Analysis on β-lactam resistance in extraintestinal Aeromonas isolated from a hospital of Shaoxing

Objective To understand the distribution of resistance genes and integrons for β-lactams in extraintestinal Aeromonas spp. isolated from Shaoxing People’s Hospital, and to analyze their effects on antibiotic resistance. Methods A total of 50 extraintestinal Aeromonas strains isolated from the patients in Shaoxing People’s Hospital from July 2015 to October 2017 were analyzed for antibiotic sensitivity of 9 kinds of β-lactams. Resistance genes and integrons for β-lactams were analyzed for drug resistance of the strains. Results The 50 extraintestinal Aeromonas strains had resistance rates of over 44.0% to cephalosporins, and low resistance rates of under 4.0% to imipenem and meropenem. The cphA gene and blaTEM gene were mainly located in Aeromonas hydrophila, accounting for 48.0% and 36.0%, respectively. The blaIMP gene was detected in two strains of Aeromonas caviae. No blaVIM or blaSHV gene was detected. The resistance rates of cphA gene positive strains to ceftriaxone (CRO) , cefepime (FEP) and aztreonam (ATM) were all above 60.0%, which were significantly higher than those of negative strains (χ2=4.711, 4.121 and 13.936, P all<0.05) . The resistance rates of blaTEM gene positive strains to 4 kinds of cephalosporins and ATM were all over 65.0%, which were significantly higher than those of negative strains (χ2=13.903, 18.733, 5.966, 29.501 and 34.722, P all<0.05) . The positive rate of intI1 integron gene was 50.0%, while none of intI2 or intI3 integron gene was detected. The resistance rates of intI1 gene positive strains to 4 kinds of cephalosporins and ATM were all over 68.0%, which were significantly higher than those of negative strains (χ2=17.014, 23.727, 11.688, 32.051 and 29.639, P all<0.01) . Conclusions The β-lactamase resistance gene cphA and blaTEM are common in the extraintestinal Aeromonas isolated from Shaoxing People’s Hospital. The resistance of the positive strains to cephalosporins and monocycle β-lactamase antibiotics is significantly higher than that of the negative strains. intI1 integrons in these strains are the most common integrons, which can significantly improve the resistance of Aeromonas to a variety of antibiotics. Key words: β-lactams; Aeromonas; Resistance; Gene; Integrons