Survey on Antimicrobial Residues in Raw Milk and Antimicrobial Use in Dairy Farms in the Emilia-Romagna Region, Italy

Screening of antibiotic residues in raw bovine milk in Lombardy, Italy: Microbial growth inhibition assay and LC-HRMS technique integration for an accurate monitoring

Antibiotic residues in food of animal origin is a great concern for public health worldwide in terms of antibiotic resistance development, potential allergic reactions and disruption of intestinal flora equilibrium. In this study the presence of antibiotic residues in raw bovine milk samples collected from farms located in Lombardy region in Italy from 2018 to 2022 was assessed in the context of the national milk quality payment system. Samples were screened with microbiological growth inhibition test Delvotest ® SP NT and a very low positivity rate ranging from 0.1% to 0.07% over the four years was determined. A total of 79 positive samples were further analysed by LC-HRMS screening technique to confirm positivity and detect the specific antibiotic compound contaminating the sample. The β-lactam antibiotics resulted to be the most frequently detected, with the penicillin G being the most abundant compound. The data suggested that low levels of antibiotic contamination are consistently maintained over the last four years and the integration of the techniques used in this study is a valuable tool for a deep and precise monitoring of antibiotic residues in milk.

Toxicologic, transcriptomic, and metabolomic insights into the effect of a mixture of 26 veterinary antimicrobials on rat liver

To evaluate the maximum possible hazard of veterinary antimicrobial mixtures at doses accessible to humans, Sprague-Dawley male rats were orally dosed with a mixture of 26 commonly used veterinary antimicrobials for 90 consecutive days. The daily dosage of each component was 100 times (G1), 10 times (G2) and, 1 time (G3) of acceptable daily intake (ADI) in China. Hematology analysis and biochemical analysis found significant changes of several parameters, suggesting liver damage. Histopathological examination further indicated that mixtures of veterinary drugs at three levels caused obvious hepatotoxicity, and the severity of damage increased with dosage. LC-MS-based metabolomics analysis was carried out to detect metabolite changes in liver tissue. In G1, G2, and G3, 208, 165, and 195 differential accumulated metabolites (DAMs) compared with the Ctrl group were filtered, respectively. Similarly, RNA-seq helped us to filter a total of 183, 118, and 38 differentially expressed genes (DEGs) in G1, G2, and G3 compared with the Ctrl group, respectively. By integrating with the transcriptomic and metabolomic data, we revealed that mineral absorption, ascorbate and aldarate metabolism may be the major pathways affected by the veterinary antimicrobial mixtures in our study. This study provided useful data for the risk assessment of multiple chemicals.

GPGMH, a New Fixed Timed-AI Synchronization Regimen for Swamp and River Crossbred Buffaloes (Bubalus bubalis)

The crossbreeding of Swamp and River type buffalo breeds is practiced for the improvement of milk yield and reproductive performance in swamp buffalo herds. This study aimed to modify the Ovsynch synchronization protocol (GPG) and improve the fixed-timed artificial insemination (FTAI) for better reproductive performance of crossbred buffaloes. Comparison of four conventional synchronization protocols [pregnant mare gonadotropin-prostaglandin F₂α-gonadotropin-releasing hormone (PmPG), gonadotropin-releasing hormone-prostaglandin F₂α-gonadotropin-releasing hormone (GPG), prostaglandin F₂α-gonadotropin-releasing hormone-prostaglandin F₂α-estradiol benzoate (PGPE), and progesterone-pregnant mare gonadotropin-prostaglandin F₂α-gonadotropin-releasing hormone (P₄PmPG)] in crossbred buffaloes showed that the GPG protocol treated buffaloes displayed higher (P < 0.05) estrus response with an increasing tendency in ovulation (84.6%) and pregnancy rates (30.8%) than PmPG, PGPE, and P₄PmPG treated buffaloes. Buffaloes treated with a dose of 0.4 (mg/kg) mifepristone combined with GPG, exhibited higher (P < 0.05) estrous response (82.4%), ovulation (94.1%), and pregnancy (47.1%) rates compared with other doses (0, 0.3, or 0.5 mg/kg) groups. Injection of mifepristone along second GnRH injection in buffaloes improved (P < 0.05) pregnancy rate (35.3%) when compared to before or after the second GnRH of GPG protocol. Single AI after 24 h of mifepristone or second GnRH injection seems the best time to enhance the pregnancy rates in buffaloes compared to double or other single AI times in the modified GPGMH protocol. In comparison, GPGMH reduced the follicular cyst incidence (P < 0.05) with increasing ovulation (P > 0.05) and pregnancy rates (P > 0.05) than the P₄GPG and GPG protocols in crossbred buffaloes. The current study supported that new synchronization protocol (modified of GPG protocol; GPGMH) by the inclusion of mifepristone (with a dose of 0.4 mg/kg along second GnRH), AI after 24 h of mifepristone or second GnRH, and human chorionic gonadotropin (hCG at day 5 of AI) enhance the ovulation and pregnancy rates in crossbred buffaloes.

