We screened mcr-1 and mcr-2 genes in 9,306 Escherichia coli strains isolated from healthy animals in the Japanese Veterinary Antimicrobial Resistance Monitoring (JVARM) system. mcr-1 was detected in 39 strains (5, 20, and 14 strains isolated from cattle, swine, and broilers, respectively), whereas mcr-2 was not detected. mcr-2 was also not detected with the investigation sequence homology search against our curated GenEpid-J database.
The high prevalence of broad-spectrum cephalosporin (BSC) resistance in Escherichia coli isolates from healthy broilers at farms is a source of grave concern in Japan. In an effort to solve this problem, the off-label use of ceftiofur (CTF) at hatcheries was voluntarily withdrawn around March 2012. The objective of this study was to assess the effect of the voluntary withdrawal on the prevalence of BSC resistance in E. coli from healthy broilers at farms. A total of 693 E. coli isolates collected from 362 fecal samples of healthy broilers at farms between 2010 and 2013 were examined to determine their antimicrobial resistance profiles and β-lactamase genes. β-Lactamase genes were characterized by polymerase chain reaction and sequencing. BSC resistance was detected in 84 of the 693 E. coli isolates (12.1%) from healthy broilers between 2010 and 2013. The percentage of BSC-resistant E. coli isolates was significantly decreased: from 16.4% (32/195) in 2010 and 16.8% (27/161) in 2011 to 9.2% (19/206) in 2012 and 4.6% (6/131) in 2013 (2010 versus 2012: p=0.024, 2010 versus 2013: p=0.001, 2011 versus 2012: p=0.038, and 2011 versus 2013: p=0.001). Regarding ß-lactamase genes, 58 of the 84 BSC-resistant E. coli isolates (69.0%) harbored blaCMY-2. The prevalence of BSC resistance in E. coli isolated from healthy broilers at farms was markedly decreased within a year after the voluntary withdrawal from CTF use at hatcheries. This indicates that BSC resistance in E. coli isolates from broilers could be controlled by restricting the use of CTF at the hatchery level.
Fluoroquinolone-resistant Campylobacter jejuni isolates from broilers in Japan were characterized using multilocus sequence typing and pulsed-field gel electrophoresis (PFGE) in order to elucidate the genetic relationship between these strains. Forty-three of the isolates were classified into 20 sequence types and were clustered into 21 PFGE types with 70% similarity. The most dominant clonal complex (CC) was CC-21 (41.9%). Diverse PFGE patterns were observed within the same CC, but the combined analysis of PFGE type and CC revealed that the strains with the same combination were isolated from the same district or neighboring districts. On the other hand, strains with the same combination pattern were also isolated from geographically distant districts. Our results elucidate two possible reasons for the prevalence of fluoroquinolone-resistant C. jejuni among broiler farms: (1) the resistant C. jejuni is clonally disseminated within the limited area, and (2) susceptible C. jejuni acquired fluoroquinolone resistance during the use of fluoroquinolone on the farms.
The off-label use of third-generation cephalosporins (3GCs) during in ovo vaccination or vaccination of newly hatched chicks has been a common practice worldwide. CMY-2-producing Escherichia coli strains have been disseminated in broiler chicken production. The objective of this study was to determine the epidemiological linkage of blaCMY-2-positive plasmids among broilers both within and outside Japan, because the grandparent stock and parent stock were imported into Japan. We examined the whole-genome sequences of 132 3GC-resistant E. coli isolates collected from healthy broilers during 2002 to 2014. The predominant 3GC resistance gene was blaCMY-2, which was detected in the plasmids of 87 (65.9%) isolates. The main plasmid replicon types were IncI1-Iγ (n = 21; 24.1%), IncI (n = 12; 13.8%), IncB/O/K/Z (n = 28; 32.2%), and IncC (n = 22; 25.3%). Those plasmids were subjected to gene clustering, network analyses, and plasmid multilocus sequence typing (pMLST). The chromosomal DNA of isolates was subjected to MLST and single-nucleotide variant (SNV)-based phylogenetic analysis. MLST and SNV-based phylogenetic analysis revealed high diversity of E. coli isolates. The sequence type 429 (ST429) cluster harboring blaCMY-2-positive IncB/O/K/Z was closely related to isolates from broilers in Germany harboring blaCMY-2-positive IncB/O/K/Z. pST55-IncI, pST12-IncI1-Iγ, and pST3-IncC were prevalent in western Japan. pST12-IncI1-Iγ and pST3-IncC were closely related to plasmids detected in E. coli isolates from chickens in North America, whereas 26 IncB/O/K/Z types were related to those in Europe. These data will be useful to reveal the whole picture of transmission of CMY-2-producing bacteria inside and outside Japan.
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