Agodi A, Marranzano M, Jones C S, Threlfall E J
Institute of General Biology, University of Catania, Sicily, Italy.
Eur J Epidemiol. 1995 Feb;11(1):33-8. doi: 10.1007/BF01719943.
The occurrence of trimethoprim (Tp) resistance in salmonellas isolated from humans and water samples in Sicily between 1985 and 1988 has been investigated and the Tp resistance mechanisms have been further characterized on the basis of hybridization with probes for the dihydrofolate reductase (DHFR) genes types I, II, IV and V. Of 765 strains examined, high level (> 1000 mg/l) resistance to Tp was identified in 23 strains (3%). In 22 of these strains, such resistance was associated with resistance to sulphonamides. Six serovars with Tp-resistant strains were identified, Salmonella typhimurium (14 strains), S. enteridis (2), S. agona (2), S. mbandaka (2), S. virchow (2), S. indiana (1). In all strains with high level Tp resistance, resistance to this antimicrobial was plasmid-encoded, in most strains by plasmids with MWs ranging from 70-100 MDa. On the basis of restriction endonuclease analysis, four different categories of Tp resistance plasmids were identified in Tp-resistant strains of S. typhimurium. Hybridization with the DHFR I probe was observed in three strains of Tp-resistant S. typhimurium and two strains of Tp-resistant S. enteritidis; in contrast, in none of the strains tested was there any detectable hybridization with the probes for DHFR types II, IV and V. It is concluded that the DHFR type I resistance mechanism, common in Tp-resistant enterobacteria in many European countries, is relatively uncommon in Tp-resistant salmonellas isolated in Sicily. Furthermore, the DHFR V resistance mechanism, previously identified in strains of Shigella sonnei isolated in Sicily and associated with travellers from Sri Lanka, has not yet appeared in salmonellas in Sicily.
对1985年至1988年期间从西西里岛的人类和水样中分离出的沙门氏菌中三甲氧苄氨嘧啶（Tp）耐药性的发生情况进行了调查，并根据与二氢叶酸还原酶（DHFR）基因I、II、IV和V型探针的杂交情况进一步表征了Tp耐药机制。在所检测的765株菌株中，有23株（3%）对Tp具有高水平（>1000mg/l）耐药性。在这些菌株中的22株中，这种耐药性与对磺胺类药物的耐药性相关。鉴定出6个带有Tp耐药菌株的血清型，鼠伤寒沙门氏菌（14株）、肠炎沙门氏菌（2株）、阿哥纳沙门氏菌（2株）、姆班达卡沙门氏菌（2株）、维尔肖沙门氏菌（2株）、印第安纳沙门氏菌（1株）。在所有具有高水平Tp耐药性的菌株中，对这种抗菌药物的耐药性是由质粒编码的，在大多数菌株中是由分子量范围为70 - 100MDa的质粒编码的。根据限制性内切酶分析，在鼠伤寒沙门氏菌的Tp耐药菌株中鉴定出四种不同类型的Tp耐药质粒。在3株Tp耐药的鼠伤寒沙门氏菌和2株Tp耐药的肠炎沙门氏菌中观察到与DHFR I探针的杂交；相反，在所测试的菌株中，没有一株与DHFR II、IV和V型探针有可检测到的杂交。得出的结论是，I型DHFR耐药机制在许多欧洲国家的Tp耐药肠杆菌中很常见，但在西西里岛分离出的Tp耐药沙门氏菌中相对不常见。此外，先前在西西里岛分离出的宋内志贺氏菌菌株中鉴定出并与来自斯里兰卡的旅行者相关的V型DHFR耐药机制，在西西里岛的沙门氏菌中尚未出现。
