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Antibiotics
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Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis
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Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "Antibiotics in Animal Health".

Deadline for manuscript submissions: closed (20 January 2025) | Viewed by 18175

Special Issue Editors

Dr. Juliano Leonel Gonçalves

E-Mail Website
Guest Editor
Veterinarian Microbiologist, Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48864, USA
Interests: udder health; antimicrobial resistance
Dr. Vera Lucia Mores Rall

E-Mail Website
Guest Editor
Department of Chemical and Biological Sciences-Microbiology and Immunology Sector University (UNESP), Botucatu 18618-691, SP, Brazil
Interests: antimicrobial resistance biofilms; staphylococcal enterotoxins
Dr. Rinosh Joshua Mani

E-Mail Website
Guest Editor
Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Michigan State University, Lansing, MI 48910, USA
Interests: vector borne disease; antimicrobial resistance; diagnostic microbiology

Special Issue Information

Dear Colleagues,

Mastitis is a bovine disease that causes great economic losses to the milk quality and dairy products production chain. The major consequences include the effect not only on milk quality and yield but also on animal welfare and the amount of antibiotics used for treatment. Antibiotics are essential for combatting bacterial diseases, and their use has contributed to the improved welfare of both humans and animals. However, antimicrobial usage (AMU) can select for resistant bacterial pathogens and clinically relevant resistance genes that threaten public health worldwide. While overuse of antibiotics for treating human disease is an important driver of resistance, the large mass of antimicrobials used in animals also contributes to the emergence and dissemination of resistant bacteria. Many classes of antimicrobials are used in both human and veterinary medicine, and several organizations have categorized them based on the importance in treating selected diseases of humans. The term ‘critically important antimicrobial’ (CIA) generally refers to classes of antimicrobials that are the only compound or one of a limited number used to treat specific diseases in humans. A review on antimicrobial resistance showed a prediction that, by 2050, more than 10 million people will die each year from superbugs, the name given to those that are resistant to antibiotics. Therefore, the increased use of antibiotics in farms worldwide suggests that further research studies would be recommended in order to help the dairy producers to benefit from antimicrobial stewardship programs and to avoid potential bacterial resistance. This Special Issue seeks manuscript submissions that further our understanding of AMU on dairy farms and how AMU is associated with the dissemination of resistant pathogens and their genetic elements on farms as well as the impact of using CIA on the development and dissemination of resistance. Submissions on the response of bovine mastitis pathogens to antimicrobials and any outcome related to antimicrobial resistance are especially encouraged.

Dr. Juliano Leonel Gonçalves
Dr. Vera Lucia Mores Rall
Dr. Rinosh Joshua Mani
Guest Editors

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Keywords

  • antimicrobial usage
  • antimicrobial stewardship
  • mastitis
  • antimicrobial resistance
  • epidemiology
  • genomics

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Published Papers (11 papers)

