Biology subjects

Parker, C. T.

Publications and source records attributed to Parker, C. T..

7 recordsLinked to original sources

bioRxiv2026

Phenotypic Resistance of Ciprofloxacin and Azithromycin Resistant Campylobacter Isolates to an Extended Panel of Antibiotics.

In this study we explored phenotypic resistance using traditional Kirby-Bauer methods in human and animal derived Campylobacter isolates that were concurrently resistant to both azithromycin and ciprofloxacin to an expanded panel of antimicrobials, including clindamycin, fosfomycin, ampicillin sulbactam and tigecycline. Out of 236 Campylobacter isolates, over 85% of C. jejuni and C. coli were resistant to clindamycin, over 60% were resistant to ampicillin sulbactam and over 30% to fosfomycin. Less than 2% of isolates were resistant to tigecycline and there was no observed resistance to Imipenem.

microbiology↗

bioRxiv2025

Growth rates and Metabolic Traits Differentiate Campylobacter jejuni Strains by Diarrheal Manifestation

IntroductionCampylobacter jejuni is the leading cause of bacterial gastroenteritis worldwide. Infections with C. jejuni can result in two different diarrheal manifestations in humans: watery diarrhea or bloody/inflammatory diarrhea. Hypothesis/Gap StatementCurrently, little is known about C. jejuni and/or host factors associated with elicitation of these two distinct diarrheal manifestations. We hypothesize that these factors may include growth and metabolic trait differences between C. jejuni strains associated with watery diarrhea and bloody/inflammatory diarrhea. AimUsing C. jejuni strains with a defined diarrheal manifestation in the neonatal piglet model, we aimed to assess differences in temperature dependent growth rates, motility, biofilm production, and carbon utilization between diarrheal manifestation groups. MethodologyStrains were initially assessed for 192 different carbon sources using phenotypic microarrays followed by specific carbon utilization, growth, motility, and biofilm assays at 37{degrees}C and/or 42{degrees}C. ResultsWe found that at 37{degrees}C, watery diarrhea associated C. jejuni strains grew significantly faster compared to bloody/inflammatory diarrhea associated C. jejuni strains. However, there was no significant growth difference at 42{degrees}C between the groups, due to bloody/inflammatory diarrhea associated strains growing faster at 42{degrees}C compared to 37{degrees}C. Additionally at 37{degrees}C, we found that L-fucose utilization was significantly higher among watery diarrhea associated strains, while L-glutamine utilization was significantly higher among bloody/inflammatory diarrhea associated strains. ConclusionThe results indicate there are distinct metabolic adaptations between watery and/or bloody/inflammatory diarrhea associated C. jejuni strains particularly at 37{degrees}C, which may be one of the factors associated with differing diarrheal manifestations.

microbiology↗

bioRxiv2025

STRAIN-SPECIFIC VIRULENCE SIGNATURES OF CAMPYLOBACTER JEJUNI ASSOCIATED WITH WATERY VERSUS BLOODY DIARRHEA IN NEONATAL PIGLET MODEL

