Search PubMed⌕ Search

Biomedical subjects

I Stock

Publications and source records attributed to I Stock.

At least 19 recordsLinked to original sources
PubMed2005

Natural antimicrobial susceptibility patterns of Kluyvera ascorbata and Kluyvera cryocrescens strains and review of the clinical efficacy of antimicrobial agents used for the treatment of Kluyvera infections.

The natural susceptibility of 58 K. ascorbata and 24 K. cryocrescens strains to 71 antimicrobial agents was investigated. MIC values were determined with a microdilution procedure in cation-adjusted Mueller Hinton broth (for all strains) and IsoSensitest broth (for some strains). Both species were naturally sensitive or of intermediate susceptibility to tetracyclines, aminoglycosides, quinolones, antifolates, chloramphenicol, nitrofurantoin, fosfomycin, aminopenicillins plus beta-lactamase inhibitors, acylureidopenicillins, carbapenems, aztreonam and some cephalosporins. Uniform natural resistance was found with several macrolides, lincosamides, streptogramins, glycopeptides, rifampicin, fusidic acid, linezolid, penicillin G, oxacillin, and amoxicillin. To the latter agent, some strains of both species were also of intermediate susceptibility. Species-related differences in natural susceptibility affecting clinical assessment criteria were seen with azithromycin, cethromycin, telithromycin, ticarcillin and some cephalosporins, to which K. ascorbata was less susceptible than K. cryocrescens. Medium-related differences in susceptibility were restricted to a few antibiotics. A data base about the natural susceptibility of the two most common Kluyvera spp. to a wide range of antimicrobial agents is presented. It can be used for the validation of forthcoming susceptibility trials of these microorganisms. Although some susceptibilty patterns might be helpful for the phenotypical separation of K. ascorbata from K. cryocrescens, they do not allow a separation of these species. The literature dealing with the clinical efficacy of antimicrobial agents used for the treatment of Kluyvera infections is discussed.

Anti-Bacterial Agents↗
PubMed2004

Natural antimicrobial susceptibility patterns and biochemical profiles of Leclercia adecarboxylata strains.

Leclercia adecarboxylata is an opportunistic human pathogen that phenotypically resembles Escherichia coli. The natural susceptibilities of 101 Leclercia strains to 70 antimicrobial agents were investigated. MICs were determined with a microdilution procedure in cation-adjusted Mueller-Hinton broth (all strains) and IsoSensitest broth (some strains). Natural susceptibility patterns were assessed using German (DIN) standards (when applicable). In addition, biochemical properties recommended for the phenotypic identification of L. adecarboxylata were evaluated, applying two commercially available identification systems for Enterobacteriaceae and seven conventional tests. L. adecarboxylata strains were naturally sensitive to tetracyclines, aminoglycosides, all but two beta-lactams, quinolones, folate pathway inhibitors, chloramphenicol, nitrofurantoin and azithromycin. They were naturally resistant to penicillin G, oxacillin, erythromycin, roxithromycin, clarithromycin, ketolides, lincosamides, streptogramins, linezolid, glycopeptides, rifampicin, fusidic acid and fosfomycin. There were only minor medium-dependent differences in susceptibility to most antibiotics. Lysine decarboxylase, malonate assimilation and acid production from arabitol and cellobiose, but not from adonitol and sorbitol, allowed definitive separation of L. adecarboxylata from E. coli. The results of this study form a database that can be applied to validate forthcoming antibiotic susceptibility tests of L. adecarboxylata, and might contribute to its reliable identification. Susceptibility patterns did not indicate obvious therapeutic difficulties for treatment of Leclercia infections. Special attention should be paid to biochemically aberrant leclerciae. Apart from biochemical features, fosfomycin susceptibility might be useful to differentiate between L. adecarboxylata and E. coli.

Anti-Bacterial Agents↗
PubMed2003

Natural antibiotic susceptibility of strains of Serratia marcescens and the S. liquefaciens complex: S. liquefaciens sensu stricto, S. proteamaculans and S. grimesii.