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Research

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14 pages, 513 KiB  
Article
Whole-Genome Sequencing Analysis Revealed High Genomic Variability, Recombination Events and Mobile Genetic Elements in Streptococcus uberis Strains Isolated from Bovine Mastitis in Colombian Dairy Herds
by Paola A. Rios Agudelo, Julián Reyes Vélez, Martha Olivera Angel, Adam M. Blanchard, Yesid Cuesta Astroz, Arley Caraballo Guzmán and Giovanny Torres Lindarte
Antibiotics 2025, 14(3), 297; https://doi.org/10.3390/antibiotics14030297 - 12 Mar 2025
Viewed by 742
Abstract
Introduction: Streptococcus uberis is a poorly controlled cause of bovine intramammary infections and a common motivation for the use antibiotics in dairy farms worldwide. Therefore, studying the genomic characteristics of this pathogen is fundamental to understand its complex epidemiology and behavior against [...] Read more.
Introduction: Streptococcus uberis is a poorly controlled cause of bovine intramammary infections and a common motivation for the use antibiotics in dairy farms worldwide. Therefore, studying the genomic characteristics of this pathogen is fundamental to understand its complex epidemiology and behavior against antimicrobials. Methods: A comparative genomic analysis of 10 S. uberis strains was performed and their antimicrobial susceptibility was assessed. Results: Ten different novel sequence types were found, and genes (tetM, tetO, patB, lnuC, lnuA, lsaE, ermB, ANT(6)-la) and mobile genetic elements previously associated with antimicrobial resistance (repUS43, ISSag2, and ISEnfa4) and virulence (315.2 phage) were detected. Additionally, our strains had the highest relative rate of recombination to mutation (8.3) compared to other S. uberis strains isolated from different continents (America: 7.7, Asia: 2.9, Europe: 5.4, and Oceania: 6.6). Most of the strains (80%) tested showed phenotypic resistance to clindamycin and 70% exhibited intermediate susceptibility to penicillin. Conclusions: The high heterogeneity of strains observed and the presence of genetic factors linked to antimicrobial resistance represent a challenge for the implementation and surveillance of measures focused on the control and elimination of this pathogen. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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18 pages, 1032 KiB  
Article
Longitudinal Patterns in the Isolation and Antimicrobial Resistance of Bovine Mastitis-Causing Bacteria in Ireland
by Amalia Naranjo-Lucena, Philip Becker, Gillian Madigan, Rebecca Cupial, Brian Byrne and Alan Johnson
Antibiotics 2025, 14(3), 243; https://doi.org/10.3390/antibiotics14030243 - 27 Feb 2025
Viewed by 747
Abstract
Background/Objectives: Bovine mastitis remains a challenge for the Irish dairy industry. This study aimed to explore the seasonality and antimicrobial resistance of mastitis pathogens obtained by the regional laboratories (RVL) of the Department of Agriculture, Food and the Marine. Methods: Seasonality [...] Read more.
Background/Objectives: Bovine mastitis remains a challenge for the Irish dairy industry. This study aimed to explore the seasonality and antimicrobial resistance of mastitis pathogens obtained by the regional laboratories (RVL) of the Department of Agriculture, Food and the Marine. Methods: Seasonality of isolation of the most common bacterial species and antimicrobial resistance of those species repeatedly obtained in the same herds in different years were explored using the RVL diagnostic data. Additionally, whole genome sequencing (WGS) was employed to establish the persistency of Staphylococcus aureus strains within the same herd. Results: A clear seasonality was observed in the isolation of Staphylococcus aureus, Streptococcus uberis, and Escherichia coli from milk. Seasonal differences were statistically significant within and between bacterium. Persistence of resistance within herds was highest in S. aureus against penicillin (35.5% of herds) and in S. uberis against pirlimycin (14% of herds), while E. coli did not show persistence of resistance to any antimicrobials. Sequencing of S. aureus isolates revealed that the strains causing mastitis in ten out of twenty-one herds were similar genetically in different years. In seven of these herds, S. aureus was persistently resistant to penicillin. Isolates from two different herds were practically identical and carried the human immune evasion cluster genes (IEC, scn, sak, chp and sea) suggesting a recent human-bovine host switch event. Conclusions: These findings underscore the importance of implementing targeted biosecurity measures and monitoring programs to mitigate the spread of mastitis-causing pathogens and enhance antimicrobial stewardship in the Irish dairy industry, while it also highlights the significance of including a One Health perspective in surveillance programs. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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16 pages, 1045 KiB  
Article
Clonality, Virulence Genes, and Antimicrobial Resistance of Dairy Ruminants in Mastitic Milk-Associated Staphylococcus aureus in Sicily
