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      The Prevalence of CTX-M-15 Extended-spectrum β-Lactamases Among Salmonella spp. and Shigella spp. Isolated from three Iranian Hospitals

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          Bacterial antimicrobial resistance mediated by the production of extended-spectrum β-lactamases (ESBLs) is considered a major threat for treatment of Salmonella and Shigella infections. This study aimed to investigate antibiotic resistance patterns of Salmonella and Shigella spp. and presence of CTX-M from three teaching hospitals in Iran. In the present study, 58 clinical Shigella and 91 Salmonella isolates were recovered between 2009 and 2013 from 3 teaching hospitals in Iran. After culture and antimicrobial susceptibility testing, ESBL-positive isolates were subjected to further investigations. These included polymerase chain reaction (PCR) amplification and DNA sequencing of bla CTX-M-15 encoding plasmid. In both genera, high sensitivity to gentamicin and amikacin, but high resistance to ampicillin, tetracycline, and trimethoprim–sulfamethoxazole, was found. Molecular investigation showed that 31.8% isolates of Salmonella spp. and 34.48% isolates of Shigella spp. were CTX-M positive and all of them were also positive for ISEcpI. Protein translation, comparing with reference sequences, showed that all CTX-M isolates belong to CTX-M-15. The present study suggests that the resistance of ESBLs-producing Salmonella and Shigella spp. in Iran hospitals is very serious. Therefore, strategies to minimize the spread of ESBL-producing isolates should be implemented.

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          Most cited references 41

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          Growing group of extended-spectrum beta-lactamases: the CTX-M enzymes.

           R Bonnet (2003)
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            Extended broad-spectrum beta-lactamases conferring transferable resistance to newer beta-lactam agents in Enterobacteriaceae: hospital prevalence and susceptibility patterns.

            Before 1985 at the Pitié-Salpêtrière Hospital in Paris (2,400 beds), resistance to cefotaxime in clinical isolates of Enterobacteriaceae involved only species producing inducible class 1 beta-lactamase. Between November 1985 and April 1987, however, 62 isolates (57 of Klebsiella pneumoniae and five of Escherichia coli) showed decreased susceptibility to cefotaxime (mean MIC, 8-16 micrograms/mL). The transferability of cefotaxime resistance in E. coli K12 was demonstrated for 15 of 16 selected isolates. By isoelectric focusing using iodometric detection with 20 mg of ceftriaxone/100 mL and determination of substrate and inhibition profiles, three beta-lactamases mediating cefotaxime resistance were identified as SHV-2 (isoelectric point [pI] 7.6), CTX-1 (pI 6.3), and "SHV-2-type" or SHV-3 (pI 6.98). The three beta-lactamases hydrolyzed penicillins and cephalosporins (including cefotaxime and ceftriaxone) and were therefore designated "extended broad-spectrum beta-lactamases" (EBS-Bla). The enzymes conferred to derivatives a high level of resistance to amoxicillin, ticarcillin, piperacillin, and cephalothin and a decreased degree of susceptibility (i.e., MICs increased by 10- to 800-fold) to cefotaxime, ceftriaxone, ceftazidime, and aztreonam. These beta-lactamases did not affect the activity of cephamycins (cefoxitin, cefotetan, moxalactam) or imipenem. Synergy between clavulanate or sulbactam (2 micrograms/mL) and amoxicillin was greater against derivatives producing EBS-Bla than against those producing TEM-1, TEM-2, or SHV-1; this synergy was greater with clavulanate than with sulbactam against derivatives producing SHV-2 and the SHV-2-type enzyme but was similar with clavulanate and sulbactam against those producing CTX-1. A double-disk synergy test performed with cefotaxime and Augmentin disks (placed 30 mm apart, center to center) seemed a useful and specific test for the detection of strains producing EBS-Bla.
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              Colistin, mechanisms and prevalence of resistance.

              Infections caused by multi-drug-resistant Gram-negative bacteria, particularly Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae, that cause nosocomial infections, represent a growing problem worldwide. The rapid increase in the prevalence of Gram-negative pathogens that are resistant to fluoroquinolones and aminoglycosides as well as all β-lactams, including carbapenems, monobactam, cephalosporins and broad-spectrum penicillins, has prompted the reconsideration of colistin as a valid therapeutic option. Colistin is an old class of cationic, which act by disrupting the bacterial membranes resulting in cellular death. Although there has been a significant recent increase in the data gathered on colistin, focusing on its chemistry, antibacterial activity, mechanism of action and resistance, pharmacokinetics, pharmacodynamics and new clinical application, the prevalence of colistin resistance has been very little reported in the literature. This review concentrates on recent literature aimed at optimizing the clinical use of this important antibiotic.

                Author and article information

                Eur J Microbiol Immunol (Bp)
                Eur J Microbiol Immunol (Bp)
                European Journal of Microbiology & Immunology
                Akadémiai Kiadó (Budapest )
                26 April 2017
                June 2017
                : 7
                : 2
                : 133-137
                [1 ] Department of Microbiology, Faculty of Medicine, Iran University of Medical Sciences , Tehran, Iran
                [2 ] Connective Tissue Diseases Research Center, Tabriz University of Medical Sciences , Tabriz, Iran
                [3 ] Infectious and Tropical Disease Research Center, Tabriz University of Medical Sciences , Tabriz, Iran
                [4 ] Biotechnology Research Center, Tabriz University of Medical Sciences , Tabriz, Iran
                [5 ] Student Research Committee, Tabriz University of Medical Sciences , Tabriz, Iran
                [6 ] Drug Applied Research Center, Faculty of Medical Sciences, Tabriz University of Medical Sciences , Tabriz, Iran
                Author notes
                * Drug Applied Research Center, Faculty of Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran; +989127184735; +984113364661; Kafilhs@

                Conflict of interest The authors declare no conflict of interest.

                © 2017, The Author(s)

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                Figures: 0, Tables: 1, Equations: 0, References: 36, Pages: 5
                Founding sources: This study was supported by Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
                Original Article

                iran, salmonella, ctx-m-15, esbl, antimicrobial resistance, shigella


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