The natural susceptibility of 77 strains of Serratia marcescens and 41 strains of the S. liquefaciens complex (S. liquefaciens sensu stricto (n=21), S. grimesii (n=10), S. proteamaculans (n=10)) to 70 antibiotics was examined using a microdilution procedure in Isosensitest broth (all strains) and cation-adjusted Mueller Hinton broth (some strains). All species were naturally resistant to benzylpenicillin, oxacillin, cefaclor, cefazolin, cefuroxime, numerous macrolides, lincosamides, streptogramins, glycopeptides, rifampicin and fusidic acid. Uniform natural sensitivity was found to most aminoglycosides, several acylureidopenicillins, ticarcillin, newer cephalosporins, carbapenems, aztreonam, quinolones and antifolates. Species-related differences in susceptibility affecting clinical assessment criteria were found for several agents. S. marcescens was less susceptible to some aminoglycosides than species of the S. liquefaciens group. It was the only species that was uniformly naturally resistant to tetracycline, amoxycillin, amoxycillin/clavulanate and loracarbef. Species of the S. liquefaciens group were naturally resistant and intermediate or naturally intermediate to the latter agents. Differences in susceptibility among the species of the S. liquefaciens complex were generally small. S. proteamaculans was most susceptible to sulphamethoxazole. S. liquefaciens sensu stricto was less susceptible than S. grimesii and S. proteamaculans to tetracyclines, chloramphenicol and nitrofurantoin; it was the only species uniformly naturally resistant to fosfomycin. This study suggested that all species examined probably express chromosomally-encoded AmpC beta-lactamases, but the amount of enzyme may vary from species to species. The naturally-occurring low-level expression of the S. marcescens aminoglycoside 6'-acetyltransferase AAC(6')-Ic and its absence in other Serratia spp. was supported by the data. All species of the S. liquefaciens complex should be considered as probable agents of human diseases.

Anti-Bacterial Agents↗
PubMed2003

Natural antibiotic susceptibility of Proteus spp., with special reference to P. mirabilis and P. penneri strains.

The natural susceptibility of 102 Proteus mirabilis and 35 Proteus penneri strains to 71 antibiotics was examined. Minimum inhibitory concentrations (MICs) were determined by applying a microdilution procedure in IsoSensitest broth (for all strains) and cation-adjusted Mueller Hinton broth (for some strains). P. mirabilis and P. penneri were naturally resistant to penicillin G, oxacillin, all tested macrolides, lincosamides, streptogramins, glycopeptides, rifampicin and fusidic acid. Both species were uniformly, naturally sensitive to all tested aminoglycosides, acylureidopenicillins, some cephalosporins, carbapenems, aztreonam, quinolones, sulfamethoxazole and co-trimoxazole. Species-specific differences in natural susceptibility affecting clinical assessment criteria were seen with tetracyclines, several beta-lactams, chloramphenicol and nitrufurantoin. P. mirabilis was naturally resistant to all tested tetracyclines, and was naturally sensitive to all beta-lactams, except penicillin G and oxacillin. Strains of P. penneri were naturally sensitive or of intermediate susceptibility to tetracyclines, and naturally resistant to amoxicillin (but sensitive or of intermediate susceptibility to aminopenicillins in the presence of beta-lactamase inhibitors) and some cephalosporins (i.e. cefaclor, cefazoline, loracarbef, cefuroxime, cefotiam, and cefdinir). P. penneri was less susceptible than P. mirabilis to chloramphenicol; P. mirabilis was less susceptible than P. penneri to nitrofurantoin. Major medium-dependent influences on the MICs were seen with fosfomycin. The present study describes a database concerning the natural antibiotic susceptibility of P. mirabilis and P. penneri strains to a range of antibiotics, which can be applied to validate forthcoming antibiotic susceptibility tests of these bacteria. It was shown that ten of fifteen amoxicillin-sensitive P. mirabilis strains produced beta-lactamases at a low level, supporting the thesis of the presence of a naturally-occurring beta-lactamase in this species. Natural susceptibility patterns are compared with those of a recent study, dealing with natural susceptibilities of species of the P. vulgaris complex.

