Molecular characteristics of carbapenem-resistant Enterobacteriaceae isolates from a Chinese Tertiary Hospital

Abstract

Objective: The aim of this study was to investigate the molecular characteristics of carbapenem-resistant Enterobacteria­ceae (CRE) isolates from a teaching hospital in Guangdong, China, during the period between January 2008 and December 2011. Methods: A total of 28 (0.9%) CRE isolates were collected among 3286 isolates. Antimicrobial susceptibility testing, Modified Hodge Test (MHT) and genotyping by pulsed-field gel electrophoresis were performed. Extended-spectrum β-lactamase (ESBL) and carbapenemase genes were detected using gene amplification and sequencing. Outer membrane porin (OMP) genes (OmpK35/OmpK36 for K. pneumoniae, OmpC/OmpF for E. cloacae were examined. Results: Seven (25.0%) isolates of the 28 carbapenem resistant Enterobacteriaceae had a positive MHT. PCR and sequenc­ing analysis revealed that 19 of the 28 isolates were molecularly confirmed to harbor ESBLs (15 isolates, 53.6%), AmpC (6 isolates, 21.4%), or IMP-4 (five isolates, 17.9%), and nine (32.1%) isolates of the 28 isolates possessed at least two different classes of β-lactamases. Specially, five (71.4%) of seven MHT-positive CRE isolates is due to the production of the carbapen­emase-encoding gene IMP-4. Almost all of the CRE isolates in the present study loss gene expressions of OmpK35 and/or OmpK36 in K. pneumoniae, OmpC and/or OmpF in E. cloacae, except for one K. pneumoniae. PFGE analysis demonstrated genomic variability. Conclusion: Carbapenem resistance in Enterobacteriaceae is due to the combined effect of β- lactamases with porin im­permeability caused by loss of OMPs observed in these organisms. To prevent both CRE transmission and infections has become significantly urgent public health objectives.

Keywords

• Molecular characteristics, Carbapenem-resistant, Enterobacteriaceae, IMP-4.

Molecular characteristics of carbapenem-resistant Enterobacteriaceae isolates from a Chinese Tertiary Hospital

Öz

ET Amaç: Bu çalışmada Çin’in Guangdong bölgesinde bulunan bir eğitim hastanesinde, Ocak 2008 ile Aralık 2011 tarihleri arasında dönemde izole edilen karbapenem dirençli Enterobacteriaceae (CRE), kökenlerinin moleküler özelliklerini incelemesi amaçlanmıştır.Yöntemler: Çalışma döneminde 3286 suştan toplam 28 (% 0,9) CRE izolatı ayrıştırıldı ve çalışmaya alındı. Antimikrobiyal duyarlılık testleri, Modifiye Hodge (MHT) testi ve genotip incelenmesinde Pulsed-field jel elektroforez kullanıldı. Genişletilmiş spektrumlu β-laktamaz (GSBL) ve karbapenemaz genlerinin varlığı, gen amplifikasyonu ve dizi analizi kullanılarak tespit edildi. Bakterilerin Dış zar porini (OMP) genleri (OmpK35 / OmpK36 K. pneumoniae, E. cloacae için OMPC / OmpF) incelendi.Bulgular: MHT ile 28 kökenin yedisi (% 25,0) dirençli Enterobacteriaceae olarak tanımlandı. PCR ve dizi analizi gibi moleküler yöntemlerle kökenlerden 15’inin (% 53,6) GSBL pozitif olduğu, altısının AmpC (% 21,4), beşinin IMP-4 (% 17,9) ve dokuzunun en az iki farklı sınıf dirence sahip olduğu görülmüştür. Özel olarak, yedi MHT pozitif kökenin beşinin (% 71,4) karbapenemaz kodlayan genlerinin IMP-4 üretimine bağlı iken PFGE analizinde bir K. pneumoniae dışında hemen hemen tüm CRE kökenlerinin, OMPC ve / veya ompF içinde OmpK35 ve / veya OmpK36 kaybı gen ifade kaybı gözlendi. PFGE analizi genomik değişkenlik gösterdi.Sonuç: Enterobacteriaceae karbapenem direnci bu organizmalarda gözlenen OMP’lerin kayb sonucu oluşan porin’e değişimi ve β-laktamazların kombine etkisi nedeniyle oluşmaktadır. CRE yayılımı ve enfeksiyonlar hem anlamlı acil halk sağlığı hedefleri haline gelmiştir önlemek için

Anahtar Kelimeler

• Moleküler özellikler, karbapenem dirençli, Enterobacteriaceae, IMP-4

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