by Nunziatina Russo, Nunzio Alberto Fazio, Francesca Licitra, Joanna Gajewska, Alessandro Stamilla, Rosario Salonia, Wioleta Chajęcka-Wierzchowska, Cinzia L. Randazzo, Cinzia Caggia, Francesco Antoci and Giuseppe Cascone
Antibiotics 2025, 14(2), 188; https://doi.org/10.3390/antibiotics14020188 - 12 Feb 2025
Viewed by 1068
Abstract
Background: Staphylococcus aureus is one of the most prevalent pathogens causing mastitis in dairy animals and represents a serious issue of public health concern due to its resistance against multiple antimicrobials. Objectives: This study assessed 101 S. aureus isolates obtained from [...] Read more.
Background: Staphylococcus aureus is one of the most prevalent pathogens causing mastitis in dairy animals and represents a serious issue of public health concern due to its resistance against multiple antimicrobials. Objectives: This study assessed 101 S. aureus isolates obtained from quarter milk of animals with subclinical mastitis in the Ragusa area (Sicily, Italy). Methods: Antibiotic resistance against nine antibiotics was evaluated using the Kirby–Bauer method, and the Minimum Inhibitory Concentration (MIC) values were measured for oxacillin (OXA) and vancomycin (VA). Additionally, the isolates were genetically characterized through multiplex PCR to identify the presence of spa, mecA, mecC, pvl, vanA, vanB, and vanC genes, along with pulsed-field gel electrophoresis analysis and multi-locus sequence typing (MLST). Results: The highest rates of antibiotic resistance were found against gentamicin (47.5%) and erythromycin (29.7%), with 86.1% of strains exhibiting resistance to at least two antimicrobials and 33.7% showing resistance to three antimicrobial classes. Furthermore, the results indicated that the presence of antibiotic resistance genes was not correlated with phenotypic resistance, and a phylogenetic analysis revealed varying phenotypic resistance profiles even within the same PFGE cluster. Lastly, alongside a new allelic profile ST 9471, MLST analysis identified five additional STs clustered into three CCs, with CC5 originating from human ancestral strains through human-to-animal host transfers, making it the dominant group. Conclusions: This study provided valuable insights into regional trends, allowing for the identification of significant antibiotic-resistant patterns and offering an understanding of bacterial dynamics in these environments, underscoring the importance of routine resistance surveillance in dairy farms. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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17 pages, 2401 KiB  
Article
Bactofencin A Displays a Delayed Killing Effect on a Clinical Strain of Staphylococcus aureus Which Is Greatly Accelerated in the Presence of Nisin
by Paula M. O’Connor, Paul D. Cotter, Colin Hill and R. Paul Ross
Antibiotics 2025, 14(2), 184; https://doi.org/10.3390/antibiotics14020184 - 11 Feb 2025
Viewed by 873
Abstract
Background/objectives: Bacteriocins can be considered a novel source of natural alternatives to antibiotics or chemical food additives with the potential to fight against clinical and food pathogens. A number have already been commercialised as food preservatives, but they also have the potential to [...] Read more.
Background/objectives: Bacteriocins can be considered a novel source of natural alternatives to antibiotics or chemical food additives with the potential to fight against clinical and food pathogens. A number have already been commercialised as food preservatives, but they also have the potential to treat drug-resistant clinical pathogens and can play a role in immune modulation. To achieve their full potential, an understanding of their mode of action is required. Methods: Bactofencin A and nisin A were purified to homogeneity by reversed-phase HPLC and their effect on the mastitis pathogen Staphylococcus aureus DPC5246 was assessed by cell viability assays and flow cytometry. Results: We report that bactofencin A displays a delayed inhibitory effect against the mastitis pathogen, Staphylococcus aureus DPC5246, suggesting an unusual mode of action. This characteristic was clearly visible on BHI plate media, where formation of inhibition zones against the staphylococcal strain took 23 h compared to 6 h for the well-characterised nisin. This delayed killing and injury was also demonstrated using flow cytometry, where damage was evident 4 h after bacteriocin addition. Treatment with 2 μM bactofencin A resulted in approximately 20-fold higher numbers of injured and 50-fold higher numbers of dead cells when compared to untreated cells. Combining bactofencin A with the lantibiotic nisin A resulted in faster killing at lower bacteriocin concentrations. When combined in an equal ratio, the combination exhibited a 4-fold increase in inhibition compared to nisin A alone. These results demonstrate that the combination may be very effective in therapeutic applications against pathogenic staphylococci. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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19 pages, 17826 KiB  
Article
Antimicrobial Resistance in Pasteurella multocida Isolates from Bovine Mastitis Can Be Associated with Multidrug-Resistance-Mediating Integrative and Conjugative Elements (ICEs)