Anti-Bacterial Agents↗
PubMed2003

Natural antibiotic susceptibility of Ewingella americana strains.

The natural susceptibility of 20 Ewingella americana strains to 72 antibiotics was examined. MIC values were determined using a microdilution procedure in cation-adjusted Mueller-Hinton broth. Evaluation of natural antibiotic susceptibility was performed applying the German standard (where applicable). Beta-lactamases were examined with a conventional nitrocefin colony testing procedure, activity and induction assays, and SDS-PAGE. Ewingella strains were naturally resistant or of intermediate susceptibility to cefaclor, loracarbef, cefazoline, cefuroxime, cefoxitin, benzylpenicillin, oxacillin, fosfomycin, erythromycin, roxithromycin, clarithromycin, lincosamides, dalfopristin-quinupristin, ketolides, linezolid, glycopeptides, fusidic acid and rifampicin. Uniform natural sensitivity was found with acylureidopenicillins except for azlocillin, ticarcillin, several cephalosporins, carbapenems, aztreonam, tetracyclines, aminoglycosides, quinolones, azithromycin, folate-pathway inhibitors and chloramphenicol. Strains of E. americana were naturally sensitive or of intermediate susceptibility to aminopenicillins (with and without beta-lactamase inhibitors), azlocillin and nitrofurantoin. All ewingellae yielded beta-lactamases; testing of representative strains revealed that these enzymes belong to Ambler class C. Inducibility of beta-lactamase was shown for E. americana ATCC 33852T, CCUG 35675 and CCUG 42782. The present study describes a database concerning the natural susceptibility of E. americana strains to a range of antibiotics, which can be applied to validate forthcoming antibiotic susceptibility tests of these bacteria. It enlarges the number of Enterobacteriaceae expressing naturally-occurring AmpC beta-lactamases.

Databases, Factual↗
PubMed2002

Natural antibiotic susceptibility of Enterobacter amnigenus, Enterobacter cancerogenus, Enterobacter gergoviae and Enterobacter sakazakii strains.

OBJECTIVE: To investigate the natural susceptibility to 69 antimicrobial agents of 107 Enterobacter strains comprising E. amnigenus (n = 18), E. cancerogenus (n = 26), E. gergoviae (n = 28) and E. sakazakii (n = 35). METHODS: Minimal inhibitory concentrations (MICs) were determined with a microdilution procedure in Isosensitest broth and cation-adjusted Mueller-Hinton broth. RESULTS: All the species were naturally sensitive or intermediate to tetracyclines, amino-glycosides, numerous beta-lactams (acylureidopenicillins, ticarcillin, ampicillin/sulbactam, several cephalosporins, carbapenems, aztreonam), quinolones, antifolates, chloramphenicol and nitrofurantoin. Natural resistance was found to penicillin G, oxacillin, several macrolides, lincosamides, streptogramins, glycopeptides, rifampicin and fusidic acid. Species-related differences in natural susceptibility were found to some beta-lactams, azithromycin and fosfomycin. Whereas E. gergoviae was the most susceptible species to azithromycin, E. cancerogenus was most susceptible to fosfomycin and was the only species showing natural resistance to amoxicillin, amoxicillin/clavulanic acid, cefaclor, cefazoline, loracarbef and cefoxitin. There were only minor medium-dependent differences in susceptibility to most antibiotics. CONCLUSIONS: The present study establishes a database concerning the natural susceptibility of recently established Enterobacter species to a wide range of antibiotics, which can be applied for the validation of routine susceptibility test results. beta-Lactam susceptibility patterns indicate the expression of species-specific beta-lactamases expressed at high or low levels in all the species except E. sakazakii.

