Differential expression of blaSHV related to susceptibility to ampicillin in Klebsiella pneumoniae

The blaCTX-M gene independently enhances drug resistance level to ampicillin in clinical isolates of Klebsiella pneumoniae

“…1 Our previous studies have shown that low or no expression of the bla SHV gene in K. pneumoniae isolates resulted in reduced ampicillin resistance levels. 2 Rice et al 3 and Corvec et al 4 have reported that the C-A mutation in -10 region of the promoter of the bla SHV gene or deletion of a downstream region of the promoter promotes high expression of the bla SHV gene, resulting in a significant elevation in the MIC of K. pneumoniae to ampicillin or co-amoxiclav, cefalothin and cefoxitin. These data indicate that the resistance level of K. pneumoniae to antibiotics is associated with the expression of the bla SHV gene.…”

Alteration of GyrA Amino Acid Required for Ciprofloxacin Resistance in Klebsiella pneumoniae Isolates in China

“…Also, most of the isolates carrying such mutations had MICs exceeding 16 g/ml, which indicates that these alterations in GyrA are prone to conferring high-level resistance to ciprofloxacin. The resistance phenotype of isolates with the "silent" alterations (mutations having no statistical association with ciprofloxacin resistance) may be attributed to other factors affecting antibiotic susceptibility, such as a change in the penetration of agents resulting from energydependent efflux and porin loss (11,12), differential expression of a resistant gene (7), and activities of regulatory loci like mar and sox, which induce decreased porin expression and increased efflux (9,10,16). In summary, we found the single mutation Ser833Ile and the double mutation Ser833Leu plus Asp873Asn to be associated with ciprofloxacin resistance in China.…”

Relative Strengths and Regulation of Different Promoter-Associated Sequences for Various <b><i>bla</i></b>_SHV Genes and Their Relationships to β-Lactam Resistance

“…However, inconsistencies were also observed, including mRNA expression extent variations in relation to the same promoter-associated sequence and different bla SHV genes, as well as discrepancies between bla SHV mRNA expression and β-lactam resistances. These phenomena have also been partly reported before in relation to other β-lactamase genes, such as bla TEMs and bla CTX-Ms [Fu et al, 2007;Lartigue et al, 2002;Liu et al, 2016;Ma et al, 2011]. These inconsistencies were possibly raised by the same promoter-associated sequence exerting variant regulation effects on different genes, and related posttranscriptional and translational regulation factors also affect β-lactamase gene expression and drug resistance phenotype exhibition [Guérin et al, 2015;McCarthy et al, 1991].…”

“…The promoter-associated sequence strengths of β-lactamase genes are reportedly related to the phenotype of β-lactam resistance [Fu et al, 2007;Lartigue et al, 2002;Seecoomar et al, 2013;Toprak et al, 2011]. Among the 49 SHV extended spectrum beta-lactamases (ESBLs) (http://www.lahey.org/ studies/webt.asp), are speculated to be ESBLs without Gly-to-Ser substitutions at residue 238 (G238S) and Gluto-Lys substitutions at residue 240 (E240K) [Barguigua et al, 2013;Corkill et al, 2001;Dhara and Tripathi, 2014;Jemima and Verghese, 2009;Mulvey et al, 2004], which are most frequently associated with SHV ESBL activities [Hammond et al, 2008].…”