Role prediction of Gram-negative species in the resistome of raw cow's milk

Extended use of antibiotics in dairy farming for therapeutic and prophylactic reasons, but also the higher prevalence of antibiotic resistant bacteria (ARB) in the farm environment raised the concern of consuming raw cow's milk and its derived products. The aim of this study was to predict by shotgun metagenomic analyses the presence of antibiotic resistance genes (ARGs) mainly correlated with Gram-negative bacteria in antibiotic residue free raw cow's milk derived exclusively from healthy animal from South Tyrol (Northern Italy), chosen as a model system. Assessment of shotgun metagenomic data of reconstructed scaffolds, revealed the existence of Pseudomonas spp. as the most abundant Gram-negative species in the raw cow's milk samples bearing ARGs. Besides, ARGs also linked to lactic acid bacteria such as Lactococcus sp. and Lactobacillus sp. ARGs correlated to microbiome found in milk samples conferred resistance towards aminoglycoside-streptothricin, beta-lactamase, macrolide, tetracycline, carbapenem, cephalosporin, penam, peptide, penem, fluoroquinolone, chloramphenicol and elfamycin antibiotics. Further bioinformatic processing included de-novo reassembly of all metagenomic sequences from all milk samples in one, to reconstruct metagenome assembled genomes (MAGs), which were further used to investigate mobile genetic elements (MGE). Analyses of the reconstructed MAGs showed that, MAG 9 (Pseudomonas sp1.) contained the oriT gene (origin of transfer gene) needed for transferring virulent factors. Although the presence of Pseudomonas is common in raw cow's milk, pasteurization treatment reduces their survivability. Nevertheless, attention should be paid on Pseudomonas spp. due to their intrinsic resistance to antibiotics and their capability of transferring virulent factors to other bacteria.

Do Dairy Farming Systems Differ in Antimicrobial Use?

Simple Summary

The overuse and misuse of antimicrobials in dairy farming may lead to the development of antimicrobial resistance and thus to the reduction of the antimicrobial treatment efficacy against animal or human bacterial diseases. This study aims to investigate antimicrobial use differences in four farm groups: mountain farms with specialized high-yield dairy breeds or with dual-purpose breeds raised for milk production, and lowland farms with specialized high-yield dairy breeds or with dual-purpose breeds raised for milk production. From the results, we found a significant difference between mountain farms with dual-purpose breeds and lowland farms with specialized breeds for the overall antimicrobial use and for the use of those antimicrobial classes that are most important in human medicine. Mountain farms have a generally lower milk production and smaller herd size than lowland farms, provide cows with access to pasture, and limit concentrates in the diet. These management practices and the use of local/dual-purpose breeds could reduce the risk of production diseases and the consequent need for antimicrobial use.

