A large self-transmissible resistance plasmid from Nigeria contains genes that ameliorate a carrying cost

Abstract

Antimicrobial resistance is rapidly expanding, in a large part due to mobile genetic elements. We screened 94 fecal fluoroquinolone-resistant Escherichia coli isolates from Nigeria for six plasmid-mediated quinolone resistance (PMQR) genes. Sixteen isolates harbored at least one of the PMQR genes and four were positive for aac-6-Ib-cr. In one strain, aac-6-Ib-cr was mapped to a 125 Kb self-transmissible IncFII plasmid, pMB2, which also bears blaCTX-M-15, seven other functional resistance genes and multiple resistance pseudogenes. Laboratory strains carrying pMB2 grew faster than isogenic strains lacking the plasmid in both rich and minimal media. We excised a 32 Kb fragment containing transporter genes and several open-reading frames of unknown function. The resulting 93 Kb mini-plasmid conferred slower growth rates and lower fitness than wildtype pMB2. Trans-complementing the deletion with the cloned sitABCD genes confirmed that they accounted for the growth advantage conferred by pMB2 in iron-depleted media. pMB2 is a large plasmid with a flexible resistance region that contains loci that can account for evolutionary success in the absence of antimicrobials. Ancillary functions conferred by resistance plasmids can mediate their retention and transmissibility, worsening the trajectory for antimicrobial resistance and potentially circumventing efforts to contain resistance through restricted use.

A plasmid-encoded papB paralogue modulates autoaggregation of Escherichia coli transconjugants

“…pMB2 was originally extracted from a commensal Escherichia isolate from Nigeria [ 20 , 21 ]. In the course of functional analyses of fitness loci [ 6 ], we additionally observed that DH5α carrying the pRMKO miniplasmid autoaggregated significantly, particularly under low nutrient conditions. As shown in Fig.…”

“…Bacterial strains (Table 1 ) were cultured in in Luria broth containing chloramphenicol (30 μg/mL), ampicillin (100 μg/mL), tetracycline (25 μg/mL), or neomycin (50 μg/mL), where required for selection, and maintained at − 70 °C in Luria broth:glycerol 1:1. Plasmid pMB2, originally isolated from an Escherichia isolate in Nigeria [ 6 ], and its derivatives are described in Table 1 .…”

“…Plasmid pMB2, originally isolated from an Escherichia isolate in Nigeria [ 6 ], and its derivatives are described in Table 1 .…”

“…Standard molecular biology procedures were used [ 12 ]. pMB2, pRMKO and pRMC were extracted using the Qiagen® Large Construct Kit, as previously described [ 6 ]. All other plasmid extractions used the Qiagen® MiniPrep Kit.…”

“…We recently isolated and sequenced a large multi-drug resistance plasmid from a commensal Escherichia strain in Nigeria and mapped a 32 Kb segment that ameliorated the 125 Kb plasmid’s carrying cost [ 6 ]. Here we report that deletion of this portion of plasmid pMB2 produces the smaller pRMKO plasmid that is sufficient to enhance autoaggregation in laboratory E. coli strains in a manner that pMB2 does not.…”