Antimicrobials are critical to contemporary high-intensity beef production. Many different antimicrobials are approved for beef cattle, and are used judiciously for animal welfare, and controversially, to promote growth and feed efficiency. Antimicrobial administration provides a powerful selective pressure that acts on the microbial community, selecting for resistance gene determinants and antimicrobial-resistant bacteria resident in the bovine flora. The bovine microbiota includes many harmless bacteria, but also opportunistic pathogens that may acquire and propagate resistance genes within the microbial community via horizontal gene transfer. Antimicrobial-resistant bovine pathogens can also complicate the prevention and treatment of infectious diseases in beef feedlots, threatening the efficiency of the beef production system. Likewise, the transmission of antimicrobial resistance genes to bovine-associated human pathogens is a potential public health concern. This review outlines current antimicrobial use practices pertaining to beef production, and explores the frequency of antimicrobial resistance in major bovine pathogens. The effect of antimicrobials on the composition of the bovine microbiota is examined, as are the effects on the beef production resistome. Antimicrobial resistance is further explored within the context of the wider beef production continuum, with emphasis on antimicrobial resistance genes in the food chain, and risk to the human population.

/pdf/antimicrobial-usage-and-resistance-in-beef-production-1hscqzg4wy.pdf

Antimicrobial usage and resistance in beef production

Cephalosporin antibiotics in the aquatic environment: A critical review of occurrence, fate, ecotoxicity and removal technologies

Bacteria from the species Trueperella pyogenes are a part of the biota of skin and mucous membranes of the upper respiratory, gastrointestinal, or urogenital tracts of animals, but also, opportunistic pathogens. T. pyogenes causes a variety of purulent infections, such as metritis, mastitis, pneumonia, and abscesses, which, in livestock breeding, generate significant economic losses. Although this species has been known for a long time, many questions concerning the mechanisms of infection pathogenesis, as well as reservoirs and routes of transmission of bacteria, remain poorly understood. Pyolysin is a major known virulence factor of T. pyogenes that belongs to the family of cholesterol-dependent cytolysins. Its cytolytic activity is associated with transmembrane pore formation. Other putative virulence factors, including neuraminidases, extracellular matrix-binding proteins, fimbriae, and biofilm formation ability, contribute to the adhesion and colonization of the host tissues. However, data about the pathogen–host interactions that may be involved in the development of T. pyogenes infection are still limited. The aim of this review is to present the current knowledge about the pathogenic potential and virulence of T. pyogenes.

Pathogenicity and Virulence of Trueperella pyogenes: A Review.

Mastitis is the most important disease in the dairy industry Antibiotics are considered to be the first choice in the treatment of the disease However, the problem of antibiotic residue and antimicrobial resistance, in addition to the impact of antibiotic abuse on public health, leads to many restrictions on uncontrolled antibiotic therapy in the dairy sector worldwide Researchers have investigated novel therapeutic approaches to replace the use of antibiotics in mastitis control These efforts, supported by the revolutionary development of nanotechnology, stem cell assays, molecular biological tools, and genomics, enabled the development of new approaches for mastitis-treatment and control The present review discusses recent concepts to control mastitis such as breeding of mastitis-resistant dairy cows, the development of novel diagnostic and therapeutic tools, the application of communication technology as an educational and epidemiological tool, application of modern mastitis vaccines, cow drying protocols, teat disinfection, housing, and nutrition These include the application of nanotechnology, stem cell technology, photodynamic and laser therapy or the use of traditional herbal medical plants, nutraceuticals, antibacterial peptides, bacteriocins, antibodies therapy, bacteriophages, phage lysins, and probiotics as alternatives to antibiotics

Bovine mastitis prevention and control in the post-antibiotic era

Despite considerable efforts to control bovine mastitis and explain its causes, it remains the most costly and common disease of dairy cattle worldwide. The role and impact of non-aureus staphylococci (NAS) in udder health are not entirely understood. These Gram-positive bacteria have become the most frequently isolated group of bacteria in milk samples of dairy cows and are associated with (mild) clinical and subclinical mastitis. Different species and strains of NAS differ in their epidemiology, pathogenicity, virulence, ecology and host adaptation, and antimicrobial resistance profiles. They have distinct relationships with the microbiome composition of the udder and may also have protective effects against other mastitis pathogens. Some appear to persist on the skin and in the teat canal and udder, while others seem to be transient residents of the udder from the environment. Analyzing genotypic and phenotypic differences in individual species may also hold clues to why some appear more successful than others in colonizing the udder. Understanding species-level interactions within the microbiome and its interactions with host genetics will clarify the role of NAS in bovine mastitis and udder health.

https://biblio.ugent.be/publication/8708677/file/8709546.pdf

Non-aureus Staphylococci and Bovine Udder Health: Current Understanding and Knowledge Gaps.

