Prevalence of qnr and aac(6')-Ⅰ b-cr genes in water-borne environmental bacteria and clinical isolates of Citrobacter freundii in China / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the prevalence of qnr and aac(6')-Ⅰ b-cr genes in water-borne environmental bacteria and clinical isolates of Citrobacter freundii, and the subtypes of qnr gene. Methods Environmental bacteria were isolated from surface water samples obtained from 10 distinct loca-tions in Hangzhou city, and clinical isolates of C. Freundii were isolated from several hospitals of 4 cities in China. Minimum inhibitory concentrations (MICa) of ciprofloxacin, levofloxacin and nalidixic acid were de-termined by agar dilution method, qnrA, qnrB, qnrS and aac(6')-Ⅰ b-cr genes were screened by PCR, and the genotypes were analyzed by DNA sequencing. Results Seventy-eight gram negative bacilli (including 33 Enterobacteriaceae, 21 Aeromonas spp., 10 Acinetobacter spp., 10 Pseudomonas app., 2 Alcaligenes app. , and 2 Plesiomonas app.) were isolated from water samples. Among these isolates, 8 of 10 C. Freundii were positive for qnrB gene. qnrS1 and aac (6')-Ⅰ b-cr were detected in two distinct Escherichia coil, and qnrS2 was detected in a Aeromonas punctata qnr and aac(6')-Ⅰ b-cr genes were present in 75 (72.8%) and 12 (11.6%) of 103 clinical isolates of C. Freundii, respectively. Three (2.9%) C. Freundii isolates were positive for qnrA1 gene, 65 (63.1%) qnrB, 1 (1.0%) qnrS2, 5 (4.8%) were positive for both qnrA1 and qnrB, and 1 was positive for both qnrS1 and qnrB. Within the subtypes of qnrB gene, qnrB9 predominated, followed by qnrB8 and qnrB6. Conclusion It was the first isolate of Aeromonas spp. Harboring qnrS2 gene outside Europe. The prevalence of qnrB in water-borne environmental and clinical isolates of C.freundii was particularly high and qnrB9, qnrB8 and qnrB6 were the most common subtypes, aac(6')-Ⅰ b-cr gene widely spread in clinical isolates of C. Freundii.