Michelle M. Banes

Genome Sequence of Edwardsiella ictaluri 93-146, a Strain Associated with a Natural Channel Catfish Outbreak of Enteric Septicemia of Catfish

Edwardsiella ictaluri is the cause of extensive mortalities and economic losses to the channel catfish industry of the southeast United States. Here we report the complete genome of Edwardsiella ictaluri 93-146. Whole-genome sequence analysis of E. ictaluri provides a tool for understanding the genomic regions specific to the species and the Edwardsiella genus.

Genome Sequence of the Fish Pathogen Flavobacterium columnare ATCC 49512

Flavobacterium columnare is a Gram-negative, rod-shaped, motile, and highly prevalent fish pathogen causing columnaris disease in freshwater fish worldwide. Here, we present the complete genome sequence of F. columnare strain ATCC 49512.

Phenotype and Virulence of a Transposon-Derived Lipopolysaccharide O Side-Chain Mutant Strain of Edwardsiella ictaluri

Abstract Using transposon mutagenesis, we isolated a lipopolysaccharide (LPS) O side-chain (O antigen) mutant strain of Edwardsiella ictaluri. Failure of the mutant to express O side chains was confirmed on sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) with silver staining and on immunoblots. In contrast, an attenuated strain developed by in vitro subculture did not express changes in LPS that were detectable by SDS–PAGE or immunoblotting. Both the O side-chain mutant and the in vitro subcultured strain were highly attenuated in channel catfish Ictalurus punctatus fingerlings compared with the parent wild-type strain. We conclude that LPS O side chains are an essential virulence factor for E. ictaluri and that loss of virulence in the in vitro subcultured strain was not associated with LPS alterations.

The Edwardsiella ictaluri O polysaccharide biosynthesis gene cluster and the role of O polysaccharide in resistance to normal catfish serum and catfish neutrophils

Edwardsiella ictaluri, the causative agent of enteric septicaemia of catfish (ESC), expresses long O polysaccharide (OPS) chains on its surface. The authors previously reported the construction of an isogenic Ed. ictaluri OPS mutant strain and demonstrated that this strain is avirulent in channel catfish. This paper reports the cloning of the Ed. ictaluri OPS biosynthesis gene cluster and identification of the mutated gene in the OPS-negative strain. The sequenced region contains eight complete ORFs and one incomplete ORF encoding LPS biosynthesis enzymes. The mutated gene (designated wbiT) was similar to other bacterial galactose-4-epimerases. Glycosyl composition analysis indicated that wild-type Ed. ictaluri OPS contains higher amounts of galactose and N-acetylgalactosamine than the OPS mutant strain, which correlated well with predicted functions of the genes identified in the OPS biosynthesis cluster. The OPS mutant had a relatively small, but significant, decrease in its ability to survive in normal catfish serum compared to wild-type Ed. ictaluri, but it retained the ability to resist killing by catfish neutrophils.

Genome Sequence of Lineage III Listeria monocytogenes Strain HCC23

More than 98% of reported human listeriosis cases are caused by Listeria monocytogenes serotypes within lineages I and II. Serotypes within lineage III (4a and 4c) are commonly isolated from environmental and food specimens. We report the first complete genome sequence of a lineage III isolate, HCC23, which will be used for comparative analysis.

Tissue Persistence and Vaccine Efficacy of an O Polysaccharide Mutant Strain of Edwardsiella ictaluri

Abstract Studies were conducted to determine the tissue persistence and vaccine efficacy of a previously constructed isogenic O polysaccharide (OPS) mutant strain (93–146 R6) of the bacterium Edwardsiella ictaluri in channel catfish Ictalurus punctatus. The OPS-negative strain retained the ability to infect channel catfish following immersion exposure and persisted in the trunk kidney at least 14 d, whereas previously reported attenuated E. ictaluri strains were cleared by 72 h postexposure. Vaccination with 93–146 R6 by intraperitoneal injection provided significant protection against subsequent immersion challenge with the virulent parental strain, but vaccination by immersion did not provide protection. The commercial vaccine RE-33 provided significant protection when fish were vaccinated by immersion, but RE-33 was more virulent than 93–146 R6 when given by intraperitoneal injection.

