Kelleher B P, Scott J M, O'Broin S D
Department of Haematology, St James's Hospital, Dublin, Ireland.
Clin Lab Haematol. 1990;12(1):87-95. doi: 10.1111/j.1365-2257.1990.tb01114.x.
The presence of certain antibiotics in patients' sera can invalidate microbiological assays for vitamin B12 using Lactobacillus leichmannii by inhibiting organism growth. Analysis of 3291 consecutive serum vitamin B12 assays in a large general hospital service showed inhibition of growth in 303 samples (9.2%). In nearly all cases the interfering substance was a beta-lactam antibiotic. The value of using a beta-lactamase preparation to eliminate antibiotic effects was studied using antibiotic-containing patient sera and also normal serum to which antibiotics were added. In-vitro additions of penicillins, cephalosporins, and other antibiotics to normal serum resulted in varying levels of organism inhibition, but excellent recovery of a control value after treatment with beta-lactamase (greater than 98%). Patient sera showing inhibition were reassayed in duplicate following treatment with beta-lactamase (n = 200), the overall effectiveness of the treatment being verified by the excellent recovery (greater than 98%) of a cyanocobalamin 'spike' added to a control. In only 0.2% of cases (6 of 3291 samples) was this treatment ineffective and it has thus proved an efficient method of eliminating the problem of antibiotic interference in the vitamin B12 microbiological assay.
患者血清中某些抗生素的存在会抑制赖氏乳杆菌的生长，从而使维生素B12的微生物检测结果无效。一家大型综合医院对3291例连续的血清维生素B12检测进行分析，结果显示有303份样本（9.2%）出现生长抑制。几乎在所有病例中，干扰物质都是β-内酰胺类抗生素。利用含抗生素的患者血清以及添加了抗生素的正常血清，研究了使用β-内酰胺酶制剂消除抗生素影响的效果。在体外将青霉素、头孢菌素和其他抗生素添加到正常血清中会导致不同程度的微生物抑制，但用β-内酰胺酶处理后对照值的恢复情况良好（大于98%）。对显示有抑制作用的患者血清在用β-内酰胺酶处理后进行了重复检测（n = 200），通过向对照中添加氰钴胺“加标”后恢复良好（大于98%）验证了该处理方法的总体有效性。在仅0.2%的病例（3291份样本中的6份）中，该处理方法无效，因此它已被证明是消除维生素B12微生物检测中抗生素干扰问题的有效方法。
