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Kerro Dego O, Vidlund J. Staphylococcal mastitis in dairy cows. Front Vet Sci 2024; 11:1356259. [PMID: 38863450 PMCID: PMC11165426 DOI: 10.3389/fvets.2024.1356259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 05/06/2024] [Indexed: 06/13/2024] Open
Abstract
Bovine mastitis is one of the most common diseases of dairy cattle. Even though different infectious microorganisms and mechanical injury can cause mastitis, bacteria are the most common cause of mastitis in dairy cows. Staphylococci, streptococci, and coliforms are the most frequently diagnosed etiological agents of mastitis in dairy cows. Staphylococci that cause mastitis are broadly divided into Staphylococcus aureus and non-aureus staphylococci (NAS). NAS is mainly comprised of coagulase-negative Staphylococcus species (CNS) and some coagulase-positive and coagulase-variable staphylococci. Current staphylococcal mastitis control measures are ineffective, and dependence on antimicrobial drugs is not sustainable because of the low cure rate with antimicrobial treatment and the development of resistance. Non-antimicrobial effective and sustainable control tools are critically needed. This review describes the current status of S. aureus and NAS mastitis in dairy cows and flags areas of knowledge gaps.
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Affiliation(s)
- Oudessa Kerro Dego
- Department of Animal Science, University of Tennessee, Knoxville, TN, United States
| | - Jessica Vidlund
- Department of Animal Science, University of Tennessee, Knoxville, TN, United States
- East Tennessee AgResearch and Education Center-Little River Animal and Environmental Unit, University of Tennessee, Walland, TN, United States
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Dendani Chadi Z, Arcangioli MA. Pulsed-Field Gel Electrophoresis Analysis of Bovine Associated Staphylococcus aureus: A Review. Pathogens 2023; 12:966. [PMID: 37513813 PMCID: PMC10385338 DOI: 10.3390/pathogens12070966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/10/2023] [Accepted: 07/14/2023] [Indexed: 07/30/2023] Open
Abstract
For decades now, DNA fingerprinting by means of pulsed-field gel electrophoresis (PFGE) continues to be the most widely used to separate large DNA molecules and distinguish between different strains in alternating pulses. This is done by isolating intact chromosomal DNA and using restriction enzymes with specific restriction sites to generate less than 30 restriction fragments from 50 Kb to 10 Mbp. These results make clone-specific band profiles easy to compare. Specialized equipment is required for the optimization of DNA separation and resolution, among which a contour-clamped homogeneous electric field (CHEF) apparatus is the most commonly used. As a result, the PFGE analysis of a bacterial genome provides useful information in terms of epidemiological investigations of different bacterial pathogens. For Staphylococcus aureus subtyping, despite its limitations and the emergence of alternative methods, PFGE analysis has proven to be an adequate choice and the gold standard for determining genetic relatedness, especially in outbreak detection and short-term surveillance in the veterinary field.
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Affiliation(s)
- Zoubida Dendani Chadi
- Laboratory of Biodiversity and Pollution of Ecosystems, Department of Veterinary Medicine, Faculty of Natural Science and Life, University of Chadli Bendjedid, El Tarf 36000, Algeria
| | - Marie-Anne Arcangioli
- VetAgro Sup, Université de Lyon, UMR Mycoplasmoses Animales, 69280 Marcy l'Etoile, France
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Ozdikmenli Tepeli S, Zorba M, Yalman M, Bilgucu E, Demirel Zorba NN. Microbiological and physicochemical properties of farm bulk tank milk and antimicrobial resistance of its dominant bacteria. J Food Saf 2022. [DOI: 10.1111/jfs.13022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Seda Ozdikmenli Tepeli
- Department of Veterinary Çanakkale Onsekiz Mart University Yenice Vocational School Çanakkale Turkey
| | - Murat Zorba
- Çanakkale Onsekiz Mart University Engineering Faculty Food Engineering Department Çanakkale Turkey
| | - Musa Yalman
