| Acinetobacter baumannii is a glucose-non-fermentative, Gram-negative coccobacillus that has emerged in recent years as a leading cause of nosocomial infections associated with elevated morbidity and mortality. A.baumannii is widely distributed in the hospital environment and human respiratory tract, blood, pleural effusion, urinary tract, surgical trauma, CNS, skin, eye, can cause hospital-acquired and ventilator-associated pneumonia, bacteremia, urinary tract infections, surgical site infections, which are more fatal for ICU patients. Multi-drug resistant and pan drug resistant A.baumannii has become an emerging global public health problem. The super foreign DNA acquisition ability of A.baumannii is the major cause of its super drug resistant characters. Integron is a popular vector of drug resistant genes in A.baumannii genomes. Acinetobacter baumannii in clone propagation way around the world, major epidemic clones are international cloning Ⅰ,Ⅱ, Ⅲ type.Between Jan2011and December2011, a total of189non-repetitive A.baumannii clinical isolates were collected from the laboratory of the second affiliated hospital of Chongqing Medical University. Among the189clinical isolates in our study, the resistance ratios were all above60%. Most isolates (93.3%) in this study were multidrug resistant (defined as resistant to more than two categories antibiotic), higher that previous reports, and38.7%isolates were resistant to all antibiotics used in the test. The proportion of isolates resistant to tested antimicrobial agents included piperacillin (92.7%), ampicillin/sulbactam(84.5%), ticarcillin/clavulanic acid(80.4%), ceftazidime(88.7%), ceftriaxone(90.2%), cefotaxime(92.2%), cefepime(93.8%), imipenem(72.2%), amikacin(78.8%), gentamicin(81.4%), tobramycin(76.8%), ciprofloxacin(89.7%), gatifloxacin(62.6%), levofloxacin(67%), and trimethoprim -sulfame-thoxazole(81.4%). The susceptibility of clinical isolates to tobramycin (21.1%) and imipenem (26.8%) is more that20%, only these two antimicrobial agents had a tolerable killing ability to clinical A.baumannii from this hospital. The data highlighted the formidable nosocomial infection challenge of drug resistant A. baumannii.Integrons were widespread among A. baumannii clinical isolates in this teaching hospital. Among the189isolates analyzed by PCR,144isolates (76.2%) were found to have the integron cassette. Among the integron positive isolates,136had I integron cassette,8had Ⅱ integron cassette. Among the136class I integron-carrying isolates, five different types of gene cassettes in segments of approximately1.3kb,1.6kb,2kb,2.5kb and3.1kb between the5’-conserved segment (CS) and3’-CS regions, were amplified by PCR. The five types I class integron cassette included:aadA2-HP-dfrA, aacCl-ORF1-ORF2-aadAl, arr-3-aacA4, dfrA17-aadA5and aadB-cat-blaOXA10-aadA1. The aadA2-HP-dfrA cassette accounted for83.9%of all integron positive cassettes, representing the most prevalent type in the integron-carrying A. baumannii isolate. There were two types class Ⅱ cassettes, comprised type4fimbriae expression regulatory protein pilR and sulfate adenylytransferase. No type III integron cassette was detected. The integron positive character of isolates was obviously correlated with the higher drug resistant ratio.Considering the serious consequences of A.baumannii infection in ICU, the epidemic linage was determined by rep-PCR and MLST. The major linage of A.baumannii in this hospital is international linage clone2. ICU A baumannii isolates resistance is significantly higher than the overall A.baumannii.Molecular epidemiological analysis of clinical isolates, including integron detection and molecular typing, revealed the epidemic characters of A.baumannii infection in this hospital, that were important for A.baumannii nosocomial infection control. |
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