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PubMed1984

Susceptibilities of enterococci to twelve antibiotics.

The susceptibilities of 347 urine isolates of enterococci (Streptococcus faecalis, 44%; S. faecalis subsp. zymogenes, 37%; S. faecalis subsp. liquefaciens, 19%) to ampicillin, azlocillin, mezlocillin, piperacillin, vancomycin, gentamicin, erythromycin, rosaramicin, rifampin, rifampin plus trimethoprim (1:4), trimethoprim-sulfamethoxazole (1:20), and chloramphenicol were determined by the agar dilution technique. There were no significant differences in susceptibility to individual agents among the subspecies of S. faecalis. Azlocillin and mezlocillin (MIC for 90% of isolates, 0.78 micrograms/ml) and piperacillin, ampicillin, and vancomycin (MIC for 90% of isolates, 1.56 micrograms/ml) were the most active agents and were significantly more potent than the other reference antibiotics tested.

Anti-Bacterial Agents↗
PubMed1984

Influence of inoculum size on comparative susceptibilities of penicillinase-positive and -negative Neisseria gonorrhoeae to 31 antimicrobial agents.

The effects of two inoculum sizes (10(4) and 10(6) CFU) on the MICs of 20 beta-lactam antibiotics, 4 aminoglycosides, and 7 other antimicrobial agents were compared for 102 unselected strains of Neisseria gonorrhoeae (26 penicillinase positive and 76 penicillinase negative), with three replicates for each test. The method was agar plate dilution on Mueller-Hinton agar supplemented with 1% hemoglobin and 1% IsoVitaleX. For penicillinase-positive strains, a large inoculum (10(6) CFU) increased the MIC greater than or equal to 16-fold for benzylpenicillin, piperacillin, azlocillin, and mezlocillin and increased the MIC greater than or equal to 8-fold for ampicillin, cefoperazone, ceftazidime, cefonicid, and cefamandole. The inoculum size had little or no influence on MICs of any antimicrobial agent for penicillinase-negative strains. For penicillinase-positive strains, the most active antibiotics (MIC, less than or equal to 0.001 microgram/ml) were the new cephalosporins: cefotaxime, ceftazidime, ceftizoxime, ceftriaxone, and cefmenoxime. For penicillinase-negative strains, the most active antibiotics were piperacillin, ceftriaxone, ceftizoxime, and cefmenoxime (MIC, less than or equal to 0.001 microgram/ml), closely followed by ceftazidime, moxalactam, azlocillin, mezlocillin, and cefuroxime.

Anti-Bacterial Agents↗
PubMed1984

Activity of apalcillin against Pseudomonas aeruginosa.

The in vitro activity of apalcillin was tested against 107 clinical isolates of Pseudomonas aeruginosa, and the results were compared to those for piperacillin, mezlocillin, azlocillin, and carbenicillin. MIC analysis showed that 97% of the isolates were susceptible to piperacillin, 97% were susceptible to apalcillin, 93% were susceptible to azlocillin, 87% were susceptible to mezlocillin, and 84% were susceptible to carbenicillin.

Ampicillin↗
PubMed1987

Leakage of beta-lactamase: a second mechanism for antibiotic potentiation by amdinocillin.

Discrepancies were observed between results of different beta-lactamase induction tests with amdinocillin, which appeared to be a strong inducer in whole-cell assays but a weak inducer in assays with cell-free sonic extracts. Results of a nitrocephin-disk test with constitutive beta-lactamase producers indicated that the positive results obtained in whole-cell assays were due to drug-produced leakage of enzyme from the cell and not to induction. Imipenem was also found to cause leakage of beta-lactamase from a similar number of constitutive enzyme producers, while cefoxitin was much less likely to cause leakage. A split-dose regimen was employed to treat mice infected with a strain of Enterobacter cloacae which appeared to leak enzyme on exposure to amdinocillin. Results indicated that prior treatment with amdinocillin significantly enhanced (P less than 0.025) the efficacy of azlocillin, an enzyme-labile drug, but did not affect the efficacy of cefotaxime, a relatively enzyme-stable drug. Conversely, prior treatment with amdinocillin did not potentiate the efficacy of either azlocillin or cefotaxime in the treatment of mice infected with an Escherichia coli strain that was highly susceptible to all three drugs. Thus, it appears that amdinocillin may potentiate the activity of other beta-lactam drugs not only by binding to a complementary penicillin-binding protein but also by causing leakage of beta-lactamase from the cell. This effect may be related to its ability to bind to penicillin-binding protein 2 and subsequently produce changes in outer membrane permeability.

