Prevalence of the aminoglycoside phosphotransferase genes aph(3′)-IIIa and aph(3′)-IIa in Escherichia coli, Enterococcus faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica and Staphylococcus aureus isolates in Austria

Markus Woegerbauer, Josef Zeinzinger, Burkhard Springer, Peter Hufnagl, Alexander Indra, Irina Korschineck, Johannes Hofrichter, Ian Kopacka, Reinhard Fuchs, Johann Steinwider, Klemens Fuchs, Kaare M. Nielsen, Franz Allerberger

¹Division for Data, Statistics and Risk Assessment, Austrian Agency for Health and Food Safety (AGES – Österreichische Agentur für Gesundheit und Ernährungssicherheit), Vienna, Austria

²Division for Public Health, Institute for Medical Microbiology and Hygiene, Austrian Agency for Health and Food Safety (AGES – Österreichische Agentur für Gesundheit und Ernährungssicherheit), Vienna, Austria

³Ingenetix, Vienna, Austria

⁴Department of Pharmacy, University of Tromsø, Norway

Correspondence
Markus Woegerbauer markus.woegerbauer{at}ages.at

Journal of Medical Microbiology 2014; 63(Pt 2):210–217 · https://doi.org/10.1099/jmm.0.065789-0

Abstract

The aminoglycoside phosphotransferase aph(3′)-IIa primarily inactivates kanamycin and neomycin, whilst aph(3′)-IIIa also inactivates amikacin. The aim of this study was to determine the frequency of both resistance genes in major human pathogens to obtain their baseline prevalence in the gene pool of these bacterial populations in Austria. In total, 10 541 Escherichia coli, Enterococcus faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica and Staphylococcus aureus isolates were collected representatively without selection bias between 2008 and 2011. Isolates were analysed by aph(3′)-IIIa/nptIII- and aph(3′)-IIa/nptII-specific TaqMan real-time PCR. For positive strains, MICs using Etests were performed and resistance gene sequences were determined. The overall prevalence of aph(3′)-IIIa/nptIII was 1.62 % (95 % confidence interval: 1.38–1.88 %). In Escherichia coli, enterococci, Staphylococcus aureus, P. aeruginosa and Salmonella spp., the aph(3′)-IIIa/nptIII prevalence was 0.47 % (0–1.47 %), 37.53 % (32.84–42.40 %), 2.90 % (1.51–5.02 %), 0 % (0–0.32 %) and 0 % (0–0.037 %), respectively. Eleven of a total of 169 carriers showed single-nucleotide polymorphisms in the resistance allele. The overall prevalence of aph(3′)-IIa/nptII was 0.0096 % (0–0.046 %). Escherichia coli (0–0.70 %), enterococci (0–0.75 %), Staphylococcus aureus (0–0.73 %) and P. aeruginosa (0–0.32 %) did not carry aph(3′)-IIa. A single Salmonella isolate was positive, resulting in an aph(3′)-IIa prevalence of 0.013 % (0–0.058 %). aph(3′)-IIIa/nptIII carriers were moderately prevalent in the strains tested except for in enterococci, which appeared to be an important reservoir for aph(3′)-IIIa. aph(3′)-IIa/nptII genes were detected at clinically irrelevant frequencies and played no significant role in the aminoglycoside resistance gene pool during the observation period.