| Objective:To investigate the biological characters?molecular typing and mechanism of carbapenem-resistant Proteus mirabilis(PM)deficient in swarming motility,understand the epidemic situation and provide guidance for the prevention and control of nosocomial infection.At the same time,the differences of antibiotic resistance between the PM isolates deficient in swarming motility and other isolates with swarming motility were compared in order to provide a scientific basis for clinical treatment caused by this type of PM.Methods:Retrospective analysis of the drug resistance rate of the PM strains from Hangzhou General Hospital of CAPF(Chinese People's Armed Police Forces)during January 2013 to December 2014;collected carbapenem resistance PM isolates deficient in swarming motility.Strains had no swarming motility after many times culture,the bacterial motility and flagella were observed by semi-solid agar culture and flagella staining;pulsed-field gel electrophoresis(PFGE)was performed for homology analysis;agar dilution and E-test methods were performed to detect the antimicrobial susceptibilities of those strains.The modified Hodge test and extended-spectrum?-lactamases(ESBLs)confirmation test were also used to screen out the resistant phenotypes.Specific polymerase chain reaction(PCR)and DNA sequencing were performed to confirm the genotype of ?-lactamases.Plasmid extraction,electroporation and SI-PFGE in combination with southern hybridizations were used to clarify the carbapenem resistance genes located on the plasmid.PCR mapping of the blaKPC gene was performed to analysis genetic environment of blaKPC gene in PM.Finally,the target gene amplification and drug sensitivity test were carried out on the transconjugants after electroporation.Results:The biological characters of PM deficient in Swarming motility are below:the cell was small and rule,and apparently lack of flagella structure by comparing with the bacterial flagella staining under the microscope.In semi-solid agar culture,the strains could grow along a piercing line,but couldn't diffuse outer of the line.It was presumed that the PM strains lacked of swarming motility due to loss of the flagella structure.The two kinds of PM strains had the same biochemical characteristics,and all of strains couldn't swarm growth on the SS or MAC panel,because of which contained bile salt medium.A total of 339 PM strains were collected during the study period,including 42 PM strains deficient in Swarming motility;The imipenem and meropenem resistance rates of migration growth PM were 6.3%and 3.2%,and the 42 PM strains were 57.2%and 52.4%,respectively.It could be found a significant difference in the carbapenem resistance rate(P<0.001);Among the 42 PM strains,24 carbapenem-resistant PM isolates deficient in Swarming motility were collected,and the percentage was 57%.PFGE analysis indicated that the 24 carbapenem-resistant PM strains belonged to three clones and the main clone(named as clone A)had 22 isolates.The modified Hodge test of the PM strains were positive,and PCR and DNA sequence analysis confirmed which carried blaKPC-2 gene.Southern blot indicated that the blaKPC-2 gene was located on plasmids varying in size about(ca.26kb,55kb and 139kb).In addition,some isolates harbored several resistance genes,such as blaTEM-1,blacTX-M-65 and rmtB.The genetic structures of isolates carrying blaKPC-2 were ISKpn8,blaKPC-2 and ISKpn6-like from upstream to downstream,this genetic structure was easy to cause the resistance gene to spread among the species.Clinical data retrospective analysis found that the majority of specimen sources were from the respiratory tract,the patient has a long-term hospitalization,using many broad-spectrum antibiotics,and most of patients were in the state of tracheotomy.Conclusion:Proteus mirabilis strains lack of swarming growth due to the loss of the flagella structure.Compared with PM isolates with swarming motility,the carbapenem-resistant rate was significantly higher in these PM isolates deficient in swarming motility.Carbapenemases KPC-2 played an important role in the carbapenem-resistance PM isolates deficient in swarming motility.There was a cloning spread trend for carbapenem-resistance PM isolates in our hospital.Clinicians should pay more attention to the risk of spreading. |
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