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Biomedical subjects

B Wiedemann

Publications and source records attributed to B Wiedemann.

At least 55 records · Page 3Linked to original sources
PubMed2000

Natural antibiotic susceptibility of Salmonella enterica strains.

The susceptibility of 100 Salmonella enterica strains belonging to S. enterica subsp. enterica (n=90) and S. enterica subsp. arizonae (n=10) was examined to 71 antibiotics. Within S. enterica subsp. enterica, strains of different serovars (typhimurium (n=17), enteritidis (n=17), dublin (n=10), typhi (n=16), paratyphi A (n=6), others (n=24)) were studied. MICs were determined using a microdilution procedure and apart from fosfomycin there were no significant differences in susceptibility between the subspecies and serovars of S. enterica. All salmonellae were sensitive or intermediately resistant to tetracyclines, aminoglycosides, most beta-lactam antibiotics, quinolones, co-trimoxazole group antibiotics, chloramphenicol, nitrofurantoin and azithromycin. S. enterica strains were intrinsically resistant to benzylpenicillin, oxacillin, most macrolides, rifampicin, lincosamides, streptogramins, glycopeptides and fusidic acid. Apart from some slight differences in antibiotic susceptibility between strains of S. enterica subsp. enterica and S. enterica subsp. arizonae, only the susceptibility to fosfomycin varied among the taxa studied. Whereas 'enteric' salmonellae including S. enterica subsp. arizonae were sensitive to fosfomycin, 'typhoid' salmonellae were intrinsically resistant. A database of the antibiotic susceptibility of S. enterica was set up. It may be of use to validate antibiotic susceptibility test results of these bacteria.

Anti-Bacterial Agents↗
PubMed2000

Natural antibiotic susceptibility of Listeria species: L. grayi, L. innocua, L. ivanovii, L. monocytogenes, L. seeligeri and L. welshimeri strains.

OBJECTIVE: To investigate the natural susceptibility to 71 antimicrobial agents of 103 Listeria strains belonging to all known Listeria species (L. monocytogenes (N = 21), L. innocua (N = 21), L. seeligeri (N = 21), L. ivanovii (N = 19), L. welshimeri (N = 11), and L. grayi (N = 10)). METHODS: MICs were determined using a microdilution procedure in H-Medium. RESULTS: All listeriae were naturally sensitive or intermediate to tetracyclines, aminoglycosides, penicillins (except oxacillin), loracarbef, cefazoline, cefaclor, cefotiam, cefoperazone, carbapenems, macrolides, lincosamides, glycopeptides, dalfopristin/quinupristin, chloramphenicol and rifampicin (probably except L. grayi). Listeria spp. were naturally resistant or intermediate to most 'modern' cephalosporins (cefetamet, cefixime, ceftibuten, ceftazidime, cefdinir, cefpodoxime, cefotaxime, ceftriaxone, cefuroxime), aztreonam, pipemidic acid, dalfopristin quinupristin and sulfamethoxazole. Significant differences in natural susceptibility among the species were seen with the quinolones, trimethoprim, co-trimoxazole, rifampicin, fosfomycin and fusidic acid. It seems likely that L. grayi is naturally resistant to all antifolates; the species was least susceptible to rifampicin and most susceptible to quinolones, whereas L. ivanovii was naturally resistant to most quinolones. L. ivanovii was naturally sensitive to fosfomycin, whereas L. innocua and L. monocytogenes were naturally resistant. L. ivanovii was also the most susceptible species to fusidic acid. CONCLUSIONS: The present study describes a database on the natural susceptibility of Listeria spp. to a wide range of antibiotics, which can be used to validate susceptibility testing results of these microorganisms.

Anti-Bacterial Agents↗
PubMed2000

Role of penicillin-binding proteins in the initiation of the AmpC beta-lactamase expression in Enterobacter cloacae.

Penicillin-binding proteins (PBPs) are involved in the regulation of beta-lactamase expression by determining the level of anhydromuramylpeptides in the periplasmatic space. It was hypothesized that one or more PBPs act as a sensor in the beta-lactamase induction pathway. We have performed induction studies with Escherichia coli mutants lacking one to four PBPs with DD-carboxypeptidase activity. Therefore, we conclude that a strong beta-lactamase inducer must inhibit all DD-carboxypeptidases as well as the essential PBPs 1a, 1b, and/or 2.

Bacterial Proteins↗
PubMed2000

Pronounced postantibiotic effect of quinupristin-dalfopristin in static cultures of Staphylococcus aureus: an effect not seen with other antibiotics.

Quinupristin-dalfopristin produced postantibiotic effects (PAEs) on exponentially growing (log phase) and nongrowing (lag phase) cultures of 0.4 to 6.9 h. PAEs of the other antibiotics tested were 0.5 to 1.9 h, determined with exponentially growing cultures. None of these antibiotics show a PAE on lag-phase bacteria.

Anti-Bacterial Agents↗
PubMed2000

Natural antibiotic susceptibility of Rahnella aquatilis and R. aquatilis-related strains.