Campylobacter jejuni is the leading cause of bacterial gastroenteritis globally, presenting with either watery or bloody/inflammatory diarrhea. Despite this clinical variability, the underlying mechanisms driving these distinct diarrheal manifestations remain unclear. The neonatal piglet model provides a unique opportunity to investigate these differences using strains with defined disease manifestations. We evaluated ten C. jejuni strains previously shown to cause consistent diarrheal manifestations in neonatal piglets: five strains associated with watery diarrhea and five associated with bloody/inflammatory diarrhea. The study found significant strain to strain variation among most assays, but overall strains associated with bloody/inflammatory diarrhea exhibited significantly higher levels of epithelial cell invasion, intracellular survival, macrophage survivability, and disruption of intestinal barrier integrity compared to watery diarrhea strains. Notably, both groups had similar levels of adherence, produced similar levels of cytolethal distending toxin (CDT) and elicited comparable IL-8 responses. While both groups facilitated translocation of commensal E. coli, only bloody/inflammatory strains caused increased paracellular permeability, as shown by TEER and FITC-dextran assays. This study reveals that there is significant variation in the virulence phenotype of C. jejuni strains and identifies several characteristics consistently associated with a specific diarrheal manifestation group. These findings provide new insights into the strain-specific pathogenic mechanisms of C. jejuni, with implications for understanding host-pathogen interactions and informing targeted diagnostic and therapeutic strategies. Author SummaryCampylobacter jejuni is one of the most common bacterial causes of diarrhea worldwide, affecting millions each year. Infected individuals may experience either watery or bloody/inflammatory diarrhea, but the reasons why different strains cause different types of illness have remained a mystery. In this study, we used a neonatal piglet model, which accurately mimics human diarrheal disease, to investigate why certain C. jejuni strains cause more severe symptoms than others. We compared strains known to cause either watery or bloody diarrhea and found key differences in their ability to invade intestinal cells, survive inside immune cells, and damage the intestinal barrier. While both groups of strains could trigger inflammation and translocate E. coli through the intestinal lining, only the strains linked to bloody diarrhea caused significant barrier disruption and had increased intracellular survival. These findings reveal that different C. jejuni strains follow distinct paths during infection, which helps explain why they produce different symptoms. Unraveling these differences improves our overall understanding of Campylobacter pathogenesis that could lead to improved diagnostics and/or treatments to reduce the burden of campylobacteriosis around the world.

microbiology↗

bioRxiv2025

American black bear (Ursus americanus) as a potential host for Campylobacter jejuni

The Gram-negative bacterium Campylobacter jejuni is part of the commensal gut microbiota of numerous animal species and a leading cause of bacterial foodborne illness in humans. Most complete genomes of C. jejuni are from strains isolated from human clinical, poultry, and ruminant samples. Here, we characterized and compared the genomes of C. jejuni that were isolated from American black bears in three states in the southeastern United States. Despite the limited sample size (n=9), the isolates displayed substantial genotypic variability, including eight distinct sequence types (STs) and variable gene content encoding surface glycan structures such as capsular polysaccharides (CPS) and lipooligosaccharides (LOS). Phylogenetic analysis identified several C. jejuni host generalist strains among the isolates from bears that clustered with isolates from domestic poultry, cattle, and environmental sources. Three isolates (SKBC94, SKBC3, SKBC5) clustered with wildlife-associated strains, exhibiting mutations or deletions in loci associated with cytolethal distending toxin production and oxidative stress resistance, potentially influencing host-specific colonization. Additionally, strains SKBC3 and SKBC5 harbored distinct Entner-Doudoroff (E-D) loci, suggesting a potential evolutionary fitness advantage. This study provides the first evidence of C. jejuni colonization in American black bears, highlighting their potential role as reservoirs for diverse C. jejuni lineages from both anthropogenic and environmental sources. Further research is needed to determine the prevalence and host specificity of C. jejuni strains in black bears and their potential implications for public and wildlife health.

microbiology↗

bioRxiv2023

Bacterial diversity and composition on the rinds of specific melon cultivars and hybrids from across different growing regions in the United States

The goal of this study was to characterize the bacterial diversity on different melon varieties grown in different regions of the US, and determine the influence that region, rind netting, and variety of melon has on the composition of the melon microbiome. Assessing the bacterial diversity of the microbiome on the melon rind can identify antagonistic and protagonistic bacteria for foodborne pathogens and spoilage organisms to improve melon safety, prolong shelf-life, and/or improve overall plant health. Bacterial community composition of melons (n = 603) grown in seven locations over a four-year period were used for 16S rRNA gene amplicon sequencing and analysis to identify bacterial diversity and constituents. Statistically significant differences in alpha diversity based on the rind netting and growing region (p < 0.01) were found among the melon samples. Principal Coordinate Analysis based on the Bray-Curtis dissimilarity distance matrix found that the melon bacterial communities clustered more by region rather than melon variety (R2 value: 0.09 & R2 value: 0.02 respectively). Taxonomic profiling among the growing regions found Enterobacteriaceae, Bacillaceae, Microbacteriaceae, and Pseudomonadaceae present on the different melon rinds at an abundance of [≥] 0.1%, but no specific core microbiome was found for netted melons. However, a core of Pseudomonadaceae, Bacillaceae, and Exiguobacteraceae were found for non-netted melons. The results of this study indicate that bacterial diversity is driven more by the region that the melons were grown in compared to rind netting or melon type. Establishing the foundation for regional differences could improve melon safety, shelf-life, and quality as well as the consumers health.

