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Cryptic silver resistance is prevalent and readily activated in certain Gram-negative pathogens
To assess the prevalence of cryptic silver (Ag+) resistance amongst clinical isolates of Gram-negative bacteria, and to examine how overt Ag+ resistance becomes activated in such strains. Established methods were used to determine the susceptibility of 444 recent clinical isolates to Ag+, and to eva...
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Published in: | Journal of antimicrobial chemotherapy 2017-11, Vol.72 (11), p.3043-3046 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | To assess the prevalence of cryptic silver (Ag+) resistance amongst clinical isolates of Gram-negative bacteria, and to examine how overt Ag+ resistance becomes activated in such strains.
Established methods were used to determine the susceptibility of 444 recent clinical isolates to Ag+, and to evaluate the potential for overt Ag+ resistance to emerge in susceptible isolates by spontaneous mutation. The genetic basis for Ag+ resistance was investigated using PCR amplification and DNA sequencing.
None of the isolates tested displayed overt Ag+ resistance. However, upon silver challenge, high-level Ag+ resistance (silver nitrate MIC >128 mg/L) was selected at high frequency (10-7 to 10-8) in 76% of isolates of Enterobacter spp., ∼58% of isolates of Klebsiella spp. and ∼0.7% of isolates of Escherichia coli. All strains in which Ag+ resistance could be selected harboured the sil operon, with resistance apparently resulting from activation of this system as a consequence of single missense mutations in silS. By contrast, Ag+ resistance was not selected in isolates lacking sil, which included all tested representatives of Pseudomonas aeruginosa, Acinetobacter spp., Citrobacter spp. and Proteus spp.
Whilst overt Ag+ resistance in Gram-negative pathogens is uncommon, cryptic Ag+ resistance pertaining to the sil operon is prevalent and readily activated in particular genera (Enterobacter and Klebsiella). |
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ISSN: | 0305-7453 1460-2091 |
DOI: | 10.1093/jac/dkx258 |