- Department of Food Technology Bandirma Onyedi Eylül University Bandirma Vocational School Balikesir Turkey
| | - Ertuğrul Bilgucu
- Food Technology Department Çanakkale Onsekiz Mart University Biga Vocational School Çanakkale Turkey
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Characterization of Biofilm Producing Coagulase-Negative Staphylococci Isolated from Bulk Tank Milk. Vet Sci 2022; 9:vetsci9080430. [PMID: 36006345 PMCID: PMC9416249 DOI: 10.3390/vetsci9080430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 07/30/2022] [Accepted: 08/08/2022] [Indexed: 11/17/2022] Open
Abstract
Coagulase-negative staphylococci (CoNS) are considered less virulent as they do not produce a large number of toxic enzymes and toxins; however, they have been increasingly recognized as an important cause of bovine mastitis. In particular, the ability to form biofilms appears to be an important factor in CoNS pathogenicity, and it contributes more resistance to antimicrobials. The aim of this study was to investigate the pathogenic potential by assessing the biofilm-forming ability of CoNS isolated from normal bulk tank milk using the biofilm formation assay and to analyze the biofilm-associated resistance to antimicrobial agents using the disc diffusion method. One hundred and twenty-seven (78.4%) among 162 CoNS showed the ability of biofilm formation, and all species showed a significantly high ability of biofilm formation (p < 0.05). Although the prevalence of weak biofilm formers (39.1% to 80.0%) was significantly higher than that of other biofilm formers in all species (p < 0.05), the prevalence of strong biofilm formers was significantly higher in Staphylococcus haemolyticus (36.4%), Staphylococcus chromogenes (24.6%), and Staphylococcus saprophyticus (21.7%) (p < 0.05). Also, 4 (11.4%) among 35 non-biofilm formers did not harbor any biofilm-associated genes, whereas all 54 strong or moderate biofilm formers harbored 1 or more of these genes. The prevalence of MDR was significantly higher in biofilm formers (73.2%) than in non-formers (20.0%) (p < 0.05). Moreover, the distribution of MDR in strong or moderate biofilm formers was 81.5%, which was significantly higher than in weak (67.1%) and non-formers (20.0%) (p < 0.05). Our results indicated that various CoNS isolated from bulk tank milk, not from bovine with mastitis, have already showed a high ability to form biofilms, while also displaying a high prevalence of MDR.
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Kim HJ, Youn HY, Kang HJ, Moon JS, Jang YS, Song KY, Seo KH. Prevalence and Virulence Characteristics of Enterococcus faecalis and Enterococcus faecium in Bovine Mastitis Milk Compared to Bovine Normal Raw Milk in South Korea. Animals (Basel) 2022; 12:ani12111407. [PMID: 35681873 PMCID: PMC9179290 DOI: 10.3390/ani12111407] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 05/25/2022] [Accepted: 05/26/2022] [Indexed: 01/27/2023] Open
Abstract
Enterococcus spp. are pathogens that cause environmental mastitis and are difficult to eliminate owing to their resistance to antibiotics. To compare the virulence characteristics of isolates from bovine mastitis milk (BMM) and bovine normal raw milk (NRM), we isolated Enterococcus spp. from 39 dairy farms in South Korea from 2015−2020. A total of 122 Enterococcus spp. were identified, with Enterococcus faecalis (73.8%) accounting for the majority, followed by Enterococcus faecium (26.2%). E. faecalis isolated from BMM harbored gelE, asa1, esp, and cylA genes with a prevalence of 85.7, 71.4, 54.3, and 30.0%, respectively. These genes were significantly more abundant in BMM than in NRM, except for asa1 (p < 0.0001). Interestingly, strong biofilm and gelatinase formation was predominately observed for BMM isolates and this was significantly correlated to the presence of esp and gelE genes (p < 0.05). BMM isolates demonstrated higher resistance to tetracycline (59.3%), followed by chloramphenicol (21.0%), rifampicin (18.5%), doxycycline (4.9%), ciprofloxacin (1.2%), and nitrofurantoin (1.2%), than those from NRM. E. faecalis harboring esp, gelE, and cylA may be causative agents for bovine mastitis and act as a reservoir for the transmission of virulence factors to humans.
