Risk Factors and Prevalence of mcr-1-Positive Escherichia coli in Fecal Carriages Among Community Children in Southern Taiwan

Prevalence of colistin-resistant mcr-1-positive Escherichia coli isolated from children patients with diarrhoea in Shanghai, 2016-2021

OBJECTIVES

The emergence of the plasmid-mediated colistin resistance 1 (mcr-1) of Escherichia coli has become a global health concern. This study reports the prevalence of mcr-1 among E. coli isolates from patients with diarrheal disease in Shanghai and the genetic characterization of mcr-1-harbouring plasmids.

METHODS

A total of 1723 E. coli strains were collected from the faeces of patients with diarrheal disease in all sentinel hospitals in Shanghai from 2016 to 2021. Antimicrobial susceptibility testing was performed by broth microdilution and plasmid conjunction transfer assay was carried out using E. coli C600 as the recipient. The mcr-1-positive E. coli strains (MCRPEC) were subjected to molecular characterization and bioinformatic analysis of the mcr-1-bearing plasmids that they harboured.

RESULTS

Only 5 (0.28%) strains were found to harbour the mcr-1 gene using PCR screening. Plasmid conjugation assay and whole-genome sequencing indicated that EC16500, one MCRPEC strain that co-exhibited mcr-1, blaTEM-1, blaOXA-1, qnrS1, qnrS2, arr-3, and catB3, could be conjugated to EC C600 by horizontal transfer with an average efficiency of 3.2 × 10-5. The plasmid pEC16500 harboured similar backbones as p70_2_15, pECGD-8-33, pNCYU-29-19-1_MCR1, and pIBMC_mcr1, and was shown to be encoded within a type IV secretion system (T4SS)-containing 32.6 kbp IncX4, next to the pap2-like membrane-associated gene, to form a 2.4-kb cassette. Furthermore, sequencing and phylogenetic analyses revealed a similarity between other MCR-1-homolog proteins, indicating that the five E. coli isolates were colistin-resistant.

CONCLUSION

Our data represents a significant snapshot of colistin resistance mcr-1 genes and highlights the need to increase active surveillance, especially among children under five years of age, in Shanghai. Great effort needs to be taken to avoid further dissemination of plasmid-mediated colistin resistance among clinically relevant Gram-negative bacterial pathogens.

Fecal carriage and molecular epidemiology of mcr-1-harboring Escherichia coli from children in southern China

BACKGROUND

The increase of multidrug-resistant Enterobacteriaceae bacteria has led to the reintroduction of colistin for clinical treatments, and colistin has become a last resort for infections caused by multidrug-resistant bacteria. Enterobacteriaceae bacteria carrying the mcr-1 gene are majorly related to colistin resistance, which may be the main reason for the continued increase in the colistin resistance rate of Enterobacteriaceae. The study aimed to investigate the sequence type and prevalence of Escherichia coli (E. coli) harboring the mcr-1 gene in the gut flora of children in southern China.

METHODS

Fecal samples (n = 2632) of children from three medical centers in Guangzhou were cultured for E. coli. The mcr-1-harboring isolates were screened via polymerase chain reaction (PCR). The colistin resistance transfer frequency was studied by conjugation experiments. DNA sequencing data of seven housekeeping genes were used for multi-locus sequence typing analysis (MLST).

RESULTS

PCR indicated that 21 of the 2632 E. coli (0.80%) isolates were positive for mcr-1; these strains were resistant to colistin. Conjugation experiments indicated that 18 mcr-1-harboring isolates could transfer colistin resistance phenotypes to E. coli J53. MLST analysis revealed that the 21 isolates were divided into 18 sequence types (STs); E. coli ST69 was the most common (14.3%), followed by E. coli ST58 (9.5%).

CONCLUSION

These results demonstrate the colonization dynamics and molecular epidemiology of E. coli harboring mcr-1 in the gut flora of children in southern China. The mcr-1 gene can be horizontally transmitted within species; hence, it is necessary to monitor bacteria that harbor mcr-1 in children.

