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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Autores principales:	Nives Maria Rosa, Ilaria Duprè, Elisa Azara, Carla Maria Longheu, Sebastiana Tola
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	<i>Streptococcus uberis</i> mastitis typing antimicrobial susceptibility resistance genes Medicine R
Acceso en línea:	https://doaj.org/article/345a08a9e08844b5b000d0a56beb2304
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spelling	oai:doaj.org-article:345a08a9e08844b5b000d0a56beb23042021-11-25T18:38:39ZMolecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk10.3390/pathogens101114892076-0817https://doaj.org/article/345a08a9e08844b5b000d0a56beb23042021-11-01T00:00:00Zhttps://www.mdpi.com/2076-0817/10/11/1489https://doaj.org/toc/2076-0817Intramammary 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.Nives Maria RosaIlaria DuprèElisa AzaraCarla Maria LongheuSebastiana TolaMDPI AGarticle<i>Streptococcus uberis</i>mastitistypingantimicrobial susceptibilityresistance genesMedicineRENPathogens, Vol 10, Iss 1489, p 1489 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	<i>Streptococcus uberis</i> mastitis typing antimicrobial susceptibility resistance genes Medicine R
spellingShingle	<i>Streptococcus uberis</i> mastitis typing antimicrobial susceptibility resistance genes Medicine R 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
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.
format	article
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
title	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_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_sort	molecular typing and antimicrobial susceptibility profiles of <i>streptococcus uberis</i> isolated from sheep milk
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/345a08a9e08844b5b000d0a56beb2304
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Molecular Typing and Antimicrobial Susceptibility Profiles of <i>Streptococcus uberis</i> Isolated from Sheep Milk

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