Extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae (K. pneumoniae) is one of the most popular pathogens that cause refractory respiratory tract infection. The genetic environment, including insertion sequences and the types of promoter, plays a key role in exploration of the mechanism of prevalence and dismission of the ESBL-producing K. pneumoniae isolates. The aim of the investigation was to target analysis the genetic environment and promoter sequences of blaCTX-M, blaSHV and blaTEM, the most popular β-lactamase genes harbored by ESBL-producing K. pneumoniae isolates.Methods
From February 2010 to July 2011, 158 of 416 K. pneumoniae isolates producing ESBL from patients with lower respiratory tract infection were collected from seven tertiary hospitals from Beijing, Anhui, Fujian, Liaoning, Hebei and Inner Mongolia Autonomous Region in China. The genetic environment including promoters of 10 types of blaCTX-M, 18 types of blaSHV and 2 types of blaTEM were analyzed by amplification and direct sequencing with various sets of PCR primers.Results
ISEcp1 was located upstream of the 5' end of the blaCTX-M gene in 130 (97.0%) out of 134 K. pneumoniae isolates harboring blaCTX-M and provided a conserved promoter to blaCTX-M. A non-coding sequence preceded by kdpC and recF was identified in all of the blaSHV genes except blaSHV-12 and blaSHV-2a. IS26 was also found upstream of 1 blaCTX-M-15, 10 blaSHV-1 strains, 4 blaTEM-1 and all of the blaSHV-2,blaSHV-2a, blaSHV-5 and blaSHV-12. Eighty-seven of 91 strains harboring blaTEM-1 carried a copy of Tn2 and IS26-blaTEM-1 fragments were also detected in 4 strains. With respect to K. pneumoniae, the genetic environment of blaCTX-M-38, blaSHV-142 and blaTEM-135 were firstly elaborated, and four kinds of novel genetic environment of blaCTX-M-3, blaCTX-M-15 and blaTEM-1 have been detected as well.Conclusions
Perfective implementation of the genetic environment information of β-lactamase gene needs to be further explored and supplemented. ISEcp1 and IS26 elements are widespread upstream of the blaCTX-M, blaSHV and blaTEM genes and contribute to horizontal transmission and genetic expression.