Nomenclature of genes encoding aminoglycoside-modifying enzymes36680

NA</p

The role of lipopolysaccharide anionic binding sites in aminoglycoside uptake in Stenotrophomonas (Xanthomonas) maltophilia36660

Aminoglycoside resistance was investigated in six clinical isolates of Stenotrophomonas (Xanthomonas) maltophilia by studying the uptake kinetics and by using a radiochemical method to detect aminoglycoside modifying enzymes. Furthermore, the lipopolysaccharides (LPS) were extracted and characterized by SDS-PAGE and chemical analysis. Dansyl-polymyxin displacement experiments confirmed the availability of anionic binding sites. Growing cells of the isolates bound dansyl-polymyxin but were not lysed</p

Aminoglycoside resistance in Gram-negative blood isolates from various hospitals in Belgium and the Grand Duchy of Luxembourg. Aminoglycoside Resistance Study Group36690

A total of 1102 consecutive clinical blood isolates, including 897 Enterobacteriaceae and 205 non-fermenting bacilli, were obtained from 13 university and university-affiliated hospitals, which were divided into a Northern and a Southern group. Resistance to gentamicin, tobramycin, netilmicin, amikacin and isepamicin was determined using a microdilution technique according to NCCLS procedures. The overall mean resistance level was 5.9% for gentamicin, 7.7% for tobramycin, 7.5% for netilmicin, 2.8% for amikacin and 1.2% for isepamicin. Resistance to amikacin and isepamicin was significantly higher in the Northern hospitals than in the Southern hospitals. In total, 157 isolates were found not to be susceptible to aminoglycosides. By PCR, 179 aminoglycoside resistance mechanisms, i.e. 150 genes encoding modifying enzymes and 29 permeability mechanisms, were detected in 148 isolates. A resistance mechanism could not be detected in nine isolates. Moreover, in a further 14 isolates the resistance profile was not fully explained by the detected genes. The aac(6&#039;)-I genes were found to be the most predominant resistance mechanism in both the Northern and Southern isolates, followed by aac(3) genes and permeability resistance. A total of 29 non-susceptible isolates harboured a combination of genes, 72.4% of which were a combination with the aac(6&#039;)-lb gene. The majority of these combinations were broad-spectrum combinations which represented 9.0% of the resistance mechanisms in non-susceptible Enterobacteriaceae and 19.3% in the non-fermenting bacilli</p

The utility of the PCR method to study aacA gene heterogeneity in Serratia marcescens36656

NA</p

Comparative in vitro activity of cefepime and four extended-spectrum beta-lactams on 1,251 aminoglycoside-resistant gram-negative hospital strains36644

Cefepime was the most active compound on the Enterobacteriaceae with a MIC90 of 0.26 microgram/ml and a resistance rate of 0.1%. Ceftazidime was the most active drug on the non-fermenting bacilli (MIC90 9.65 micrograms/ml; resistance rate 3%). Amikacin- and gentamicin-resistant strains showed a decreased susceptibility to the beta-lactams, though the Enterobacteriaceae and the non-fermenters remained fairly sensitive to cefepime and ceftazidime, respectively. Aminoglycoside-3-N-acetyltransferase was the most prevalent enzyme and was often associated with intermediate resistance or resistance to beta-lactams. Non-fermenters showing aminoglycoside impermeability were very often intermediately resistant or resistant to beta-lactams</p

Changes in major populations of methicillin-resistant Staphylococcus aureus in Belgium36669

A total of 102 epidemic methicillin-resistant Staphylococcus aureus (MRSA) isolates collected in 13 Belgian hospitals during two periods (1981-1985 and 1991-1992) were tested for phage-type, for the presence of aminoglycoside-modifying enzymes (AME), and examined by arbitrarily primed polymerase chain reaction (AP-PCR). All isolates, but five, belonged to a few distinct phage-types of group III. Most isolates expressed a combination of AAC(6&#039;)-APH(2&quot;) with APH(3&#039;)III, and ANT(4&#039;,4&quot;) or both. Both phage-typing and AME suggested a change in the MRSA population between the two periods but the AP-PCR method revealed only slight differences</p

