Foodborne infections with antimicrobial-resistant Campylobacter spp. remain an important public health concern. Publicly available data collected by the National Antimicrobial Resistance Monitoring System for Enteric Bacteria related to antimicrobial resistance (AMR) in Campylobacter spp. isolated from broiler chickens and turkeys at the slaughterhouse level across the United States between 2013 and 2021 were analysed. A total of 1,899 chicken-origin (1,031 Campylobacter coli (C. coli) and 868 Campylobacter jejuni (C. jejuni)) and 798 turkey-origin (673 C. coli and 123 C. jejuni) isolates were assessed. Chicken isolates exhibited high resistance to tetracycline (43.65%), moderate resistance to ciprofloxacin (19.5%), and low resistance to clindamycin (4.32%) and azithromycin (3.84%). Turkey isolates exhibited very high resistance to tetracycline (69%) and high resistance to ciprofloxacin (39%). The probability of resistance to all tested antimicrobials, except for tetracycline, significantly decreased during the latter part of the study period. Turkey-origin Campylobacter isolates had higher odds of resistance to all antimicrobials than isolates from chickens. Compared to C. jejuni isolates, C. coli isolates had higher odds of resistance to all antimicrobials, except for ciprofloxacin. The study findings emphasize the need for poultry-type-specific strategies to address differences in AMR among Campylobacter isolates.

Turkeys are important sources of antimicrobial-resistant Campylobacter. A total of 1063 isolates were obtained from 293 turkey flocks across Canada between 2016 and 2021 to evaluate their antimicrobial resistance (AMR) prevalence, patterns, distribution, and association with antimicrobial use (AMU). A high proportion of C. jejuni and C. coli isolates were resistant to tetracyclines and fluoroquinolones, despite the very low use of these drugs. C. jejuni isolates had a higher probability of being resistant to tetracyclines than C. coli isolates. The chance of C. jejuni isolates being resistant to fluoroquinolones, macrolides, and lincosamides was lower compared to C. coli. Isolates from the western region had a higher probability of being resistant to fluoroquinolones than isolates from Ontario. Isolates from Ontario had higher odds of being resistant to tetracyclines than isolates from Quebec. No associations were noted between the resistance and use of the same antimicrobial, but the use of certain antimicrobial classes may have played a role in the maintenance of resistance in Campylobacter (fluoroquinolone resistance – bacitracin and streptogramin use, tetracycline resistance – flavophospholipids and streptogramins use, macrolide resistance – flavophospholipid use). Low-level multidrug-resistant Campylobacter was observed indicating a stable AMR in turkeys. This study provided insights aiding future AMU and AMR surveillance.

Monocytes and macrophages are involved in a wide range of biological processes and parasitic diseases. The characterization of the molecular mechanisms governing such processes usually requires precise control of the expression of genes of interest. We implemented a tetracycline-controlled gene expression system in the U937 cell line, one of the most used in vitro models for the research of human monocytes and macrophages. Here we characterized U937-derived cell lines in terms of phenotypic (morphology and marker expression) and functional (capacity for phagocytosis and for Leishmania parasite hosting) changes induced by phorbol-12-myristate-13-acetate (PMA). Finally, we provide evidence of tetracycline-inducible and reversible Lamin-A gene silencing of the PMA-differentiated U937-derived cells.

Food borne transmission of antibiotic resistant strains of Escherichia coli from contaminated food has been recognised as an important hazard for human health in the past few decades and pathogenic strains of E. coli have long been considered as serious zoonotic hazards. Poultry meat is attractive for consumers worldwide, so the measures to preserve the safety of poultry meat are important issues. Tetracyclines are one of the most frequently used antibiotics in poultry farming and are still used in human medicine. The widespread use of tetracyclines in poultry farming may have resulted in the development and transmission of resistance strains from poultry to humans via the food chain. The relationship between the use of tetracyclines and the presence of resistant strains of E. coli in poultry meat, mainly due to the irregular use of antibiotics, is reviewed in this paper. The need for prudent use of antibiotics, particularly those which are used in human medicine is highlighted. Continuous monitoring and reporting on incidents in the future should improve the current regulations.