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Affiliation(s)
- Hyeon-Jin Kim
- Center for One Health, College of Veterinary Medicine, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (H.-J.K.); (H.-Y.Y.); (Y.-S.J.); (K.-Y.S.)
| | - Hye-Young Youn
- Center for One Health, College of Veterinary Medicine, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (H.-J.K.); (H.-Y.Y.); (Y.-S.J.); (K.-Y.S.)
| | - Hye-Jeong Kang
- Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si 39660, Gyeonsangbuk-do, Korea; (H.-J.K.); (J.-S.M.)
| | - Jin-San Moon
- Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si 39660, Gyeonsangbuk-do, Korea; (H.-J.K.); (J.-S.M.)
| | - Yong-Seok Jang
- Center for One Health, College of Veterinary Medicine, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (H.-J.K.); (H.-Y.Y.); (Y.-S.J.); (K.-Y.S.)
| | - Kwang-Young Song
- Center for One Health, College of Veterinary Medicine, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (H.-J.K.); (H.-Y.Y.); (Y.-S.J.); (K.-Y.S.)
| | - Kun-Ho Seo
- Center for One Health, College of Veterinary Medicine, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (H.-J.K.); (H.-Y.Y.); (Y.-S.J.); (K.-Y.S.)
- Correspondence: ; Tel.: +82-2-450-4121; Fax: +82-2-3436-4128
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Jung HR, Kim K, Lee YJ. Comparative analysis of genetic characterization of β-lactam-resistant Escherichia coli from bulk tank milk in Korea. Ir Vet J 2021; 74:26. [PMID: 34548104 PMCID: PMC8454163 DOI: 10.1186/s13620-021-00203-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 08/25/2021] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND This study was conducted to analyze the genetic characteristics of 41 β-lactam-resistant Escherichia coli isolates, which are one of the common causes of environmental mastitis, isolated from the bulk tank milk of 290 dairy farms in five factories operated by three dairy companies in Korea. RESULTS Analysis of the phenotypic and genotypic characteristics of β-lactam-resistant E. coli isolates revealed differences between factories even within the same company. Isolates from factory A1 and C1 showed high resistance to cephalothin (76.9 and 100%, respectively), which is a first-generation cephalosporins, whereas resistance to tetracycline was showed by only the isolates from factories B1 (60.0%), C2 (66.7%), and C3 (100%). Although all the 41 β-lactam-resistant E. coli isolates were positive for blaOXA-1, blaTEM-1 was highly prevalent in isolates from factories C2 (100%) and C3 (100%). Among 17 isolates resistant to both β-lactams and aminoglycosides, the most common multilocus sequence type was ST399 (13isolates, 76.5%). Furthermore, 2 (11.8%) and 12 (70.6%) isolates belonged to the phylogenetic groups B2 and D, respectively, which are invasive strains that cause intestinal infections, respectively. The predominant serogroup was O15 (70.6%), which is a globally distributed extraintestinal pathogen. Interestingly, one isolate from factory A1 belonged to O157 and carried six virulence genes, simultaneously. CONCLUSIONS Although E. coli isolates were isolated from bulk tank milk, and not the clinical mastitis samples, the presence of the phylogenetic groups B2 and D, and the serogroups O15 and O157, which harbor antimicrobial resistance genes and virulence factors, can pose a threat to public health.
