Abstract
Background: Plasmid and chromosomal extended-spectrum beta-lactamases (ESBLs) have been increasingly spread everywhere and blaCTX-M1 is one predominant beta-lactamase. Objectives: This study was fulfilled to determine the production of ESBL and prevalence of blaCTX-M1, blaSHV, and blaTEM among Escherichia coli blood isolates in Tehran. Patients and Methods: Twenty-three isolates were adopted to be studied during 2015-2016. The antibiotic susceptibility testing was performed using Kirby–Bauer method. The combined disk method was used for the detection of phenotypic ESBL production. The most effective antibiotics were piperacillin, amikacin, and ofloxacin. The minimum inhibitory concentration (MIC) of ceftazidime was determined using micro-broth dilution method. Polymerase chain reaction (PCR) was used for detecting the blaCTX-M1, blaSHV, and blaTEM genes. Results: In the broth dilution test, 19 (82%) isolates showed MIC ≥1, and 18 (78.3%) isolates were ceftazidime resistant. In the combined disk test, 19 (82%) isolates were ESBL producers. The results of the MIC and ceftazidime resistance were the same for ESBL selection. The results of MIC, in fact confirmed the disk diffusion in determining the phenotypic ESBL production. The frequency of blaCTX-M1, blaSHV, and blaTEM genes among blood ESBL producing isolates was 26% (n = 6), 8.6% (n = 2), and 0%, respectively. Isolates that showed higher MIC were positive for these genes. Conclusion: The prevalence of multidrug-resistant blood isolates and ESBL phenotype was high in military hospitals. A low number of blood strains amplified blaCTXM1 and blaSHV type beta–lactamases. There was a relationship between the MIC and the presence of beta-lactamase genes.
Highlights
Plasmid and chromosomal extended-spectrum beta-lactamases (ESBLs) have been increasingly spread everywhere and blaCTX-M1 is one predominant beta-lactamase
There was a correlation between ceftazidime resistance and minimum inhibitory concentration (MIC) results for ESBL production
Among non-beta-lactam antibiotics, amikacin exhibited the highest activity against the isolates (63%)
Summary
Plasmid and chromosomal extended-spectrum beta-lactamases (ESBLs) have been increasingly spread everywhere and blaCTX-M1 is one predominant beta-lactamase. The genetic location of extended-spectrum beta-lactamases (ESBLs) is the mobile elements and the chromosome of Enterobacteriaceae.[1] Recent data have shown that blaCTX-M1 clones are mostly widespread at an endemic status worldwide and in Iran.[2] The ESBLs are increasing everywhere.[3] These ESBLs are inhibited by clavulanic acid, sulbactam, and tazobactam that help their detection.[4] On the other hand, resistance due to ESBLs is often accompanied with resistance to other antibiotics, including fluoroquinolones, aminoglycosides, and sulfamethoxazole /trimethoprim.[5] The pandemic E. coli clone of ST131 with a high virulent potential encoding CTX-M-15 was characterized by the multidrug resistance (MDR) through the co-production of OXA-1 or TEM-1b as well as aac(6’)-Ibeta-cr This clone produces blaCTX-M-15 beta-lactamase.[6,7,8] CTXM-type ESBLs are complex and heterogeneous families and may be subdivided into 5 major groups (CTX-M-1, 2, 8, 9 and CTX-M-25).[9,10] These enzymes have spread worldwide and are the most ESBLs detected in Enterobacteriaceae. Several studies have demonstrated a relationship between ESBL enzymes and minimum inhibitory concentration (MIC) to third and fourth generation cephalospo-
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