Abstract

The quantitative assessment of antimicrobial use (AMU) in food-producing animals contributes to the provision of essential information for developing relevant and effective policies to reduce use and to control antimicrobial resistance. Information on AMU is available mainly for intensive dairy farming systems and specialized high-yielding breeds. The aim of this study is to investigate AMU in different dairy farming systems by comparing the treatment incidence in mountain farms with specialized high-yield dairy breeds or with dual-purpose breeds raised for milk production to the treatment incidence in lowland farms with specialized high-yield dairy breeds or with dual-purpose breeds raised for milk production. Significant differences were found only between the overall treatment incidence, as well as the treatment incidence of highest-priority critically important antimicrobials for human medicine, in lowland farms with high-yielding breeds and mountain farms with dual-purpose breeds. Mountain farms have a generally lower milk production and smaller herd size than lowland farms, provide cows with access to pasture, and limit concentrates in the diet. These management practices and the use of local/dual-purpose breeds could reduce the risk of production diseases and the consequent need for AMU.

Antimicrobial Usage in Animal Production: A Review of the Literature with a Focus on Low- and Middle-Income Countries

Antimicrobial use (AMU) in animal production is a key contributor to antimicrobial resistance (AMR) worldwide. As consumption of animal protein and associated animal production is forecast to increase markedly over coming years in low- and middle-income countries (LMICs), accurate monitoring of AMU has become imperative. We summarized data from 89 scientific studies reporting AMU data in animal production published in English since 1998, identified through the 'ISI Web of Knowledge' search engine. The aims were as follows: (a) to describe methodologies and metrics used to quantify AMU; (b) to summarize qualitative (on-farm prevalence of use) and quantitative (amounts of antimicrobial active principle) data, in order to identify food animal species at the highest risk of AMU; and (c) to highlight data gaps from LMICs. Only 17/89 (19.1%) studies were conducted in LMICs. Sixty (67.3%) reported quantitative data use, with 'daily doses per animal-time' being the most common metric. AMU was greatest in chickens (138 doses/1000 animal-days [inter quartile range (IQR) 91.1⁻438.3]), followed by swine (40.2 [IQR 8.5⁻120.4]), and dairy cattle (10.0 [IQR 5.5⁻13.6]). However, per kg of meat produced, AMU was highest in swine, followed by chickens and cattle. Our review highlights a large deficit of data from LMICs, and provides a reference for comparison with further surveillance and research initiatives aiming to reduce AMU in animal production globally.

Detection of tetracycline and other antimicrobial residues in milk from cows with clinical mastitis treated by combination therapy

The purpose of this study was to determine tetracycline and other antimicrobial residues in milk from dairy cows treated for clinical mastitis. Data on cow health and drugs used were obtained from the farm veterinarians. A milk sample from each affected udder quarter of each cow was taken for bacterial identification before treatment. All 35 cows in the study were treated with an intramammary product containing tetracycline, neomycin, bacitracin, and prednisolone (tetracycline injector) and also simultaneously with other drugs via the intramammary or parenteral route. The withhold period of the 'tetracycline product' was eight milkings but, in all cases, longer withhold periods were prescribed due to off-label application of additional combinations of drugs. Milk samples from treated udder quarters, taken two milkings before and two after the prescribed withhold period, were analysed for antimicrobial residues. Additionally, milk samples were taken from untreated healthy udder quarters to check if any crossover of drugs had occurred. Three screening tests were used for antimicrobial detection. In 15 (42·9%) cows the milk samples from the treated infected quarters contained tetracycline residues above the maximum residue limit (MRL) after the prescribed withhold period and, in two cases (5·7%) the same was true for neomycin and cefquinome residues. Cephalexin above the MRL was detected in only one case (2·9%). Beta-lactams did not exceed the MRL after the prescribed withhold period. Antimicrobial residues were not detected in milk samples from untreated quarters. Cow condition including parity, decreased milk production and severity of mastitis significantly influenced the excretion of antimicrobials in milk (P ≤ 0·05). No significant differences were found between the tetracycline positive and tetracycline negative cows regarding the bacteria involved, combination antimicrobial therapy, or treatment interval and duration.