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Affiliation(s)
- Hye-Ri Jung
- College of Veterinary Medicine & Zoonoses Research Institute, Kyungpook National University, Daegu, 41566 Republic of Korea
| | - Koeun Kim
- College of Veterinary Medicine & Zoonoses Research Institute, Kyungpook National University, Daegu, 41566 Republic of Korea
| | - Young Ju Lee
- College of Veterinary Medicine & Zoonoses Research Institute, Kyungpook National University, Daegu, 41566 Republic of Korea
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Park SY, Lee M, Lim SR, Kwon H, Lee YS, Kim JH, Seo S. Diversity and Antimicrobial Resistance in the Streptococcus bovis/ Streptococcus equinus Complex (SBSEC) Isolated from Korean Domestic Ruminants. Microorganisms 2021; 9:98. [PMID: 33406675 PMCID: PMC7824528 DOI: 10.3390/microorganisms9010098&set/a 837648689+998116719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023] Open
Abstract
S. bovis/S. equinus complex (SBSEC) includes lactic acid-producing bacteria considered as the causative agent associated with acute rumen lactic acidosis in intensive ruminants. Considering the limited information on the detailed characteristics and diversity of SBSEC in Korea and the emergence of antimicrobial resistance (AMR), we investigated the diversity of SBSEC from domestic ruminants and verified the presence of antimicrobial resistance genes (ARGs) against several antimicrobials with their phenotypic resistance. Among 51 SBSEC isolates collected, two SBSEC members (S. equinus and S. lutetiensis) were identified; sodA-based phylogenetic analyses and comparisons of overall genome relatedness revealed potential plasticity and diversity. The AMR rates of these SBSEC against erythromycin, clindamycin, and tetracycline were relatively lower than those of other SBSEC isolates of a clinical origin. An investigation of the ARGs against those antimicrobials indicated that tetracycline resistance of SBSECs generally correlated with the presence of tet(M)-possessing Tn916-like transposon. However, no correlation between the presence of ARGs and phenotypic resistance to erythromycin and clindamycin was observed. Although a limited number of animals and their SBSEC isolates were examined, this study provides insights into the potential intraspecies biodiversity of ruminant-origin SBSEC and the current status on antimicrobial resistance of the bacteria in the Korean livestock industry.
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Affiliation(s)
- Seon Young Park
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
- Division of Animal and Dairy Sciences, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea;
| | - Mingyung Lee
- Division of Animal and Dairy Sciences, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea;
| | - Se Ra Lim
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
| | - Hyemin Kwon
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
| | - Ye Seul Lee
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
| | - Ji Hyung Kim
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
- Correspondence: (J.H.K.); (S.S.); Tel.: +82-(42)-879-8272 (J.H.K.)
| | - Seongwon Seo
- Division of Animal and Dairy Sciences, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea;
- Correspondence: (J.H.K.); (S.S.); Tel.: +82-(42)-879-8272 (J.H.K.)
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Diversity and Antimicrobial Resistance in the Streptococcus bovis/Streptococcus equinus Complex (SBSEC) Isolated from Korean Domestic Ruminants. Microorganisms 2021. [DOI: 10.3390/microorganisms9010098
expr 822437316 + 998765163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023] Open
Abstract
S. bovis/S. equinus complex (SBSEC) includes lactic acid-producing bacteria considered as the causative agent associated with acute rumen lactic acidosis in intensive ruminants. Considering the limited information on the detailed characteristics and diversity of SBSEC in Korea and the emergence of antimicrobial resistance (AMR), we investigated the diversity of SBSEC from domestic ruminants and verified the presence of antimicrobial resistance genes (ARGs) against several antimicrobials with their phenotypic resistance. Among 51 SBSEC isolates collected, two SBSEC members (S. equinus and S. lutetiensis) were identified; sodA-based phylogenetic analyses and comparisons of overall genome relatedness revealed potential plasticity and diversity. The AMR rates of these SBSEC against erythromycin, clindamycin, and tetracycline were relatively lower than those of other SBSEC isolates of a clinical origin. An investigation of the ARGs against those antimicrobials indicated that tetracycline resistance of SBSECs generally correlated with the presence of tet(M)-possessing Tn916-like transposon. However, no correlation between the presence of ARGs and phenotypic resistance to erythromycin and clindamycin was observed. Although a limited number of animals and their SBSEC isolates were examined, this study provides insights into the potential intraspecies biodiversity of ruminant-origin SBSEC and the current status on antimicrobial resistance of the bacteria in the Korean livestock industry.
