Risk assessment modelling of fecal shedding caused by extended-spectrum cephalosporin-resistant Escherichia coli transmitted through waste milk fed to dairy pre-weaned calves

An Overview of Waste Milk Feeding Effect on Growth Performance, Metabolism, Antioxidant Status and Immunity of Dairy Calves

Waste milk (WM) is a part of the milk produced on dairy farms, which is usually unsuitable for human consumption. The WM contains transition milk, mastitis milk, colostrum, milk with somatic cells, blood (Hemolactia), harmful pathogens, pathogenic and antibiotic residues. Due to the high cost of milk replacer (MR), dairy farmers prefer raw WM to feed their calves. It has been well established that WM has a greater nutritive value than MR. Hence WM can contribute to improved growth, rumen development, and immune-associated parameters when fed to dairy calves. However, feeding raw WM before weaning has continuously raised some critical concerns. The pathogenic load and antibiotic residues in raw WM may increase the risk of diseases and antibacterial resistance in calves. Thus, pasteurization has been recommended as an effective method to decrease the risk of diseases in calves by killing/inhibiting the pathogenic microorganisms in the raw WM. Altogether, the current review provides a brief overview of the interplay between the positive role of raw WM in the overall performance of dairy calves, limitations of raw WM as a feed source and how to overcome these issues arising from feeding raw WM.

Reduced Antibacterial Drug Resistance and bla CTX-M β-Lactamase Gene Carriage in Cattle-Associated Escherichia coli at Low Temperatures, at Sites Dominated by Older Animals, and on Pastureland: Implications for Surveillance

Little is known about the drivers of critically important antibacterial resistance in species with zoonotic potential present on farms (e.g., CTX-M β-lactamase-positive Escherichia coli). We collected samples monthly between January 2017 and December 2018 on 53 dairy farms in South West England, along with data for 610 variables concerning antibacterial usage, management practices, and meteorological factors. We detected E. coli resistant to amoxicillin, ciprofloxacin, streptomycin, and tetracycline in 2,754/4,145 (66%), 263/4,145 (6%), 1,475/4,145 (36%), and 2,874/4,145 (69%), respectively, of samples from fecally contaminated on-farm and near-farm sites. E. coli positive for bla _CTX-M were detected in 224/4,145 (5.4%) of samples. Multilevel, multivariable logistic regression showed antibacterial dry cow therapeutic choice (including use of cefquinome or framycetin) to be associated with higher odds of bla _CTX-M positivity. Low average monthly ambient temperature was associated with lower odds of bla _CTX-M E. coli positivity in samples and with lower odds of finding E. coli resistant to each of the four test antibacterials. This was in addition to the effect of temperature on total E. coli density. Furthermore, samples collected close to calves had higher odds of having E. coli resistant to each antibacterial, as well as E. coli positive for bla _CTX-M Samples collected on pastureland had lower odds of having E. coli resistant to amoxicillin or tetracycline, as well as lower odds of being positive for bla _CTX-M IMPORTANCE Antibacterial resistance poses a significant threat to human and animal health and global food security. Surveillance for resistance on farms is important for many reasons, including tracking impacts of interventions aimed at reducing the prevalence of resistance. In this longitudinal survey of dairy farm antibacterial resistance, we showed that local temperature-as it changes over the course of a year-was associated with the prevalence of antibacterial-resistant E. coli We also showed that prevalence of resistant E. coli was lower on pastureland and higher in environments inhabited by young animals. These findings have profound implications for routine surveillance and for surveys carried out for research. They provide important evidence that sampling at a single time point and/or single location on a farm is unlikely to be adequate to accurately determine the status of the farm regarding the presence of samples containing resistant E. coli.

The Effects of Feeding Waste Milk Containing Antimicrobial Residues on Dairy Calf Health

A number of studies have reported that there is a high prevalence of antimicrobial-resistant faecal bacteria excreted by dairy calves. Although faecal shedding is influenced by a variety of factors, such as the environment and calf age, feeding milk with antimicrobial residues contributes significantly to an increased prevalence of antimicrobial-resistant (AMR) bacteria, such as extended spectrum beta-lactamase (ESBL)-producing E. coli. As a follow-up to the European Food Safety Authority (EFSA) Scientific Opinion on the risk of AMR development in dairy calves published in January 2017, this review aims to illustrate more recent research in this area, focusing on the period 2016 to 2020. A total of 19 papers are reviewed here. The vast majority assess the commensal faecal bacteria, E. coli, isolated from dairy calves, in particular its antimicrobial-resistant forms such as ESBL-producing E. coli and AmpC-producing E. coli. The effect of waste milk feeding on the prevalence of pathogens such as Salmonella spp. has also been investigated. Current research findings include positive effects on daily liveweight gain and other advantages for calf health from feeding waste milk compared to milk replacer. However, the negative effects, such as the demonstrable selection for antimicrobial-resistant bacteria, the shift in the intestinal microbiome and the possible negative consequences that these could have on global public health, should always be taken into consideration.

