赖氨酸脱羧酶单管试验在诊断EIEC中的效用

LYSINE DECARBOXYLASE TEST ( SINGLE-TUBE-OULTURE METHOD ) IN THE DIAGNOSIS OF ENTEROINVASIVE ESCHERICHIA COLI ( EIEC )

从Falkow法(常规法)抽去基础培养基蛋白胨,代以氯化钠称单管法。56株EIEC血清型大肠菌用单管法和常规法对比赖氨酸脱羧酶试验(赖酶试验)。并以140-Md质粒(140-Md)检测和豚鼠角膜结膜炎试验(Sereny试验)分析三者关系。结果发现:凡140-Md(+)菌株,单管法赖酶试验均(-)。25株140-Md(-)株,两法均在24小时内脱羧。但常规法中8株140-Md(+)株3～4天内脱羧,其中5株Sereny试验(+)。作者根据EIEC血清型大肠菌140-Md(+)与单管法赖酶试验(-)一致性的结果,对少数140-Md(+)而Sereny试验(-)株应纳入EIEC范畴进行了诊断依据的讨论。

0.3% NaCl used as a substitute for the 0.5% peptone in the culture medium in Falkow's lysine decarboxylase test was called single-tube-culture method (STC) . For comparison, Falkow's method and STC were run in parallel for the identification of 56 strains of E. coli belonging to EIEC serotypes. Agarose gel electrophoresis showed that lysine decarboxylase negative strains in STC were all with 140 Md plasmid. Of 26 strains without 140 Md plasmid in two methods were all lysine decarboxylase positive within 24 hours. But 8 strains with 140 Md plasmid in Falkow's method were lysine decarboxylase positive within 3-4 days. Of these 8 strains, 5 showed positive in Sereny test. It was proved that strains with 140 Md plasmid revealing positive lysine decarboxylase test within 3-4 days can turn to negative STC on the sixth day. AS a rule, in EIEC, positive 140 Md plasmid always accompanies with negative lysine decarboxylase. Authors are of the opinion that those with 40 Md plasmid but non-invasive strains [d.e., the strains isolated from the human stool showing biochemical characteristics of E. coli-s. Shigella strains with positive indole test and negative decarboxylase test in STC,and nonmotile strains (except O24:H30) ] should be included in EIEC surogroups.