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R Vanhoof

Publications and source records attributed to R Vanhoof.

At least 19 recordsLinked to original sources

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

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.

Aminoglycosides

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).

The polymerase chain reaction (PCR) was used to identify the aacA-aphD, aphA3 and aadC genes, encoding the aminoglycoside-modifying enzymes AAC(6')-APH(2"), APH(3')III and ANT(4'4"), 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')-APH(2") was the enzyme encountered most frequently. The prevalence of APH(3')III decreased significantly in the 1991-1992 period, while ANT(4',4") 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.

Acetylation

Identification of the aadB gene coding for the aminoglycoside-2"-O-nucleotidyltransferase, ANT(2"), by means of the polymerase chain reaction.

The polymerase chain reaction (PCR) was used to identify the gene encoding the aminoglycoside-2"-O-nucleotidyltransferase, ANT(2"). 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") 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.

Bacillus

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

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.

Aminoglycosides

A 56-month prospective surveillance study on the epidemiology of aminoglycoside resistance in a Belgian general hospital.

In this survey, we studied the effect of extensive amikacin usage on the epidemiology of aminoglycoside resistance in a general hospital. The baseline resistance in the 12 months before amikacin was 5.8% for amikacin, 15.2% for gentamicin, 16.4% for tobramycin and 14.0% for netilmicin. During the following 44 months, amikacin was the aminoglycoside of first choice. In the first 2 years of this phase, resistance to amikacin did not change significantly. Later, amikacin resistance rose significantly, mainly due to the introduction of amikacin-resistant Enterobacter aerogenes strains. In general there was a significant decrease in resistance to gentamicin and tobramycin. Resistance mechanisms were examined in 380 strains. AAC(3)V, and AAC(6')I alone or coupled with ANT(2") or AAC(3) were the most prevalent enzymes. In the amikacin phase, we noticed a significant increase of strains harbouring the AAC(6')I enzyme, while strains with the AAC(3)V were less frequently isolated. Strains with permeability resistance did not become more prevalent during the period of extensive amikacin use.

Amikacin

Characterization of Staphylococcus aureus and Salmonella spp. strains isolated from bovine meat in Zaïre.

A large majority (87.4%) of 190 Staphylococcus aureus isolates from fresh beef in Lubumbashi (Zaïre) belonged to the human St. aureus ecovar; 81.2% of the phage-typed human strains were partially or solely lysed by phages of group III. Thirteen of the 52 tested strains (25.0%) were enterotoxin producers; nine of these (69.2%) were positive for staphylococcal enterotoxin A. Sixteen serotypes were identified among the 122 Salmonella isolates and nearly all these strains were susceptible to the 8 different antibiotics tested.

Animals

Activity of cefotiam in combination with beta-lactam antibiotics on enterobacterial hospital strains.

By using checkerboard titrations the effect of cefotiam combined with different beta-lactam antibiotics on fifty strains of Enterobacteriaceae moderately susceptible (minimal inhibiting concentration greater than or equal to 8 mg/l) or resistant (minimal inhibiting concentration greater than or equal to 64 mg/l) to cefotiam was evaluated. The following compounds were tested: cefamandole, cefazolin, cefmenoxime, cefotaxime, cefotiam, ceftazidime, cefuroxime, mecillinam and piperacillin. The synergistic effect varied markedly. The combination cefotiam-mecillinam showed the highest rate of synergistic activity. Antagonism was found in 1% of the combinations.

Anti-Bacterial Agents

In vitro activities of new antimicrobial agents against multiresistant Staphylococcus aureus isolated from septicemic patients during a Belgian national survey from 1983 to 1985.

The antimicrobial agents most active against bacteremic isolates of oxacillin-resistant Staphylococcus aureus isolated from 1983 to 1985 were new fluoroquinolones, including PD 117,596 and PD 127,391 (MIC for 90% of isolates [MIC90] in agar, in micrograms per milliliter, 0.1) and temafloxacin, pefloxacin, and ofloxacin (MIC90, 0.4). Other active antimicrobial agents included fusidic acid (MIC90, 0.2) and fosfomycin (MIC90, 12.5). Vancomycin was active against all isolates. Mupirocin was very active (MIC90, 0.4).

Anti-Bacterial Agents

[Antibacterial activity of carumonam and cefpirome on hospital strains resistant to gentamicin and cephalothin: comparison with other beta-lactam antibiotics, new fluoroquinolones, aminoglycosides and other antibiotics].

