Abstract
<p class="1Body">Knowledge of antimicrobial resistance patterns in <em>E. coli</em>, the predominant pathogen associated with urinary tract infections (UTI) is important as a guide in selecting empirical antimicrobial therapy. To describe the antimicrobial susceptibility of <em>E. coli</em> associated with UTI in a major university hospital in Tehran (Iran), seventy-six clinical isolates of <em>E. coli</em> were studied for susceptibility to Beta-lactam antibiotics by the disc diffusion method and Minimal Inhibitory Concentrations determination. All isolates were resistant to ampicillin, amoxicillin and oxacillin. Resistance to the other tested antibiotics was shown to be 93.4% to cefradine, 76.3% to carbenicillin, 47.3% to cefazoline, 50% to cefalexin and 32.8% to cephalothin while 1.3% expressed resistance to cefoxitime, and 2.6% were resistant to ceftizoxime and ceftriaxone. Substrate hydrolysis by ultra violet spectroscopy showed that 87.4% harbored penicillinases, 9% produced cephlosporinases and 3.6% degraded both substrates. Clavulanic acid inhibited enzyme activity in 82.9%, of which 78.95% was penicillinases (group IIa) and 3.95% was cephalosporinases (group IIb) of the Bush classification system. These results indicate that <em>E. coli</em> can posses a variety of Beta-lactamases that are responsible for Beta-lactam resistance. Members of the family Enterobacteriaceae, particularly Escherichia coli is the most common causes of urinary tract infections in hospitals and societies. Beta-lactam antibiotics, particularly the third and fourth generation of cephalosporins are effective in treating these infections.</p>
Highlights
Urinary Tract Infections (UTI) are the second most common infections present in community practice (Gonzalez & Schaeffer, 1999)
We studied 76 urinary isolates of E. coli for their susceptibility to 12 β-lactam antibiotics
Seventy-six clinical isolates of E. coli were selected from a collection of urinary Enterobacteriaceae from the Bacteriology Laboratory of Vali-E-Asr Hospital in Tehran (Iran) (Hosseini-Mazinani, Jafar-Nejad, & Ghandili, 2003)
Summary
Urinary Tract Infections (UTI) are the second most common infections present in community practice (Gonzalez & Schaeffer, 1999). Members of Enterobacteriaceae, E. coli are the main causes of urinary infections (Gupta, 2003). The resistance of Enterobacter spp. to β-lactam antibiotics is most frequently mediated by production of TEM, SHV and AmpC β-lactamase (Barnaud et al, 2001). Production of plasmidmediated ESBL which hydrolyzes a wide range of the most recently developed cephalosporins, has been recognized as an additional important emerging mechanism of resistance among members of the family Enterobacteriaceae including clinical isolates of E. coli (Bradford, 2001; Pitout et al, 1998). The first plasmid mediated βlactamases (TEM-1) was described in E. coli in 1960 and within a few years, it was found in many different genera of Gram-negative bacteria (Bradford, 2001). We studied 76 urinary isolates of E. coli for their susceptibility to 12 β-lactam antibiotics. DNA amplification of βlactamase types TEM, SHV and AmpC genes was carried out by PCR using type specific primers of blaTEM, ampC and SHV genes for all of the isolates
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