Publication: Marmara Üniversitesi Hastanesinde izole edilen ilk imipeneme dirençli bacteroides fragilis kökeninin fenotipik ve genotipik özelliklerinin araştırılması
Abstract
Giriş:. Bacteroides fragilis grubu kökenler, anaerop bakteriler arasında en sık görülen insan patojen/erindendir. Aynı zamanda pek çok antibiyotiğe direnç gösteren bu bakteriler, karbapenemler, beta-laktam/beta-laktamaz inhibitörleri, metronidazol ve kloramfenikol gibi sınırlı sayıda antibiyotiklere duyarlıdır. Ancak son zamanlarda bazı ülkelerde karbapenemlere dirençli B. fragilis kökenleri bildirilmiştir. Karbapenemlere direnç, diğer beta-laktamlara. da dirence neden olan metallo-beta-laktamaz aktivitesiyle gerçekleşmektedir. Fenotipik direnç, sadece "insertion sequence (IS)" elementinin metallobeta-laktamaz (cfiA) geninin hemen önünde yer alması ve direnç geninin ekspresyonunu tembihlemesiyle gerçekleşmektedir. Materyal ve Metod: Bu çalışmada, aspirasyon pnömonisi gelişen hastanın alt solunum yolundan izole edilen, imipeneme dirençli B. fragilis kökeninin polimeraz zincir reaksiyonu, nükleotid dizi analizi ve enzim inhibisyonu çalışmalarıyla karbapenemez aktivitesi araştırılmıştır. Bulgular: B. fragilis kökeninde cfiA pozitifliği ve cfiA geninin hemen önünde IS1187 elementi saptanmıştır. Yapılan dizi analizinde polimeraz zincir reaksiyonu ürününün cfiA2 geni ile %100 benzer olduğu görülmüştür. Kökenimizin EDTA ile inaktive olabilen Zn2+/ya bağımlı beta-laktamaz ürettiği saptanmıştır. Sonuç: Hastanemizde klinik örnekten, karbapenem direncini kodlayan cfiA geni, hemen önünde yer alan ve geni aktive eden IS elementine sahip ilk imipeneme dirençli B. fragilis izole edilmiştir. Metallo-beta-laktamaz üreten kökenler nadir görülmekle beraber, diğer beta-laktam antibiyotiklere de direnç oluşturması nedeniyle klinikte büyük problemler oluşturabilmektedir. Bu nedenle hastanelerde kökenlerin metallo-beta-laktamaz üreten B. fragilis yönünden yakından izlenmesi büyük önem taşımaktadır.
Introduction: Bacteroides fragilis group strains are the most prevalent human pathogens among anaerobic bacteria. Moreover, these strains, which show resistance to most of the antimicrobial agents, are susceptible to a limited number of the antimicrobial agents as carbapenems, beta-lactam/beta-lactamase inhibitors, nitroimidazoles and chloramphenicols. However, carbapenem-resistant B. fragilis strains have been reported from several countries in recent years. The carbapenem resistance mechanism is mediated by metallo-beta-lactamases, which can confer resistance to a wide variety of beta-lactams. Phenotypic resistance develops only when the metal-lo-beta-lactamase gene (cfiA) is preceded by an insertion sequence (IS) element that can upregulate the expression of the resistance gene. Materials and Methods: In this study, an imipenem-resistant B. fragilis strain isolated from the lower respiratory tract of a patient with aspiration pneumonia was investigated for carbapenemase activity by means of polymerase chain reaction (PCR) assay, nucleotide sequencing and enzyme inhibition studies. Results: B. fragilis strain was cfiA-positive and harbored I S1187 element upstream of the resistance gene. The nucleotide sequencing of the PCR products of the strain shared 100% similarity with the cfiA2 gene. The strain produced (Zn2+)-dependent beta-lactamase, which was inactivated by EDTA. Conclusion: This is the first report in our hospital on the isolation of an imipenem-resistant B. fragilis strain from clinical material with a regular resistance mechanism to carbapenem, carrying a cfiA gene activated by the upstream insertion of an IS element. Although the presence of metallo-beta-lactamase-producing strains is rare, they still pose a large clinical problem because they are resistant to all -beta-lactam agents available. Therefore, it is important to follow up isolates carefully for the metallo-beta-lactamase-producing B. fragilis strains in hospitals.
Introduction: Bacteroides fragilis group strains are the most prevalent human pathogens among anaerobic bacteria. Moreover, these strains, which show resistance to most of the antimicrobial agents, are susceptible to a limited number of the antimicrobial agents as carbapenems, beta-lactam/beta-lactamase inhibitors, nitroimidazoles and chloramphenicols. However, carbapenem-resistant B. fragilis strains have been reported from several countries in recent years. The carbapenem resistance mechanism is mediated by metallo-beta-lactamases, which can confer resistance to a wide variety of beta-lactams. Phenotypic resistance develops only when the metal-lo-beta-lactamase gene (cfiA) is preceded by an insertion sequence (IS) element that can upregulate the expression of the resistance gene. Materials and Methods: In this study, an imipenem-resistant B. fragilis strain isolated from the lower respiratory tract of a patient with aspiration pneumonia was investigated for carbapenemase activity by means of polymerase chain reaction (PCR) assay, nucleotide sequencing and enzyme inhibition studies. Results: B. fragilis strain was cfiA-positive and harbored I S1187 element upstream of the resistance gene. The nucleotide sequencing of the PCR products of the strain shared 100% similarity with the cfiA2 gene. The strain produced (Zn2+)-dependent beta-lactamase, which was inactivated by EDTA. Conclusion: This is the first report in our hospital on the isolation of an imipenem-resistant B. fragilis strain from clinical material with a regular resistance mechanism to carbapenem, carrying a cfiA gene activated by the upstream insertion of an IS element. Although the presence of metallo-beta-lactamase-producing strains is rare, they still pose a large clinical problem because they are resistant to all -beta-lactam agents available. Therefore, it is important to follow up isolates carefully for the metallo-beta-lactamase-producing B. fragilis strains in hospitals.