Microbiology
Nafiseh Izadi; Mahboubeh Naderi Nasab; Elnaz Harifi Mood; Zahra Meshkat
Abstract
Background and Objectives: Since the fluoroquinolones are the broad-spectrum antibiotics, they affect both Gram-negative and Gram-positive bacteria. These antibiotics are widely prescribed by physicians. As a result, some bacteria, especially Enterobacteriaceae, have shown a resistance to this family ...
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Background and Objectives: Since the fluoroquinolones are the broad-spectrum antibiotics, they affect both Gram-negative and Gram-positive bacteria. These antibiotics are widely prescribed by physicians. As a result, some bacteria, especially Enterobacteriaceae, have shown a resistance to this family of antibiotics. The current study aimed at detecting the frequency of qnrA, qnrB, and qnrS genes, novel plasmid-mediated quinolone-resistance genes, among extended-spectrum β-lactamases (ESBL)-positive and ESBL-negative Klebsiella pneumoniae isolates. Materials and Methods: One hundred and thirty isolates of K. pneumoniae were collected from Imam Reza Hospital and its associated clinics from May 2011 to July 2012. The isolates were tested for ESBLs by the conventional methods. Polymerase chain reaction (PCR) was performed to amplify qnr A, B, and S. Results: Thirty-eight (29.3%) isolates were ciprofloxacin-resistant. Among 130 K. pneumoniae infectious isolates, 56 (43%) were capable of producing ESBL; 10.8% (n=14), 15.4% (n=20), and 20.8% (n=27) of ESBL-producing K. pneumonia were positive for qnrA, qnrS, and qnrB, respectively, and 13.8% (n=18) of the isolates harbored 2 or 3 qnr genes. Conclusion: The results of the current study showed that quinolone-resistance genes were more frequent in ESBL-producing K. pneumoniae (37.5%) isolates, compared with the ESBL-negative isolates (20.89%). The prevalence of qnr genes was high in K. pneumoniae isolates, with higher frequency in ESBL-positive strains. Most of the isolates were positive for all 3 groups of qnr genes and the qnrB was the most common one.
Parviz Owlia; Zakaria Bameri; Mohsen Chitsaz
Volume 5, Issue 3 , June 2010, , Pages 137-142
Abstract
Background and Objective: Organisms producing CTX-M β-lactamases are emerging as a source of resistance to oxyiminocefalosporins such as ceftriaxone and ceftazidime. However, the laboratory detection of these strains is not well defined. In this study, phenotypic assay for screening of extended-spectrum ...
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Background and Objective: Organisms producing CTX-M β-lactamases are emerging as a source of resistance to oxyiminocefalosporins such as ceftriaxone and ceftazidime. However, the laboratory detection of these strains is not well defined. In this study, phenotypic assay for screening of extended-spectrum β-lactamases producing strains and molecular assay for the identification of CTX-M β-lactamases genes was developed and used to investigate the prevalence of these enzymes among clinical isolates of Klebsiella pneumoniae in three general hospitals of Tehran, Iran. Materials and Methods: Phenotypic detection was used for screening of isolates by agar dilution method. A decrease of ≥3 doubling dilution in an MIC for either ceftriaxone or ceftazidime tested in combination with 4 mg/l clavulanic acid (prepared from Glasco Smith company) versus its MIC when tested alone, confirmed an ESBL-producing organism. The PCR assay consisted of four primer sets. Results: In initial screening test, 117 (69%) from 168 clinical isolates were positive and 51 isolates (31%) were negative. From the positive isolates, 96 isolates were positive in phenotypic confirmatory test. Using molecular assay, 117 strains potentially producing extended-spectrum-β-lactamases were examined for the presence of CTX-M enzymes: 88 strains (75.2%) were positive for blactx-m group І genes, 1 strain (0.85%) was positive for blactx-m group ІІІ genes , and 2 strains (1.7%) were positive for blactx-m group ІV. Conclusion: The prevalence of extended-spectrum β-lactamases (ESBLs) are increasing significantly in hospitals of Tehran. In other side, we found that the CTX-M І group had the most prevalence than other CTX-M groups.