Molecular Epidemiological Study Of Clinically Isolated Multidrug-resistant Acinetobacter Baumannii And A Case Of Whole Genome Sequencing Analysis Of Acinetobacter Pittii

ObjectiveTo understand the drug-resistant phenotype of clinically isolated multi-drug resistantAcinetobacter baumannii?MDR-AB?,and to explore the?-lactamase resistance gene carried by these strains.Through the homology analysis of multi-drug resistant Acinetobacter baumanniiin intensive care unit,the epidemic trend was observed.At the same time,a case of Acinetobacter pittii was analyzed by whole genome sequencing analysis to understand the specific genomic feature.Methods?1?Collecting clinically isolated multi-drug resistant Acinetobacter baumanniistrains and their clinical data.?2?The general clinical data of the strains were analyzed,such as the age and sex of the patients,the distribution of the departments,and the source of the specimens.?3?The strains were initially identified by VITEK-2 COMPACT automatic microbial analysis.At the same time,three unique genes rRNA gene spacer?ITS?,recA and bla_OXA-51 were amplified by PCR to re-identified the strains.?4?The strains were tested for drug susceptibility testand carbapenem inactivation method to understand their resistant phenotypes.?5?The bacterial DNA was extracted,the?-lactamase resistance genes were amplified by PCR,and the gene fragments of the positive results were sequenced and compared on the BLAST website.?6?The multilocus sequence typing?MLST?was performed on 28 MDR-AB in one ICU ward,and sequence types were obtained on pubmlst,and the data was analyzed using the eBURST software.?7?Whole genome sequencing and bioinformatics analysis were used to understand the clinically isolated Acinetobacter pittii.ResultsOf the 73 cases of Acinetobacter baumannii,68.5%were from male patients and most of these strains were from elder patients.Specimens were mainly from the ICU ward and were most commonly found in respiratory systems.All of the 73 strains were resistant to piperacillin,cephalosporin,imipenem,meropenem,ciprofloxacin,and piperacillin/tazobactam.In addition to the high sensitivity to polymyxin,tigecycline and minocycline,most strains were highly resistant to other antibiotics.All strains carried the bla _AmpC gene,and 97.3%carried the ISAba1-AmpC gene.The strains mainly carried the bla_TEM and bla_OXA-23 acquired resistance genes,and all strains carried at least one of these two genes.At the same time,the strains carrying these two genes reached 58.9%.This study detected a multi-drug resistant Acinetobacter baumannii carrying bla_KPC,bla_SHV,bla_TEM and ISAba1-AmpC genes.The MLST results of 28 MDR-AB in ICU ward showed a total of 9 sequence types?ST?,including four new STs,ST1779,ST1789and ST195 were the main infected clones accounting for 67.9%of all strains.The eBURST software analysis yielded one group and two singletons.At the same time,this study found a case of Acinetobacter pittii carrying bla_NDM-1,bla_OXA-421 and bla_AmpCmpC genes.ConclusionThe MDR-AB strains in this hospital is highly resistant,and extensively synthesize carbapenemases;?-lactamase resistance genes are widely present in MDR-AB,and for Acinetobacter baumannii,carrying of?-lactamase resistance genes are related to the resistance of?-lactam antibiotics.The ICU is an important department of Acinetobacter baumannii infection,and the infection of Acinetobacter baumannii in ICU is easy to outbreaks.Here,we first report the clinical isolate of Acinetobacter pittii in Anhui province,and the strain carries three drug resistance genes,bla _NDM-1,bla_OXA-421 and bla_AmpC,among which bla_OXA-421 gene was first discovered in China.