Amdinocillin↗
PubMed1989

Do double-beta-lactam combinations prolong neutropenia in patients undergoing chemotherapy or bone marrow transplantation for hematological disease?

The total period of neutropenia was assessed in 174 episodes after chemotherapy or bone marrow transplantation in which patients received antibiotics for fever in a randomized prospective trial. Log rank analysis demonstrated no significant difference in the total duration of neutropenia between patients receiving netilmicin plus either piperacillin or azlocillin and those given ceftazidime plus either piperacillin or azlocillin. Of 86 patients in the single-beta-lactam group, 27 had a persistent neutrophil count of 0.1 x 10(9) per liter during treatment compared with 27 of 88 patients in the double-beta-lactam group, and 29 of 68 patients treated with the single-beta-lactam combination had a total period of neutropenia greater than 30 days versus 36 of 75 in the double-beta-lactam group. The use of two beta-lactam antibiotics rather than one does not appear to prolong neutropenia in patients undergoing treatment of hematological malignancy. However, in order to determine the effect of a single-beta-lactam combination, a similar carefully controlled prospective randomized study in which such treatment is compared with a non-beta-lactam-containing regimen is required.

Adult↗
PubMed1991

Comparative inactivation of isepamicin, amikacin, and gentamicin by nine beta-lactams and two beta-lactamase inhibitors, cilastatin and heparin.

This study was undertaken to compare the susceptibility to inactivation of isepamicin with amikacin and gentamicin when exposed to different beta-lactams, beta-lactamase inhibitors, and heparin. The aminoglycosides (5, 10, 20, and 50 micrograms/ml) were incubated in human serum with ampicillin, azlocillin, aztreonam, carbenicillin, ceftazidime, piperacillin, and ticarcillin (100 and 600 micrograms/ml) and with clavulanate, cilastatin, 1:1 imipenemcilastatin, oxacillin, and sulbactam (20 and 120 micrograms/ml) for 48 h at 37 degrees C. Aminoglycoside concentrations were measured by fluorescence polarization immunoassay (FPI) after 0, 8, and 48 h of incubation and by radial diffusion bioassay after 48 h of incubation. Each of the three aminoglycosides was also added to whole blood containing either heparin (100 U/ml) or 0.5% EDTA as a control and assayed after 6 h by FPI. The degree of inactivation of isepamicin by the beta-lactams was significantly less than that by amikacin (P less than 0.003) and gentamicin (P less than 0.0002) when determined by bioassay. Piperacillin, carbenicillin, and azlocillin produced the greatest amount of inactivation, and cilastatin and oxacillin produced the least. A similar pattern was observed when the degree of inactivation was measured by FPI. A significant difference in the degree of inactivation was noted between isepamicin and gentamicin (P less than 0.003 at 8 h and P less than 0.006 at 48 h) but not between isepamicin and amikacin (P greater than 0.7 at 8 h and P greater than 0.08 at 48 h). Aminoglycoside determinations by FPI were not influenced by the presence of heparin. In summary, isepamicin was found to be at least as stable as amikacin against inactivation by beta-lactam compounds and beta-lactamase inhibitors. Heparin (100 U/ml) did not influence aminoglycoside determinations by FPI.

Amikacin↗
PubMed1985

Comparative antibacterial activities of new beta-lactam antibiotics against Pseudomonas aeruginosa.

In vitro activity of nine new cephalosporins and penicillins was determined against 417 isolates of Pseudomonas aeruginosa. Carbenicillin, ticarcillin, gentamicin, tobramycin and netilmicin were also included in the study. Imipenem showed highest activity. More than 90% of the isolates were susceptible to ticarcillin, piperacillin, azlocillin, cefoperazone, cefsulodin and to tobramycin. 57 isolates included in the study were resistant to gentamicin (MIC greater than 4 mg/l); of these, none were resistant to imipenem, and more than 80% were susceptible to piperacillin, azlocillin, cefoperazone and cefsulodin.

