Data_Sheet_1_Spread of Carbapenem Resistance by Transposition and Conjugation Among Pseudomonas aeruginosa.PDF

The emergence of carbapenem-resistant Pseudomonas aeruginosa represents a worldwide problem. To understand the carbapenem-resistance mechanisms and their spreading among P. aeruginosa strains, whole genome sequences were determined of two extensively drug-resistant strains that are endemic in Dutch hospitals. Strain Carb01 63 is of O-antigen serotype O12 and of sequence type ST111, whilst S04 90 is a serotype O11 strain of ST446. Both strains carry a gene for metallo-β-lactamase VIM-2 flanked by two aacA29 genes encoding aminoglycoside acetyltransferases on a class 1 integron. The integron is located on the chromosome in strain Carb01 63 and on a plasmid in strain S04 90. The backbone of the 159-kb plasmid, designated pS04 90, is similar to a previously described plasmid, pND6-2, from Pseudomonas putida. Analysis of the context of the integron showed that it is present in both strains on a ∼30-kb mosaic DNA segment composed of four different transposons that can presumably act together as a novel, active, composite transposon. Apart from the presence of a 1237-bp insertion sequence element in the composite transposon on pS04 90, these transposons show > 99% sequence identity indicating that transposition between plasmid and chromosome could have occurred only very recently. The pS04 90 plasmid could be transferred by conjugation to a susceptible P. aeruginosa strain. A second class 1 integron containing a gene for a CARB-2 β-lactamase flanked by an aacA4′-8 and an aadA2 gene, encoding an aminoglycoside acetyltransferase and adenylyltransferase, respectively, was present only in strain Carb01 63. This integron is located also on a composite transposon that is inserted in an integrative and conjugative element on the chromosome. Additionally, this strain contains a frameshift mutation in the oprD gene encoding a porin involved in the transport of carbapenems across the outer membrane. Together, the results demonstrate that integron-encoded carbapenem and carbapenicillin resistance can easily be disseminated by transposition and conjugation among Pseudomonas aeruginosa strains.

耐碳青霉烯类铜绿假单胞菌（Pseudomonas aeruginosa）的出现已成为全球性公共卫生难题。为阐明碳青霉烯类耐药机制及其在铜绿假单胞菌菌株中的传播流行特征，研究人员对两株泛耐药（extensively drug-resistant）菌株完成了全基因组测序，这两株菌在荷兰医院中呈地方流行。菌株Carb01 63属于O抗原血清型（O-antigen serotype）O12，序列型（sequence type，ST）为ST111；而S04 90则为O抗原血清型O11的ST446型菌株。两株菌均在1类整合子（class 1 integron）上携带金属β-内酰胺酶（metallo-β-lactamase）VIM-2编码基因，该基因两侧各有一个编码氨基糖苷乙酰转移酶（aminoglycoside acetyltransferase）的aacA29基因。该整合子在Carb01 63菌株中定位于染色体（chromosome），而在S04 90菌株中则位于质粒（plasmid）上。命名为pS04 90的159kb质粒其骨架与此前报道的恶臭假单胞菌（Pseudomonas putida）质粒pND6-2高度相似。对整合子遗传背景的分析显示，两株菌中该整合子均位于一段约30kb的嵌合DNA片段上，该片段由四种不同的转座子（transposon）组成，推测可协同构成一种新型活性复合转座子（composite transposon）。除pS04 90上的复合转座子中存在一段1237bp的插入序列元件（insertion sequence element）外，这些转座子的序列同源性均超过99%，这表明质粒与染色体间的转座事件可能仅在近期发生。pS04 90质粒可通过接合转移（conjugation）至敏感铜绿假单胞菌菌株。Carb01 63菌株还携带另一1类整合子，其内含CARB-2 β-内酰胺酶编码基因，该基因两侧分别为编码氨基糖苷乙酰转移酶的aacA4′-8基因与编码腺苷酰转移酶（adenylyltransferase）的aadA2基因。该整合子同样位于一段复合转座子上，而该转座子插入于染色体中的整合接合元件（integrative and conjugative element）内。此外，该菌株的oprD基因存在一处移码突变（frameshift mutation），该基因编码参与碳青霉烯类药物跨外膜（outer membrane）转运的孔蛋白（porin）。综上，本研究结果证实，整合子编码的碳青霉烯类与羧苄青霉素耐药性可通过转座与接合作用在铜绿假单胞菌菌株间快速传播。