A database is described of the natural susceptibilities of 70 Rahnella strains to 71 antibiotics. MIC values were determined by a microdilution procedure and evaluated by a table calculation program. Rahnella aquatilis and R. aquatilis-related strains were naturally resistant to amoxycillin, ticarcillin, fosfomycin and to antibiotics to which other species of Enterobacteriaceae are also intrinsically resistant, i.e. macrolides (except azithromycin), benzylpenicillin, oxacillin, rifampicin, fusidic acid, lincosamides and glycopeptides. Rahnella strains were also naturally resistant or intermediate to cefazolin, cefuroxime and loracarbef. All rahnellae were naturally sensitive or intermediate to doxycycline, minocycline, aminoglycosides, some penicillins and cephalosporins, carbapenems, aztreonam, quinolones, sulfamethoxazole, trimethoprim, cotrimoxazole, chloramphenicol and nitrofurantoin. Bimodal or broad MIC distributions were seen for several antibiotics, e.g. quinolones and cephalosporins. With the exception of quinolones no differences in natural antibiotic susceptibility were seen between reference strains of Rahnella genomovar 1 (n=6) and 2 (n=7). Reference strains of genomovar 1 were pyrase-positive and more susceptible to quinolones than reference strains of genomovar 2, which were pyrase-negative. By discrimination of all rahnellae in the pyrase-positive and pyrase-negative strains the MIC distributions for quinolones became smaller and unimodal. Under the conditions described pyrase might be a parameter to differentiate strains of Rahnella genomovars 1 and 2.

Amoxicillin↗
PubMed2000

Chemical characterization and biological activity of Macfadyena unguis-cati (Bignoniaceae).

Macfadyena unguis-cati (L.) has been widely used in folk medicine as an anti-inflammatory, antimalarial and antivenereal. The purpose of this study was to chemically characterize the main plant components, and to evaluate the biological properties of some of the fractions derived from leaves (MACb) and liana (MACa) of this plant. Chemical characterization allowed the identification of the compounds corymboside, vicenin-2, quercitrin, chlorogenic acid, isochlorogenic acid, lupeol, beta-sitosterol, beta-sitosterylglucoside, allantoin and lapachol. The biological screening of fractions and/or purified substances derived from fractions revealed antitumoral and antitrypanosomal activities in fractions MACa/lapachol and MACb/MACb21, respectively. The anti-lipoxygenase and anti-cyclooxygenase effect seen in fractions MACa and MACb showed a partial correlation with the anti-inflammatory property attributed to this plant.

Animals↗
PubMed1999

Natural antibiotic susceptibility of Escherichia coli, Shigella, E. vulneris, and E. hermannii strains.

The natural antibiotic susceptibility of 139 Escherichia coli strains (including 18 enterohemorrhagic E. coli), 73 Shigella strains (S. sonnei (n = 37), S. flexneri (n = 29), S. boydii (n = 6), S. dysenteriae (n = 1)), 23 E. vulneris, and 20 E. hermannii strains toward 71 antibiotics was examined. MICs were determined using a microdilution procedure. All examined taxa were naturally sensitive/intermediate toward tetracyclines, aminoglycosides, some penicillins (amoxycillin/clavulanate, ampicillin/sulbactam, piperacillin [with and without tazobactam], mezlocillin, azlocillin), cephalosporins, carbapenems, monobactams, quinolones, trimethoprim, cotrimoxazole, and chloramphenicol and were naturally resistant/intermediate toward benzylpenicillin, oxacillin, macrolides, lincosamides, glycopeptides, rifampicin, and fusidic acid. No differences in natural antibiotic susceptibility were seen between enterohemorrhagic and other E. coli strains. Likewise, with one exception, no significant differences in natural antibiotic susceptibility were seen either among the Shigella subgroups or between Shigella and E. coli. The natural population of S. flexneri was slightly more susceptible to chloramphenicol than the natural populations of other taxa within the Shigella-E. coli complex. E. vulneris and E. hermannii showed susceptibility patterns to many antibiotics similar to Shigella and E. coli, but there were other antibiotics toward which there were significant differences in natural susceptibility. E. vulneris and E. hermannii were less susceptible to nitrofurantoin and slightly more susceptible to several aminoglycosides than E. coli and Shigella. E. hermannii was the only species that was naturally resistant/intermediate to ticarcillin and amoxycillin (DIN standard). The addition of clavulanic acid to the latter resulted in a decrease of seven twofold dilution steps (E. vulneris: four twofold dilution steps, E. coli/Shigella: two twofold dilution steps) of the MICs of the natural population. With the exception of cefoperazone and cefepime, E. hermannii was more susceptible to cephalosporins than strains of the other species. E. vulneris was the species most susceptible to ticarcillin and the only species that was highly resistant to fosfomycin (MIC > 256 micrograms/mL). The antibiotic susceptibility to fosfomycin was also unique for E. hermannii (MIC 32-128 micrograms/mL), whereas the natural populations of E. coli and Shigella showed lower MIC values. The data of this study represent an assessment of the natural susceptibility of strains of Escherichia spp. and Shigella subgroups to a wide range of antibiotics. These databases can be used for the validation of antibiotic susceptibility test results of Escherichia spp. and shigellae. The conformity of the natural antibiotic susceptibility test results not only among the Shigella subgroups but also between Shigella and E. coli support the status of Shigella as a subgroup of the species E. coli.

Anti-Bacterial Agents↗