Fecal Carriage and Whole-Genome Sequencing-Assisted Characterization of CMY-2 Beta-Lactamase-Producing Escherichia coli in Calves at Czech Dairy Cow Farm

The study aimed to monitor the fecal shedding of cefotaxime-resistant Escherichia coli (CREC) in a cohort of healthy calves on a dairy farm with documented antimicrobial usage and to characterize selected AmpC beta-lactamase-producing E. coli isolates. Fecal samples from 13 suckling calves (1-63 d of age; 113 samples in total) were repeatedly collected and cultivated on MacConkey agar with cefotaxime (2 mg/L). Resistant colonies were counted, and one colony obtained from the highest dilution of each fecal sample was identified by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry. Susceptibility to antimicrobials and production of AmpC and extended-spectrum beta-lactamase (ESBL) were tested. No ESBL-producing E. coli was found, but representative AmpC-positive E. coli isolates were subjected to further typing and whole-genome sequencing (WGS) for the analysis of clonal relationships, resistance genes, virulence factors, and plasmid replicons. High amounts of CREC were detected in the feces of all 13 calves during the study. The number of CREC colonies varied from 1.0 log₁₀ to 8.0 log₁₀ colony-forming unit per gram. Drops in CREC density or its discontinued shedding were recorded at the end of the study period. A total of 82 (94%, n = 87) CREC isolates were confirmed as AmpC producers and all but one showed resistance to multiple antimicrobials. Twenty-nine selected AmpC-positive E. coli isolates belonged to 12 and 13 unique rep-PCR fingerprints and pulsed-field gel electrophoresis types, respectively, highlighting the variation in E. coli genotypes in individual calves. WGS of 10 selected isolates showed diverse antimicrobial resistance and virulence gene content and the presence of a bla_CMY-2 gene carried by an IncK2 plasmid. Clinically important multiresistant E. coli isolates belonging to emerging extraintestinal pathogenic E. coli ST69 and ST648 lineages were found. Our findings reinforce the urgency of efforts to prevent the spread of ESBL-/AmpC-producing bacteria in dairy cow farms.

Risk factors associated with E. coli causing neonatal calf diarrhea

Calf diarrhea is one of the major health challenges in cattle herds. The bacteriological examination of fecal samples collected from apparently healthy and diarrheic calves' revealed isolation of 26 E. coli isolates out of 56 calves with an incidence of 46.4%. Serogroups O1, O26, O44, O55, O115, O119, O125, O146, and O151 were identified from the collected fecal samples. Using PCR all isolates was positive for ompA gene species specific for E. coli. While stx1 and eaeA genes detected with incidence of 3.8 and 19.2% respectively from the isolates. The presence of stx2 gene was negative in the fecal isolates. Among colostrum samples 4 E. coli isolates were detected and serogrouped to O26, O55 and O119. They were negative for eaeA, stx1 and stx2 except strain number 4 (O55) was positive for stx1. E. coli strains were sensitive to norfloxacin (80.7%) and resistant to ampicillin and cefotaxime (100% each). Based on our findings, there was no association between occurrence of E. coli and age of calf (2–14 days), while bottle feeding calf colostrum may be a source of E. coli contamination.

Multidrug residues and antimicrobial resistance patterns in waste milk from dairy farms in Central California

Waste milk (WM) is a common source of feed for preweaned calves in US dairy farms. However, limited information is available about characteristics of this product, including concentration of drug residues and potential hazards from antibiotic-resistant bacteria present in the milk. The aims of this cross-sectional study were to (1) identify and measure the concentration of antimicrobial residues in raw WM samples on dairy farms in the Central Valley of California, (2) survey farm management practices for factors associated with the occurrence of specific antimicrobial residues in raw WM, (3) characterize the antimicrobial resistance patterns of E. coli cultured from raw WM samples, and (4) evaluate the potential association between WM quality parameter and risk of identifying drug residues in milk. A single raw bulk tank WM sample was collected from dairy farms located in California's Central Valley (n = 25). A questionnaire was used to collect information about farm management practices. Waste milk samples were analyzed for a multidrug residue panel using liquid chromatography-tandem mass spectrometry. Bacteria were cultured and antimicrobial resistance was tested using standard techniques; milk quality parameters (fat, protein, lactose, solids-not-fat, somatic cell count, coliform count, and standard plate count) were also measured. Of the 25 samples collected, 15 (60%) contained detectable concentrations of at least 1 antimicrobial. Of the drug residue-positive samples, 44% (11/25) and 16% (4/25) had detectable concentrations of β-lactams and tetracycline, respectively. The most prevalent drug residues were ceftiofur (n = 7, 28%), oxytetracycline (n = 4, 16%), and cephapirin (n = 3, 12%). No significant associations were identified between farm characteristics or management practices and presence of drug residues in WM. In this study, 20% of farms did not pasteurize WM before feeding to calves. Two of the 10 Escherichia coli isolated from WM samples were multidrug resistant. Streptococcus spp. (n = 21, 84%) was the most common genus cultured from WM samples, followed by Staphylococcus spp. (n = 20, 80%) and E.coli (n = 10, 40%). Mycoplasma spp. was cultured from 2 WM samples (n = 2, 8%). The presence of drug residues in WM at concentrations that increase selection of resistant bacteria indicates the need for additional studies targeting on-farm milk treatments to degrade drug residues before feeding to calves. The presence of multidrug-resistant E. coli in WM urges the need for on-farm practices that reduce calf exposure to resistant bacteria, such as pasteurization.