Population characteristics of pathogenic Escherichia coli in puerperal metritis of dairy cows in Ningxia region of China: a systemic taxa distribution of virulence factors and drug resistance genes

Abstract

Escherichia coli (E. coli) is closely associated with the occurrence of puerperal metritis in dairy cows. E. coli carries some the virulence and multi-drug resistant genes, which pose a serious threat to the health of postpartum cows. In this study, E. coli was isolated and identified from the uterine contents of postpartum cows with puerperal metritis in the Ningxia region of China, and its phylogenetic subgroups were determined. Meanwhile, virulence and drug resistance genes carried by E. coli and drug sensitivity were detected, and the characteristics of virulence and drug resistance genes distribution in E. coli phylogroups were further analyzed. The results showed that the isolation rate of E. coli in puerperal metritis samples was 95.2%. E. coli was mainly divided into phylogroups B2 and D, followed by groups A and B1, and was more connected to O157:H7, O169:H4, and ECC-1470 type strains. The virulence genes were mainly dominated by ompF (100%), traT (100%), fimH (97%), papC (96%), csgA (95%), Ang43 (93.9%), and ompC (93%), and the resistance genes were dominated by TEM (99%), tetA (71.7%), aac(3)II (66.7%), and cmlA (53.5%). Additionally, it was observed that the virulence and resistance gene phenotypes could be divided into two subgroups, with subgroup B2 and D having the highest distributions. Drug sensitivity tests also revealed that the E. coli was most sensitive to the fluoroquinolones enrofloxacin, followed by macrolides, aminoglycosides, tetracyclines, β-lactams, peptides and sulfonamides, and least sensitive to lincosamides. These results imply that pathogenic E. coli, which induces puerperal metritis of dairy cows in the Ningxia region of China, primarily belongs to the group B2 and D, contains multiple virulence and drug resistance genes, Moreover, E. coli has evolved resistance to several drugs including penicillin, lincomycin, cotrimoxazole, and streptomycin. It will offer specific guidelines reference for the prevention and treatment of puerperal metritis in dairy cows with E. coli infections in the Ningxia region of China.

Keywords: Escherichia coli; dairy cows; drug resistance gene; drug sensitivity; puerperal metritis; virulence gene.

Figure 1

PCR amplification results of strains.

Figure 2

Phylogenetic tree created by E. coli 16S rDNA PCR amplification and sequencing. There are 99 isolate samples of 16S rDNA target sequences, corresponding to the sequences of (NXDCA1-A32), (NXDCB33-B41), (NXDCC42-C56), (NXDCD57-D77), and (NXDCE78-E99). There are 15 16S rDNA reference sequences, and the different color represent the reference sequences of different origins and types, including bovine uterus: KT152814.1, avian origin: AY098487.1, porcine origin: JF513979.1,sheep origin: EF025907.1, human origin: CU656137.1, and 10 classics strains of different types of E. coli CP067426.1 (O22:H8), CP024223.1 (O169:H41), CP010344.1 (ECC-1470), two types of CP062901 (O152:H23), CP060946.1 (O157:H7), CP047094.1 (Salmonella sp), two types of CP067426 (O22:H8), and CP097884.1 (K-12).

Figure 3

Phylogenetic subgroups of E. coli strains from different regions.

Figure 4

Matrix of distribution patterns of virulence factors in E. coli phylum taxa. Classification and clustering of 99 E. coli strains based on the association between virulence factors and phylogroups. The given genetic phenotypes are represented by black rectangles, and virulence factors and types are located on the right side of the graph. Systematic taxa are represented by different color codes, as indicated by the color labeling in the upper left corner of the figure above. The branches and names of the genes of the strains are indicated above and below, respectively.

Figure 5

Matrix of the distribution patterns of drug resistance genes in E. coli phylogroups. Classification and clustering of 99 E. coli strains based on their drug resistance gene phenotypes in association with phylogroups and evolution. The identified genetic phenotypes are represented by black rectangles, and drug-resistance genes are located on the right side of the graph. Systematic taxa are indicated by different color coding, as depicted by the colors presented in the upper left corner of the figure above. The branches and names of the genes of the strains are displayed above and below, respectively.