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- Mapping of key bacterial species for Postmorteminterval calculationPublication . Ferreira, Ana Cláudia; Barbosa, Daniel J.; Campos, Carla; Oliveira, Ricardo Jorge Dinis; Freitas, Ana R.Estimation of the PostmortemInterval (PMI), the time elapsed since death, is one of the most challenging issues in forensic sciences. Most studies focus on extensive bacterial sequencing, but culture-based experiments for higher taxonomic resolution remain scarce. We aimed to analyze total bacterial counts and map Enterococcus faecalis, Staphylococcus aureusand Escherichia coliin different organs and timepoints. Male C57BL/6J SPF mice underwent three independent assays during 11 postmortemtimepoints. Feces and organs (n=10: intestine/stomach/skeletical muscle/liver/spleen/kidney/bladder/lungs/ brain/heart) were collected and resuspended in buffered peptone water, then plated onto enriched nonselective and selective culture media (n=4). Following routine aerobic incubation, Colony Forming Units (CFU) per gram/tissue or per mL/sample were quantified for total/individual bacterial loads. Species were identified by MALDI-TOF MS and statistics were done in GraphPad-Prism v.10.0.1. Species (n=44) from 13 families and 3 phyla were identified, with notable consistency in the presence of Staphylococcus xylosus, E. faecalis, and E. coliacross all experiments. Particular families were consistently identified across all organs, including Enterococcaceae and Enterobacteriaceae mostly in the later stages of decomposition, and Bacillaceae resisting often until the last timepoint, whereas Staphylococcaceae was variably detected. The early and substantial contamination observed in skeletal muscle, stomach, and intestine, makes them unsuitable for PMI calculations. E. faecalisappeared promising as a potential biomarker for kidney, liver, and, possibly, brain invasion at later timepoints, whereas E. faecalisand E. coliin the bladder, and E. coliin the spleen and heart, warrant further investigation for similar biomarker potential. This is one of the first quantitative cultural studies assessing how time elapsing postmortem affects the growth/evolution of key bacterial species, with E. faecalisand E.coliemerging as promising traceable biomarkers in real postmortem contexts. While recognizing the limitations of not considering the complex microbiota network, our pilot study brings an easy species-specific approach and offers a baseline for future human-oriented investigations.
- Dairy cattle and the iconic autochthonous cattle in northern Portugal are reservoirs of multidrug-resistant Escherichia coliPublication . Quinteira, Sandra; Dantas, Rui; Pinho, Luís; Campos, Carla; Freitas, Ana R.; Brito, Nuno V.; Miranda, Carla; Campos, CarlaAnimals destined for human consumption play a key role in potentially transmitting bacteria carrying antibiotic resistance genes. However, there is limited knowledge about the carriage of antibiotic-resistant bacteria in native breeds. We aimed to characterize the phenotypic profiles and antibiotic resistance genes in Escherichia coli isolated from bovines, including three native Portuguese bovine breeds. Forty-nine E. coli isolates were selected from 640 fecal samples pooled by age group (eight adult or eight calf samples) from each farm, representing both dairy cattle raised in intensive systems and meat cattle raised in extensive systems in Northern Portugal. The presumptive E. coli colonies plated onto MacConkey agar were confirmed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The antibiotic resistance profiles were screened by antimicrobial susceptibility testing (EUCAST/CLSI guidelines), and the antibiotic resistance genes by PCR. Most isolates showed resistance to ampicillin (69%), tetracycline (57%), gentamicin (55%), and trimethoprim + sulfamethoxazole (53%), with no resistance to imipenem. Resistance to at least one antibiotic was found in 92% of isolates, while 59% exhibited multidrug resistance. Most calf isolates, including those from native breeds, showed a multidrug-resistant phenotype. Among the adults, this was only observed in Holstein-Friesian and Barrosã cattle. None of the Holstein-Friesian isolates were susceptible to all the tested antibiotics. ESBL-producing E. coli was identified in 39% of isolates, including those from Holstein-Friesian calves and adults, Cachena calves and Minhota adults. The sul2 gene was detected in 69% of isolates, followed by blaCTX-M (45%), aac(3′)-IV (41%), and aac(6′)-Ib-cr (31%), with a higher prevalence in adults. This pioneering study highlights the concerning presence of multidrug-resistant E. coli in native Portuguese cattle breeds.