A large self-transmissible plasmid from Nigeria confers resistance to multiple antibacterials without 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 bla CTX-M-15 , seven other functional resistance genes and multiple resistance pseudogenes. We hypothesized that pMB2 had been selected by antimicrobials and that its large size would confer a growth disadvantage.However, laboratory strains carrying pMB2 grew at least as fast as isogenic strains lacking the plasmid in both rich and minimal media. We excised a 32 Kb fragment containing the sitABCD and another putative transporter, pefB, a papB homolog, 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. The mini-plasmid additionally conferred autoaggregation and was less transmissible and both phenotypes could be complemented with a pefB clone. pMB2 is a large plasmid with a flexible resistance region that contains multiple 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

“…The papB/pefB paralogue we describe is highly conserved among them and therefore the autoaggregation it represses is likely common, warranting further study. Our ndings add to experimentally validated reports of two other non-resistance loci of pMB2 that promote E. coli survival and adaptability [6,28]. Thus there are multiple genes resistance plasmids hat compensate the costs of…”

“…Strains and plasmids: Bacterial strains (Table 1) were cultured in in Luria broth containing chloramphenicol (30 mg/mL), ampicillin (100 mg/mL), tetracycline (25 mg/mL), or neomycin (50 mg/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. General microbiology and molecular biology procedures: Standard molecular biology procedures were used [12].…”

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

“…The papB/pefB paralogue we describe is highly conserved among them and therefore the autoaggregation it represses is likely common. Our ndings add to experimentally validated reports of two other non-resistance loci of pMB2 that promote E. coli survival and adaptability [6,28]. Thus there are multiple genes resistance plasmids hat compensate the costs of their carriage or, as in this case, potentially propagate transmission.…”

“…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.…”

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

“…Strains and plasmids: Bacterial strains (Table 1) were cultured in in Luria broth containing chloramphenicol (30 mg/mL), ampicillin (100 mg/mL), tetracycline (25 mg/mL), or neomycin (50 mg/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.…”