Biomedical subjects

Lisa K Nolan

Publications and source records attributed to Lisa K Nolan.

22 records · Page 2Linked to original sources

PubMedDate not supplied

Monoclonal antibodies to avian Escherichia coli Iss.

Escherichia coli infections are a major problem for the poultry industry in the United States. Yet, the virulence mechanisms operative in avian E. coli are poorly understood. In the present studies, monoclonal antibodies (MAbs) have been generated that may facilitate study of the pathogenesis of avian colibacillosis. These MAbs are directed against the Iss protein because results from our laboratory have shown that the possession of iss DNA sequences is strongly correlated with the E. coli implicated in avian colibacillosis. As part of an overall effort to explore the role of iss/Iss in colibacillosis pathogenesis, Iss protein has been purified, MAbs to Iss have been generated, and the MAbs are being evaluated. B cells from mice immunized with an Iss fusion to glutathione-S-transferase produced antibodies specifically against Iss, and these cells were used to generate the MAbs. These anti-Iss MAbs, when used in western blotting assays, can be used to distinguish iss-positive and -negative E. coli isolates, suggesting that they may be useful as reagents in the detection and study of virulent avian E. coli.

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PubMedDate not supplied

Prediction of chicken embryo lethality with the avian Escherichia coli traits complement resistance, colicin V production, and presence of the increased serum survival gene cluster (iss).

Differentiating between virulent and avirulent avian Escherichia coli isolates continues to be a problem for poultry diagnostic laboratories and the study of colibacillosis in poultry. The ability of a laboratory to conduct one simple test that correlates with virulence would simplify studies in these areas; however, previous studies have not enabled researchers to establish such a test. In this study, the occurrence of certain phenotypic and genotypic traits purported to contribute to avian E. coli virulence in 20 avian E. coli isolates was correlated with the results of embryo challenge studies. This analysis was undertaken in an effort to determine which trait(s) best identified each avian E. coli isolate as virulent or avirulent. Traits selected were complement resistance, production of colicin V (ColV), motility, type F1 pili expression, presence of the temperature-sensitive hemagglutinin gene (tsh), and presence of the increased serum survival genetic locus (iss). ColV production, complement resistance, and presence of the iss genetic element were the three traits most highly correlated with high embryo lethality. A logistic regression model was used to predict the embryo lethality results on the basis of the most frequent isolate characteristics. Results indicate that ColV, complement resistance, and if are significant predictor variables for the percentage of embryo lethality resulting from challenge with a specific avian E. coli isolate. However, no single trait has the ability to predict virulent isolates 100% of the time. Such results suggest the possibility that the embryo lethality assay may prove to be the one test needed to determine if an avian E. coli isolate is virulent.

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PubMedDate not supplied

Characterizing avian Escherichia coli isolates with multiplex polymerase chain reaction.

Colibacillosis caused by Escherichia coli infections account for significant morbidity and mortality in the poultry industry. Yet, despite the importance of colibacillosis, much about the virulence mechanisms employed by avian E. coli remains unknown. In recent years several genes have been linked to avian E. coli virulence, many of which reside on a large transmissible plasmid. In the present study, a multiplex polymerase chain reaction (PCR) protocol to detect the presence of four of these genes is described. Such a protocol may supplement current diagnostic schemes and provide a rapid means of characterizing the E. coli causing disease in poultry. The targets of this procedure included iss, the increased serum survival gene; tsh, the temperature sensitive hemagglutinin gene; cvi, the ColV immunity gene; and iucC, a gene of the aerobactin operon. Organisms, known for their possession or lack of these genes, were used as a source of the template DNA to develop the multiplex PCR protocol. Identity of the amplicons was confirmed by size, DNA:DNA hybridization with specific gene probes, and DNA sequencing. When the multiplex PCR protocol was used to characterize 10 E. coli isolates incriminated in avian colibacillosis and 10 from the feces of apparently healthy birds, nine of the isolates from apparently healthy birds contained no more than one gene, while the 10th contained all four. Also, eight of the isolates incriminated in colibacillosis contained three or more genes, while the remaining two contained two of the target genes. Interestingly, the isolates of sick birds containing only two of the targeted genes killed the least number of embryos,and the isolate of healthy birds that contained all the genes killed the most embryos amongthis group. These genes were not found among the non-E. coli isolates tested, demonstrating the procedure's specificity for E. coli. Overall, these results suggest that this protocol might be useful in characterization and study of avian E. coli.

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PubMedDate not supplied

Multiple antimicrobial resistance region of a putative virulence plasmid from an Escherichia coli isolate incriminated in avian colibacillosis.

Infections due to Escherichia coli have been costly to the poultry industry, but the exact virulence mechanisms used by these organisms to cause disease in birds remain undefined. Several factors have been shown to contribute to the virulence of avian E. coli, and many of the genes encoding these factors have been found on large conjugative plasmids. Because of the occurrence of antimicrobial resistance genes on these same plasmids, it is possible that the use of antimicrobial agents may select for persistence of E. coli containing such plasmids. In the present study, a subclone of one of these plasmids was identified as likely containing some virulence and antimicrobial resistance genes. In an effort to better understand the relationship between virulence and resistance in these plasmids, this subclone was sequenced and the sequence analyzed. Analysis of this 30-kilobase (kb) region of plasmid pTJ100 revealed a mosaic of virulence genes, insertion sequences, antimicrobial resistance cassettes, and their remnants. Many of the resistance genes found in this region were expressed under laboratory conditions, indicating that certain antimicrobial agents, including disinfectants, antibiotics, and heavy metals, could promote selection of E. coli containing such plasmids in the production environment. Also, analysis of the G + C content of this clone indicated that it is the likely consequence of a complex evolution with components derived from various sources. The occurrence of many mobile elements in conjunction with antimicrobial resistance and virulence genes in this 30-kb region may indicate that the genetic constitution of the clone is quite plastic. Although further study will be required to better define this plasmid's role in avian E. coli virulence, the sequence described here is, to our knowledge, the longest known contiguous sequence of a ColV plasmid yet presented. Analysis of this sequence indicates that this clone and its parent plasmid may be important to the pathogenesis of avian colibacillosis and the evolution of avian E. coli virulence.

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