B群链球菌显色培养基性能评价

Performance evaluation of colour medium for group B Streptococcus

目的评价B群链球菌(group B Streptococcus,GBS)显色培养基在孕产妇围产期GBS筛查中的敏感性、特异性和选择性能。方法选取2019年1月至2019年6月在本院产科门诊就诊的35~37周孕妇阴道拭子标本1 500例,已知GBS菌株10例,采用三区划线直接接种于血琼脂培养基(bood agar plate,BAP)和GBS显色培养基(chromogenic medium chromID Strepto B agar,STRB),记录鉴定结果。比较直接接种血琼脂培养基和显色培养基筛查GBS的敏感性、特异性及选择性能。结果在BAP和STRB上接种的已知10例GBS菌株全部检出,检出率为100.0%。孕产妇标本共筛查出125例GBS,阳性率为8.3%(125/1 500)。其中培养24 h后,BAP与STRB阳性率分别为6.2%(94/1 500)和8.1%(122/1 500);培养48 h后,BAP与STRB阳性率均为8.3%(125/1 500),高于24 h阳性率。STRB筛查GBS敏感性为97.60%,特异性为99.35%。STRB与BAP筛查GBS阳性率比较差异有统计学意义(χ^(2)=3.911,P<0.05)。BAP上接种24 h及48 h后,分别有32.3%及31.8%的非目标菌群被完全抑制。STRB上接种24 h及48 h后,分别有72.6%及70.9%的非目标菌群被完全抑制。孵育24 h后,BAP与STRB非目标菌群生长密度比较差异有统计学意义(χ^(2)=32.684,P<0.05)。结论 B群链球菌显色培养基对于临床GBS筛查有良好的敏感性和特异性,可较好的抑制非目标菌群,选择性能良好,结果易于判断,与直接使用普通血琼脂培养基相比可降低漏检率,值得临床推广运用。

Objective To evaluate the sensitivity, specificity and selectivity of group B Streptococcus(GBS) colour medium for screening GBS during perinatal period. Methods 1 500 vaginal swab specimens were collected from late pregnant women and 10 GBS strains were selected. The three zoning lines were directly inoculated into blood agar plate(BAP) and GBS chromogenic medium chromID Strepto B agar(STRB) to record the identification results. To compare the sensitivity, specificity and selectivity of GBS screening by direct inoculation of blood agar medium and chromogenic medium. Results All the 10 cases known GBS strains inoculated on BAP and STRB were detected, and the detection rate was 100.0%. 125 cases of GBS were screened out from maternal specimens, the positive rate was 8.3%(125/1 500). After 24 h of culture, the positive rates of BAP and STRB were 6.2%(94/1 500) and 8.1%(122/1 500), respectively. The positive rates of BAP and STRB were 8.3%(125/1 500) after 48 h of culture,which was higher than that of 24 h. The sensitivity and specificity of STRB screening for GBS were 97.60% and 99.35%. There was significant difference in GBS positive rate between STRB and BAP screening(χ^(2)= 3.911, P<0.05). After 24 hours and 48 hours of inoculation, 32.3% and 31.8% of non-target bacteria were completely inhibited, respectively. After 24 hours and 48 hours of STRB inoculation, 72.6% and 70.9% of non-target bacteria were completely inhibited, respectively. After 24 hours of incubation, the growth densities of BAP and STRB non-target flora were significantly difference(χ^(2)=32.684, P<0.05). Conclusion The colour medium of group B Streptococcus has good sensitivity and specificity for clinical GBS screening. It can inhibit non-target bacteria better and has good selectivity. The results are easy to judge. Compared with the normal blood agar medium, it can reduce the rate of missed detection and it is worthly of application and promotion in the work.