Horizontal transfer of antibiotic resistance genes on abiotic touch surfaces: implications for public health

Abstract

Horizontal gene transfer (HGT) is largely responsible for increasing incidence of antibiotic-resistant infections worldwide. Whilst studies have focussed on HGT in vivo, this work investigates whether the ability of pathogens to persist in the environment, particularly on touch surfaces, may also play an important role. Escherichia coli, virulent clone ST131, and Klebsiella pneumoniae encoding extended-spectrum ?-lactamase (ESBL) bla CTX-M-15 and metallo-?-lactamase bla NDM-1, respectively, exhibited prolonged survival on stainless steel with approximately 104 viable cells remaining from an inoculum of 107cfu per cm2 after one month at 21oC. HGT of bla to an antibiotic-sensitive but azide-resistant recipient E. coli occurred on stainless steel dry touch surfaces and in suspension, but not on dry copper. Conjugation frequency was approximately 10-50 times greater, occurred immediately and resulting transconjugants were more stable with ESBL E. coli as donor cell compared to K. pneumoniae but bla NDM-1 transfer increased with time. Transconjugants also exhibited the same resistance profile as donor suggesting multiple gene transfer. Rapid death, inhibition of respiration and destruction of genomic and plasmid DNA of both pathogens occurred on copper alloys accompanied by a reduction in bla copy number. Naked E. coli DNA degraded on copper at 21oC and 37oC but slowly at 4oC suggesting a direct role for the metal. Persistence of viable pathogenic bacteria on touch surfaces may not only increase risk of infection transmission but also contribute to spread of antibiotic resistance by HGT. The use of copper alloys as antimicrobial touch surfaces may help reduce infection and HGT.

More information

Identifiers

ORCID for C.W. Keevil: orcid.org/0000-0003-1917-7706

Catalogue record

Export record

Altmetrics