The tetracyclines (TTC) and sulfonamides are among the most common residues found in bulk raw milk samples. Detection of drug residues in bulk milk (BM) tankers demonstrates that the product is not suitable for human consumption. Discarding BM with residue-contaminated milk is a waste of a valuable commodity, and a repurposing for consumption at calf ranches is a way to recapture some value. However, if calves consuming milk with drug residues are slaughtered for veal, their meat could contain drug residues. The objective of this review is to provide a residue avoidance strategy for TTC and sulfonamide residues in veal. To determine the pharmacokinetic properties of each drug a structured review of the literature was performed and the study inclusion criteria were that the publication used dairy breed calves, with body weight <330 kg or <6 months of age. The most pertinent parameters were determined to be plasma, tissue elimination half-lives, and systemic bioavailability. The results of this review were integrated with milk and tissue testing levels of quantification and tissue tolerances to formulate a recommended withdrawal interval for calves ingesting this milk. The suggested withdrawal interval of 20 days will ensure that no veal calves will test positive for residues from being fed this milk.

The gastrointestinal tract (GIT) microbiota has been identified as an important reservoir of antibiotic resistance genes (ARGs) that can be horizontally transferred to pathogenic species. Maternal GIT microbes can be transmitted to the offspring, and recent work indicates that such transfer starts before birth. We have used culture-independent genetic screenings to explore whether ARGs are already present in the meconium accumulated in the GIT during fetal life and in feces of 1-week-old infants. We have analyzed resistance to β-lactam antibiotics (BLr) and tetracycline (Tcr), screening for a variety of genes conferring each. To evaluate whether ARGs could have been inherited by maternal transmission, we have screened perinatal fecal samples of the 1-week-old babies’ mothers, as well as a mother–infant series including meconium, fecal samples collected through the infant’s 1st year, maternal fecal samples and colostrum. Our results reveal a high prevalence of BLr and Tcr in both meconium and early fecal samples, implying that the GIT resistance reservoir starts to accumulate even before birth. We show that ARGs present in the mother may reach the meconium and colostrum and establish in the infant GIT, but also that some ARGs were likely acquired from other sources. Alarmingly, we identified in both meconium and 1-week-olds’ samples a particularly elevated prevalence of mecA (>45%), six-fold higher than that detected in the mothers. The mecA gene confers BLr to methicillin-resistant Staphylococcus aureus, and although its detection does not imply the presence of this pathogen, it does implicate the young infant’s GIT as a noteworthy reservoir of this gene.

The tetracyclines (TCs) are widely used in the treatment of several diseases of cattle and their residues may be present in milk. To control these residues it is necessary to have available inexpensive screening methods, user-friendly and capable of analysing a high number of samples. The purpose of this study was to design a bioassay of microbiological inhibition in microtiter plates with spores of Bacillus pumilus to detect TCs at concentrations corresponding to the Maximum Residue Limits (MRLs). Several complementary experiments were performed to design the bioassay. In the first study, we determined the concentration of spores that produce a change in the bioassay's relative absorbance in a short time period. Subsequently, we assessed the concentration of chloramphenicol required to decrease the detection limit (DL) of TCs at MRLs levels. Thereafter, specificity, DL and cross-specificity of the bioassay were estimated. The most appropriate microbiological inhibition assay had a B. pumilus concentration of 1·6 × 109 spores/ml, fortified with 2500 μg chloramphenicol/l (CAP) in Mueller Hinton culture medium using brilliant black and toluidine blue as redox indicator. This bioassay detected 117 μg chlortetracycline/l, 142 μg oxytetracycline/l and 105 μg tetracycline/l by means of a change in the indicator's colour in a period of 5 h. The method showed good specificity (97·9%) which decreased slightly (93·3%) in milk samples with high somatic cell counts (>250 000 cells/ml). Furthermore, other antimicrobials studied (except neomycin) must be present in milk at high concentrations (from >5 to >100 MRLs) to produce positive results in this assay, indicating a low cross specificity.

