Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk
Intramammary infections are a major problem for dairy sheep farms, and <i>Streptococcus uberis</i> is one of the main etiological agents of ovine mastitis. Surveys on antimicrobial resistance are still limited in sheep and characterization of isolates is important for acquiring informati...
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MDPI AG
2021-11-01
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| Series: | Pathogens |
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| Online Access: | https://www.mdpi.com/2076-0817/10/11/1489 |
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| author | Nives Maria Rosa Ilaria Duprè Elisa Azara Carla Maria Longheu Sebastiana Tola |
| author_facet | Nives Maria Rosa Ilaria Duprè Elisa Azara Carla Maria Longheu Sebastiana Tola |
| author_sort | Nives Maria Rosa |
| collection | DOAJ |
| description | Intramammary infections are a major problem for dairy sheep farms, and <i>Streptococcus uberis</i> is one of the main etiological agents of ovine mastitis. Surveys on antimicrobial resistance are still limited in sheep and characterization of isolates is important for acquiring information on resistance and for optimizing therapy. In this study, a sampling of 124 <i>S.</i> <i>uberis</i> isolates collected in Sardinia (Italy) from sheep milk was analyzed by multilocus-sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) for genetic relatedness. All isolates were also subjected to antimicrobial susceptibility analysis by the disk diffusion test using a panel of 14 antimicrobials. Resistance genes were detected by PCR assays. MLST analysis revealed that the isolates were grouped into 86 sequence types (STs), of which 73 were new genotypes, indicating a highly diverse population of <i>S. uberis</i>. The most frequently detected lineage was the clonal complex (CC)143, although representing only 13.7% of all characterized isolates. A high level of heterogeneity was also observed among the <i>Sma</i>I PFGE profiles, with 121 unique patterns. Almost all (96.8%) isolates were resistant to at least one antimicrobial, while all exhibited phenotypic susceptibility to oxacillin, amoxicillin-clavulanic acid and ceftiofur. Of the antimicrobials tested, the highest resistance rate was found against streptomycin (93.5%), kanamycin (79.8%) and gentamicin (64.5%), followed by novobiocin (25%) and tetracycline-TE (19.3%). Seventy-four (59.7%) isolates were simultaneously resistant to all aminoglycosides tested. Seventeen isolates (13.7%) exhibited multidrug resistance. All aminoglycosides-resistant isolates were PCR negative for <i>aad</i>-6 and <i>aph</i>A-3′ genes. Among the TE-resistant isolates, the <i>tet</i>M gene was predominant, indicating that the resistance mechanism is mainly mediated by the protection of ribosomes and not through the efflux pump. Three isolates were resistant to erythromycin, and two of them harbored the <i>erm</i>B gene. This is the first study reporting a detailed characterization of the <i>S. uberis</i> strains circulating in Sardinian sheep. Further investigations will be needed to understand the relationships between <i>S. uberis</i> genotypes, mastitis severity, and intra-mammary infection dynamics in the flock, as well as to monitor the evolution of antimicrobial resistance. |
| first_indexed | 2024-03-10T05:09:46Z |
| format | Article |
| id | doaj.art-345a08a9e08844b5b000d0a56beb2304 |
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| language | English |
| last_indexed | 2024-03-10T05:09:46Z |
| publishDate | 2021-11-01 |
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| spelling | doaj.art-345a08a9e08844b5b000d0a56beb23042023-11-23T00:54:05ZengMDPI AGPathogens2076-08172021-11-011011148910.3390/pathogens10111489Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep MilkNives Maria Rosa0Ilaria Duprè1Elisa Azara2Carla Maria Longheu3Sebastiana Tola4Istituto Zooprofilattico Sperimentale della Sardegna G. Pegreffi, 07100 Sassari, ItalyIstituto Zooprofilattico Sperimentale della Sardegna G. Pegreffi, 07100 Sassari, ItalyIstituto Zooprofilattico Sperimentale della Sardegna G. Pegreffi, 07100 Sassari, ItalyIstituto Zooprofilattico Sperimentale della Sardegna G. Pegreffi, 07100 Sassari, ItalyIstituto Zooprofilattico Sperimentale della Sardegna G. Pegreffi, 07100 Sassari, ItalyIntramammary infections are a major problem for dairy sheep farms, and <i>Streptococcus uberis</i> is one of the main etiological agents of ovine mastitis. Surveys on antimicrobial resistance are still limited in sheep and characterization of isolates is important for acquiring information on resistance and for optimizing therapy. In this study, a sampling of 124 <i>S.</i> <i>uberis</i> isolates collected in Sardinia (Italy) from sheep milk was analyzed by multilocus-sequence typing (MLST) and pulsed field gel electrophoresis (PFGE) for genetic relatedness. All isolates were also subjected to antimicrobial susceptibility analysis by the disk diffusion test using a panel of 14 antimicrobials. Resistance genes were detected by PCR assays. MLST analysis revealed that the isolates were grouped into 86 sequence types (STs), of which 73 were new genotypes, indicating a highly diverse population of <i>S. uberis</i>. The most frequently detected lineage was the clonal complex (CC)143, although representing only 13.7% of all characterized isolates. A high level of heterogeneity was also observed among the <i>Sma</i>I PFGE profiles, with 121 unique patterns. Almost all (96.8%) isolates were resistant to at least one antimicrobial, while all exhibited phenotypic susceptibility to oxacillin, amoxicillin-clavulanic acid and ceftiofur. Of the antimicrobials tested, the highest resistance rate was found against streptomycin (93.5%), kanamycin (79.8%) and gentamicin (64.5%), followed by novobiocin (25%) and tetracycline-TE (19.3%). Seventy-four (59.7%) isolates were simultaneously resistant to all aminoglycosides tested. Seventeen isolates (13.7%) exhibited multidrug resistance. All aminoglycosides-resistant isolates were PCR negative for <i>aad</i>-6 and <i>aph</i>A-3′ genes. Among the TE-resistant isolates, the <i>tet</i>M gene was predominant, indicating that the resistance mechanism is mainly mediated by the protection of ribosomes and not through the efflux pump. Three isolates were resistant to erythromycin, and two of them harbored the <i>erm</i>B gene. This is the first study reporting a detailed characterization of the <i>S. uberis</i> strains circulating in Sardinian sheep. Further investigations will be needed to understand the relationships between <i>S. uberis</i> genotypes, mastitis severity, and intra-mammary infection dynamics in the flock, as well as to monitor the evolution of antimicrobial resistance.https://www.mdpi.com/2076-0817/10/11/1489<i>Streptococcus uberis</i>mastitistypingantimicrobial susceptibilityresistance genes |
| spellingShingle | Nives Maria Rosa Ilaria Duprè Elisa Azara Carla Maria Longheu Sebastiana Tola Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk Pathogens <i>Streptococcus uberis</i> mastitis typing antimicrobial susceptibility resistance genes |
| title | Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk |
| title_full | Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk |
| title_fullStr | Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk |
| title_full_unstemmed | Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk |
| title_short | Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk |
| title_sort | molecular typing and antimicrobial susceptibility profiles of i streptococcus uberis i isolated from sheep milk |
| topic | <i>Streptococcus uberis</i> mastitis typing antimicrobial susceptibility resistance genes |
| url | https://www.mdpi.com/2076-0817/10/11/1489 |
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