Identification of Klebsiella pneumoniae strains harboring inactive extended-spectrum beta-lactamase antibiotic-resistance genes

Background The extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae has increasingly become a major contributor to nosocomial infections and can exhibit multiple antibiotic resistance.Previous studies have focused on the resistance genes in ESBL-producing strains,and the resistanc...

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Veröffentlicht in:Chinese medical journal 2014, Vol.127 (17), p.3051-3057
Hauptverfasser: Xu, Li, Zhai, Yao, Lyu, Yuan, Wang, Qi, An, Shuchang, Chen, Jichao, Chen, Yusheng, Liu, Lin, Li, Jiabin, Gao, Zhancheng
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Sprache:eng
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Zusammenfassung:Background The extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae has increasingly become a major contributor to nosocomial infections and can exhibit multiple antibiotic resistance.Previous studies have focused on the resistance genes in ESBL-producing strains,and the resistance-associated genetic environment of non-ESBL-producing strains has been ignored until now.Here,we investigated the occurrence and characteristics of non-ESBL-producing K.pneumoniae,which potentially carries unexpressed resistance genes.Methods K.pneumoniae strains were collected from five medical institutions in China from February 2010 to August 2013.The VITEK-2 ESBL detection system was used as a primary screen to identify the ESBL-producing phenotype,and the three primary types of ESBL-associated genes (CTX,SHV,and TEM) were detected by polymerase chain reaction (PCR) to confirm the strains presenting with a non-ESBL-producing phenotype.mRNA expression in the non-ESBL-producing strains was further screened by reverse-transcription PCR (RT-PCR) to validate their transcriptional efficiency.Results Out of 224 clinically isolated antibiotic-sensitive K.pneumoniae strains with a non-ESBL-producing phenotype,5 (2.2%) were identified to carry inactivated ESBL blaSHV genes with intact upstream promoter regions and resistance gene sequences.Interestingly,three of the five antibiotic-sensitive K.pneumoniae strains containing ESBL blaSHV genes still exhibited mRNA transcription of blasHv,while the other two exhibited no mRNA transcription.Conclusion These findings suggest that inactivated ESBL genes exist in non-ESBL-producing antibiotic-sensitive K.pneumoniae strains,which have the potential to transform the strain into an ESBL phenotype if an inappropriate application or overdose of antibiotics is implemented during clinical management.
ISSN:0366-6999
2542-5641
DOI:10.3760/cma.j.issn.0366-6999.20140628