Abstract
Class 1 integrons are mobile genetic elements considered to be responsible for the transfer of multidrug resistance. This study aimed to investigate the distribution of type 1 integrons in multidrug-resistantEscherichiacolifrom hospital-acquired lower respiratory tract infections. Clinical strains of E. coli were isolated from patients with hospital-acquired lower respiratory tract infections in the emergency intensive care unit from January to December 2014. Drug sensitivity testing was performed using the Kirby-Bauer method. The combination disk method was used to detect extended-spectrum β-lactamase (ESBL), and polymerase chain reaction (PCR) amplification was used to detect the intI1 gene. Among 58 E. coli strains, resistance to β-lactam antibiotics ranked as follows: imipenem (0.0%), cefoperazone/sulbactam sodium (25.9%), ceftazidime (37.9%), and cefepime (39.7%); other β-lactam antibiotic resistance rates were all > 50%. The resistance rates to amikacin, ciprofloxacin, gentamicin, and cotrimoxazole were32.8%, 63.8%, 70.7%, and 81.0%, respectively. In total, 31 (53.4%) isolates were positive for class 1 integron and carried 4 different sizes of amplification fragments: 800, 1,600, 1,900, and 2,600 bp. Among 43 ESBL-positive isolates, 27 (62.8%) also carried class 1 integron; among 15 ESBL-negative isolates, 4 carried class 1 integron (26.7%). The positive rate for class 1 integron in ESBL-producing strains was significantly higher than that in non-ESBL-producing strains. The rates of resistance of integron-positive isolates to ceftriaxone, cefotaxime, amikacin, ciprofloxacin, and cotrimoxazole were significantly higher than those in integron-negative isolates. Class 1 integrons are widely distributed in E. coli and are associated with multidrug resistance.
Highlights
Class 1 integrons are mobile genetic elements considered to be responsible for the transfer of multidrug resistance
Gramnegative bacteria accounted for 73.8% (276/374), with 58 (21.0%) identified as E. coli; Gram-positive bacteria accounted for 13.9% (52/374), and fungi accounted for 12.3% (46/374)
Many studies have indicated that class 1 integrons play a crucial role in the dissemination of antibiotic resistance in Gram-negative bacteria and occur frequently in E. coli by carrying and capturing genes via site-specific recombination catalyzed by specific integrase genes [8]
Summary
Class 1 integrons are mobile genetic elements considered to be responsible for the transfer of multidrug resistance. Methodology: Clinical strains of E. coli were isolated from patients with hospital-acquired lower respiratory tract infections in the emergency intensive care unit from January to December 2014. The rates of resistance of integron-positive isolates to ceftriaxone, cefotaxime, amikacin, ciprofloxacin, and cotrimoxazole were significantly higher than those in integron-negative isolates. Previous studies have shown that 65% of clinical isolates of E. coli produce extended-spectrum β-lactamases (ESBLs) in China[1]. Based on the integrase coding sequence, there are currently nine classes of integrons, of which class 1 integrons are the most commonly encountered type clinically, playing an important role in transferring drug resistance [4]. Class 1 integrons carry the integrase gene (intI1), which codes for the site-specific recombinase responsible for cassette insertion.
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