Anti-Bacterial Agents↗
PubMed2002

Natural antibiotic susceptibility of Enterobacter spp., with special reference to Enterobacter aerogenes and Enterobacter intermedius strains.

The natural susceptibility to 71 antibiotics of 44 strains of Enterobacter aerogenes and 12 strains of Enterobacter intermedius was examined using a microdilution procedure in Isosensitest broth (for all strains) and cation-adjusted Mueller Hinton broth (for some strains). Both species were naturally sensitive or sensitive and intermediate to tetracyclines, all tested aminoglycosides, several penicillins and cephalosporins, carbapenems, aztreonam, quinolones, folate-pathway inhibitors, chloramphenicol and nitrofurantoin. Uniform natural resistance was found to cefoxitin and to antibiotics to which most other Enterobacteriaceae are also intrinsically resistant, e.g. several macrolides, lincosamides, streptogramins and glycopeptides. Major species-specific differences in susceptibility affecting clinical assessment criteria were found with amoxycillin, amoxycillin-clavulanate, some narrow-spectrum cephalosporins and fosfomycin. With the exception of penicillin G, oxacillin and cefoxitin, E. intermedius was naturally sensitive or naturally sensitive and intermediate (azlocillin) to all beta-lactams tested. Natural antibiotic susceptibility patterns of E. aerogenes and E. intermedius were analyzed with regard to the underlying mechanisms. The data were compared with the results from two recent studies dealing with natural susceptibilities of other clinically-relevant Enterobacter spp. With reference to beta-lactam susceptibility patterns, it can be assumed that all human-affecting Enterobacter species examined produce species-specific, chromosomally-encoded beta-lactamases of the AmpC type. The naturally-expressed amount of enzyme depends on the species.

Anti-Bacterial Agents↗
PubMed2001

Natural antibiotic susceptibility of recently established coryneform bacteria.

The natural susceptibility of 20 strains each of Brevibacterium casei (formerly CDC coryneform groups B-1 and B-3), Dermabacter hominis (formerly CDC coryneform groups 3 and 5), and Turicella otitidis (formerly coryneform group ANF-1-like) isolated from clinical specimens to 71 antibiotics was investigated. Susceptibility testing was carried out with a microdilution procedure using H medium. All three species were naturally sensitive to tetracyclines, most aminoglycosides, carbapenems, macrolides, lincosamides, glycopeptides, and rifampin. Susceptibility patterns indicating natural resistance to pipemidic acid, sulfamethoxazole, and cotrimoxazole also were found for all three species. Species-dependent discrepancies in susceptibility leading to completely different categorizations (changing from sensitive to resistant or vice versa) were found for some penicillins (e.g., oxacillin and amoxicillin), a few cephalosporins (e.g., ceftibutene), aztreonam, tobramycin, norfloxacin, fleroxacin, trimethoprim, nitrofurantoin, fosfomycin, and fusidic acid. For the majority of antibiotics, Brevibacterium casei was the least susceptible species and Turicella otitidis the most susceptible taxon. The present study describes a database on the natural susceptibility of Brevibacterium casei, Dermabacter hominis, and Turicella otitidis to a wide range of antibiotics. This database can be applied for the validation of susceptibility testing results of these recently established coryneform bacteria.

Actinomycetales↗
PubMed2001

Natural antibiotic susceptibility of strains of the Enterobacter cloacae complex.