by Johanna Jahnen, Dennis Hanke, Kristina Kadlec, Stefan Schwarz and Henrike Krüger-Haker
Antibiotics 2025, 14(2), 153; https://doi.org/10.3390/antibiotics14020153 - 4 Feb 2025
Viewed by 1483
Abstract
Background/Objectives: Pasteurella multocida commonly colonizes the bovine respiratory tract and can occasionally cause intramammary infections. Here, eight P. multocida isolates from clinical cases of bovine mastitis were investigated for their molecular characteristics as well as phenotypic and genotypic antimicrobial resistance (AMR) properties. [...] Read more.
Background/Objectives: Pasteurella multocida commonly colonizes the bovine respiratory tract and can occasionally cause intramammary infections. Here, eight P. multocida isolates from clinical cases of bovine mastitis were investigated for their molecular characteristics as well as phenotypic and genotypic antimicrobial resistance (AMR) properties. Methods: The isolates originated from quarter milk samples obtained in Germany for diagnostic purposes. Antimicrobial susceptibility testing (AST) by broth microdilution was performed according to the Clinical and Laboratory Standards Institute. Closed whole-genome sequences were generated by hybrid assembly of Illumina MiSeq short-reads and Oxford Nanopore MinION long-reads, followed by consecutive sequence analysis. Results: The P. multocida isolates belonged either to capsular:lipopolysaccharide type A:3 (n = 7) or A:6 (n = 1), and multi-locus sequence types 1 (n = 7) or 7 (n = 1). Seven isolates carried AMR genes, such as mef(C), mph(G), strA, strB, aphA1, aadA31, tet(H), tet(Y), floR, catA3, and sul2, as part of an integrative and conjugative element (ICE). These mobile genetic elements, 58,382–78,401 bp in size, were highly similar to the ICEs Tn7406 or Tn7407 that have been previously described in bovine Mannheimia haemolytica and P. multocida, respectively. Moreover, the isolates showed elevated minimal inhibitory concentrations corresponding to the identified AMR determinants. Conclusions: Molecular typing and ICE organization suggest the bovine respiratory tract as reservoir of the investigated mastitis-associated P. multocida. Horizontal cross-genus transfer of multidrug-resistance-mediating ICEs seems to occur under in vivo conditions among different pathogens from cattle in Germany, which underlines the importance of pathogen identification followed by AST for successful bovine mastitis therapy. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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14 pages, 901 KiB  
Article
Mapping Antimicrobial Resistance in Staphylococcus epidermidis Isolates from Subclinical Mastitis in Danish Dairy Cows
by Desiree Corvera Kløve, Mikael Lenz Strube, Peter M. H. Heegaard and Lærke Boye Astrup
Antibiotics 2025, 14(1), 67; https://doi.org/10.3390/antibiotics14010067 - 10 Jan 2025
Viewed by 957
Abstract
Background/Objectives: Although Staphylococcus epidermidis is a key cause of subclinical mastitis in Danish dairy cows, its sensitivity to antimicrobials remains unexplored. Here, we analyzed sixty S. epidermidis isolates derived from 42 dairy cows across six conventional dairy herds in Denmark. Methods: Phenotypic resistance [...] Read more.
Background/Objectives: Although Staphylococcus epidermidis is a key cause of subclinical mastitis in Danish dairy cows, its sensitivity to antimicrobials remains unexplored. Here, we analyzed sixty S. epidermidis isolates derived from 42 dairy cows across six conventional dairy herds in Denmark. Methods: Phenotypic resistance was measured by antimicrobial susceptibility testing and minimum inhibitory concentration (MIC) analysis, and genotypic resistance was examined through whole-genome sequencing and identification of antimicrobial resistance genes (ARGs). Correspondence between phenotypic and genotypic resistance was then evaluated by Cohen’s kappa statistics. Furthermore, the presence of plasmid replicon genes and the strain diversity among the S. epidermidis isolates was investigated to associate these findings with the observed AMR patterns. Results: Results showed that 30/60 isolates (50.0%) were resistant to penicillin phenotypically, while 35/60 (58.3%) were positive for a corresponding blaZ gene (κ = 0.83, p < 0.01). A fosB gene, encoding fosfomycin resistance, was detected in all 60/60 isolates (100.0%), but fosfomycin resistance was not analyzed phenotypically. Based on MIC analysis, 3/60 isolates (5.0%) were multi-drug resistant, showing resistance towards penicillin, erythromycin, and tetracycline. However, in 11/60 genomes (18.3%), ARGs encoding resistance towards ≥3 antimicrobial classes (e.g., beta-lactams, phosphonic acid, tetracyclines, aminoglycosides, macrolides, lincosamides, and fusidane) were detected. Eleven different ARGs were detected among the 60 isolates in total. No methicillin-resistant Staphylococcus epidermidis (MRSE) were recorded. Results further showed that each herd had one primary sequence type (ST) and resistance profile associated with it, and plasmid-mediated horizontal gene transfer of ARGs was indicated This study underscores the importance of routine resistance surveillance and species-specific diagnoses to improve treatment outcomes and ensure prudent use of antimicrobials. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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7 pages, 191 KiB  
