Vega Clara, Pérez-Pérez Lucía, Argüello Héctor, Gómez-García Manuel, Puente Héctor, Fernández-Usón Ignacio, Rubio Pedro, Carvajal Ana
Department of Animal Health, Faculty of Veterinary Medicine, Universidad de León, Campus de Vegazana S/N, 24007, León, Spain.
INDEGSAL, Universidad de León, Campus de Vegazana S/N, 24007, León, Spain.
Porcine Health Manag. 2022 Dec 1;8(1):48. doi: 10.1186/s40813-022-00291-w.
The treatment of swine dysentery (SD) has become constrained in recent years due to the limited availability of effective drugs combined with a rise in antimicrobial resistance. Gentamicin, an aminoglycoside antibiotic, is authorised for the control of this disease in several European countries but has not been extensively used so far. In this study, the in vitro susceptibility of 56 Brachyspira hyodysenteriae field isolates was evaluated against gentamicin using a broth microdilution test. The molecular basis of decreased susceptibility to gentamicin was also investigated by sequencing the 16S rRNA gene and phylogenetic relatedness by multiple-locus variable number tandem-repeat analysis (MLVA).
Most B. hyodysenteriae isolates presented low minimum inhibitory concentration (MIC) values to gentamicin, with a mode of 2 µg/mL, a median or MIC of 4 µg/mL and percentile 90 or MIC of 16 µg/mL. The distribution of these values over the period studied (2011-2019) did not show a tendency towards the development of resistance to gentamicin. Differences in susceptibility among isolates could be explained by two point-mutations in the 16S rRNA gene, C990T and A1185G, which were only present in isolates with high MICs. These isolates were typed in three different MLVA clusters. Analyses of co-resistance between gentamicin and antimicrobials commonly used for the treatment of SD revealed that resistance to tiamulin and valnemulin was associated with low MICs for gentamicin.
The results provide an accurate characterisation of antimicrobial sensitivity to gentamicin and possible mechanisms of resistance in Spanish B. hyodysenteriae isolates. These findings allow us to propose gentamicin as an alternative in the antibiotic management of SD, particularly in outbreaks caused by pleuromutilin resistant isolates.
近年来，由于有效药物供应有限以及抗菌药物耐药性增加，猪痢疾（SD）的治疗受到限制。庆大霉素是一种氨基糖苷类抗生素，在几个欧洲国家被批准用于控制这种疾病，但迄今为止尚未得到广泛应用。在本研究中，使用肉汤微量稀释试验评估了56株猪痢疾短螺旋体田间分离株对庆大霉素的体外敏感性。还通过对16S rRNA基因进行测序以及多基因座可变数目串联重复分析（MLVA）研究了对庆大霉素敏感性降低的分子基础。
大多数猪痢疾短螺旋体分离株对庆大霉素的最低抑菌浓度（MIC）值较低，众数为2μg/mL，MIC中位数为4μg/mL，第90百分位数MIC为16μg/mL。在所研究的时间段（2011 - 2019年）内，这些值的分布未显示出对庆大霉素耐药性发展的趋势。分离株之间敏感性的差异可由16S rRNA基因中的两个点突变C990T和A1185G解释，这两个突变仅存在于高MIC的分离株中。这些分离株被分为三个不同的MLVA簇。对庆大霉素与常用于治疗SD的抗菌药物之间的共同耐药性分析表明，对泰妙菌素和伐地那非的耐药性与庆大霉素的低MIC相关。
研究结果准确描述了西班牙猪痢疾短螺旋体分离株对庆大霉素的抗菌敏感性以及可能的耐药机制。这些发现使我们能够提出将庆大霉素作为SD抗生素管理中的一种替代药物，特别是在由截短侧耳素耐药分离株引起的疫情中。
