Heir Even, Lindstedt Bjørn-Arne, Leegaard Truls M, Gjernes Elisabet, Kapperud Georg
Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, N-0403 Oslo, Norway.
Ann Clin Microbiol Antimicrob. 2004 Jul 8;3:12. doi: 10.1186/1476-0711-3-12.
Class 1 integrons contain genetic elements for site-specific recombination, capture and mobilization of resistance genes. Studies investigating the prevalence, distribution and types of integron located resistance genes are important for surveillance of antimicrobial resistance and to understand resistance development at the molecular level.
We determined the prevalence and genetic content of class 1 integrons in Enterobacteriaceae (strain collection 1, n = 192) and E. coli (strain collection 2, n = 53) from bloodstream infections in patients from six Norwegian hospitals by molecular techniques. Class 1 integrons were also characterized in 54 randomly selected multiresistant E. coli isolates from gastrointestinal human infections (strain collection 3).
Class 1 integrons were present in 10.9% of the Enterobacteriaceae blood culture isolates of collection 1, all but one (S. Typhi) being E. coli. Data indicated variations in class 1 integron prevalence between hospitals. Class 1 integrons were present in 37% and 34% of the resistant blood culture isolates (collection 1 and 2, respectively) and in 42% of the resistant gastrointestinal E. coli. We detected a total of 10 distinct integron cassette PCR amplicons that varied in size between 0.15 kb and 2.2 kb and contained between zero and three resistance genes. Cassettes encoding resistance to trimethoprim and aminoglycosides were most common. We identified and characterized a novel plasmid-located integron with a cassette-bound novel gene (linF) located downstream of an aadA2 gene cassette. The linF gene encoded a putative 273 aa lincosamide nucleotidyltransferase resistance protein and conferred resistance to lincomycin and clindamycin. The deduced LinF amino acid sequence displayed approximately 35% identity to the Enterococcus faecium and Enterococcus faecalis nucleotidyl transferases encoded by linB and linB' CONCLUSIONS: The present study demonstrated an overall low and stable prevalence of class 1 integron gene cassettes in clinical Enterobacteriaceae and E. coli isolates in Norway. Characterization of the novel lincosamide resistance gene extends the growing list of class 1 integron gene cassettes that confer resistance to an increasing number of antibiotics.
1类整合子包含用于位点特异性重组、捕获和移动耐药基因的遗传元件。研究整合子定位的耐药基因的流行情况、分布和类型，对于监测抗菌药物耐药性以及从分子水平了解耐药性的发展具有重要意义。
我们通过分子技术，确定了来自挪威六家医院患者血流感染的肠杆菌科细菌（菌株集合1，n = 192）和大肠杆菌（菌株集合2，n = 53）中1类整合子的流行情况和基因内容。还对从人类胃肠道感染中随机选择的54株多重耐药大肠杆菌分离株（菌株集合3）中的1类整合子进行了特征分析。
在菌株集合1的肠杆菌科血培养分离株中，1类整合子的存在率为10.9%，除一株（伤寒沙门氏菌）外均为大肠杆菌。数据表明各医院之间1类整合子的流行情况存在差异。1类整合子在耐药血培养分离株中分别占37%（菌株集合1）和34%（菌株集合2），在耐药胃肠道大肠杆菌中占42%。我们总共检测到10种不同的整合子盒式PCR扩增产物，大小在0.15 kb至2.2 kb之间，包含零至三个耐药基因。编码对甲氧苄啶和氨基糖苷类耐药的盒式结构最为常见。我们鉴定并表征了一种新的位于质粒上的整合子，其在aadA2基因盒下游有一个与盒式结构相连的新基因（linF）。linF基因编码一种推定的273个氨基酸的林可酰胺核苷酸转移酶耐药蛋白，赋予对林可霉素和克林霉素的耐药性。推导的LinF氨基酸序列与粪肠球菌和屎肠球菌中由linB和linB'编码的核苷酸转移酶显示出约35%的同一性。结论：本研究表明，挪威临床肠杆菌科细菌和大肠杆菌分离株中1类整合子基因盒的总体流行率较低且稳定。新型林可酰胺耐药基因的表征扩展了赋予对越来越多抗生素耐药性的1类整合子基因盒的不断增加的清单。
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