microbiology↗

bioRxiv2023

Urbanization spreads antimicrobial resistant enteric pathogens in wild bird microbiomes

Human behaviour is dramatically changing global ecology. Nowhere is this more apparent than in urbanization, where novel high human density habitats are disrupting long established ecotones. Resultant changes to the transitional areas between organisms, especially enhanced contact between humans and wild animals, provides new opportunities for the spread of zoonotic pathogens, posing a serious threat to global public health. Here, by studying the multi-host enteric pathogen Campylobacter jejuni isolated from the gut of 30 bird species in 8 countries, we investigated how proximity to urbanization influenced the spread of antimicrobial resistant (AMR) strains. Generalized linear models compared multiple behavioural and ecological traits and confirmed a positive correlation between proximity to urbanization and the number of C. jejuni genotypes and AMR genes in wild bird hosts. Wild birds from highly urban areas harboured up to four times more C. jejuni genotypes and six times more AMR genes. This is consistent with increased frequency of transition events. Quantifying zoonotic transmission and gene pool spread is essential for quantitative one health surveillance and control measures against future zoonosis emergences.

genomics↗

bioRxiv2021

Utilization efficiency of human milk oligosaccharides by human-associated Akkermansia is strain-dependent

Akkermansia muciniphila are mucin degrading bacteria found in the human gut and are often associated with positive human health. However, despite being detected as early as one month of age, little is known about the role of Akkermansia in the infant gut. Human milk oligosaccharides (HMOs) are abundant components of human milk and are structurally similar to the oligosaccharides that comprise mucin, the preferred growth substrate of human-associated Akkermansia. A limited subset of intestinal bacteria has been shown to grow well on HMOs and mucin. We therefore examined the ability of genomically diverse strains of Akkermansia to grow on HMOs. First, we screened 85 genomes representing the four known Akkermansia phylogroups to examine their metabolic potential to degrade HMOs. Furthermore, we examined the ability of representative isolates to grow on individual HMOs in a mucin background and analyzed the resulting metabolites. All Akkermansia genomes were equipped with an array of glycoside hydrolases associated with HMO-deconstruction. Representative strains were all able to grow on HMOs with varying efficiency and growth yield. Strain CSUN-19 belonging to the AmIV phylogroup, grew to the highest level in the presence of fucosylated and sialylated HMOs. This activity may be partially related to the increased copy numbers and/or the enzyme activities of the -fucosidases, -sialidases, and {beta}-galactosidases. Utilization of HMOs by strains of Akkermansia suggests that ingestion of HMOs by an infant may enrich for these potentially beneficial bacteria. Further studies are required to realize this opportunity and deliver long-lasting metabolic benefits to the human host. ImportanceHuman milk oligosaccharides (HMOs) are utilized by a limited subset of bacteria in the infant gut. Akkermansia are detected in infants as young as one month of age and are thought to contribute to the HMO deconstruction capacity of the infant. Here, using phylogenomics, we examined the genomic capacity of different Akkermansia phylogroups to potentially deconstruct HMOs. Furthermore, we experimentally showed that strains from all the currently known phylogroups of Akkermansia can deconstruct all the major types of HMOs, albeit with different utilization efficiencies. This study thus examines Akkermansia-HMO interactions that can potentially influence the gut microbial ecology during the first 1,000 days of life - a critical phase for the development of the gut microbiome and infant health. This study will be of interest to a wide range of scientists from microbiologists, glycochemists/glycobiologists, to functional food developers investigating Akkermansia as probiotics or functional foods containing milk oligosaccharides as prebiotics.

microbiology↗