从耐药鲍曼不动杆菌中发现β-内酰胺酶ADC基因和膜孔蛋白carO基因新的变异型

Emergence of novel variants of β-lactamase gene blaADC and outer membrane porin gene carO in drug-resistant Acinetobacter baumannii

目的调查一组耐药鲍曼不动杆菌中β-内酰胺酶基因和膜孔蛋白基因的存在和变异情况。方法收集2010年1月至2010年12月浙江某医院ICU患者痰液标本中分离的多耐药和泛耐药鲍曼不动杆菌各10株,用分子鉴定法鉴定菌种,再用聚合酶链反应(PCR)及序列分析的方法分析34种β-内酰胺酶基因与膜孔蛋白carO基因。结果本组20株耐药鲍曼不动杆菌共检出TEM-1型20株(100%)、OXA-23型10株(50.0%)、ADC-30型12株(60.0%)、ADC基因新的变异型ADC-60型8株(40.0%)(GenBank登录号:JQ692087)。10株PDR菌均检出OXA-23型β-内酰胺酶基因,而10株MDR菌则均未检出OXA-23型β-内酰胺酶基因。20株耐药鲍曼不动杆菌膜孔蛋白carO基因均存在有义突变,19株测得序列相同,翻译成氨基酸序列后与鲍曼不动杆菌敏感株(SDF)比较,一致率为76.0%。8号株carO基因序列与其他19株测得DNA序列不同,第351位缺失了12个碱基并导致过早出现终止密码子。结论本组鲍曼不动杆菌对β-内酰胺类药物耐药主要与产TEM、ADC、OXA-23和carO基因存在有义突变相关。OXA-23型β-内酰胺酶基因阳性是PDR菌耐碳青霉烯类药物的原因。ADC基因存在新变异型:ADC-60是国内外首次报道。

Objective To investigate the distribution and variety of β-lactamase genes and outer membrane porin gene carO in a group of drug-resistant Acinetobacter baumannii.Methods 10 strains of multidrug-resistant Acinetobacter baumannii and 10 strains of pandrug-resistant Acinetobacter baumannii isolated from the sputum samples of inpatients in ICU of a hospital in Zhejiang,China during January to December 2010 were collected.Then the strains were identified by molecule identification,and 34 kinds of β-lactamase genes and outer membrane porin gene carO were analyzed by PCR and DNA sequencing.Results In the 20 strains of Acinetobacter baumannii,4 kinds of β-lactamase genes were positive： 20 strains of TEM-1（100%）,10 strains of OXA-23（50.0%）,12 strains of ADC（60.0%）,8 strains of novel variants of ADC,ADC-60（40.0%）（GenBank accession number： JQ692087）.OXA-23 was positive in all 10 strains of pandrug-resistant Acinetobacter baumannii,while negative in all 10 strains of multidrug-resistant Acinetobacter baumannii.In addition,the outer membrane porin gene carO of all 20 strains had missense mutation,and the carO genes of 19 strains were the same,and the consistency rate of amino acid sequence of carO genes between the 19 strains and sensitive strain（SDF） of Acinetobacter baumannii was 76.0%.Moreover,the carO gene of Strain No.8 was different from the other 19 strains due to loss of 12 bases at site 351,resulting in premature stop codon.Conclusion In this group of Acinetobacter baumannii,the production of β-lactamase genes TEM,ADC and OXA-23,and missense mutations of carO gene play a key role in the resistance to β-lactams.OXA-23 contributes to the resistance to carbapenems in pandrug-resistant strains.And this is the first report on a novel variant of ADC genes,ADC-60,discovered in the world.