The present study aimed to identify, determine the susceptibility, and detect gene cassettes of Arcanobacterium (Actinomyces) pyogenes isolates from cows with endometritis. Arcanobacterium pyogenes isolates were identified first by using the API Coryne Vit system test, and further through PCR. Minimum inhibitory concentrations of 23 antimicrobial agents against A. pyogenes were tested using standard broth microdilution assays according to the protocols of the Clinical and Laboratory Standards Institute. The genes of integrons I and II were amplified by PCR using specific primers. Thirty-two A. pyogenes isolates were isolated from 136 endometritic cows in the Hohhot region. Antibiotic susceptibility tests revealed that all isolates were highly sensitive to fluoroquinolones (100%), macrolides (approximately 81.2 to 100%) and florfenicol (90.6%), aminoglycosides (approximately 15.6 to 81.2%), and tetracyclines (approximately 43.7 to 68.7%). However, 53.1% were resistant to clindamycin, approximately 50 to 65.6% were resistant to penicillins, and approximately 37.5 to 71.9% were resistant to cephalosporins. One hundred percent were resistant to sulfonamides and bacitracin zinc. The integrons were further confirmed by sequencing. No class II integrons were detected, whereas 50% (n = 16) of the A. pyogenes isolates were positive for the presence of the intI I gene, but only 13 contained gene cassettes. Sequence analysis of gene cassettes revealed 6 gene cassettes, 4 of which encode resistant determinants of aminoglycosides (aadA1, aadA5, aadA24, and aadB) and 1 of which encodes the resistance gene of chloramphenicol (cmlA6). The function of the sixth identified cassette, designated ORF1, is unknown. The gene cassette arrays aadA24-ORF1, aadA5, and aadA1-addB-cmlA6 were found in 46.13% (6/13), 38.46% (5/13), and 38.46% (5/13) of the isolates, respectively. These cassettes segregated according to a consistent pattern, with aadA5 always alone, ORF1 always with aadA24, and aadA1-aadB and cmlA6 always together. Most of the positive integrons existed in the multiresistant isolates (n = approximately 3 to 7), indicating that the integrons played an important role in the dissemination and spread of antimicrobial resistance. This is the first report of A. pyogenes infections in dairy cows in China and of detection of gene cassettes and integrons in A. pyogenes.

Chinese oak silkworm, Antheraea pernyi Guérin-Méneville 1855 (Lepidoptera: Saturniidae), is a traditional edible insect in China and is considered the edible insect with the highest potential. Information on the mitochondrial genome (mitogenome) of the first modern improved strain of this silkworm, Qinghuang_1, is currently unavailable. Here, we determine the mitogenome of Qinghuang_1 by long PCR amplification followed by Illumina sequencing and then compare the resulting mitogenome with the five available mitogenomes of this species. The mitogenome of Qinghuang_1 is 15,573 bp in length and exhibits an identical gene organisation to known A. pernyi mitogenomes. The base A content of this mitogenome is higher than those of the other four strains but lower than that of the wild type. Sequence comparisons identified 200 single-nucleotide variants (1.28%) and 32 amino acid changes among the five inbred strains, indicating a considerable degree of nucleotide diversity in the mitogenomes of A. pernyi germplasm resources. The 3’ end of ND1 was identified as a hotspot in the A. pernyi mitogenome. Ka/Ks analysis indicated that all protein-coding genes evolved under negative selection except for ND5, which presented values larger than 1, suggesting that positive selection may act on this gene. The phylogenetic analyses confirmed the basal position of Qinghuang_1 among the inbred strains of A. pernyi. Our results indicated that the mitogenome is helpful for understanding the intraspecific phylogenetic relationships of A. pernyi and for its genetic improvement.