Biology subjects

Blum, S. E.

Publications and source records attributed to Blum, S. E..

4 recordsLinked to original sources

bioRxiv2026

Extended-Spectrum and Last-Resort β-Lactams Exert Increasing Impacts on Chicken Manure-Derived Copiotrophic Microbiomes and Resistomes

Understanding the environmental dissemination of antimicrobial resistance (AMR) is crucial for mitigating its spread and for reducing the clinical burden of resistant infections. Within a One Health framework, animal husbandry systems, and particularly animal gut microbiomes, are widely used as models for agricultural environments, because their high densities and recurrent antibiotic exposure create strong selective pressures that can impact both environmental and human resistomes. In a previous study, we demonstrated that copiotrophic enrichment in medium that stimulates growth of gut-associated bacteria, can reveal clinically associated bacterial populations and associated antibiotic resistance genes (ARGs) that are not detected by direct environmental sampling. In the present study, we applied this enrichment approach to poultry manure to examine how {beta}-lactamase-resistant antibiotics (cefotaxime and meropenem) shape copiotrophic gut-like microbial community composition and resistance profiles relative to an earlier {beta}-lactam (ampicillin) and to antibiotic-free controls. Our results show that {beta}-lactamase-resistant antibiotics induced more pronounced shifts in both microbial diversity and ARG profiles than the early {beta}-lactam. When focusing on specific taxa, differential responses were observed correlating to antimicrobial range of action. Together, these findings underline how the diversity of pathogen and AMR indicators in gut microbiomes may be shaped by different selective pressures imposed by {beta}-lactamase-resistant antibiotics.

microbiology↗

bioRxiv2024

Occurrence of "under-the-radar" antibiotic resistance in anthropogenically affected produce

With global climate change, treated-wastewater (TWW) irrigation and manure amendment are becoming increasingly important in sustainable agriculture in water- and nutrient-stressed regions. Yet, these practices can potentially disseminate pathogens and antimicrobial resistance (AMR) determinants to crops, resulting in serious health risks to humans through the food chain. Previous studies demonstrated that pathogen and AMR indicators from wastewater and manure survive poorly in the environment, suggesting that ecological barriers prevent their dissemination. However, we recently found that these elements can persist below detection levels in low quality TWW-irrigated soil, and potentially proliferate under favorable conditions. This "under the radar" phenomenon was further investigated here, in TWW irrigated- and poultry litter-amended lettuce plants, using an enrichment platform that resembles gut conditions, and an analytical approach that combined molecular and cultivation-based techniques. Enrichment uncovered clinically-relevant multidrug resistant pathogen indicators and a myriad of antibiotic resistance genes in the litter amended and TWW-irrigated lettuce that were not detected by direct analyses, or in the enriched freshwater irrigated samples. Selected resistant E. coli isolates were capable of horizontally transferring plasmids carrying multiple resistance genes to a susceptible strain. Overall, our study underlines the hidden risks of under-the-radar pathogen and AMR determinants in anthropogenically affected agroenvironments, providing a novel platform to improve quantitative microbial risk assessment models in the future.

microbiology↗

bioRxiv2019

The physiological response in the mammary gland to Escherichia coli infection reflects a conflict between glucose need for milk production and immune response

Upon entry into the mammary gland, mammary pathogenic strains of Escherichia coli rapidly grow using milk as a nutrient source, in a manner highly dependent on the expression of the ferric-dicitrate system by these bacteria. Intra-mammary challenge with distinct mammary pathogenic E. coli (MPEC) strains result in development of clinical acute mastitis, with peak bacterial counts in milk at 16-24 h post-challenged and profound immune changes found in the milk. The main biochemical changes measured in milk were partially in accord with lipopolysaccharide-induced mastitis, with increased glucose-6-phosphate and lactate dehydrogenase activity or prolonged lactate dehydrogenase, and Glu6P/Glu alterations. Changes also reflect physiological responses to inflammation in the mammary gland, as in the balance between aerobic and anaerobic metabolism (citrate to lactate ratios). Some alterations measured in milk resolved with days after challenge but other remained for above one month, regardless of bacterial clearance. The results suggest that E. coli mastitits can be divided into two stages: an acute, clinical phase, as an immediate response to bacterial infection in the mammary gland and a chronic phase, independent of bacteria clearance, and in response to the tissue damage caused in the first phase.

physiology↗

bioRxiv2019

Increasing the value of raw bulk milk quality based on mammary glands as production units vs. the udder in dairy cows with mastitis

The current study measured the influence of milk of subclinically infected glands by different bacteria species on the cows milk and suggests different parameters for milk payment. The effects of bacterial infection or inflammation on gland milk yield were related to the bacteria species that caused the infection. The volume of milk of the inflamed gland from the cows milk yield was significantly lower (P<0.001) for the glands previously infected by Escherichia coli (PIEc) and those infected with Streptococcus dysgalactiae. Coagulation properties, rennet clotting time (RCT) and curd firmness (CF) also depended on the bacteria causing the infection. RCT values of all the inflamed glands were significantly longer (P<0.001) and CF values were significantly lower than that of the healthy ones. Moreover, in the whole milk, CF was also significantly lower and not proportional to the volume of the milk from the inflamed gland of the cows milk. Calculating the predicted 40% dry matter curd weight (PCW) on the cow level, including the healthy and inflamed glands or the healthy glands alone, found that for 9 of 13 PIEc cows, the presence of the affected glands milk in the whole cow milk resulted in a negative PCW value. Likewise, 5 of 20 cows infected by S. dysgalactiae had negative delta values. Unlike the latter bacteria, PCW from milk of glands infected with CNS increased, although in a lower magnitude than in the healthy glands. No correlation was found between logSCC in the whole cow milk (healthy and inflamed glands) and PCW.

systems biology↗