Prevalence of 16S rRNA methylase, modifying enzyme, and extended-spectrum beta-lactamase genes among Acinetobacter baumannii isolates. (August 2015)

• Record Type: Journal Article
• Authors: Liu, Zhenru; Ling, Baodong; Zhou, Liming
• Is Part Of: Journal of chemotherapy. Volume 27:Number 4(2015:Aug.)
• Page Start: 207
• Page End: 212
• Publication Date: 2015-08
• Subjects: Chemotherapy -- Periodicals; Drug Therapy -- Periodicals; 615.58
• DOI: 10.1179/1973947814Y.0000000190
• Languages: German
• ISSNs: 1120-009X

Abstract

<abstract> <title> <x content-type="archive" xml:space="preserve">Abstract</x> </title> <p>Multidrug-resistant <italic>Acinetobacter baumannii</italic> has become a worldwide problem, and methylation of 16S rRNA has recently emerged as a new mechanism of resistance to aminoglycosides, which is mediated by a newly recognized group of 16S rRNA methylases. 16S rRNA methylase confers a high-level resistance to all 4, 6-substituted deoxystreptamine aminoglycosides that are currently used in clinical practice. Some of the <italic>A. baumannii</italic> isolates have been found to coproduce extended-spectrum beta-lactamases (ESBLs), contributing to their multidrug resistance. The aim of this study was to detect the determinants of the 16S rRNA methylase genes <italic>armA</italic>, <italic>rmtA</italic>, <italic>rmtB</italic>, <italic>rmtC</italic>, <italic>rmtD</italic>, <italic>rmtE</italic>, and <italic>npmA</italic>, the modifying enzyme genes <italic>aac(6′)-Ib</italic>, <italic>ant(3″)-Ia</italic>, <italic>aph(3′)-I</italic>, and the extended-spectrum beta-lactamase genes <italic>bla</italic><sub>TEM</sub>, <italic>bla</italic><sub>SHV</sub>, and <italic>bla</italic><sub>CTX-M-3</sub> among <italic>A. baumannii</italic> isolates in northeastern Sichuan, China.</p> <p>Minimum inhibitory concentrations (MICs) of 21 different antimicrobial agents against the <italic>A. baumannii</italic> isolates were determined. The clinical isolates showed a high level of resistance (MIC≧256 μg/ml) to aminoglycosides, which ranged from 50·1 to 83·8%. The resistances to meropenem and imipenem, two of the beta-lactam antibiotics and the most active antibiotics against <italic>A. baumannii</italic>, were 9·1 and 8·2%, respectively.</p> <p>Among 60 amikacin-resistant isolates, only the 16S rRNA methylase gene <italic>armA</italic> was found to be prevalent (66·7%), but the other 16S rRNA methylase genes <italic>rmtA</italic>, <italic>rmtB</italic>, <italic>rmtC</italic>, <italic>rmtD</italic>, <italic>rmtE</italic>, and <italic>npmA</italic> were not detected. The prevalences of the modifying enzyme genes <italic>aac (6′)-Ib</italic>, <italic>ant (3″)-Ia</italic>, and <italic>aph (3′)-I</italic> were 51·7, 81·7, and 58·3%, respectively, which are different from a previous study in which the occurrences of these genes were 3, 64, and 72%, respectively. Among the 40 isolates that were <italic>armA</italic>-positive, the prevalences of <italic>bla</italic><sub>TEM</sub>, <italic>bla</italic><sub>SHV</sub>, and <italic>bla</italic><sub>CTX-M-3</sub> genes were detected for the first time in China, and their occurrences were 45, 65, and 52·5%, respectively.</p> <p>In all, <italic>A. baumannii</italic> with all the 16S rRNA methylase, modifying enzyme, and ESBL genes is extremely prevalent in northeastern Sichuan, China, posing a serious clinical concern with a major therapeutic threat in the future.</p> </abstract>