Prevalence of pleuromutilin antibiotic resistance genes in different laying hen breeding stages in China.

Antimicrobial resistance is a rapidly evolving and extremely complex issue, particularly due to the use of various types of antimicrobials within human, animal, and environmental sectors. Pleuromutilin antibiotics are used to prevent and control respiratory diseases in the rearing stage of hen chicks, but the current status of pleuromutilin resistance in the laying hen breeding process is unclear. ATP-binding cassette transporters encoded by lsa(A), lsa(E), lsa(C), and vga(D) can be transferred by plasmids and transposons, thereby posing a potential dissemination risk. To investigate pleuromutilin resistance genes in the laying hen production chain in China, 95 samples from five environmental types were collected in four breeding stages to determine the abundances of the main resistance genes by qPCR, i.e. lsa(A), lsa(E), lsa(C), and vga(D). The abundance (5.16 log10GC/g) and detection rate (100%) of lsa(E) was highest in all of the samples, thereby suggesting high contamination with the lsa(E) gene across the large-scale laying hen breeding environment and feces. The lsa(A) (6.02 log10GC/g) and lsa(E) (6.18 log10GC/g) genes were most abundant in flies, and the abundance of vga(D) (4.50 log10GC/g) was highest in dust (P < .05). In addition to feces, flies and dust were important sources of contamination with pleuromutilin resistance along the laying hen production chain. In summary, we determined the abundances of four pleuromutilin resistance genes in the laying hen production chain and provided direct evidence of pleuromutilin resistance transmission and environmental contamination. In particular, the chicken breeding stage needs further attention.

Prevalence and transmission of antimicrobial-resistant Staphylococci and Enterococci from shared bicycles in Chengdu, China.

Shared bicycles are prevailing in China but the extent to which they contribute to maintaining and transmitting pathogens and antibiotic-resistant bacteria remain largely unknown. To fill the knowledge gap, herein, swab samples (n = 963) were collected from handlebars of shared bicycles in areas of hospital, school, metro station (n = 887) and riders (n = 76) in Chengdu, China. Staphylococci (n = 241) and Enterococci (n = 69) were widely distributed across sampling locations at a frequency of 2.3%-12.9%, and 0.08%-5.5%, respectively. Bicycle or rider-borne Gram-positive bacteria were frequently resistant to clinically important antibiotics including linezolid, fosfomycin, and vancomycin, and a significant portion of these isolates (3.4%-16.6% for Staphylococci and 0.1%-13.8% for Enterococci) indicated multidrug resistance. Nineteen Staphylococcus aureus isolates were identified in this collection and 52.6% of which were considered as methicillin-resistant S. aureus. Whole genome sequencing further characterized 26 antimicrobial resistance genes (ARGs) including fosB, fusB, and lnu(G) in S. aureus and 21 ARGs including optrA in Enterococci. Leveraging a complementary approach with conventional MLST, whole genome SNP and MLST analyses, we present that genetically closely-related bacteria were found in bicycles and riders across geographical-distinct locations suggesting bacterial transmission. Further, five new ST types 5697-5701 were firstly characterized in S. aureus. ST 942 and ST 1640 are new ST types observed in E. faecalis, and E. faecium, respectively. Our results highlighted the risk of shared bicycle system in disseminating pathogens and antibiotic resistance which warrants effective disinfections.

Genome sequence of multidrug-resistant Erysipelothrix rhusiopathiae ZJ carrying several acquired antimicrobial resistance genes.

OBJECTIVES: This study aimed to determine the genetic environment of antimicrobial resistance genes (ARGs) in Erysipelothrix rhusiopathiae strain ZJ isolated from a pig with symptoms of swine erysipelas in China. METHODS: Illumina MiSeq (200× coverage) and PacBio RS II (100× coverage) platforms were used for genome sequencing. ARGs and prophages were identified using ResFinder 3.0 and PHASTER, respectively. A conjugation experiment, induced prophage infection and long-term passage assay were performed to determine the transferability and stability of ARGs in this strain. RESULTS: The assembled circular genome of E. rhusiopathiae ZJ was 1 945 689 bp with a GC content of 36.48%; no plasmid sequence was detected. Eleven acquired ARGs were identified in the genome. A novel integrative and conjugative element (ICE) encoding a multidrug resistance (MDR) gene cluster [aadE-apt-spw-lsa(E)-lnu(B)-aadE-sat4-aphA3] was identified in strain ZJ. A prophage Φ1605 harbouring mef(A)-msr(D) and tet(M) was also found in this strain, which can take a circular form and can be induced by mitomycin C to infect E. rhusiopathiae G4T10 for ARG transfer. CONCLUSION: To our knowledge, this is the first report of a complete genome sequence of E. rhusiopathiae carrying multiple ARGs obtained from a pig farm. This is the first identification of a novel chimeric ICE carrying a MDR gene cluster and a prophage carrying ARGs in E. rhusiopathiae, which will provide a valuable reference to understand the potential transfer mechanism of MDR gene clusters carried by ICEs and prophages in Gram-positive bacteria.