Canadian journal of microbiology最新文献

Streptococcus suis and Glaesserella parasuis are commensal organisms that can shift from a benign to pathogenic state and cause severe disease in swine. We hypothesized that a change in host temperature and/or interactions with G. parasuis could impact S. suis growth dynamics. We compared phenotypic properties of a clinical S. suis serovar 9 strain (SS9C) with clinical serovar 2 and healthy serovar 9 isolates grown at 37 and 41 °C. We further investigated how co-culturing with G. parasuis affected biofilm formation of SS9C. Crystal violet staining indicated that SS9C produced significantly more biofilm than the other strains when grown at 37 °C; this difference was amplified at 41 °C. However, cell counts did not increase at the higher temperature. Biofilms of SS9C at 37 and 41 °C were unaffected by DNase I digestion, while other strains were both susceptible at 41 °C. All biofilms were susceptible to proteinase K and α-amylase digestion at both temperatures. We showed that growth at 41 °C increased biofilm formation and shifted the phenotype of SS9C; however, neither increased temperature nor co-culture with G. parasuis increased planktonic or sessile cell counts. Our study suggests that increased temperature in the host may be an important factor in understanding S. suis disease development.

Antimicrobial resistance is an environmental, agricultural, and public health problem that is impacting the health of humans and animals. The role of the environment as a source of and transmission pathway for antibiotic resistant bacteria and antibiotic resistance genes is a topic of increasing interest that, to date, has received limited attention. This study aimed to describe the sources and possible pathways contributing to antimicrobial resistance dissemination through bioaerosols, water, and soil in Canada using a scoping review methodology and systems thinking approach. A systems map was created to describe the occurrence and relationships between sources and pathways for antimicrobial resistance dissemination through water, soil, and bioaerosols. The map guided the development of the scoping review protocol, specifically the keywords searched and what data were extracted from the included studies. In total, 103 studies of antimicrobial resistance in water, 67 in soil, and 12 in air were identified. Studies to detect the presence of antimicrobial resistance genes have mainly been conducted at wastewater treatment plants and commercial animal livestock facilities. We also identified elements in the systems map with little or no data available (e.g., retail) that need to be investigated further to have a better understanding of antimicrobial resistance dissemination through different Canadian environments.

Bacteria encounter various stressful conditions within a variety of dynamic environments, which they must overcome for survival. One way they achieve this is by developing phenotypic heterogeneity to introduce diversity within their population. Such distinct subpopulations can arise through endogenous fluctuations in regulatory components, wherein bacteria can express diverse phenotypes and switch between them, sometimes in a heritable and reversible manner. This switching may also lead to antigenic variation, enabling pathogenic bacteria to evade the host immune response. Therefore, phenotypic heterogeneity plays a significant role in microbial pathogenesis, immune evasion, antibiotic resistance, host niche tissue establishment, and environmental persistence. This heterogeneity can result from stochastic and responsive switches, as well as various genetic and epigenetic mechanisms. The development of phenotypic heterogeneity may create clonal populations that differ in their level of virulence, contribute to the formation of biofilms, and allow for antibiotic persistence within select morphological variants. This review delves into the current understanding of the molecular switching mechanisms underlying phenotypic heterogeneity, highlighting their roles in establishing infections caused by select bacterial pathogens.

As it flows through the collection system, maple sap is likely to be contaminated by microorganisms that colonize the tubing, potentially compromising its quality in terms of physicochemical properties, microbial load, and flavor. This study investigates the effect of microbial inoculation, as protective cultures, on the sap collection system to improve maple syrup quality. The research explored how inoculating collection tubing with specific bacterial strains influences the microbial composition, physicochemical properties (pH, Brix, conductivity, sugars, and organic acids content), and sensory attributes of both maple sap and syrup. Three strains selected for their capacity to produce biofilm on plastic tubing and their impact on maple syrup production from inoculated sap, Pseudomonas sp. MSB2019, Janthinobacterium lividum 100-P12-9, and Pseudomonas fluorescens ATCC 17926, were inoculated to independent sap collection system throughout two sugaring seasons. A non-inoculated system was included. Pseudomonas sp. MSB2019 treatment resulted in a distinct bacterial composition in sap and impact the organoleptic properties of syrup by the end of second flow season, particularly the maple and overall flavor intensity scores were higher. While sap yield and primary microbial load remained unaffected, inoculation treatments corresponded to shifts in flavor attributes of the syrup. These findings indicate that inoculating sap collection systems with targeted strains can positively influence maple syrup quality, particularly in enhancing desirable flavor profiles, suggesting promising applications for syrup production.

Many arthropods, including economically important pests of stored grains, host intracellular bacterial symbionts. These symbionts can have diverse impacts on host morphology, stress tolerance, and reproductive success. The ability to rapidly determine the infection status of host insects and the identity of intracellular symbionts, if present, is vital to understanding the biology and ecology of these organisms. We used a microbiome profiling method based on amplicon sequencing to rapidly screen 35 captive insect colonies. This method effectively revealed single and mixed infections by intracellular bacterial symbionts, as well as the presence or absence of a dominant symbiont, when that was the case. Because no a priori decisions are required about probable host-symbiont pairing, this method is able to quickly identify novel associations. This work highlights the frequency of endosymbionts, indicates some unexpected pairings that should be investigated further, such as dominant bacterial taxa that are not among the canonical genera of endosymbionts, and reveals different colonies of the same host insect species that differ in the presence and identity of endosymbiotic bacteria.

