Biology subjects

Kochan, T. J.

Publications and source records attributed to Kochan, T. J..

3 recordsLinked to original sources

bioRxiv2026

Comparison of Galleria mellonella, Epithelial Cell Cytotoxicity, and Mouse Model of Bacteremia to Measure Pseudomonas aeruginosa Virulence

Considerable effort has focused on identifying alternatives to mouse models in research studies. In the field of bacterial pathogenesis, Galleria mellonella and epithelial cell lines have been widely used for this purpose, but the concordance of these models with mice remains unclear. To begin to address this knowledge gap, we used 105 clinical isolates of Pseudomonas aeruginosa for which the virulence had been previously determined in a mouse bacteremia model. A semistrong correlation was observed between G. mellonella median time to 50% mortality and mouse 50% pre-lethal dose (LD50) values (Spearmans rank correlation coefficient [{rho}] = 0.75), whereas percent A549 epithelial-like cell lysis during co-culture showed a weak correlation to mouse LD50 values ({rho} = -0.47). Given the stronger correlation between G. mellonella and mouse virulence, we next examined whether G. mellonella could substitute for mice when asking questions about the virulence of large numbers of P. aeruginosa isolates. Results from mice indicated that isolates with resistance to more antibiotics were significantly less virulent, and the use of G. mellonella identified the same inverse correlation. Furthermore, both models found no evidence for the existence of hypervirulent clonal lineages. In particular, isolates belonging to sequence types defined as high-risk clones were not consistently more virulent than other isolates, despite the known association of high-risk clones with poor clinical outcomes. These findings suggest that G. mellonella can serve as an adequate substitute for mice when addressing specific population-based virulence questions, although conclusions should be confirmed in mice. Author SummaryWe found that virulence measurements in a G. mellonella infection model showed a semistrong correlation with those from a mouse bacteremia model and that this insect larval model adequately detected population-level trends similarly to mice. In contrast, A549 epithelial-like cell lysis during bacterial co-culture correlated less well with mouse virulence. Together, these results support the use of G. mellonella as a scalable, low-cost, and humane first-line model for assessing P. aeruginosa virulence but also indicate that conclusions should be validated in mice.

microbiology↗

bioRxiv2023

Genome-wide screens reveal shared and strain-specific genes that facilitate enteric colonization by Klebsiella pneumoniae

Gastrointestinal (GI) colonization by Klebsiella pneumoniae is a risk factor for subsequent infection as well as transmission to other patients. Additionally, colonization is achieved by many strain types that exhibit high diversity in genetic content. Thus, we aimed to study strain-specific requirements for K. pneumoniae GI colonization by applying transposon insertion sequencing to three classical clinical strains: a carbapenem-resistant strain, an extended-spectrum beta-lactamase producing strain, and a non-epidemic antibiotic-susceptible strain. The transposon insertion libraries were screened in a murine model of GI colonization. At three days post-inoculation, 27 genes were required by all three strains for colonization. Isogenic deletion mutants for three genes/operons (acrA, carAB, tatABCD) confirmed colonization defects in each of the three strains. Additionally, deletion of acrA reduced bile tolerance in vitro, while complementation restored both bile tolerance in vitro and colonization ability in vivo. Transposon insertion sequencing suggested that some genes were more important for colonization of one strain than the others. For example, deletion of the sucrose porin-encoding gene scrY resulted in a colonization defect in the carbapenemase-producing strain but not in the extended-spectrum beta-lactamase producer or the antibiotic-susceptible strain. These findings demonstrate that classical K. pneumoniae strains use both shared and strain-specific strategies to colonize the mouse GI tract. IMPORTANCEKlebsiella pneumoniae is a common cause of difficult-to-treat infections due to its propensity to express resistance to many antibiotics. For example, carbapenem-resistant K. pneumoniae (CR-Kp) has been named an urgent threat by the United States Centers for Disease Control and Prevention. Gastrointestinal colonization of patients with K. pneumoniae has been linked to subsequent infection, making it a key process to control in prevention of multidrug-resistant infections. However, the bacterial factors which contribute to K. pneumoniae colonization are not well understood. Additionally, individual strains exhibit large amounts of genetic diversity, begging the question of whether some colonization factors are strain-dependent. This study identifies the enteric colonization factors of 3 classical strains using transposon mutant screens to define a core colonization program for K. pneumoniae as well as detecting strain-to-strain differences in colonization strategies.

microbiology↗

bioRxiv2021

Genomic and phenotypic characterization of Pseudomonas hygromyciniae, a novel bacterial species discovered from a commercially purchased antibiotic

A purchased lot of the antibiotic hygromycin B was found to be contaminated with a novel bacterial species, which we designate Pseudomonas hygromyciniae. Characteristics of P. hygromyciniae include its ability to use a variety of compounds as carbon sources, its pathogenicity towards lettuce and Galleria mellonella, and its ability to inhibit the growth of an E. coli strain. P. hygromyciniae is unlikely to be a human pathogen, as it did not survive at 37 {degrees}C and was not cytotoxic towards a mammalian cell line. The P. hygromyciniae strain harbors a novel 250 kb megaplasmid which confers resistance to hygromycin B and contains numerous other genes predicted to encode replication and conjugation machinery. These findings indicate that commercially manufactured antibiotics represent another extreme environment that may support the growth of novel bacterial species. IMPORTANCEMicrobial ecologists have surveyed numerous natural and manmade environments in search of new microbial species. In some instances, these microbes are discovered in harsh conditions, such as deep-sea vents, and their discovery leads to better understanding of how microbes adapt to their environment. Here, we have discovered a new species of bacteria from an extreme manmade environment: a lyophilized, commercially available bottle of the antibiotic hygromycin B.

microbiology↗