Tehran University Medical Journal

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Background: The incidence of ESBL producing species have been steadily increased in recent years, resulting in limitation of infection control issues and therapeutic options.The purpose of this study was to evaluate prevalence of Enterobacteriaceae and also assess epidemiology ESBL producing strains isolated from patients admitted in ICUs.
Methods: A total of one hundred fifty isolates were collected from urine, sputum, blood, wound and other clinical samples from patient admitted in ICU and then were identified by biochemical tests .All of the samples were screened by DAD method according to The NCCLS Guideline. The species that met NCCLS screening criteria was further tested for Clavulanic Acid effect by confirmatory method.
Results: A total of one hundred fifty isolates,133(89.3%) were found to be resistant at least on of the indicators cephalosporin tested according to NCCLS Guideline. 121(80.6%) of the isolates were resistant to all the indicators tested .89(59.3) isolateds were confirmed as ESBL producers. The number of isolates ESBL producing was as follow: Klebsiella pneumoniae 33 (76.74%), E.coli 20 (60.60%), Enterobacter cloacae 8 (47.05%), Citrobacter diversus 6 (54.54%), Enterobacter aerogenes 7 (53.84%), Citrobacter freundii 4 (40%), Klebsiella oxytoca 6 (62.5%), Proteus mirabilis 4 (50%), Serratia marcescens 2 (40%), Proteus Volgaris 0%.All of the isolates sensitive to imipenem.
Conclusion: The present study shows high prevalence of ESBL producing Enterobacteriaceae from patients admitted in ICU .The increased rate of these species in most cases due to the administration of inadequate and irrational antimicrobial therapy .To overcome this problem, it needs to develop new antimicrobial agents, limiting the Unnecessary Use of antimicrobial and increasing compliance with infection control issues.

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Background: The resistance of Pseudomonas aeruginosa strains to broad spectrum cephalosporins may be mediated by extended spectrum b-lactamases (ESBLs). These enzymes are encoded by different genes located either on chromosome or plasmids. In this study, we determined the antimicrobial resistance patterns of P. aeruginosa isolates and screened for ESBL production.

Methods: After isolation from burn patients in Tehran Hospital, identification of P. aeruginosa isolates were assessed using biochemical tests. We then performed disk agar diffusion (DAD) according to CLSI guidelines to determine the pattern of antimicrobial resistance. The frequency of ESBLs and prevalence of the OXA-10 and PER-1 genes were determined with combined disk and polymerase chain reaction (PCR) methods, respectively.

Results: One hundred strains of P. aeruginosa were isolated. The resistance of these strains to cephpodoxime, aztreonam, ciprofloxacin, ofloxacin, ceftazidime, cefepime, imipenem, meropenem, cefotaxime, levofloxacin, piperacilin- tazobactam and ceftriaxon was 100%, 90%, 83%, 92%, 85%, 88%, 63%, 66%, 98%, 89%, 70% and 91%, respectively. Of these, 40 strains (40%) were ESBL positive, 29 strains (29%) were OXA-10 positive and 18 strains (18%) were PER-1 positive.

Conclusion: Our results confirm the need for proper antimicrobial therapy in burn hospitals, considering the resistance pattern and frequency of strains producing ESBLs and the presence of the OXA-10 and PER-1 genes. Since an increase in the prevalence of ESBL in P. aeruginosa strains might lead to the transfer of these ESBL genes to other gram-negative bacteria, we recommend the use of appropriate drugs, especially cephalosporins, in burn hospitals.

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Background: Beta- lactamase enzymes are the most important resistant factors to beta lactam antibiotics among gram negative bacteria. Nowadays, the prevalence of beta- lactamase infection is increasing worldwide and drawn the scientists attention as an important subject. Due to high prevalence of bacteria contained TEM beta lactamase and AmpC enzymes, using molecular methods especially designing universal primers could be valuable to detect all of them. The aim of this study was to determine the prevalence of TEM and AmpC (Dha and MOX) beta- lactamase genes using universal primers.

Methods: A total of 500 clinical specimens from various Hospitals in Tehran, Iran were collected and analyzed for E. coli based on biochemical tests. These clinical specimens were also screened by Disk diffusion agar, combined disk method and PCR to detect the samples producing extended- spectrum beta- lactamase.

Results: Overall 200 isolates of Escherichia coli were collected from the 500 clinical specimens out of which 128(64%) isolates were positive by PCR assay and showed bla- TEM, bla- AmpC (Dha, MOX) genes, 74(57.8%) and 5(3.9%) to have bla- TEM and bla Dha, respectively. Mox gene was not detected in any of the specimens.

Conclusions: Our results revealed that using the molecular methods with phenotype methods is very essential for complete detection of Beta- lactamases. There is the need for updating the treatment protocol because the prevalence of this resistance is increasing.

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Background: Resistance to beta-lactam antibiotics in clinical isolates frequently results from the production of β-lactamase enzymes. In recent years, the production of extended spectrum β-lactamases (ESBLs) and AmpC β-lactamase have greatly increased, especially in clinically isolated Escherichia coli. On the other hand, beta lactamase genes have several subfamilies and designing universal primers could be valuable in their detection. The beta-lactamase-producing E. coli which is resistant to beta-lactam antibiotics may pose a great risk to the patients. The CTX-M-1 gene is responsible for beta lactamase resistance. The purpose of this study was to find the percentage of CTX-M-1 carrying E. coli strains. Methods: A total of 500 urine samples were collected from different hospitals in Tehran, Iran during September to February 2009. The samples were cultured on EMB agar and incubated at 37 C for 24 hours. Some biochemical tests were carried out on the isolated samples. The presence of CTX-M-1 gene was determined by PCR on the isolates already identified phenotypically by disk diffusion agar and combined disks. Results: In general, 200 out of the initial 500 samples were identified as E. coli, among which 128 (79.5%) were ESBLs producing strains. PCR used for the detection of CTX-M- 1 gene, showed that 99 (77.34%) out of 128 isolates contained such gene. Conclusion: The results of this study showed a high percentage of β-lactamase resistant E. coli strains. This is a serious matter and would pose a public hazard and every step should be taken to avoid such hazard.