Department of Veterinary Sciences, University of Turin, Largo Paolo Braccini 2-5, 10095, Grugliasco, Italy.
Istituto Zooprofilattico Sperimentale delle Venezie, Viale dell'Università 10, 35020, Legnaro, PD, Italy.
BMC Vet Res. 2020 Nov 23;16(1):455. doi: 10.1186/s12917-020-02670-3.
Surgical sterilization is the most effective method of contraception for dogs. It also prevents pyometra and reduces the risk of mammary tumour development. However, this procedure also has negative effects, such as urinary incontinence. Steroid hormone deprivation following gonadectomy could also affect canine vaginal mucosa conditions and the microbial community colonizing the vaginal tract. This hypothesis was tested by comparing the vaginal cytology and microbial community of two groups of bitches, including 11 in anoestrus and 10 sterilized bitches (post-pubertal sterilization in the last 4 years). Bacteria were identified through metataxonomic analysis, amplifying the V3-V4 regions of 16S rRNA gene, and culturing methods.
Vaginal mucosa cytology was suggestive of dystrophic conditions in sterilized bitches, whereas a typical anoestrus pattern with parabasal and intermediate cells was appreciable in anoestrous animals. Metataxonomic analysis revealed large inter-individual variability. Salmonella, Mycoplasma and Staphylococcus were present in moderate quantities in almost all the samples in both groups. Mollicutes (class level) and Tenericutes (phylum level) were commonly present in moderate quantities in anoestrus samples, whereas these microbes were present at high levels in a single sample from the sterilized group. Based on culturing, a higher number of different species were isolated from the anoestrous bitches, and Mycoplasma canis was exclusively identified in an anoestrous bitch. Staphylococcus spp. was the most frequently isolated genus in both groups, followed by Streptococcus spp., and, among gram-negative bacteria, Escherichia spp. and Haemophilus spp. A comparison of the numbers of the most frequently isolated genera of bacteria from vaginal cultures of bitches revealed that Pasteurella and Proteus were the most frequently identified in sterilized animals based on metataxonomic analysis (p-value = 0.0497 and 0.0382, respectively), whereas Streptococcus was significantly and most frequently isolated from anoestrous bitches using culture methods (p value = 0.0436).
In this preliminary investigation, no global patterns of the vaginal bacteria community were noted that characterized the condition of the bitches; however, cytology suggested local modifications. Sterilization after puberty caused minimal alterations in the vaginal microbial community of bitches within 4 years after surgery.
绝育手术是犬类最有效的避孕方法。它还可以预防子宫蓄脓，并降低乳腺肿瘤发展的风险。然而，这种手术也有负面影响，如尿失禁。去势后类固醇激素的缺乏也可能影响犬阴道黏膜状况和定植于阴道的微生物群落。本研究通过比较两组母犬（11 只乏情和 10 只绝育犬）的阴道细胞学和微生物群落来验证这一假说，绝育犬为青春期后 4 年内绝育。细菌通过分类学分析、扩增 16S rRNA 基因的 V3-V4 区和培养方法进行鉴定。
绝育犬的阴道黏膜细胞学提示存在营养不良，而乏情动物则表现出典型的乏情模式，即有巴氏细胞和中层细胞。分类学分析显示个体间存在较大差异。在两组样本中，几乎所有样本中都存在中等数量的沙门氏菌、支原体和葡萄球菌。在乏情样本中，莫拉氏菌（纲水平）和柔膜体纲（门水平）通常以中等数量存在，而在绝育组的单个样本中，这些微生物以高水平存在。基于培养，乏情母犬分离的不同物种数量更多，而犬支原体仅在一只乏情母犬中被鉴定出来。葡萄球菌属是两组中最常分离到的菌属，其次是链球菌属，在革兰氏阴性菌中，埃希氏菌属和嗜血杆菌属最常分离到。比较两组母犬阴道培养中最常分离到的细菌属的数量发现，基于分类学分析，巴氏杆菌属和变形杆菌属在绝育动物中最常被识别（p 值分别为 0.0497 和 0.0382），而链球菌属则是通过培养方法从乏情母犬中最常分离到的菌属（p 值为 0.0436）。
在这项初步研究中，没有发现能够描述母犬状况的阴道细菌群落的整体模式，但细胞学提示存在局部变化。青春期后绝育在手术后 4 年内对母犬阴道微生物群落的影响很小。
