Prevalence and Characterization of Class I Integrons among Pseudomonas aeruginosa and Acinetobacter baumannii Isolates from Patients in Nanjing, China

Abstract

Class I integrons were detected in 40.8% (40/98) of Pseudomonas aeruginosa strains and 52.8% (56/106) of Acinetobacter baumannii strains in the Nanjing area of China, including several cassette arrays not previously reported.The rapid dissemination of antibiotic resistance genes among bacterial isolates is an increasing problem in infectious disease. Recent studies have shown that a conserved DNA sequence, integron, may be carried on these episomal genetic structures (12,14). Integrons possess two conserved segments separated by a variable region that includes integrated cassettes, which often include antibiotic resistance genes (11). Many resistance genes are present as gene cassettes within integrons, which may themselves be located on transmissible plasmids and transposons (11). In China, resistance to various antibiotics is common in clinical isolates, often more so than in Western countries, especially among Pseudomonas aeruginosa and Acinetobacter baumannii isolates (7,8,16). However, the frequencies, characteristics, and roles of integrons and gene cassettes in the two species have not yet been investigated in a large-scale study.In order to study the roles of gene cassettes in the two species, we obtained 98 P. aeruginosa isolates and 106 Acinetobacter sp. isolates from four general hospitals in the Nanjing area of China during June 2003 and June 2005. The strains were randomly obtained from a variety of clinical specimens from diverse units of the four hospitals. All bacterial strains were identified by the analytical profile index procedure (API-20NE system; bioMerieux, France). Susceptibility to antimicrobial agents was tested by the disk diffusion method on Mueller-Hinton agar plates, according to Clinical and Laboratory Standards Institute guidelines (2). DNA used for PCR was prepared as described previously (9). All isolates were screened for integrons by PCR using degenerate primers hep35 (5Ј TGCGGGTYAARGATBTKGATTT 3Ј) and hep36 (5Ј CARCACATGCGTRTARAT 3Ј) and HinfI restriction analysis of the integrase gene product (18). Class I integron

Screening of Class 1 and Class 2 Integrons in Clinical Isolates of Pseudomonas aeruginosa Collected from Seven Hospitals in Turkey: A Multicenter Study

“…Recent studies have shown that resistance genes might have been carried by an integron. Many resistance genes exist as gene cassettes within integrons, which may themselves be located on transmissible plasmids and transposons [36]. Production of an integrinmediated β-lactamases from different molecular classes (carbenicillinases and extended-spectrum β-lactamases belonging to class A, class D oxacillinases and class B carbapenem hydrolysing enzymes) and synthesis of aminoglycoside modifying enzymes (phosphoryl-transferases, acetyltransferases and adenylyltransferases) are some of the resistance mechanisms in P. aeruginosa [37].…”

Novel Class 1 Integrons in Multi-drug Resistant Isolates from Eastern China

“…In China, resistance to various antibiotics is common in clinical isolates, often more so than in western countries, especially among the most common causes of hospitalacquired opportunistic pathogens such as Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii [8,9]. Over the past decades, much work has been done on the epidemiology of integrons and their important roles in bacterial resistance in both clinical and natural environments [2,4,[8][9][10][11].…”

“…Over the past decades, much work has been done on the epidemiology of integrons and their important roles in bacterial resistance in both clinical and natural environments [2,4,[8][9][10][11]. Surveillance of integrons therefore is essential for the investigation of MDR bacteria evolution.…”

Analysis of integrons and associated gene cassettes of metallo-β-lactamase-positive Pseudomonas aeruginosa in Malaysia

“…To identify the presence of integrons in our isolates, PCR-RFLP was performed by using the degenerate primers hep35 and hep36 (Table 1). The expected amplicon size (491 bp) was ascertained by electrophoresis on a 1.5 % agarose gel with appropriate molecular size markers (100 bp DNA ladder; MBI Fermentas), and the PCR products were further restricted using HinfI (MBI Fermentas) to determine the class of integron (Gu et al, 2007).…”

“…To identify the presence of integrons in our isolates, PCR-RFLP was performed by using the degenerate primers hep35 and hep36 (Table 1). The expected amplicon size (491 bp) was ascertained by electrophoresis on a 1.5 % agarose gel with appropriate molecular size markers (100 bp DNA ladder; MBI Fermentas), and the PCR products were further restricted using HinfI (MBI Fermentas) to determine the class of integron (Gu et al, 2007).Amplification and sequencing of gene cassette regions. The gene cassettes of the class 1 integron were amplified using specific primers for 59 and 39 conserved segments (59CS and 39CS; Table 1) combined with primers VIM-R/IMP-R and VIM-F/IMP-F, respectively (Pitout et al, 2007).…”