Atherton J C, Cover T L, Twells R J, Morales M R, Hawkey C J, Blaser M J
Department of Medicine, Division of Gastroenterology, University Hospital, University of Nottingham, Nottingham, United Kingdom.
J Clin Microbiol. 1999 Sep;37(9):2979-82. doi: 10.1128/JCM.37.9.2979-2982.1999.
Alleles of the vacuolating cytotoxin gene (vacA) of Helicobacter pylori vary between strains, particularly in the region encoding the signal sequence (which may be type s1 or s2) and the midregion (which may be type m1 or m2). Using a PCR-based typing system developed in the United States, we showed that 36 strains from Asia and South America were all vacA signal sequence type s1; 3 were midregion type m1 and 11 were m2, but 22 could not be typed for the vacA midregion. All strains possessed cagA (cytotoxin-associated gene A), another virulence marker. vacA nucleotide sequence analysis showed that midregion typing failure was due to base substitutions at the primer annealing sites. Using the new sequence data, we developed two new PCR-based vacA midregion typing systems, both of which correctly typed 41 U.S. strains previously typed by the old system and successfully typed all 36 of the non-U.S. strains. All previously untypeable strains were vacA m1, other than one m1/m2 hybrid. In summary, we describe and validate a simple PCR-based system for typing vacuolating cytotoxin (vacA) alleles of H. pylori and show that this system correctly identifies the signal and midregion types of vacA in 77 strains from Asia and North and South America.
幽门螺杆菌空泡毒素基因（vacA）的等位基因在不同菌株间存在差异，尤其是在编码信号序列（可能是s1型或s2型）和中间区域（可能是m1型或m2型）的区域。我们使用在美国开发的基于聚合酶链反应（PCR）的分型系统，发现来自亚洲和南美洲的36株菌株均为vacA信号序列s1型；3株为中间区域m1型，11株为m2型，但22株无法对vacA中间区域进行分型。所有菌株均携带细胞毒素相关基因A（cagA），这是另一种毒力标志物。vacA核苷酸序列分析表明，中间区域分型失败是由于引物退火位点的碱基替换所致。利用新的序列数据，我们开发了两种基于PCR的新型vacA中间区域分型系统，这两种系统均能正确分型先前用旧系统分型的41株美国菌株，并成功分型所有36株非美国菌株。除了一株m1/m2杂交菌株外，所有先前无法分型的菌株均为vacA m1型。总之，我们描述并验证了一种简单的基于PCR的系统，用于对幽门螺杆菌空泡毒素（vacA）等位基因进行分型，并表明该系统能正确识别来自亚洲以及北美洲和南美洲的77株菌株中vacA的信号和中间区域类型。