The antibacterial in vitro activity of carumonam, a new monobactam, and cefpirome, a new cephalosporin, was studied on 483 hospital strains resistant to gentamicin and cephalothin, in comparison with amikacin, azlocillin, aztreonam, cefmenoxim, cefoperazone, cefotaxim, cefsulodin (for Pseudomonas), ceftazidime, ceftriaxone, cefuroxim, chloramphenicol, ciprofloxacin, doxycycline, enoxacin, netilmicin, norfloxacin, pefloxacin, piperacillin, rifampicin, tobramycin and trimethoprim. In general the two compounds have a very good in vito activity on Enterobacteriaceae but are less active on non-fermenting microorganisms. For the Enterobacteriaceae the minimal inhibitory concentrations 90% for carumonam was less than or equal to 1.1 mg/l excepted for Enterobacter spp. (43,6 mg/l) and M. morganii (56.8 mg/l) . All the Enterobacteriaceae are susceptible to cefpirome (minimal inhibitory concentrations 90% less than or equal to 5.3 mg/l). The activity of carumonam and cefpirome on Enterobacteriaceae is comparable with that of the third generation cephalosporins. Carumonam is more active than cefpirome and other beta-lactams, ceftazidime excepted, on Pseudomonas aeruginosa and Pseudomonas spp. On the other hand, both compounds reveal to have only a low activity on the other non-fermenters which minimal inhibitory concentrations 90% values of 115.4 mg/l for carumonam and 32.0 mg/l for cefpirome.

Aminoglycosides

Three-year survey of amikacin use and aminoglycoside resistance in a general hospital in Belgium.

The aim of the study was to evaluate the effect of intensive use of amikacin on the resistance levels to amikacin, gentamicin, tobramycin, netilmicin and dibekacin. The base-line resistance in the preamikacin phase (three months of amikacin use less than 1%; 676 isolates) was 1.0% for amikacin, 11.4% for gentamicin, 8.0% tobramycin, 6.2% for netilmicin and 8.3% for dibekacin. During the amikacin phase (36 months of average amikacin use of 89%; 6048 isolates) there was no significant change in aminoglycoside resistance except for dibekacin (from 8.3% to 10.9%, 0.05 greater than p greater than 0.02). Isolated amikacin resistance was not observed.

Amikacin

[In vitro bacteriostatic and bactericidal effect of ciprofloxacin and others quinolone derivatives on Campylobacter jejuni].

The in vitro bacteriostatic (MIC) and bactericidal (MBC) activities of ciprofloxacin and seven other quinolone derivatives on Campylobacter jejuni from human origin were determined. Ciprofloxacin, pefloxacin and rosoxacin exhibited the best bacteriostatic and bactericidal activities. For the three compounds the MIC90 was less than or equal to 0.33 microgram/ml while the MBC90 was resp. 0.36, 0.56 and 0.56 microgram/ml. The MBC values were always significantly higher than the MIC values (P less than 0.001). An attempt was made to select strains with an induced resistance against the quinolone derivatives.

Anti-Bacterial Agents

Antibacterial activity of enoxacin: comparison with aminoglycosides, beta-lactams and other antimicrobial agents.

The activity of enoxacin, a new quinolone carboxylic acid, was evaluated against 3014 clinical isolates of Enterobacteriaceae, Pseudomonas and other non-fermenters and Staphylococcus aureus. Comparison was made with gentamicin, tobramycin, amikacin, netilmicin, ampicillin, piperacillin, carbenicillin, ticarcillin, ticarcillin plus clavulanic acid, trimethoprim, cotrimoxazole and erythromycin. In general enoxacin was the most active compound and resistance was only rarely encountered.

Aminoglycosides

In vitro antimicrobial sensitivity of Neisseria gonorrhoeae from Rwanda.

The in vitro sensitivity of 104 isolates of Neisseria gonorrhoeae to six antimicrobial agents was tested. More than 50% of the isolates produced penicillinase. Of those that did not produce penicillinase, 26% were resistant (minimum inhibitory concentration (MIC)) greater than or equal to 0.5 mg/l), and 68% showed a decreased sensitivity for penicillin G (0.06 less than or equal to MIC less than or equal to 0.25 mg/l). Twenty six per cent and 50% of the strains, respectively, showed a decreased sensitivity to thiamphenicol (MIC greater than or equal to 1 mg/l) and tetracycline (MIC greater than or equal to 2 mg/l). All isolates were sensitive to spectinomycin, kanamycin, and norfloxacin. Of 20 penicillinase producing N gonorrhoeae (PPNG) isolates examined, seven contained the 3.4 megadalton R-plasmid, another seven contained both the 3.4 megadalton and 22.5 megadalton plasmids, five the 4.3 megadalton and 22.5 megadalton plasmids, and one isolate harboured both the 3.4 and 4.3 R-plasmids, together with the 22.5 megadalton plasmid. A disturbing increase in resistance to penicillin has been observed since the publication of earlier surveys, and the clinical implications of these findings are discussed.

Anti-Bacterial Agents