Biomedical subjects

G A Uhlich

Publications and source records attributed to G A Uhlich.

12 recordsLinked to original sources

PubMed2001

Mutations in the csgD promoter associated with variations in curli expression in certain strains of Escherichia coli O157:H7.

Single-base-pair csgD promoter mutations in human outbreak Escherichia coli O157:H7 strains ATCC 43894 and ATCC 43895 coincided with differential Congo red dye binding from curli fiber expression. Red phenotype csgD::lacZ promoter fusions had fourfold-greater expression than white promoter fusions. Cloning the red variant csgDEFG operon into white variants induced the red phenotype. Substrate utilization differed between red and white variants.

Bacterial Proteins↗

PubMed2000

FnrP interactions with the Pasteurella haemolytica leukotoxin promoter.

Pasteurella haemolytica FnrP is homologous to Fnr, the global transcriptional regulator of anaerobic respiration in Escherichia coli. To investigate the role of O(2) in the expression of P. haemolytica leukotoxin, we tested a lktC::lacZ fusion constructed in E. coli for a FnrP-mediated regulatory effect under aerobic and anaerobic growth conditions. Both E. coli Fnr and FnrP suppressed leukotoxin transcription under aerobic conditions. Under anaerobic conditions, Fnr suppressed transcription, while FnrP increased transcription. These results were confirmed using FnrP*, a mutant form of FnrP that activates anaerobically inducible genes under aerobic conditions. In mobility shift assays, partially purified FnrP bound to a potential regulatory site in a P. haemolytica lktC promoter fragment.

Aerobiosis↗

PubMed1999

Cloning and characterization of the gene encoding Pasteurella haemolytica FnrP, a regulator of the Escherichia coli silent hemolysin sheA.

A Pasteurella haemolytica A1 gene was identified from a recombinant library clone that expressed hemolysis in host Escherichia coli cells. The gene, designated fnrP, had sequence identity to E. coli fnr, a global transcriptional regulator of genes required for conversion to anaerobic growth. FnrP complemented anaerobic deficiencies of a fnr-null mutant strain of E. coli and increased expression of the Fnr-dependent, anaerobic terminal reductase gene, frdA. FnrP was purified, identified by immunoblotting, and shown to be nonhemolytic. When FnrP was expressed in E. coli DeltasheA, a null mutant of the cryptic hemolysin SheA, the transformants were nonhemolytic, indicating that FnrP activates this silent hemolysin.

Anaerobiosis↗

PubMed1998

Comparison of serologic and protective responses induced by two Pasteurella vaccines.

Vaccine development for the prevention of pneumonic pasteurellosis remains a critical issue for the feedlot industry. Most currently available Pasteurella vaccines are formulated to stimulate immunity by either providing an adequate antigenic mass in the administered dose, or by relying on subsequent production of antigens by in vivo growth of live organisms. The ability of these different types of vaccines to stimulate rapid and high titres to key antigens is a key factor that will influence subsequent resistance to disease. The serologic and protective responses to a streptomycin-dependent, modified-live vaccine and a killed (bacterin-toxoid) vaccine against experimental pneumonic pasteurellosis were compared. Calves were vaccinated with a single injection of either a test vaccine or phosphate-buffered saline, challenged 14 d later by transthoracic injection with Pasteurella haemolytica, and euthanized 3 d post-challenge to evaluate the severity of pneumonia. On days 0, 7, and 14, serologic responses to various P. haemolytica antigens, including cell-associated and soluble antigens, were determined by enzyme-linked immunosorbent assays, and anti-leukotoxin antibody levels were determined by leukotoxin neutralization. The bacterin-toxoid elicited significantly greater serologic responses compared to controls for all antigens. The modified-live vaccine elicited a significantly greater response compared to controls for a whole-cell antigen preparation. Lesion scores were significantly smaller (greater protection) in calves that received the bacterin-toxoid, but not the modified-live vaccine, compared to controls.

Animals↗

PubMed1995

Lectin histochemistry of normal and herpesvirus-infected bovine nasal mucosa.

Proliferation of Pasteurella haemolytica serotype 1 in the nasal cavity following stress or viral infection is an important event in the pathogenesis of bovine pneumonic pasteurellosis. Enhanced adhesion of P. haemolytica to nasal mucosa could be one factor that predisposes animals to this proliferation. Nasal mucosa from normal and bovine herpesvirus-1 (BHV1)-infected cattle were examined histochemically for their glycoconjugate composition. Twenty lectins were screened, six of which were chosen for subsequent study. Three of these were specific for N-acetylgalactosamine (NAGal) (Dolichos biflorus, Glycine max, and Vicia villosa), and one each was specific for N-acetylgalactosamine/galactose (Griffonia simplicifolia-I), mannose/glucose (Canavalia ensiformis), and N-acetylglucosamine (Triticum vulgaris). For the surface mucosa and submucosal glands, there was greater reactivity in samples from BHV1-infected than from normal cattle for all six lectins. Reactivity was most prominent for the NAGal-specific lectins. Neuraminidase treatment of samples from normal and BHV1-infected cattle tended to result in greater lectin reactivity. Lectin reactivity was generally more intense in focally inflamed areas, but diffuse reactivity was not substantially affected by inflammation. BHV1-induced alteration of nasal mucosal glycoconjugates could enhance adhesion and colonization of P. haemolytica to nasal surfaces and may be one factor responsible for the increased number of P. haemolytica serotype 1 in the nasal cavity following viral infection.

Animals↗

PubMed1991