Class 1 integrons in Acinetobacter baumannii: a weak expression of gene cassettes to counterbalance the lack of LexA-driven integrase repression

Abstract

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Spreading of extended-spectrum β-lactamase-producing Escherichia coli ST131 and Klebsiella pneumoniae ST11 in patients with pneumonia

“…[57,58] MGEs including transposons, integrons, prophages, integrative and conjugative elements, and genomic islands, which carried anti-microbial resistance and adaptability associated genes, made K. pneumoniae ST11 formidable adaptive and caused drug-resistant infections in hospitals. [59,60] Our results indicated epidemic trends of multi-drug or pandrug resistant K. pneumoniae ST11 harboring bla NDM-1 and bla KPC-2 in patients with pneumonia in the hospital, which is a serious threat to the public health. Thus, continuous surveillance on the prevalence of K. pneumoniae ST 11 was of great significance to control the outbreak of the resistant strain.…”

Molecular Detection of Carbapenemase-Encoding Genes in Multidrug-Resistant Acinetobacter baumannii Clinical Isolates in South Africa

“…ISAba1 and other IS may modulate the expression and transfer of OXA-type carbapenemase genes [10]. Integrons have been demonstrated to play a major role in the dissemination of multidrug-resistance among Gramnegative bacteria through the capture and expression of resistant genes embedded within cassettes [11].…”

Integron Functionality and Genome Innovation: An Update on the Subtle and Smart Strategy of Integrase and Gene Cassette Expression Regulation

“…The LexA protein is absent in Acinetobacter baumannii, suggesting that intI1 expression in this species is probably constitutive. However, a recent study demonstrated that class 1 integrons identified in Acinetobacter predominantly harbor the PcS configuration, the strongest cassette promoter variant [43]. As already mentioned, the PcS configuration determines the least efficient integrase variant (IntI1R32_N39) [26] and, consequently, the lowest fitness cost for bacteria.…”

“…It was revealed distinct relative transcription strengths that directly affect the expression of resistance gene cassettes inserted in class 1 integrons and, consequently, the level of antibiotic resistance. Several groups have performed such studies on Pc promoter activity in different moments and using different approaches [2,3,26,28,29,38,42,43], what limited the comparison of the results. Jové and Colleagues compiled all Pc variants described until that occasion, including those for which transcription activity was unknown and new variants identified in that study, and determined their transcription efficiencies under the same conditions [26], as detailed in Table 2.…”

“…Although A. baumannii and E. coli RNA polymerases and σ 70 factors share considerable conservation, such inter-species differences in Pc activity could result from differences in their transcriptional machinery [118]. Therefore, this regulatory mechanism represents an adaptive response designed to reduce the fitness cost and contribute to integron stabilization in this species [43].…”