Relationship between antimicrobial resistance and aminoglycoside-modifying enzyme gene expressions in Acinetobacter baumannii

• Published in: Chinese medical journal Vol. 118; no. 2; pp. 141 - 145
• Main Authors: Shi, Wei-feng, Jiang, Jian-ping, Mi, Zu-huang
• Format: Journal Article
• Language: English
• Published: China Department of Clinical Laboratory, Third Affiliated Hospital, Suzhou University, Changzhou 213003, China%Wuxi Cloning Technique Research Institute, Wuxi 214026, China 20.01.2005
• Subjects: Acinetobacter baumannii - drug effects; Acinetobacter baumannii - enzymology; Acinetobacter baumannii - genetics; Aminoglycosides - metabolism; Aminoglycosides - pharmacology; Base Sequence; Drug Resistance, Multiple, Bacterial; Gene Expression Regulation, Bacterial; Genotype; Microbial Sensitivity Tests; Molecular Sequence Data; 不动杆菌; 基因表达; 抗菌剂; 抵抗力; 氨基糖苷类; 调节酶基因; aminoglycoside-modifying enzyme; DNA sequence; Acinetobacter baumannii; drug resistance
• ISSN: 0366-6999; 2542-5641

Background Acinetobacter baumannii is one of the main gram-negative bacilli in clinical practice. Nosocomial infections caused by multi-drug resistance Acinetobacter baumannii is very difficult to treat. This study was designed to investigate the antimicrobial resistance characteristics and four resistant gene expressions of aminoglycoside-modifying enzymes including N-acetyltransferases and O-phosphotransferases in Acinetobacter baumannii. Methods Bacterial identification and antimicrobial susceptibility test were performed by Phoenix^TM system in 247 strains of Acinetobacter baumannii. Minimal inhibitory concentrations (MICs) of seven aminoglycosides including gentamicin, amikacin, kanamycin, tobramycin, netilmicin, neomycin and streptomycin in 15 strains of multi-drug resistant Acinetobacter baumannii were detected by agar dilution. Four aminoglycoside-modifying enzyme genes were amplified by polymerase chain reaction (PCR) and verified by DNA sequencer. Results The resistance rates of 247 strains of Acinetobacter baumannii against cefotaxime, levofloxacin, piperacillin, aztreonam, tetracycline, ciprofloxacin and chloramphenicol were more than 50%. Imipenem and meropenem showed high antibacterial activities with resistance rates of 3.2% and 4. 1%. MIC50 and MIC90 of gentamicin, amikacin, streptomycin and kanamycin in 15 strains of multi-drug resistant Acinetobacter baumanii were all more than 1024 mg/L, and the resistance rates were 100%, 100%, 100% and 93.3%, respectively. But their resistance rates to tobramycin, netilmicin and neomycin were 86.7%, 93.3% and 46.7%, respectively. Three modifying enzyme genes, including aacC1, aacC2 and aacA4 genes, were found in 15 strains, but aphA6 had not been detected. Their positive rates were 93.3%, 20. 0% and 20. 0%, respectively. These three genes existed simultaneously in No. 19 strain. Nucleotide sequences of aacC1, aacC2 and aacA4 genes shared 100%, 97.9% and 99.7% identities with GenBank genes (AY307113, S68058 and AY307114). Conclusion Multi-drug resistant Acinetobacter baumannii strains are rapidly spreading in our hospital, and their resistance to aminoglycosides may be associated with aminoglycoside-modifying enzyme gene expressions.