The natural susceptibility to 70 antibiotics of 104 strains of the Enterobacter cloacae complex was examined using a microdilution procedure in Isosensitest broth. One hundred and one clinical strains designated as 'E. cloacae' were identified as E. hormaechei (n=65), E. asburiae (n=20) and E. cloacae genospecies 1 or 2 (n=16). Apart from fosfomycin susceptibility, there were only minor differences in natural antibiotic susceptibility patterns. All species were naturally sensitive or naturally sensitive and intermediate to numerous beta-lactams (e.g. carbapenems, aztreonam, acylaminopenicillins, ticarcillin, and some 'modern' cephalosporins), quinolones, aminoglycosides, tetracyclines, antifolates, chloramphenicol, and nitrofurantoin. Uniform natural resistance was found in benzylpenicillin, oxacillin, amoxycillin, amoxycillin/clavulanate, cefoxitin, rifampicin, lincosamides, glycopeptides, streptogramins and fusidic acid. Enterobacter hormaechei was the species most susceptible to fosfomycin. beta-Lactam susceptibility patterns pointed to the presence of chromosomally-encoded AmpC enzymes in all taxa of the E. cloacae complex.

Anti-Bacterial Agents↗
PubMed2001

beta-Lactam-susceptibility patterns of Plesiomonas shigelloides strains: importance of inoculum and medium.

The susceptibility of 10 Plesiomonas shigelloides strains to 30 beta-lactam antibiotics was examined. Susceptibility testing was carried out with a microdilution procedure using 3 media (Isosensitest broth, Mueller-Hinton broth and cation-adjusted Mueller-Hinton broth) and 4 inocula [1 x 10(4), 1 x 10(5), 1 x 10(6) and 1 x 10(7) colony-forming units (CFU)/ml]. A high inoculum dependency of MIC values was found for numerous beta-lactams. Each strain showed 2 completely different susceptibility patterns to several cephalosporins and aztreonam, but the same patterns were found with little variation in each strain. Using an inoculum of 1 x 10(4) CFU/ml the strains showed a high susceptibility to aztreonam and to all cephalosporins in all media (pattern 1), whereas they showed a decreased susceptibility to aztreonam and numerous cephalosporins with an inoculum of 1 x 10(7) CFU/ml (pattern 2). Using an inoculum of 1 x 10(6) CFU/ml, 4/10 strains in lsosensitest broth and 2/10 strains in Mueller-Hinton media showed pattern 1. Susceptibility testing of numerous penicillins revealed a medium-independent inoculum dependency, characterized by a step-to-step correlation between MICs and inocula. The beta-lactam susceptibility patterns arising from different inocula point to new beta-lactamase expression and regulation mechanisms in Plesiomonas. The potential to be resistant to a variety of beta-lactams under conceivable testing conditions should question the use of numerous beta-lactams for the treatment of Plesiomonas infections.

Animals↗
PubMed2001

Natural antimicrobial susceptibilities of Plesiomonas shigelloides strains.

The natural susceptibility of 74 Plesiomonas shigelloides strains isolated from humans (n = 50), water (n = 22) and animals (n = 2) to 71 antibiotics was examined. MICs were performed using a microdilution procedure with Mueller-Hinton broth and an inoculum of 1 x 10(6) cfu/mL. Plesiomonas strains were naturally susceptible or naturally susceptible and intermediate to tetracyclines, several aminoglycosides, aminopenicillins in combination with beta-lactamase inhibitors, all cephalosporins except cefoperazone, ceftazidime and cefepime, carbapenems, aztreonam, quinolones, trimethoprim, sulfamethoxazole, azithromycin, chloramphenicol, nitrofurantoin and fosfomycin. Uniform natural resistance was found to all penicillins tested, roxithromycin, clarithromycin, lincosamides, streptogramins, glycopeptides and fusidic acid. Plesiomonas strains were naturally resistant and intermediate to streptomycin, erythromycin and rifampicin. There were two susceptibility patterns to piperacillin/tazobactam, several cephalosporins and aztreonam. In contrast to a previous study with beta-lactam antibiotics, susceptibility testing of non-beta-lactams revealed no alterations of the MICs of most antibiotics, using different inocula and media. A database is described of the natural susceptibility of P. shigelloides strains to a wide range of antibiotics. It can be used for the validation of susceptibility test results of these bacteria.

