Culture, identification and related mechanism research of Proteus vulgaris KM-19

ObjectiveTo analyze the biological characteristics, drug resistance mechanism and genomic characteristics of a beta hemolytic Proteus vulgaris KM-19 strain isolated and identified from middle urinary culture deficient in migratory growth, and provide evidence for clinical rational use of antibiotics.

MethodsThe strain was cultured and isolated by using conventional methods. Then, VITEK-2 Compact automatic microbiological analyzer was used for the strain identification and drug sensitivity test in vitro. The absence of flagella was observed by staining and semisolid dynamic test. The whole genome of the strain was sequenced by high-throughput sequencing. The sequence assembly, gene prediction and functional annotation were carried out with bioinformatics method, and gene clusters related to phenotypic mechanism and drug resistance mechanism of the strain were further explored.

ResultsVITEK-2 Compact identified the strain as Proteus vulgaris. The whole genome sequencing results showed that 48 Contigs were obtained from genome assembly; the total length of the gene was 3 319 152 bp, and the average length was 904.89 bp, accounting for 85.50% of the total length of the genome; the genome had no repeat sequence and had 38% C+G content. This strain was most likely to be Proteus vulgaris, which also verified the accurate identification result of the VITEK-2 Compact. This Proteus vulgaris strain was resistant to the first and second generation of cephalosporin, ampicillin, furantoin, compound neostigmine and tigecycline, but is was sensitive to the other drugs. No flagellum structure was observed under oil microscope and semisolid dynamic test was negative. The comparison between the genome sequencing sequence and the VFDB database showed that the bacterial flagellar gene and related genes were not missing, but, in flagellar gene sequences, the Methyl-accepting chemotaxis protein Ⅲ/Ⅰ genes was found. Methyltransferase genes and hlyB genes were also found in the genome. In addition, the comparison between the genome sequence and the CARD database showed that there were OXY and CTX-M genes and active efflux pump genes.

ConclusionThe main mechanism of no migrating growth of this strain might be the methylation of flagellar genes or related genes, which indicated that the bacteria wasunable to effectively express flagellin in vitro and lost the ability of migrating growth. The beta hemolytic phenotype might be due to the insertion of exogenous hemolysin gene (hlyB), which was expressed effectively the bacterial genome. The drug resistance in vitro was closely related to OXY and CTX-M genes and active efflux pump genes.