Article
Retrospective Analysis of Penicillin G Minimum Inhibitory Concentration for Gram-Positive Isolates of Non-Severe Clinical Mastitis
by Stefanie Leimbach, Franziska Nankemann, Anne Tellen, Doris Klocke, Nicole Wente, Yanchao Zhang and Volker Krömker
Antibiotics 2025, 14(1), 21; https://doi.org/10.3390/antibiotics14010021 - 2 Jan 2025
Viewed by 834
Abstract
Background: Despite penicillin having a longstanding reputation as being scientifically approved for the treatment of bovine mastitis, its market share and practical application rate seem rather low. While in some countries, cases of mild and moderate mastitis are treated almost completely with [...] Read more.
Background: Despite penicillin having a longstanding reputation as being scientifically approved for the treatment of bovine mastitis, its market share and practical application rate seem rather low. While in some countries, cases of mild and moderate mastitis are treated almost completely with simple penicillin, in other countries, penicillin is rarely used as a mono-substance in udder tubes. Methods: Based on minimal inhibitory concentration (MIC) studies of 1489 isolates of Gram-positive microorganisms isolated from bovine mastitis cases, the extent to which penicillin preparations can fulfil their role as first-line treatment and in how many cases insufficient efficacy must be assumed was assessed in comparison with more recent studies on the achievable levels of active substances in milk. Results: Of the isolates, 76% had an MIC of ≤0.125 µg/mL and 95% of the isolates had an MIC of ≤1 µg/mL. Conclusions: The data show that in Northern Germany, it can be assumed that penicillin is a good choice in most cases of mastitis caused by Gram-positive mastitis pathogens, at least from the perspective of antibiotic resistance. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
12 pages, 1041 KiB  
Article
Long-Term Co-Circulation of Host-Specialist and Host-Generalist Lineages of Group B Streptococcus in Brazilian Dairy Cattle with Heterogeneous Antimicrobial Resistance Profiles
by Laura Maria Andrade de Oliveira, Leandro Correia Simões, Chiara Crestani, Natália Silva Costa, José Carlos de Figueiredo Pantoja, Renata Fernandes Rabello, Lucia Martins Teixeira, Uzma Basit Khan, Stephen Bentley, Dorota Jamrozy, Tatiana de Castro Abreu Pinto and Ruth N. Zadoks
Antibiotics 2024, 13(5), 389; https://doi.org/10.3390/antibiotics13050389 - 25 Apr 2024
Cited by 3 | Viewed by 2141
Abstract
Group B Streptococcus (GBS) is a major cause of contagious bovine mastitis (CBM) in Brazil. The GBS population is composed of host-generalist and host-specialist lineages, which may differ in antimicrobial resistance (AMR) and zoonotic potential, and the surveillance of bovine GBS is crucial [...] Read more.
Group B Streptococcus (GBS) is a major cause of contagious bovine mastitis (CBM) in Brazil. The GBS population is composed of host-generalist and host-specialist lineages, which may differ in antimicrobial resistance (AMR) and zoonotic potential, and the surveillance of bovine GBS is crucial to developing effective CBM control and prevention measures. Here, we investigated bovine GBS isolates (n = 156) collected in Brazil between 1987 and 2021 using phenotypic testing and whole-genome sequencing to uncover the molecular epidemiology of bovine GBS. Clonal complex (CC) 61/67 was the predominant clade in the 20th century; however, it was replaced by CC91, with which it shares a most common recent ancestor, in the 21st century, despite the higher prevalence of AMR in CC61/67 than in CC91, and high selection pressure for AMR from indiscriminate antimicrobial use in the Brazilian dairy industry. CC103 also emerged as a dominant CC in the 21st century, and a considerable proportion of herds had two or more GBS strains, suggesting poor biosecurity and within-herd evolution due to the chronic nature of CBM problems. The majority of bovine GBS belonged to serotype Ia or III, which was strongly correlated with CCs. Ninety-three isolates were resistant to tetracycline (≥8 μg/mL; tetO = 57, tetM = 34 or both = 2) and forty-four were resistant to erythromycin (2.0 to >4 μg/mL; ermA = 1, ermB = 38, mechanism unidentified n = 5). Only three isolates were non-susceptible to penicillin (≥8.0 μg/mL), providing opportunities for improved antimicrobial stewardship through the use of narrow-spectrum antimicrobials for the treatment of dairy cattle. The common bovine GBS clades detected in this study have rarely been reported in humans, suggesting limited risk of interspecies transmission of GBS in Brazil. This study provides new data to support improvements to CBM and AMR control, bovine GBS vaccine design, and the management of public health risks posed by bovine GBS in Brazil. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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16 pages, 840 KiB  
Article
Genetic and Phenotypic Characterization of Subclinical Mastitis-Causing Multidrug-Resistant Staphylococcus aureus
by Amanda Thaís Ferreira Silva, Juliano Leonel Gonçalves, Stéfani Thais Alves Dantas, Vera Lúcia Mores Rall, Pollyanne Raysa Fernandes de Oliveira, Marcos Veiga dos Santos, Rodolfo de Moraes Peixoto and Rinaldo Aparecido Mota
