Mobility of β-lactam resistance under ampicillin treatment in gut microbiota suffering from pre-disturbance

Abstract

Ingestion of food- or waterborne antibiotic-resistant bacteria may lead to dissemination of antibiotic resistance genes (ARGs) in the gut microbiota. The gut microbiota often suffers from various disturbances. It is not clear whether and how disturbed microbiota may affect ARG mobility under antibiotic treatments. For proof of concept, in the presence or absence of streptomycin pre-treatment, mice were inoculated orally with a β-lactam-susceptible Salmonella enterica serovar Heidelberg clinical isolate (recipient) and a β-lactam resistant Escherichia coli O80:H26 isolate (donor) carrying a blaCMY-2 gene on an IncI2 plasmid. Immediately following inoculation, mice were treated with or without ampicillin in drinking water for 7 days. Faeces were sampled, donor, recipient and transconjugant were enumerated, blaCMY-2 abundance was determined by quantitative PCR, faecal microbial community composition was determined by 16S rRNA amplicon sequencing and cecal samples were observed histologically for evidence of inflammation. In faeces of mice that received streptomycin pre-treatment, the donor abundance remained high, and the abundance of S. Heidelberg transconjugant and the relative abundance of Enterobacteriaceae increased significantly during the ampicillin treatment. Co-blooming of the donor, transconjugant and commensal Enterobacteriaceae in the inflamed intestine promoted significantly (P<0.05) higher and possibly wider dissemination of the blaCMY-2 gene in the gut microbiota of mice that received the combination of streptomycin pre-treatment and ampicillin treatment (Str–Amp) compared to the other mice. Following cessation of the ampicillin treatment, faecal shedding of S. Heidelberg transconjugant persisted much longer from mice in the Str–Amp group compared to the other mice. In addition, only mice in the Str–Amp group shed a commensal E. coli O2:H6 transconjugant, which carries three copies of the blaCMY-2 gene, one on the IncI2 plasmid and two on the chromosome. The findings highlight the significance of pre-existing gut microbiota for ARG dissemination and persistence during and following antibiotic treatments of infectious diseases.

Gut Microbiome Perturbation Affected Conjugative Transfer of Antimicrobial Resistance Genes

“…As such, immediately following antibiotic treatment, the gut microbiome may provide a great ecological opportunity for ARB to colonize and disseminate their ARGs, even in the absence of antibiotics [32,33]. Previous studies have demonstrated the conjugative transfer of antibiotic resistance plasmids following heavy-dose streptomycin treatments for clearing the mouse gut [19,20]. Depending on the chemical composition, formulation and administration route, antibiotics may cause different magnitudes of perturbation to the gut microbiome [34].…”

“…Moreover, through indirect pre-exposure, heavy antibiotic dosages (e.g. one oral dose of streptomycin at 1 g kg -1 ) can disrupt the gut microbiota, promoting the colonization and expansion of ARB and fostering conjugation [19,20]. However, it remains unclear whether ARB are able to colonize and disseminate their ARGs within the gut microbiome that have been pre-exposed to clinical or veterinary uses of antibiotics.…”

Factors and Mechanisms Influencing Conjugation In Vivo in the Gastrointestinal Tract Environment: A Review

“…Under the treatment of antibiotics, the donor bacteria (cells carrying drug-resistant plasmids) and Enterobacteriaceae (the main recipient cell) in the gastrointestinal tract grow in large numbers, thereby promoting plasmid conjugation. For example, the CF of plasmids carrying the bla CMY-2 gene was significantly increased after the intestinal microbiota was exposed to ampicillin, and the gene maintained a relatively high abundance in the intestine for a long time ( Table 1 ) [ 39 ]. Therefore, the selective action of antibiotics against bacteria carrying resistant plasmids and Enterobacteriales is a key factor affecting the density of donor and recipient bacteria and the transmission efficiency of ARGs in the gastrointestinal tract.…”

Dynamic Effect of β-Lactam Antibiotic Inactivation Due to the Inter- and Intraspecies Interaction of Drug-Resistant Microbes

“…The β-lactam class of antibiotics encompasses a broad spectrum of antimicrobials, including ampicillin, penicillin, and cephalosporins, comprising 65% of the world market for antibiotics . To date, β-lactamases have been considered as one of the major mechanisms of resistance in the fight against β-lactam class of antibiotics by acting on the bacterial cell wall synthesis. , This mechanism of resistance is even more common in microorganisms that reside in the human gut and play a protective role in minimizing the damage caused by antibiotics. − Conceptualized approaches to β-lactamase administration were shown to impart changes to the gut resistome through antibiotic inactivation. , These studies emphasized the potential of the inactivation of β-lactam antibiotics to protect the gut microbiome in the gastrointestinal tract (GI) tract. However, the role of β-lactamases on various organisms is not fully understood due to the lack of model systems that can facilitate the evaluation of specific organisms’ interaction in a dynamic manner.…”