MCR-3 detected in study of English pigs
A study of pigs has detected the presence of the MCR-3 colistin-resistance gene in England for the first time, United Kingdom researchers reported yesterday in the Journal of Antimicrobial Chemotherapy. But the study also found that stopping the use of colistin can mitigate long-term on-farm persistence.
To gain a better understanding of the molecular epidemiology of MCR-positive Enterobacteriaceae, circulating plasmids, and their on-farm persistence, researchers from the UK's Animal and Plant Health Agency used whole-genome sequencing to analyze MCR-1-positive Enterobacteriaceae isolates from pig samples on a single pig farm. They collected fecal samples from three cohorts of pigs: one that was initially treated with colistin following diarrhea, a younger cohort that was untreated but overlapped with the first cohort over a period of 5 months, and a third cohort on the same farm 20 months after the initial diagnostic submission.
The results showed that Escherichia coli harboring MCR-1 and multiple resistance genes were detected in the colistin-treated cohort of pigs as well as the untreated cohort. The researchers theorize that the presence of MCR-1 in the untreated pigs may have been because these pigs had moved into accommodations previously occupied by the treated pigs and had been exposed to environmental contamination with MCR-1 E coli. Additionally, the researchers found MCR-3 in seven of the E coli isolates from the treated cohort, with some isolates also harboring multiple copies of MCR-1 on different plasmids.
Neither MCR-1 nor MCR-3 were detected when the farm was re-sampled after 20 months.
"In conclusion, this study indicated that although mcr E. coli had become widespread on a farm in England, measures taken to mitigate on-farm risk were successful," the authors wrote.
Aug 14 J Antimicrob Chemother study
Study shows emergence of E coli ST131 clade in Europe
In another study yesterday in the Journal of Antimicrobial Chemotherapy, a team of European researchers report the emergence of an extended-spectrum beta-lactamase (ESBL)-producing E coli ST131 clade in European hospital patients.
In the study, 688 ESBL E coli isolates were obtained from rectal swabs of patients in hospitals in Berlin, Geneva, Madrid, and Utrecht. The researchers were looking to assess the prevalence, geographical distribution, and microbiological characteristics of E coli ST13—a multidrug-resistant pandemic clone causing urinary tract and bloodstream infections—and its dominant sublineage, C/H30.
The analysis found that the ST131 detection rate among ESBL E coli carriers was 20.5% (141/688), with 16% (46/295) prevalence in Madrid, 18% (31/172) prevalence in Utrecht, 23% (31/135) in Berlin, and 38% (33/86) in Geneva. Subclone typing further revealed that C/H30 subset compromised the majority of the ST131 isolates (70.2%, 99/141). But there was significant difference in subclone prevalence, with C1/H30R1 isolates more prevalent in Geneva (49%, 16/33) and C2/H30Rx more prevalent in Madrid (67%, 31/46). While the C2/H30Rx isolates were significantly associated with the CTX-M-15 enzyme, the C1/H30R1 isolates were more associated with the CTX-M-27 enzyme.
Isolates belonging to this new ST131-C1-M27 clade have previously been detected among Japanese, French, and German isolates, but the detection of isolates from this clade in all four hospitals suggest it is circulating throughout Europe. The authors of the study say the findings demonstrate a changing epidemiology of ESBLs in Europe caused by ST131 subclones.
Aug 14 J Antimicrob Chemother abstract