 15.98 min. However; spice isolate cocktail, plasmid-borne ent control cocktail (FD-5603 and FD-153), and a chromosome-borne ent control (NTCT 8239) were unable to germinate and outgrowth at 20oC. Inoculation in laboratory medium FTG indicated the same result as hamburger at 20oC. The ability of C. perfringens spores in spices to potentially survive cooking procedures can be followed by germination and growth of vegetative cells during improper cooling to levels associated with foodborne illness caused by this organism. Our results suggest that retail spices are potential vehicles of transmission of enterotoxin-positive C. perfringens.

In a large agricultural operation, such as the one at Cal Poly San Luis Obispo, disposal of deceased animals is an immense issue. The cost of transporting and rendering every dead animal is inhibitory to the general function of the agricultural operations and their thin budget. Therefore, we propose that composting mortalities could be an economical alternative. Composting is a recognized method for taking animal waste products along with carbon waste and turning it into a pathogen-free, nutrient-rich topsoil. Carcass composting is in fact performed in other countries and states to varying degrees of success. However, the California EPA limits carcass composing to only private land. Therefore, the purpose of this work was to determine the efficacy of killing pathogens by composting using bench top composting models. Ultimately, our goal is to provide “proof of concept” data in order to gain permission for a full-scale carcass compost pile to be set up at Cal Poly San Luis Obispo. Using thermo tolerant Salmonella senftenberg as an indicator organism, we performed bench top trials of traditional and carcass compost in the lab. Samples were inoculated with S. senftenberg and kept at 55°C for 15 days in accordance with the California EPA and Test Method for the Examination of Composting and Compost (TMECC). Samples were then plated and processed for multiple tube analysis and most probable number. Samples were also partitioned for a viability qPCR with propidium monoazide (PMA) to compare to the classic techniques. Using these methods we were then able to track and produce thermal death time data for S. senftenberg in both traditional and carcass compost. By comparing the types of compost, we were able to determine that the composting method presented by the California EPA and the TMECC produces safe, pathogen free compost, even when inoculated carcasses were introduced. However, even with removal of dead cells by PMA, qPCR did not outperform the classical microbiological methods for as tracking pathogen killing.

Mycobacterium tuberculosis (Mtb) is one of the most virulent and prevalent bacterial pathogens across the world. As Mtb infects millions of people a year, it remains essential to study its physiology with the goal of developing new therapeutic interventions. A critical part of the bacteria’s ability to propagate is through successful cell division. Although the process of bacterial cell division and the key proteins therein are well understood in Escherichia coli, much remains to be understood about division in mycobacteria. Genetic and cell biological approaches have recently begun to identify key divisome components in Mycobacterium smegmatis. However, questions remain regarding the role and function of one divisome protein in particular, the DNA translocase FtsK. In this dissertation, I investigated the necessity of FtsK for the growth of mycobacteria. Using an inducible knockdown of FtsK, I present evidence that complete loss of FtsK is required to inhibit growth in both Mtb and M. smegmatis, and that these orthologs share a homologous function. Additional work suggests extended loss of FtsK may be lethal to bacteria. These observations support that FtsK is an essential member of the divisome in mycobacteria, facilitating the processes of growth and division.

Over time, “superbugs,” or bacteria that have become resistant to antibiotics, have become a great concern in modern medicine. Viable alternates are currently being looked into as effective and safe ways to prevent or treat infections caused by these superbugs. One such method is through the utilization of the second messenger molecule cyclic-di-GMP (c-di-GMP) that has been shown to regulate phenotypes within other bacteria that may control surface colonization in Acinetobacter baumannii. Through a series of experiments, the active enzymes that create c-di-GMP - diguanylate cyclases - and break down c-di- GMP - phosphodiesterases - have been inactivated in mutants to test phenotypes including biofilm formation, motility, antibiotic resistance, and desiccation survival. The research’s objective is to show that manipulation of c-di-GMP within the multi-drug resistant strain of Acinetobacter baumannii may serve as a means to control this bacteria.

C-reactive protein (CRP) is a part of the innate immune system, is synthesized in the liver, its blood level increases in inflammatory states, and it binds to Streptococcus pneumoniae. The conformation of CRP is altered under conditions mimicking an inflammatory milieu and this non-native CRP also binds to immobilized/aggregated/pathogenic proteins. Experiments in mice have revealed that one of the functions of CRP is to protect against pneumococcal infection. For protection, CRP must be injected into mice within two hours of administering pneumococci, thus, CRP is protective against early-stage infection but not against late-stage infection. It is unknown how CRP protects or why CRP does not protect against late-stage infection. The hypotheses are that the protection requires complement activation by CRP-pneumococci complexes and that CRP cannot protect if pneumococci have time to recruit complement inhibitor factor H on their surface to become complement attack-resistant. To test these hypotheses, we generated CRP mutants by site-directed mutagenesis: a mutant that binds to pneumococci but does not activate complement and a mutant that binds to immobilized factor H. We found that mutant CRP incapable of activating complement was not protective against infection and that mutant CRP capable of binding to factor H was protective against both early and late stage infections. Additional experiments showed that CRP enhances the effects of the antibiotic clarithromycin in reducing bacteremia in infected mice. Moreover, we observed that mutant CRP capable of binding to factor H bound to several proteins immobilized on plastic, suggesting that CRP recognizes a pattern, probably an amyloid-like structure, on immobilized proteins. Indeed, mutant CRP, after binding to amyloid b peptides, prevented the formation of pathogenic amyloid fibrils. Lastly, employing a hepatic cell line, we investigated the mechanism of CRP expression in response to pro-inflammatory cytokines. We found that the transcription factor C/EBPb and two C/EBP-binding sites on the CRP promoter were critical for inducing CRP expression. We conclude that complement activation is necessary for CRP-mediated protection against infection, that CRP functions in two structural conformations, that CRP and clarithromycin act synergistically, that CRP has anti-amyloidogenic properties, and the increased CRP expression requires C/EBPb.