Identification and characterization of 10 Francisella philomiragia strains
10.13602/j.cnki.jcls.2017.04.09
- VernacularTitle:10株蜃楼弗朗西斯菌的鉴定与特征分析
- Author:
Lei ZHANG
;
Daning YE
;
Yan ZHU
;
Haiyun CHAI
;
Qingyi ZHU
;
Cha CHEN
;
Pinghua QU
- Keywords:
Francisella philomiragia;
identification;
MALDI-TOF MS
- From:
Chinese Journal of Clinical Laboratory Science
2017;35(4):271-276
- CountryChina
- Language:Chinese
-
Abstract:
Objectives To identify and characterize 10 strains of Francisella philomiragia-like organisms isolated from blood samples and environmental water.Methods The 10 clinical and environmental isolates were identified by traditional morphological examination and biochemical characterization,matrix-assisted laser desorption/ionization time of flight(MALDI-TOF) mass spectrometry(MS) systems and sequencing based on 16S rRNA gene.The minimum inhibitory concentrations were tested by E-test methods.Results All the 10 isolates were gram-negative coccobacilli appearing tiny and faint counterstain of safranin,negative for urease,nitrate reduction and X and/or V factor requirement,but positive for oxidase and catalase.The isolates grew rapidly in sheep blood agar,chocolate agar and BCYE plate forming white opaque,colorless transparent or gray smooth colonies with about 2-mm diameters,but did not grow in M-H agar and MacConkey agar.The sequencing for 16S rRNA gene indicated that the 10 isolates shared more than 99.6％ similarity to Francisella philomiragia,and fell into the same clusters of Francisella philomiragia on phylogenetic tree.The MALDI-TOF MS analysis also showed the typical peaks with 6 153 m/z,5 180 m/z,7 757 m/z and 9 392 m/z which were similar to Francisella philomiragia ATCC 25015.However,they may be misidentified to be Sphingomonas paucimobilis by using Vitek 2 GN cards,Neisseria cinerea by using Vitek 2 NH cards,Myroides odoratimimus by using API 20NE strips and Haemophilus by using API NH cards.The results of antimicrobial susceptibility showed that they were all sensitive to chloramphenicol,doxycycline,tetracycline,gentamicin,ofloxacin and ciprofloxacin.Conclusion The 10 isolates could be identified as Francisella philomiragia,so we should pay more attention to the infrequent pathogen for its inactive biochemical reaction and the misidentification by commercial detection systems.