Advances in nanotechnology observe new applications in many areas. Recently a great extent of research has been focused on the study of magnetic nanoparticles due to their potential application in areas such as bioscience and medicine. Magnetic nanoparticles are frequently used in biomedical and biotechnology applications since these particles associated to a given medicine are good candidates for drug release.

In this work zeta potential measurements of both hexagonal barium ferrites (magnetic nanoparticles), and an antibiotic known as tetracycline were carried out. The knowledge of the measured values establishes the possibility of bringing the two particles together in order to adsorb the tetracycline on the magnetic nanoparticles, since the surface charge play an essential role in the adsorption of the pharmaceutical drug on nanomaterials (i.e., tetracycline on barium ferrites).

Experimental results show the feasibility to adsorb tetracycline nanoparticles on barium hexaferrite solids at pH 7.0, based on the knowledge of the opposite electrical surface charge of the two solid species through the zeta potential measurement.

In higher eukaryotes, the regulation of pre-mRNA processing is still poorly known. The accumulation of various mature mRNAs, which can be observed in the nuclei of mammalian cells, is suggestive of a regulatory role of transport. However, the significance of these nuclear mRNA is presently unknown. We have used a tetracycline-regulated promoter to investigate the dynamics of these pools of mRNAs upon arrest of transcription. We observed, for β-globin and LT-α genes, a slow disappearance of these mRNA from the nucleus, with an apparent half-life that is similar to their cytoplasmic half-life. In view of these dynamics, these mRNA cannot simply be mature mRNAs in transit to the cytoplasm. They could be mRNAs retained in the nucleus, provided that the regulation of mRNA stability is comparable in the nucleus and the cytoplasm. But, because of their limited stability, these nuclear mRNAs cannot constitute a significant stock for gene expression. Alternatively, they could reflect a bidirectional transport of mRNA, that is, to and from the cytoplasm, which would provide a direct explanation for the similarity in both compartments of their half-life and poly(A) tail shortening over time.

Le rythme de dépôt des microstries sur les otolithes de Epinephelus microdon a été mesuré grâce à l'injection d'un marqueur fluorescent, la tétracycline ; 14 poissons adultes répartis en cinq lots ont été maintenus en élevage pendant plus de 1 année et leurs otolithes marqués suivant des plans d'expérience différents. En comparant le nombre de microstries comptées entre deux marques fluorescentes ou entre une marque fluorescente et le bord externe de l'otolithe au nombre de jours écoulés entre deux injections ou entre une injection et le sacrifice du poisson, il a été possible d'établir qu'une microstrie est formée en moyenne tous les 2 jours. Cette fréquence varie d'un individu à l'autre et il est montré que le rythme de dépôt des stries est corrélé positivement avec la croissance du poisson mais est indépendant de sa longueur. Parmi les hypothèses envisagées pour expliquer l'écart avec la fréquence journalière, l'arrêt du dépôt des microstries, lors d'interruptions de la croissance squelettique, a été jugée comme la seule explication satisfaisante. Cette étude met donc en évidence la nécessité de valider la période de ces stries avant toute utilisation pour estimer l'âge de poissons adultes par la technique de lecture des otolithes.

The effects of applying varying doses of an antibiotic to fifth instar larvae of Philosamia ricini on the silk glands were studied. Transaminases were increased by low doses, while RNA accumulation was reduced after administration of tetracycline. The levels of DNA showed little response to treating with antibiotic. However, the incorporation of amino acids into silk proteins was generally increased. The overall effects on the silk gland was reflected by its weight, cocoon weight, quantity of raw silk and quality of silk. All these indices were improved by administration of tetracycline.