Antibiotics 2023, 12(9), 1353; https://doi.org/10.3390/antibiotics12091353 - 23 Aug 2023
Cited by 8 | Viewed by 2475
Abstract
The core objective of this study was to genetically and phenotypically characterize subclinical mastitis-causing multidrug-resistant Staphylococcus aureus (MDRSA). In addition, risk factors associated with subclinical mastitis caused by MDRSA were investigated. Bacterial cultures were performed on 2120 mammary quarters, 40 swabs of milk [...] Read more.
The core objective of this study was to genetically and phenotypically characterize subclinical mastitis-causing multidrug-resistant Staphylococcus aureus (MDRSA). In addition, risk factors associated with subclinical mastitis caused by MDRSA were investigated. Bacterial cultures were performed on 2120 mammary quarters, 40 swabs of milk utensils, 5 bulk tank milk samples, and 11 nostril and 11 hand swabs from milkers from five dairy farms. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was conducted for S. aureus identification. Antimicrobial resistance was screened phenotypically using the disk diffusion test in all S. aureus isolates. A biofilm formation assay; detection of genes associated with beta-lactam resistance, efflux pump, and biofilm formation; and pulsed-field gel electrophoresis (PFGE) were performed in all MDRSA isolates. Multi-locus sequence typing (MLST) was carried out in cefoxitin-resistant MDRSA isolates. A total of 188 S. aureus isolates from milk as well as two from milking utensils and one from bulk tank milk were identified. Most of the isolates (92.7%; 177 of 191) showed beta-lactam resistance, and 7% (14 of 191) were MDRSA. Interestingly, 36% (5 of 14) of MDRSA isolates were cefoxitin-resistant, but none carried mecA or mecC genes. Based on PFGE results, it was observed that S. aureus strains were more likely to be unique to a specific herd. Two clonal complexes were identified, CC97 (ST126; commonly livestock-associated) and CC1 (ST7440; usually community-associated). To the best of our knowledge, this is the first report of ST7440 isolated from bovine mastitis in Brazil. The risk factor results underscored the importance of considering parity, stage of lactation, SCC, milk production, and herd size when studying the risk of subclinical mastitis and antimicrobial resistance in S. aureus. Thus, to implement effective strategies to prevent subclinical mastitis in dairy herds and to minimize MDRSA spread, it is important to understand MDRSA strains’ distribution and their antimicrobial resistance profile. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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14 pages, 2418 KiB  
Article
The Emergence of Antimicrobial Resistance and Virulence Characteristics in Enterococcus Species Isolated from Bovine Milk
by Beatriz Rizzo Paschoalini, Karen Vanessa Munive Nuñez, Juliana Takahashi Maffei, Hélio Langoni, Felipe Freitas Guimarães, Clarice Gebara, Natylane Eufransino Freitas, Marcos Veiga dos Santos, Carlos Eduardo Fidelis, Roberto Kappes, Mônica Correia Gonçalves and Nathália Cristina Cirone Silva
Antibiotics 2023, 12(8), 1243; https://doi.org/10.3390/antibiotics12081243 - 28 Jul 2023
Cited by 11 | Viewed by 2496
Abstract
Enterococcus spp., including E. faecalis and E. faecium, pose risks to dairy farms as opportunistic pathogens. The study evaluates antimicrobial resistance (AMR) and virulence characteristics of Enterococcus spp. isolated from bovine milk. Bile esculin agar was used to assess 1471 milk samples, [...] Read more.
Enterococcus spp., including E. faecalis and E. faecium, pose risks to dairy farms as opportunistic pathogens. The study evaluates antimicrobial resistance (AMR) and virulence characteristics of Enterococcus spp. isolated from bovine milk. Bile esculin agar was used to assess 1471 milk samples, followed by colony identification, gram staining, catalase tests, and 45 °C incubation. PCR analysis targeted E. faecalis and E. faecium in characteristic Enterococcus spp. colonies, with MALDI-TOF used for negative samples. Multiple tests, including disk diffusion, chromogenic VRE agar for vancomycin resistance, Vancomycin Etest® for MIC determination, and PCR for virulence factors (cylA, esp, efaA, ace, asa1, gelE, and hyl genes), were performed. Out of 100 identified strains, E. durans (30.66%), E. faecium (26.28%), and E. faecalis (18.25%) were predominant. AMR in Enterococcus spp. varied, with the highest rates against rifampicin (27%), tetracycline (20%), and erythromycin (18%). Linezolid (5%), vancomycin, ciprofloxacin, and teicoplanin (3% each) had lower prevalence. E. faecium and E. faecalis showed high AMR to rifampicin, erythromycin, and tetracycline. Thirty-two strains (18.98%) grew on VRE Chromoselect agar, while 4 (2 E. faecalis and 2 E. faecium) showed vancomycin resistance by MIC values. E. faecalis carried gelE (45.5%) and asa1 (36%), and E. gallinarum had 9.1% with the asa1 gene. Detecting resistant Enterococcus in bovine milk supports control strategies for enterococci on dairy farms, highlighting AMR concerns in the food chain. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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Review