Animals↗
PubMed2001

Natural antibiotic susceptibilities of Edwardsiella tarda, E. ictaluri, and E. hoshinae.

The natural antibiotic susceptibilities to 71 antibiotics of 102 Edwardsiella strains belonging to E. tarda (n = 42), E. ictaluri (n = 41), and E. hoshinae (n = 19) were investigated. MICs were determined using a microdilution procedure according to NCCLS criteria and German standards. All edwardsiellae were naturally sensitive to tetracyclines, aminoglycosides, most beta-lactams, quinolones, antifolates, chloramphenicol, nitrofurantoin, and fosfomycin. Edwardsiella species were naturally resistant to macrolides, lincosamides, streptogramins, glycopeptides, rifampin, fusidic acid, and oxacillin. Although slight species-dependent differences in natural susceptibilities to some antibiotics (e.g., macrolides and cefaclor) were seen, differences in natural susceptibility affecting clinical assessment criteria were only seen with benzylpenicillin. Whereas E. tarda was naturally resistant to benzylpenicillin, E. hoshinae was naturally sensitive. Natural sensitivity and resistance to this penicillin were found among the strains of E. ictaluri. The observed oxacillin sensitivity of E. ictaluri was attributed to the failure of the species to grow at higher salt concentrations found in oxacillin-containing microtiter plates. The present study describes a database concerning the natural susceptibility of Edwardsiella species to a wide range of antibiotics, which can be applied to validate forthcoming antibiotic susceptibility tests of these microorganisms.

Anti-Bacterial Agents↗
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

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↗
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↗
PubMed1999

An in-vitro study of the antimicrobial susceptibilities of Yersinia enterocolitica and the definition of a database.

The antibiotic susceptibilities of 151 Yersinia enterocolitica strains isolated from humans, animals and the environment, and belonging to biovars 1A (n = 22), 1B (n = 13), 2 (n = 12), 3 (n = 31), 4 (n = 63) and 5 (n = 10) to 71 antibiotics were examined. Biovars could be characterized phenotypically by their similar antibiograms. For the majority of biovars only minor differences in susceptibilities were detected. Ninety-nine percent of all Yersinia strains were resistant to amoxycillin, but biovar-related differences in MICs were demonstrated. Significant differences, characteristic of specific biovars, were detected for fosfomycin, some beta-lactams (in particular amoxycillin/clavulanate, and ticarcillin). Strains of biovar 1A were resistant or of intermediate susceptibility to ticarcillin and had fosfomycin MICs of 16-64 mg/L and amoxycillin/clavulanate MICs of 4-32 mg/L. Most strains of biovar 1B (n = 11) were sensitive to amoxycillin/clavulanate (MIC = 0.5-2 mg/L). Most strains of biovar 2 (n = 10) showed an antibiotic phenotype resembling that of strains of biovar 1A, but they were more susceptible to fosfomycin (MIC = 4-16 mg/L). Twenty-seven strains of biovar 3 had amoxycillin/clavulanate MICs of 4-32 mg/L; 19 of them were sensitive to ticarcillin and fosfomycin. Biovar 4 strains were uniformly sensitive or of intermediate susceptibility to amoxycillin/clavulanate (MIC = 0.5-4 mg/L), sensitive to fosfomycin (MIC = 1-4 mg/L) but resistant to ticarcillin. The prevailing antibiotic phenotype of biovar 5 (n = 7) was similiar to the phenotype of biovar 4, although these biovar 5 strains were slightly more susceptible to amoxycillin/clavulanate and showed a heterogeneous pattern of susceptibility to fosfomycin (MIC = 1-32 mg/L). The results of this study show that unambiguous statements cannot be made about the natural antibiotic susceptibility to certain beta-lactams and fosfomycin of Y. enterocolitica. The data indicate a complex regulation of beta-lactamases in Y. enterocolitica. Some beta-lactamases are found more frequently or will be expressed predominantly in specific biovars.

Anti-Bacterial Agents↗