Identification of the aadB gene coding for the aminoglycoside-2&quot;-O-nucleotidyltransferase, ANT(2&quot;), by means of the polymerase chain reaction36645

The polymerase chain reaction (PCR) was used to identify the gene encoding the aminoglycoside-2&quot;-O-nucleotidyltransferase, ANT(2&quot;). Two primers, delineating a DNA fragment of 188 bp, and a specific probe within this fragment were constructed, based on the nucleotide sequence of the aadB gene encoding this enzyme. Reference strains producing different aminoglycoside-modifying enzymes were used to evaluate the specificity and the sensitivity of the test. Strains producing the ANT(2&quot;) enzyme showed the expected 188 bp DNA fragment after amplification. The oligonucleotide primers did not interact with genes encoding other aminoglycoside-modifying enzymes. Evaluation of a one-step single colony technique demonstrated that it was an acceptable alternative to the classic PCR test. The PCR method was used successfully to detect the presence of the aadB gene in 17 gentamicin-resistant clinical isolates</p

Detection by polymerase chain reaction of genes encoding aminoglycoside-modifying enzymes in methicillin-resistant Staphylococcus aureus isolates of epidemic phage types. Belgian Study Group of Hospital Infections (GDEPIH/GOSPIZ)36655

The polymerase chain reaction (PCR) was used to identify the aacA-aphD, aphA3 and aadC genes, encoding the aminoglycoside-modifying enzymes AAC(6&#039;)-APH(2&quot;), APH(3&#039;)III and ANT(4&#039;4&quot;), respectively, and the methicillin resistance determinant mecA, in epidemic aminoglycoside and methicillin-resistant isolates of Staphylococcus aureus. In total, 37 isolates collected in the period 1980-1985 and 81 isolates from the period 1991-1992 were obtained from 10 different Belgian hospitals. Epidemic isolates from the earlier period were characterised by phage type C (6/47/54/75) of phage group III, whereas two other epidemic phage types of group III-types A (77) and B (47/54/75/77/84/85)--were commonest in isolates from the second period. The bifunctional AAC(6&#039;)-APH(2&quot;) was the enzyme encountered most frequently. The prevalence of APH(3&#039;)III decreased significantly in the 1991-1992 period, while ANT(4&#039;,4&quot;) was found solely in isolates from this period. Resistance mechanisms were more complex in isolates from the 1991-1992 period and the mecA gene was detected in all isolates. The PCR results corresponded well with those obtained in the radiochemical phosphocellulose paper binding assay. Isolates from the 1991-1992 period were shown to express significantly higher levels of acetyltransferase activity than isolates from the 1980s</p

Characterization of the 6'-N-aminoglycoside acetyltransferase gene aac(6')-Im [corrected] associated with a sulI-type integron.

The amikacin resistance gene aac(6')-Im [corrected] from Citrobacter freundii Cf155 encoding an aminoglycoside 6'-N-acetyltransferase was characterized. The gene was identified as a coding sequence of 521 bp located down-stream from the 5' conserved segment of an integron. The sequence of this aac(6')-Im [corrected] gene corresponded to a protein of 173 amino acids which possessed 64.2% identity in a 165-amino-acid overlap with the aac(6')-Ia gene product (F.C. Tenover, D. Filpula, K.L. Phillips, and J. J. Plorde, J. Bacteriol. 170:471-473, 1988). By using PCR, the aac(6')-Im [corrected] gene could be detected in 8 of 86 gram-negative clinical isolates from two Belgian hospitals, including isolates of Citrobacter, Klebsiella spp., and Escherichia coli. PCR mapping of the aac(6')-Im [corrected] gene environment in these isolates indicated that the gene was located within a sulI-type integron; the insert region is 1,700 bases long and includes two genes cassettes, the second being ant (3")-Ib