title: MALDI-TOF MS distinctly differentiates nontypable Haemophilus influenzae from Haemophilus haemolyticus.
abstract: Nontypable Haemophilus influenzae (NTHi) and Haemophilus haemolyticus exhibit different pathogenicities, but to date, there remains no definitive and reliable strategy for differentiating these strains. In this study, we evaluated matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) as a potential method for differentiating NTHi and H. haemolyticus. The phylogenetic analysis of concatenated 16S rRNA and recombinase A (recA) gene sequences, outer membrane protein P6 gene sequencing and single-gene PCR were used as reference methods. The original reference database (ORD, provided with the Biotyper software) and new reference database (NRD, extended with Chinese strains) were compared for the evaluation of MALDI-TOF MS. Through a search of the ORD, 76.9% of the NTHi (40/52) and none of the H. haemolyticus (0/20) strains were identified at the species level. However, all NTHi and H. haemolyticus strains used for identification were accurately recognized at the species level when searching the NRD. From the dendrogram clustering of the main spectra projections, the Chinese and foreign H. influenzae reference strains were categorized into two distinct groups, and H. influenzae and H. haemolyticus were also separated into two categories. Compared to the existing methods, MALDI-TOF MS has the advantage of integrating high throughput, accuracy and speed. In conclusion, MALDI-TOF MS is an excellent method for differentiating NTHi and H. haemolyticus. This method can be recommended for use in appropriately equipped laboratories.
authors: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
authors: Bingqing
authors: B
authors: Zhu
authors: Di
authors: D
authors: Xiao
authors: Huifang
authors: H
authors: Zhang
authors: Yongchan
authors: Y
authors: Zhang
authors: Yuan
authors: Y
authors: Gao
authors: Li
authors: L
authors: Xu
authors: Jing
authors: J
authors: Lv
authors: Yingtong
authors: Y
authors: Wang
authors: Jianzhong
authors: J
authors: Zhang
authors: Zhujun
authors: Z
authors: Shao
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000235:genetics; D006190:Haemophilus / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D006192:Haemophilus Infections / Q000175:diagnosis* / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012015:Reference Standards; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S