Prevalence and antibiotic resistance pattern of extended spectrum beta lactamase producing Escherichia coli isolated from urinary tract infection

1Student Research Committee, Kurdistan University of Medical Sciences, Sanandaj, Iran 2Department of Internal Medicine, Faculty of Medicine, Kurdistan University of Medical Sciences, Sanandaj, Iran 3Lung Diseases and Allergy Research Center, Kurdistan University of Medical Sciences, Sanandaj, Iran 4Medical Student Research Committee & Social Determinant of Health Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, IR Iran 5Department of Radiation Oncology, Firoozgar Hospital, Firoozgar Clinical Research Development Center (FCRDC), Iran University of Medical Sciences (IUMS), Tehran, Iran


Introduction
Urinary tract infection (UTI) is one of the most common infectious disease that affects about more than 150 million people every year (1).Escherichia coli is the most common urinary tract pathogen, accounting for 50% to 90% of UTI isolates (2).E. coli as an enterobacteriaceae member is gram negative and facultative anaerobic bacterium (3).β-lactam antibiotics (beta-lactam antibiotics) are the commonly prescribed antibiotics for UTI.Beta-lactam antibiotics are a class of broad-spectrum antibiotics, consisting of all antibiotic agents that contain a beta-lactam ring in their molecular structure (4).Betalactamases are enzymes that hydrolyze beta-lactam ring, inactivating the antibiotic (5).Extended-spectrum betalactamase (ESBL) are enzymes that confer resistance to most common beta-lactam antibiotics such as penicillins, cephalosporins and monobactam (6).ESBL-producing bacteria were first reported in 1983, and now infection due to ESBL-producing bacteria including E. coli has become widespread (7).Studies have shown a trend toward higher mortality, longer hospitalization, greater hospital expenses and reduced rates of clinical and microbiologic response in ESBL UTI (8,9).

Objectives
The aim of this study is to determinate the prevalence and antibiotic resistance pattern of ESBL-producing E. coli isolated from UTI.

Patients
This cross-sectional study was conducted on all urine samples (3126 samples) sent to the cultivating to the central laboratory of Tohid hospital in Sanandaj from October 2016 to September 2017.

Intervention and biochemical measurements
Urine specimens were collected from the midstream urine samples in sterile containers and by using a calibrated loop (0.01 mL), they were cultured in sterile conditions on Eosin Methylene Blue (EBM).The Blood agar and then samples were examined at 37°C after 18-24 hours incubation.The samples that number of colonies grown on their culture medium were more than 10 5 CFU/mL were examined as a positive urine culture to identify genus and bacterial species based on standard methods.After the final diagnosis, the disk diffusion standard method (Kirby Bauer) was used to test the susceptibility of the drug on Muller-Hinton agar plates.Creating or not creating and the size of inhibition zone around the disk were reviewed based on the Clinical and Laboratory Standards Institute (CLSI) criteria.The most commonly used antibiotics in UTIs were reviewed in studied antibiogram.The reviewing of ESBL-producing uropathogens was carried out using Combined Disk Test (CDT) and CLSI protocol.At first, a microbial suspension equivalent to half McFarland was prepared from pure bacterial culture and it was cultured on Muller-Hinton agar medium by sterile swab.Then, the cefotaxime (CTX; 30 µg) and cefotaxime-clavulanic acid (CTX; 30 µg /CA; 10 µg) disks were placed at the distance of at least 2.5 cm from each other in medium.After 24 hours of incubation at 37°C, producing ESBL was studied.If the inhibition zone around the cefotaxime-clavulanic acid was equal 3 mm or it was greater than inhibition zone around cefotaxime, that bacteria was considered as ESBL producing.

Ethical issues
The study was in accordance with the Declaration of Helsinki and all participants gave their informed consent to enter the study.The study was approved by the Research Committee and the Ethical Committee of the Kurdistan University of Medical Sciences.(Ethic code: IR.MUK.REC.1397.5014).

Data analysis
The data were analyzed by SPSS 23 software.To compare qualitative variables, chi-square test was applied.Level of significance was P < 0.05.

Conclusion
Given the dramatic increase in the prevalence of ESBLproducing E. coli and its consequences, including higher mortality, longer hospitalization, greater hospital expenses and reduced rates of clinical and microbiologic response, evaluation of their prevalence and antibiotic resistance pattern are recommended.According to the results of our study, it is recommended that cephalosporins, penicillins and cotrimoxazole are not administered in the treatment of ESBL-producing E. coli.On the other hand, carbapenems as a first line and aminoglycosides as the next step in the treatment of ESBL-producing E. coli are recommended.

Limitations of the study
The limitation of this study was that the standard and correct method is the MIC method, while this method has

Table 1 .
Comparison of results of studies