Intestinal colonization with multidrug-resistant Enterobacterales: screening, epidemiology, clinical impact, and strategies to decolonize carriers

The clinical impact of infections due to extended-spectrum β-lactamase (ESBL)- and/or carbapenemase-producing Enterobacterales (Ent) has reached dramatic levels worldwide. Infections due to these multidrug-resistant (MDR) pathogens-especially Escherichia coli and Klebsiella pneumoniae-may originate from a prior asymptomatic intestinal colonization that could also favor transmission to other subjects. It is therefore desirable that gut carriers are rapidly identified to try preventing both the occurrence of serious endogenous infections and potential transmission. Together with the infection prevention and control countermeasures, any strategy capable of effectively eradicating the MDR-Ent from the intestinal tract would be desirable. In this narrative review, we present a summary of the different aspects linked to the intestinal colonization due to MDR-Ent. In particular, culture- and molecular-based screening techniques to identify carriers, data on prevalence and risk factors in different populations, clinical impact, length of colonization, and contribution to transmission in various settings will be overviewed. We will also discuss the standard strategies (selective digestive decontamination, fecal microbiota transplant) and those still in development (bacteriophages, probiotics, microcins, and CRISPR-Cas-based) that might be used to decolonize MDR-Ent carriers.

Distribution and Genomic Characterization of Third-Generation Cephalosporin-Resistant Escherichia coli Isolated from A Single Family and Home Environment: A 2-Year Longitudinal Study

Third-generation cephalosporin-resistant Escherichia coli (CREC), particularly strains producing extended-spectrum β-lactamases (ESBLs), are a global concern. Our study aims to longitudinally assemble the genomic characteristics of CREC isolates from fecal samples from an index patient with recurrent CREC-related urinary tract infections and his family and swabs from his home environment 12 times between 2019 and 2021 to investigate the distribution of antibiotic resistance genes. CREC identified using the VITEK 2 were subjected to nanopore whole-genome sequencing (WGS). The WGS of 27 CREC isolates discovered in 137 specimens (1 urine, 123 feces, and 13 environmental) revealed the predominance of ST101 and ST131. Among these sequence types, bla_CTX-M (44.4%, n = 12) was the predominant ESBL gene family, with bla_CTX-M-14 (n = 6) being the most common. The remaining 15 (55.6%) isolates harbored bla_CMY-2 genes and were clonally diverse. All E. coli isolated from the index patient’s initial urine and fecal samples belonged to O25b:H4-B2-ST131 and carried bla_CTX-M-14. The results of sequence analysis indicate plasmid-mediated household transmission of bla_CMY-2 or bla_CTX-M-55. A strong genomic similarity was discovered between fecal ESBL-producing E. coli and uropathogenic strains. Furthermore, bla_CMY-2 genes were widely distributed among the CREC isolated from family members and their home environment.

Rapid Detection of Multi-Resistance Strains Carrying mcr-1 Gene Using Recombinase-Aided Amplification Directly on Clinical Samples

With the increasingly severe problem of bacterial resistance, colistin, as the last line of defense, has attracted attention again. Mobile colistin resistance (mcr-1) gene is involved in the horizontal transmission of colistin resistance in Gram-negative bacteria (GNB), which is a serious threat to human health. Therefore, rapid detection of mcr-1 gene presence in clinical samples is crucial. In this study, a Recombinase-aided amplification(RAA) method for mcr-1 was successfully constructed, with sensitivity of 20 copies/reaction. In addition, amplification signal could only be detected in the strain containing mcr-1 gene among 14 different bacterial species. The method was then used to test a total of 672 clinical samples from a pediatric hospital in Beijing. Five strains harbored mcr-1 genes were isolated from mcr-1-positive clinical samples and identified as Escherichia coli. Multi-locus sequence typing (MLST) analysis showed that the five E. coli belonged to different ST types. Notably, the mcr-1 gene from the isolates could be transferred conjugately to the recipient strain E. coli J53, with highest transfer efficiency up to 57–58%, suggesting that the mcr-1 gene was located on the plasmid. These findings showed that the RAA assay has potential to be a rapid and sensitive mcr-1 gene screening test for clinical samples, and mcr-1 could be transmitted vertically and horizontally between and within bacterial species in a plasmid-mediated manner.