The aim of the study was to determine the in vitro sensitivity of 161 Arcanobacterium pyogenes strains and 99 Escherichia coli strains isolated from the uteri of 312 cows with metritis/endometritis. Animals with pathological discharges were clinically diagnosed per rectum and per vaginum, and then swabs from the lumen of the uterus were aseptically collected. Bacteriological examination of swabs was according to commonly accepted procedures with the additional use of API tests. Sensitivity to antibiotics was tested by the disk diffusion method and performed in Mueller-Hinton agar. Arc. pyogenes strains were the most sensitive to amoxicillin/clavulanic acid (Amc) (97.3%), bacitracin (96.7%), ceftiofur (95.8%) and cephapirin (77.5%). E. coli strains were the most sensitive to norfloxacin (98.1%), marbofloxacin (95.8%), gentamycin (88%), Amc (80.7%) and ceftiofur (73.1%). Arc. pyogenes and E. coli were most resistant to oxytetracycline (63.7% and 31%, respectively).

Sensitivity to antibiotics of Arcanobacterium pyogenes and Escherichia coli from the uteri of cows with metritis/endometritis.

Twenty-eight Prototheca spp. strains were isolated from secretion of clinically and subclinically inflamed quarters of 25 cows. The strains showed hydrolytic activity of 6 enzymes, assimilated glucose and glycerol and were sensitive or intermediate sensitive to nystatin (85.7%), amphotericine B (42.8%), pimaricine (19.7%), gentamicin (62.5%), neomycin (41.7%) and streptomycin (29.2%). Based upon their morphologic features, assimilation patterns and antibiotic sensitivity, all isolates were identified as Prototheca zopfii.

http://www.piwet.pulawy.pl/doc/biuletyn_46-2/malinowski_317.pdf

Isolation of Prototheca zopfii from inflamed secretion of udders

The objective of this study was to determine the antimicrobial resistance of 319 yeast strains and 168 algae strains isolated from cowsmastitic milk. The in vitro susceptibility to 10 antifungals and 10 antibiotics was examined by disc diffusion method. Above 75% of yeast strains were resistant to amphotericin B, 66% to fluconazole, and 40% to pimaricin and itrakonazole. Algae strains were resistant to the most of the tested antifungals. Only nystatin, amphotericin B, and pimaricin were active against the most of these microorganisms. Algae showed the high resistance to antibiotics too. Only the aminoglycosides: gentamycin (75.5% of strains), kanamycin (71.7%), and neomycin (30.6%) inhibited the growth of these organisms in vitro. This study demonstrates that only a few antifungal and antimicrobial agents are active in vitro against algae; however, yeast strains show the high in vitro susceptibility to the most antifungals.

Resistance of yeasts and algae isolated from cow mastitic milk to antimicrobial agents

The aim of this study was to investigate the prese nce of virulence genes in 46 coagulase-negative sta phylococci (CNS) strains isolated from 46 udder quarters of 46 cows with subclinical mastitis. The isolates were examin ed phenotypically (cultural features, Gram stain, catalase, coagulase, API test s) and genotypically for: icaA , icaAB , icaD , atlE , bhp , agrA , sarA , mecA , and blaZ genes. These isolates had no nuc and coa genes, and were identified as S. warneri (11 strains), S. chromogenes (10), S. xylosus (seven), S. epidermidis (one), S. hyicus (one), and other Staphylococcus species (16). The single virulence genes or their combinations were detected in nine (19.6 %) of isol ates. The following genes were found: blaZ (in four isolates), mecA (3), sarA (3), agrA (3), and atlE (three). None of the strains harboured the bhp , icaA , icaD , and icaAB genes. In conclusion, subclinical mastitis in cows can be caused by different species of CNS that harbour different virulence factors.

Virulence factors in coagulase-negative staphylococci isolated from cows with subclinical mastitis

The isolates of Staphylococcus aureus strains were examined phenotypically by cultural features, tube coagulase test and clumping factor (CF), and genotypically by conventional PCR. The strains had positive reaction in CF test, but were negative in tube coagulase test. The analysed strains from the same cows in each year expressed also nuc and coa genes. About 25% of the strains were examined by the disc diffusion method for their sensitivity to antibiotics. During three years, the strains were highly susceptible in vitro to amoxicillin with clavulanic acid, oxacillin, bacitracin, and cefoperazone (more than 90%), and highly resistant to tetracycline, neomycin, and streptomycin. Forty randomly chosen strains, and eight strains from the same cows in each year were analysed for minimal inhibitory concentration of penicillin G using microdilution method. An increasing resistance to the penicillin was noted. Moreover, eight strains, the same in each year, were also examined for β-lactamase production and methicillin resistance. No β-lactamase producers and no methicillin resistant strains were found using phenotypic and genotypic methods. In conclusion, it can be stated that antimicrobial susceptibility can change from one year to another.

Changes in Antibiotic Susceptibility Pattern of Atypical Staphylococcus Aureus Strains Isolated from Cows of the same Herd in 2008-2010

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