Rosa Nives Maria, Duprè Ilaria, Azara Elisa, Longheu Carla Maria, Tola Sebastiana
Istituto Zooprofilattico Sperimentale della Sardegna G. Pegreffi, 07100 Sassari, Italy.
Agris Sardegna, Servizio per la Ricerca nelle Produzioni Animali, Loc. Bonassai, SS291 km 18.600, 07100 Sassari, Italy.
Pathogens. 2021 Nov 16;10(11):1489. doi: 10.3390/pathogens10111489.
Intramammary infections are a major problem for dairy sheep farms, and 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 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 . 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 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 -6 and A-3' genes. Among the TE-resistant isolates, the 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 B gene. This is the first study reporting a detailed characterization of the strains circulating in Sardinian sheep. Further investigations will be needed to understand the relationships between genotypes, mastitis severity, and intra-mammary infection dynamics in the flock, as well as to monitor the evolution of antimicrobial resistance.
乳房内感染是奶羊养殖场的一个主要问题，并且是绵羊乳腺炎的主要病原体之一。绵羊中关于抗菌药物耐药性的调查仍然有限，对分离株进行特征分析对于获取耐药性信息和优化治疗很重要。在本研究中，对从意大利撒丁岛绵羊奶中收集的124株分离株进行了多位点序列分型（MLST）和脉冲场凝胶电泳（PFGE）分析，以确定其遗传相关性。所有分离株还通过纸片扩散法使用14种抗菌药物进行了药敏分析。通过PCR检测耐药基因。MLST分析表明，分离株被分为86个序列型（STs），其中73个是新基因型，表明存在高度多样化的群体。最常检测到的谱系是克隆复合体（CC）143，尽管仅占所有已鉴定分离株的13.7%。在PFGE图谱中也观察到高度的异质性，有121种独特的模式。几乎所有（96.8%）分离株对至少一种抗菌药物耐药，而所有分离株对苯唑西林、阿莫西林-克拉维酸和头孢噻呋均表现出表型敏感性。在所测试的抗菌药物中，对链霉素（93.5%）、卡那霉素（79.8%）和庆大霉素（64.5%）的耐药率最高，其次是新生霉素（25%）和四环素-TE（19.3%）。74株（59.7%）分离株对所有测试的氨基糖苷类药物同时耐药。17株（13.7%）分离株表现出多重耐药性。所有对氨基糖苷类药物耐药的分离株的-6和A-3'基因PCR检测均为阴性。在对四环素耐药的分离株中，M基因占主导地位，表明耐药机制主要是通过核糖体保护介导而非通过外排泵。3株分离株对红霉素耐药，其中2株携带B基因。这是第一项报道撒丁岛绵羊中流行的菌株详细特征的研究。需要进一步研究以了解菌株基因型、乳腺炎严重程度和羊群中乳房内感染动态之间的关系，以及监测抗菌药物耐药性的演变。
