In this study 107 Gram negative bacilli resistant to ceftazidime were collected from a clinical microbiology laboratory of a public hospital in Cairo, Egypt. Isolates were screened for their ability to produce metallo-β-lactamase (MBL) using the double disc synergy test (DDST). This test was conducted using imipenem (IPM) and ceftazidime discs (CAZ) as substrates and ethylene diamine tetra-acetic acid (EDTA) and 2-mercapto propionic acid (MPA) as inhibitors. Fourteen isolates that were inhibited by both tests and not with EDTA were selected for further investigations. Biochemical characterization using Api20E strips resulted in; Pseudomonas fluorescence (4), Klebsiella pneumoniae (3), Pseudomonas aeruginosa (2), Pseudomonas spp, Proteus mirabilis, Enterobacter cloacae, Escherichia coli and CDC group. The minimum inhibitory concentration of (CAZ) and (IPM) ranged from 8 to 64 µg/ml and 2 to 32 µg/ml, respectively. Polymerase chain reaction (PCR) was used to study the occurrence of the most common blaMBL-genes (blaIMP, blaVIM, blaSPM, blaGIM, blaSIM and blaNDM), resulted in the detection of the examined bla-genes in 13 isolates. The number of detected genes in each isolate was varied and ranged between 1 to 4. The prevalence of genes in the isolates was; 69.2, 61.5, 38.55, 30.8 and 15.4% for blaSPM, blaVIM, blaSIM, blaGIM and blaNDM, respectively. Moreover, blaIMP allele was not detected in any of the studied isolates. To the best of our knowledge this is the first study detect the six most common MBL genes in Egypt.
Key words: Gram-negative, ceftazidime, imipenem, (EDTA), metallo-β-lactamases and blagenes
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