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16 pages, 366 KiB  
Review
Extended-Spectrum Beta-Lactamase-Producing Escherichia coli and Other Antimicrobial-Resistant Gram-Negative Pathogens Isolated from Bovine Mastitis: A One Health Perspective
by Breno Luis Nery Garcia, Stéfani Thais Alves Dantas, Kristian da Silva Barbosa, Thatiane Mendes Mitsunaga, Alyssa Butters, Carlos Henrique Camargo and Diego Borin Nobrega
Antibiotics 2024, 13(5), 391; https://doi.org/10.3390/antibiotics13050391 - 25 Apr 2024
Cited by 4 | Viewed by 2262
Abstract
Antimicrobial resistance (AMR) poses an imminent threat to global public health, driven in part by the widespread use of antimicrobials in both humans and animals. Within the dairy cattle industry, Gram-negative coliforms such as Escherichia coli and Klebsiella pneumoniae stand out as major [...] Read more.
Antimicrobial resistance (AMR) poses an imminent threat to global public health, driven in part by the widespread use of antimicrobials in both humans and animals. Within the dairy cattle industry, Gram-negative coliforms such as Escherichia coli and Klebsiella pneumoniae stand out as major causative agents of clinical mastitis. These same bacterial species are frequently associated with severe infections in humans, including bloodstream and urinary tract infections, and contribute significantly to the alarming surge in antimicrobial-resistant bacterial infections worldwide. Additionally, mastitis-causing coliforms often carry AMR genes akin to those found in hospital-acquired strains, notably the extended-spectrum beta-lactamase genes. This raises concerns regarding the potential transmission of resistant bacteria and AMR from mastitis cases in dairy cattle to humans. In this narrative review, we explore the distinctive characteristics of antimicrobial-resistant E. coli and Klebsiella spp. strains implicated in clinical mastitis and human infections. We focus on the molecular mechanisms underlying AMR in these bacterial populations and critically evaluate the potential for interspecies transmission. Despite some degree of similarity observed in sequence types and mobile genetic elements between strains found in humans and cows, the existing literature does not provide conclusive evidence to assert that coliforms responsible for mastitis in cows pose a direct threat to human health. Finally, we also scrutinize the existing literature, identifying gaps and limitations, and propose avenues for future research to address these pressing challenges comprehensively. Full article
(This article belongs to the Special Issue Antimicrobial Resistance of Pathogens Isolated from Bovine Mastitis)
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