M13 bacteriophages form self-assembled nanorods with the ability to self-assemble into complex materials with higher-order structures. These features make them useful templates for material fabrication. Their use in soft materials, bio-nano systems, and biomedical applications is well established. For these bio-interfacial applications, it is crucial that phages remain biocompatible and their production sustainable. Here, we review the bioprocessing of M13 phages and genetic engineering strategies that retain their natural assets in nanomaterials or bulk materials. Specifically, we highlight the extensively studied fermentation process of M13 phages with Escherichia coli (E. coli) and common downstream processing methods suitable for materials manufacturing. The ease of phage production contributes to its wide use for phage display, enabling the creation of large libraries of functional mutants. For materials purposes, genetic engineering often targets the pIII and pVIII proteins, enabling different geometries and fragment sizes. We also review common peptides displayed on phages, including arginine-glycine-aspartic acid (RGD) peptides, used for surface plasmon resonance (SPR) probes, targeted medicine, cell regeneration, or tissue scaffolding. We study glutamate-modified phages for metal binding, biomineralization, and electronics in bulk materials. By considering self-assembly, bioprocessing, and genetic engineering, material engineers can fully harness M13 phages for diverse functional and sustainable devices.

Pyrimidine base and ribonucleoside salvage metabolism was investigated in Pseudomonas putida ATCC 17536 cells. In ATCC 17536 cell extracts, the pyrimidine ribonucleoside salvage enzymes nucleoside hydrolase and cytosine deaminase activities were measurable, while uridine phosphorylase activity was not. Carbon and nitrogen sources influenced the levels of the salvage pathway enzyme activities in P. putida ATCC 17536. Catabolite repression by a glucose metabolite of nucleoside hydrolase and cytosine deaminase synthesis in ATCC 17536 cells compared to cells grown on the carbon source succinate or ribose was observed, while a nitrogen metabolite appeared to be controlling pyrimidine salvage enzyme synthesis. When glucose was the carbon source, ATCC 17536 cells grown on uracil or 5-methylcytosine as a nitrogen source caused at least a five-fold increase in hydrolase and deaminase synthesis relative to their activities in ammonium sulfate-grown cells. In succinate-grown ATCC 17536 cells, thymine or 5-methylcytosine as a nitrogen catabolite produced at least double the hydrolase or deaminase activity relative to either activity in ammonium sulfate-grown cells. Overall, the pyrimidine base and ribonucleoside salvage enzymes in P. putida ATCC 17536 biovar B cells were regulated by the carbon or nitrogen source with pyrimidine salvage metabolism differing in biovar A and B strains.

Highly pathogenic avian influenza (HPAI) H5N1 has caused the deaths of more than 100 million birds since 2021, and human cases since 1997 have been associated with significant morbidity and mortality. Given recent detections of HPAI H5N1 in dairy cattle and H5N1 RNA detections in pasteurized retail milk in the United States, we established the pan-Canadian Milk Network in April 2024. Through our network of collaborators from across Canada, retail milk was procured longitudinally, approximately every 2 weeks, and sent to a central laboratory to test for the presence of influenza A virus RNA. Between 29 April and 17 July 2024, we tested 109 retail milk samples from all 10 Canadian provinces (NL, NS, PEI, NB, QC, ON, MB, SK, AB, and BC). All samples tested negative for influenza A virus RNA. This nationwide initiative was established for rapid retail milk screening as per the earliest reports of similar undertakings in the United States. Our independent testing results have aligned with reporting from federal retail milk testing initiatives. Despite no known HPAI infections of dairy cattle in Canada to date, H5N1 poses a significant threat to the health of both humans and other animals. By performing routine surveillance of retail milk on a national scale, we have shown that academic networks and initiatives can rapidly establish nationwide emerging infectious disease surveillance that is cost-effective, standardized, scalable, and easily accessible. Our network can serve as an early detection system to help inform containment and mitigation activities if positive samples are identified and can be readily reactivated should HPAI H5N1 or other emerging zoonotic viruses be identified in agricultural or livestock settings, including Canadian dairy cattle.

Whole-genome sequence-based surveillance of bacteria for determinants of antimicrobial resistance (AMR) promises many advantages over traditional, wet-lab approaches. However, adjustments to parameters used to identify genetic determinants from sequencing data can affect results and interpretation of the important determinants in circulation. Using a dataset of whole-genome sequences from 1633 isolates of Salmonella Heidelberg and S. Kentucky collected from surveillance of Canadian poultry production, we queried the genomic data using an in silico AMR detection tool, StarAMR, applying a range of parameter values required for the detection pipeline to test for differences in detection accuracy. We compared the results from each iteration to phenotypic antimicrobial susceptibility results, and generated estimates of sensitivity and specificity using regression models that controlled for the effects of multiple sampling events and variables, and interactions between covariates. Results from our analyses revealed small, yet significant effects of the input parameters on the sensitivity and specificity of the AMR detection tool, and these effects differed based on the serovar and drug class in question. Findings from this study may have implications for the incorporation of whole-genome sequence-based approaches to the surveillance of AMR determinants in bacteria sampled from food products and animals related to food production.