Verhelst Rita, Verstraelen Hans, Claeys Geert, Verschraegen Gerda, Van Simaey Leen, De Ganck Catharine, De Backer Ellen, Temmerman Marleen, Vaneechoutte Mario
Department Clinical Chemistry, Microbiology & Immunology, Ghent University Hospital, UGent, Ghent, Belgium.
BMC Microbiol. 2005 Oct 14;5:61. doi: 10.1186/1471-2180-5-61.
The microbiological diagnosis of bacterial vaginosis is usually made using Nugent's criteria, a useful but rather laborious scoring system based on counting bacterial cell types on Gram stained slides of vaginal smears. Ison and Hay have simplified the score system to three categories and added a fourth category for microflora with a predominance of the Streptococcus cell type. Because in the Nugent system several cell types are not taken into account for a final score, we carried out a detailed assessment of the composition of the vaginal microflora in relation to standard Gram stain in order the improve the diagnostic value of the Gram stain. To this purpose we compared Gram stain based categorization of vaginal smears with i) species specific PCR for the detection of Gardnerella vaginalis and Atopobium vaginae and with ii) tDNA-PCR for the identification of most cultivable species.
A total of 515 samples were obtained from 197 pregnant women, of which 403 (78.3%) were categorized as grade I microflora, 46 (8.9%) as grade II, 22 (4.3%) as grade III and 8 (1.6%) as grade IV, according to the criteria of Ison and Hay. Another 36 samples (7.0%) were assigned to the new category 'grade I-like', because of the presence of diphtheroid bacilli cell types. We found that 52.7% of the grade I-like samples contained Bifidobacterium spp. while L. crispatus was present in only 2.8% of the samples and G. vaginalis and A. vaginae were virtually absent; in addition, the species diversity of this category was similar to that of grade II specimens.Based on the presence of different Lactobacillus cell types, grade I specimens were further characterized as grade Ia (40.2%), grade Iab (14.9%) and grade Ib (44.9%). We found that this classification was supported by the finding that L. crispatus was cultured from respectively 87.0% and 76.7% of grade Ia and Iab specimens while this species was present in only 13.3% of grade Ib specimens, a category in which L. gasseri and L. iners were predominant.
Further refinement of Gram stain based grading of vaginal smears is possible by distinguishing additional classes within grade I smears (Ia, Iab and Ib) and by adding a separate category, designated grade I-like. A strong correlation was found between grade Ia and the presence of L. crispatus and between grade I-like and the presence of bifidobacteria. This refinement of Gram stain based scoring of vaginal smears may be helpful to improve the interpretation of the clinical data in future studies, such as the understanding of response to treatment and recurrence of bacterial vaginosis in some women, and the relationship between bacterial vaginosis and preterm birth.
细菌性阴道病的微生物学诊断通常采用纽金特标准，这是一种基于对阴道涂片革兰氏染色玻片上细菌细胞类型进行计数的有用但相当繁琐的评分系统。伊森和海伊将评分系统简化为三类，并增加了第四类以涵盖以链球菌细胞类型为主的微生物群落。由于在纽金特系统中，最终评分未考虑几种细胞类型，我们对阴道微生物群落的组成与标准革兰氏染色进行了详细评估，以提高革兰氏染色的诊断价值。为此，我们将基于革兰氏染色的阴道涂片分类与以下两种方法进行了比较：i）用于检测阴道加德纳菌和阴道阿托波菌的种特异性聚合酶链反应（PCR），以及ii）用于鉴定大多数可培养菌种的tDNA-PCR。
从197名孕妇中总共获得了515份样本。根据伊森和海伊的标准，其中403份（78.3%）被归类为I级微生物群落，46份（8.9%）为II级，22份（4.3%）为III级，8份（1.6%）为IV级。另外36份样本（7.0%）因存在类白喉杆菌细胞类型而被归入新类别“类I级”。我们发现，52.7%的类I级样本含有双歧杆菌属，而卷曲乳杆菌仅存在于2.8%的样本中，阴道加德纳菌和阴道阿托波菌几乎不存在；此外，该类别的物种多样性与II级样本相似。基于不同乳酸杆菌细胞类型的存在，I级样本进一步分为Ia级（40.2%）、Iab级（14.9%）和Ib级（44.9%）。我们发现，Ia级和Iab级样本分别有87.0%和76.7%培养出卷曲乳杆菌，而该菌种仅存在于13.3%的Ib级样本中，Ib级样本中以加氏乳杆菌和惰性乳杆菌为主，这一发现支持了这种分类。
通过在I级涂片中区分额外的类别（Ia、Iab和Ib）并增加一个单独的类别（称为类I级），可以进一步完善基于革兰氏染色的阴道涂片分级。发现Ia级与卷曲乳杆菌的存在以及类I级与双歧杆菌的存在之间存在很强的相关性。这种基于革兰氏染色的阴道涂片评分的完善可能有助于在未来的研究中改进临床数据的解读，例如对某些女性治疗反应和细菌性阴道病复发的理解，以及细菌性阴道病与早产之间的关系。
