Detection of Isoniazid and Rifampin Resistance in Mycobacterium tuberculosis Clinical Isolates from Sputum Samples by High-Resolution Melting Analysis.

The effective management of multidrug-resistant tuberculosis (MDR-TB) and the need for rapid and accurate screening of rifampin (RIF) and isoniazid (INH)-resistant Mycobacterium tuberculosis (Mtb) isolates are the most fundamental and difficult challenges facing the global TB control. The present study aimed to compare the diagnostic accuracy of high-resolution melting-curve analysis (HRMA) in comparison to multiplex allele-specific PCR (MAS-PCR) and xpert MTB/RIF as well as the conventional drug-susceptibility test (DST) and gene sequencing for the detection of INH and RIF resistance in the Mtb isolates. In the present study, a total of 431 Mtb isolates including 11 MDR (%2.55), 7 INH resistance (%1.62), two RIF resistance (%0.46), and 411 sensitive isolates were phenotypically confirmed. HRMA assay identified katG gene mutations and the mabA-inhA promoter region in 15 of 18 INH-resistant samples and rpoB gene mutations were successfully evaluated in 11 out of 13 RIF-resistant samples. The sensitivity and specificity of the HRMA method were 83.3% and 98.8% for INH and 84.6% and 99% for RIF, respectively. The most common mutation in RIF-resistance-determining region (RRDR) occurred at codon 531 (TCG → TTG)(84.6%) and then at codon 513 (CAA → GTA)(7.6%) and 526 (CAC → TAC) (7.6%), which resulted in the amino-acid changes. Also, 88.8% of INH-resistant samples had mutations in the katG gene and the mabA-inhA promoter region, of which the highest mutation occurred at codon 315 (AGC → ACC) of the katG gene. In conclusion, all these results indicated that the sensitivity and specificity of the HRM method were increased when the katG gene and the mabA-inhA promoter region were used as a target.

The Frequency of qnr Genes in Extended-Spectrum ß-lactamases and non-ESBLs Klebsiella pneumoniae Species Isolated from Patients in Mashhad, Iran.

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 ß-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.

Co-infection of long-standing extensively drug-resistant Mycobacterium tuberculosis (XDR-TB) and non-tuberculosis mycobacteria: A case report.

We report a 69-years-old Iranian HIV negative male patient, with long-standing pulmonary tuberculosis (eleven years) co-infected with non-tuberculosis mycobacteria. Despite of initiation of first line anti-tuberculosis therapy after diagnosis the patient poorly respond because of low compliance with anti-TB treatment. After several incomplete treatments the smear was still positive and thus drug susceptibility tests were performed on isolated organism which revealed that the organisms was resistant not only against isoniazid and rifampin but also against Ofloxacin (OFX), Capreomycin (CAP), p-aminosalicylic acid (PAS), ethionamide (ETH), Kanamycin (KAN), ciprofloxacin (Cip), amikacin (AMK) and cycloserine (CYC). Persistence and resistance of infection had led us to do more investigation using molecular methods, which revealed co-infection with Non-tuberculosis mycobacteria (NTM). The patient is still alive with cough and shortness of breath.

Prevalence of Quinolone Resistance Genes Among Extended-Spectrum B-Lactamase-Producing Escherichia coli in Mashhad, Iran.

BACKGROUND: Escherichia coli is an important bacterial species based on incidence and associated infection severity. Some E. coli strains produce extended-spectrum beta lactamase (ESBL) and are called ESBL-producing E. coli. These strains are resistant to most classes of cephalosporin and a number of other classes of antibiotics. Plasmids carrying qnr genes have been found to transmit quinolone resistance. OBJECTIVES: The aim of this study was to determine the frequency of qnr genes in ESBL-producing and non-ESBL-producing E. coli isolated from outpatient and hospitalized patient clinical specimens from Imam Reza hospital in Mashhad, Iran. MATERIALS AND METHODS: Two hundred E. coli strains, isolated from different clinical specimens were used. ESBL-producing E. coli were detected by determining susceptibility to ceftazidime, cefotaxime, and cefpodoxime with the phenotypic confirmatory test (PCT). PCR analysis was employed to detect the qnrA, qnrB, qnrS, bla TEM , and bla SHV genes. RESULTS: Eighty-six (43%) isolates were ciprofloxacin-resistant. The PCT identified 85 (42.5%) of 200 E. coli isolates as ESBL-producing. The bla TEM , bla SHV , qnrA, qnrB, and qnrS gene were found in 65 (76.47%), 23 (27%), 63 (31%), 34 (17%), and 14 (7%) isolates, respectively. CONCLUSIONS: The high prevalence of quinolone resistance genes, which indicates antibiotic resistance, in the Imam Reza Hospital of Mashhad is a major concern. Hence, the antibiotics prescription policy should be revised, and infection control measures should be improved.