Complete Genome Sequence of Channel Catfish Gastrointestinal Septicemia Isolate Edwardsiella tarda C07-087.

ABSTRACT Edwardsiella tarda is a Gram-negative facultative anaerobe causing disease in animals and humans. Here, we announce the complete genome sequence of the channel catfish isolate E. tarda strain C07-87, which was isolated from an outbreak of gastrointestinal septicemia on a commercial catfish farm.

Genome comparison of Listeria monocytogenes serotype 4a strain HCC23 with selected lineage I and lineage II L. monocytogenes strains and other Listeria strains.

More than 98% of reported human listeriosis cases are caused by specific serotypes within genetic lineages I and II. The genome sequence of Listeria monocytogenes lineage III strain HCC23 (serotype 4a) enables whole genomic comparisons across all three L. monocytogenes lineages. Protein cluster analysis indicated that strain HCC23 has the most unique protein pairs with nonpathogenic species Listeria innocua. Orthology analysis of the genome sequences of representative strains from the three L. monocytogenes genetic lineages and L. innocua (CLIP11262) identified 319 proteins unique to nonpathogenic strains HCC23 and CLIP11262 and 58 proteins unique to pathogenic strains F2365 and EGD-e. BLAST comparison of these proteins with all the sequenced L. monocytogenes and L. innocua revealed 126 proteins unique to serotype 4a and/or L. innocua; 14 proteins were only found in pathogenic serotypes. Some of the 58 proteins unique to pathogenic strains F2365 and EGD-e were previously published and are already known to contribute to listerial virulence.

Clinical, pathological, and genetic characterization of Listeria monocytogenes causing sepsis and necrotizing typhlocolitis and hepatitis in a foal

Listeria monocytogenes was isolated from the blood, lungs, and liver of a 5-week-old American Quarter Horse filly that presented with a 2-day history of fever, lethargy, ataxia, and seizure activity. The foal was born on a well-managed breeding facility to a multiparous mare with no periparturient complications. At 8 hr of age, the foal had an adequate passive transfer of immunity (immunoglobulin G > 2,000 mg/dl). Since the time of birth, the foal reportedly had mild, intermittent diarrhea that responded to gastrointestinal protectants and probiotics. Despite prompt and aggressive treatment after hospital referral, the foal’s condition deteriorated, and the foal was humanely euthanized. Postmortem gross and histopathologic examination revealed severe hepatitis with necrosis and fibrinonecrotic typhlitis and colitis. In addition to a positive blood culture for L. monocytogenes, immunohistochemistry confirmed the presence of this bacterium in the liver, cecum, and colon. Furthermore, a multiplex polymerase chain reaction identified the etiologic organism as a virulent L. monocytogenes strain.

Protective efficacy of four recombinant fimbrial proteins of virulent Aeromonas hydrophila strain ML09-119 in channel catfish

Aeromonas hydrophila is a reemerging pathogen of channel catfish (Ictalurus punctatus); recent outbreaks from 2009 to 2014 have caused the loss of more than 12 million pounds of market size catfish in Alabama and Mississippi. Genome sequencing revealed a clonal group of A. hydrophila isolates with unique genetic and phenotypic features that is highly pathogenic in channel catfish. Comparison of the genome sequence of a representative catfish isolate (ML09-119) from this virulent clonal group with lower virulence A. hydrophila isolates revealed four fimbrial proteins unique to strain ML09-119. In this work, we expressed and purified four A. hydrophila fimbrial proteins (FimA, Fim, MrfG, and FimOM) and assessed their ability to protect and stimulate protective immunity in channel catfish fingerlings against A. hydrophila ML09-119 infection for vaccine development. Our results showed catfish immunized with FimA, Fim, FimMrfG, and FimOM exhibited 59.83%, 95.41%, 85.72%, and 75.01% relative percent survival, respectively, after challenge with A. hydrophila strain ML09-119. Bacterial concentrations in liver, spleen, and anterior kidney were significantly (p<0.05) lower in vaccinated fish compared to the non-vaccinated sham groups at 48h post-infection. However, only the Fim immunized group showed a significantly higher antibody titer in comparison to the non-vaccinated treatment group (p<0.05) at 21days post-vaccination. Altogether, Fim and FimMrfG recombinant proteins have potential for vaccine development against virulent A. hydrophila infection.