Determination of Extended-spectrum Beta-lactamase Genes (blaTEM, blaSHV, blaCTX-M) in Escherichia coli Strains Isolated from Clinical Specimenes in Ali-Ibne Abi Talib Hospital in Qom, Iran

Escherichia coli (E.coli) is an opportunistic Gram-negative bacterium, which causes common nosocomial infections, including pneumonia, septicemia, meningitis, diarrhea, bacteremia, etc. Antibiotic resistance is a serious problem for human health, so that the World Health Organization in called the year 2011 as the year of antibiotic resistance. One of the reasons of these resistances is production of broad-spectrum β-lactamases (ESBLs), which are able to hydrolyze broad-spectrum β-lactam antibiotics. This study was performed aiming at determining the prevalence of cefotaxime-resistant strains and evaluating the ESBL genes (bla TEM, bla SHV and blaCTX-M) in E. coli isolates.
In this cross-sectional study during a 5-month period (April to September 2014), specimens sent to the laboratory of Ali-Ibne Abi Talib Hospital of Qom, such as blood, urine, wound, etc., were examined. After identification and isolation of E.coli strains, their antibiotic resistance and ESBL production were determined by disk diffusion method, MIC, and combination disk method according to CLSI guidline. Then, detection of blaCTX-M, SHV, and TEM genes was performed using PCR.
Of 160 isolated E. coli and based on the results of disk diffusion and MIC, 31 (19%) isolates were resistant to cefotaxime. Also, based on the phenotypic results, 24 (77%) cefotaxime-resistant ESBL-producing strains, were idetified. The blaCTX-M, blaTEM, and blaSHV genes were determined in 90%, 42%, and 3% of the strains, respectively.
The results revealed that prevalence of ESBL-producing E .coli is high. Therefore, there is a need to manage the use of antibiotics and identify the source and distribution of β-lactamase-producing isolates.