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Park SY, Lee M, Lim SR, Kwon H, Lee YS, Kim JH, Seo S. Diversity and Antimicrobial Resistance in the Streptococcus bovis/ Streptococcus equinus Complex (SBSEC) Isolated from Korean Domestic Ruminants. Microorganisms 2021; 9:microorganisms9010098. [PMID: 33406675 PMCID: PMC7824528 DOI: 10.3390/microorganisms9010098] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 12/24/2020] [Accepted: 12/31/2020] [Indexed: 01/12/2023] Open
Abstract
S. bovis/S. equinus complex (SBSEC) includes lactic acid-producing bacteria considered as the causative agent associated with acute rumen lactic acidosis in intensive ruminants. Considering the limited information on the detailed characteristics and diversity of SBSEC in Korea and the emergence of antimicrobial resistance (AMR), we investigated the diversity of SBSEC from domestic ruminants and verified the presence of antimicrobial resistance genes (ARGs) against several antimicrobials with their phenotypic resistance. Among 51 SBSEC isolates collected, two SBSEC members (S. equinus and S. lutetiensis) were identified; sodA-based phylogenetic analyses and comparisons of overall genome relatedness revealed potential plasticity and diversity. The AMR rates of these SBSEC against erythromycin, clindamycin, and tetracycline were relatively lower than those of other SBSEC isolates of a clinical origin. An investigation of the ARGs against those antimicrobials indicated that tetracycline resistance of SBSECs generally correlated with the presence of tet(M)-possessing Tn916-like transposon. However, no correlation between the presence of ARGs and phenotypic resistance to erythromycin and clindamycin was observed. Although a limited number of animals and their SBSEC isolates were examined, this study provides insights into the potential intraspecies biodiversity of ruminant-origin SBSEC and the current status on antimicrobial resistance of the bacteria in the Korean livestock industry.
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Affiliation(s)
- Seon Young Park
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
- Division of Animal and Dairy Sciences, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea;
| | - Mingyung Lee
- Division of Animal and Dairy Sciences, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea;
| | - Se Ra Lim
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
| | - Hyemin Kwon
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
| | - Ye Seul Lee
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
| | - Ji Hyung Kim
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea; (S.Y.P.); (S.R.L.); (H.K.); (Y.S.L.)
- Correspondence: (J.H.K.); (S.S.); Tel.: +82-(42)-879-8272 (J.H.K.)
| | - Seongwon Seo
- Division of Animal and Dairy Sciences, College of Agriculture and Life Science, Chungnam National University, Daejeon 34134, Korea;
- Correspondence: (J.H.K.); (S.S.); Tel.: +82-(42)-879-8272 (J.H.K.)
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Kim K, Yoon S, Kim YB, Lee YJ. Virulence Variation of Salmonella Gallinarum Isolates through SpvB by CRISPR Sequence Subtyping, 2014 to 2018. Animals (Basel) 2020; 10:ani10122346. [PMID: 33317043 PMCID: PMC7763567 DOI: 10.3390/ani10122346] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 12/07/2020] [Accepted: 12/07/2020] [Indexed: 11/25/2022] Open
Abstract
Simple Summary Salmonella Gallinarum causes fowl typhoid in all ages of chickens, which results in economic loss of commercial chicken farms. The disease has been eradicated in many developed countries, but is still prevalent in Korea. In this study, we investigated virulence and genetic variation of S. Gallinarum from Korea, between 2014 and 2018. The results indicated that virulence was increased, which was associated with genetic change over time. Therefore, surveillance of genetic change associated with virulence increase is necessary for monitoring of S. Gallinarum isolates for dissemination. Abstract Salmonella Gallinarum is a Gram-negative bacteria that causes fowl typhoid, a septicemic disease with high morbidity and mortality that affects all ages of chickens. Although vaccines and antimicrobials have been used nationwide to eradicate the disease, the malady is still prevalent in Korea. In this study, we investigated the virulence and genetic variation of 116 S. Gallinarum isolates from laying hens between 2014 and 2018. A total of 116 isolates were divided into five Gallinarum Sequence Types (GST) through clustered regularly interspaced short palindromic repeats (CRISPR) subtyping method. The GSTs displayed changes over time. The 116 isolates showed no difference in virulence gene distribution, but the polyproline linker (PPL) length of the SpvB, one of the virulence factors of Salmonella spp., served as an indicator of S. Gallinarum pathogenicity. The most prevalent PPL length was 22 prolines (37.9%). The shortest PPL length (19 prolines) was found only in isolates from 2014 and 2015. However, the longest PPL length of 24 prolines appeared in 2018. This study indicates that PPLs of S. Gallinarum in Korea tend to lengthen over time, so the pathogenic potency of the bacteria is increasing. Moreover, the transition of GST was associated with PPL length extension over time. These results indicate that surveillance of changing GST and PPL length are necessary in the monitoring of S. Gallinarum isolates.
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