Detection of extended-spectrum & Plasmid-mediated AmpC Beta-Lactasmases in nosocomial Klebsiella isolates

Abstract

Objective: The coexistence of enzymes in the same Klebsiella strain may result in false-negative tests for the detection of ESBLs as pAmpCs resist inhibition by clavulanic acid so masking ESBL presence. This study was to highlight the detection rates of ESBLs and pAmpCs by using phenotypic method; MAST 4-disc test and multiplex polymerase chain reaction (PCR) method. In addition, it aimed to evaluate the sensitivity of the phenotypic method in detection of these enzymes. Methods: Klebsiella isolates were collected from clinical samples in different wards in Zagazig University Hospitals. The antibiogram of these bacteria was determined by disc diffusion method. The presence of ESBLs and pAmpCs within the isolates was determined using the phenotypic MAST 4-disc test followed by a multiplex PCR method. Results: In total, 38 Klebsiella pneumoniae strains were evaluated. Among these isolates, 65.8% were ESBL producers, 2.6% were pAmpC producers, and 31.6% were neither ESBL nor pAmpC producers. The most frequent genotype of ESBL was SHV (84%); followed by TEM (44%) pAmpC producers were of DHA genotype. The distribution of different ESBL genotypes was SHV (84%), TEM (44%), CTX-M II genotype (28%) and followed by SHV and CTX-M IV genotype (24%). Using multiplex PCR as a reference method, MAST 4-disc test was of 92% sensitivity and 86.7% specificity. Conclusion: A rising alarm of ESBL producing strains among K. pneumoniae isolates. The exact detection of ESBLs in isolates that produce both enzymes is important for both treatment and epidemiology.

Keywords

• ESBL, pAmpC, Β-Lactasmases, Nosocomial, Klebsiella

Detection of extended-spectrum & Plasmid-mediated AmpC Beta-Lactasmases in nosocomial Klebsiella isolates

Öz

Amaç: Aynı Klebsiella suşunda heriki enzimin bir arada bulunması GSBL için yanlış-negatif test sonucuna neden olabilir; pAmpC’lerin klavulanik asit tarafından inhibisyona direnç göstermesi sonucu GSBL maskelenebilir. Bu çalışma fenotipik yöntem olan MAST 4-disk testi ile ve multipleks polimeraz zincir reaksiyonu (PCR) yöntemi ile GSBL ve pAmpC oranlarının saptanmasını amaçladı. Buna ek olarak bu enzimlerin tespitinde fenotipik yöntemin duyarlılığının değerlendirmesi amaçlandı.Yöntemler: Klebsiella izolatları Zagazig Üniversitesi Hastaneleri’nin farklı koğuşlarından elde edilen klinik örneklerden toplandı. Bu bakterilerin antibiyogramı disk difüzyon yöntemi ile belirlendi. İzolatlarda GSBL ve pAmpC varlığı fenotipik MAST 4-disk testi ve akabinde multiplex PCR yöntemi kullanılarak tespit edildi.Bulgular: Toplam olarak 38 Klebsiella pneumoniae suşu değerlendirildi. Bu izolatların % 65,8’i GSBL üretiyordu, % 2,6’sı pAmpC üretiyordu ve % 31,6’sı ne GSBL ne de pAmpC üretiyordu. En sık GSBL genotipi CMY (% 84) idi; bunu CMY (%44) izledi, PAmpC üretenler CMY genotipindeydi. Farklı GSBL genotiplerinin dağılımı CMY (% 84), CMY (% 44), CTX-M II genotipi (28%), CMY ve CTX-M IV genotipi (% 24) şeklinde idi. Referans yöntem olarak multipleks PCR alındığında MAST 4-disk testinin duyarlılığı % 92 ve özgüllüğü % 86,7 idi.Sonuç: K. pneumoniae arasında GSBL üreten suşların yükselen alarmı. Her iki enzimi üreten izolatlarda GSBL’lerin kesin tespiti, hem tedavi hem de epidemiyolojide önemlidir

Anahtar Kelimeler

• GSBL, pAmpC, Β-Laktamazlar, Hastane, Klebsiella

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