Anti-Bacterial Agents↗
PubMed1986

In vitro activity of cefpimizole sodium (U-63196E) and other antimicrobial agents against Haemophilus isolates from pediatric patients.

In vitro activity of cefpimizole, an experimental third generation cephalosporin, and 10 other antimicrobials (ampicillin, azlocillin, cefamandole, cefoperazone, cefotaxime, mezlocillin, moxalactam, piperacillin, rifampin and sulfamethoxazole/trimethoprim) were determined for 181 isolates of Haemophilus obtained from pediatric patients. For 156 beta-lactamase-negative isolates, MIC50 values of cefoperazone, cefpimizole, and cefamandole were 4, 8, and 16 times greater than those of moxalactam and cefotaxime (0.06 micrograms/ml). 25 beta-lactamase-producing isolates were resistant to ampicillin, azlocillin, mezlocillin, and piperacillin, however, MIC50 of all third generation cephalosporin were similar to those obtained for beta-lactamase-negative organisms. Rifampin and SMX/TMP demonstrated low MIC50 values for all isolates.

Anti-Bacterial Agents↗
PubMed1988

Pseudomonas aeruginosa: in vitro susceptibility to antimicrobial drugs, single and combined, with and without defibrinated human blood.

Twelve clinical isolates of Pseudomonas aeruginosa of distinct pyocin type varied in susceptibility to 14 of 17 antimicrobial drugs. The 2 x MIC concentrations of 16 antimicrobial drugs combined with 55% (v/v) of fresh, defibrinated human blood yielded additive effects. Additive effects were noted with blood plus the MIC concentrations of all drugs tested except cefoperazone, gentamicin, and netilmicin. Blood combined with subinhibitory (1/2 MIC) concentrations of aztreonam, ceftazidime, ciprofloxacin, fleroxacin, imipenem, and tobramycin, respectively, yielded additive effects; indifferent effects were observed with the remaining 10 blood plus 1/2 MIC drug combinations. The following drug combinations additively augmented the antibacterial activity of 65% (v/v) of human blood against two selected isolates of P. aeruginosa: tobramycin (1 microgram/ml) plus the MIC or 2 x MIC concentrations of azlocillin, aztreonam, ceftazidime, ciprofloxacin, imipenem, norfloxacin, ofloxacin, piperacillin, and ticarcillin, respectively. Imipenem (8 micrograms/ml) combined with ceftazidime, cefoperazone, and piperacillin, but not aztreonam, enhanced the bactericidal activity of human blood. Rifampin (2 micrograms/ml) plus tobramycin (0.5-1 microgram/ml) combined with 8 or 16 micrograms/ml of azlocillin, aztreonam, cefoperazone, ceftazidime, imipenem, and piperacillin, respectively, enhanced blood-mediated killing of three representative multiple-drug-resistant P. aeruginosa isolates. Additional effective triple-drug combinations with human blood were rifampin + tobramycin + polymyxin B, rifampin + ciprofloxacin + imipenem, and rifampin + amikacin + imipenem. Ciprofloxacin (2 micrograms/ml) was the most potent intraphagocytic bactericidal drug of 16 tested agents (greater than or equal to 2 x MBC concentrations) against P. aeruginosa control strain ATCC 27853.

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↗
PubMed2005

Interaction of zwitterionic penicillins with the OmpF channel facilitates their translocation.

To study translocation of beta-lactam antibiotics of different size and charge across the outer bacterial membrane, we combine an analysis of ion currents through single trimeric outer membrane protein F (OmpF) porins in planar lipid bilayers with molecular dynamics simulations. Because the size of penicillin molecules is close to the size of the narrowest part of the OmpF pore, penicillins occlude the pore during their translocation. Favorably interacting penicillins cause time-resolvable transient blockages of the small-ion current through the channel and thereby provide information about their dynamics within the pore. Analyzing these random fluctuations, we find that ampicillin and amoxicillin have a relatively high affinity for OmpF. In contrast, no or only a weak interaction is detected for carbenicillin, azlocillin, and piperacillin. Molecular dynamics simulations suggest a possible pathway of these drugs through the OmpF channel and rationalize our experimental findings. For zwitterionic ampicillin and amoxicillin, we identify a region of binding sites near the narrowest part of the channel pore. Interactions with these sites partially compensate for the entropic cost of drug confinement by the channel. Whereas azlocillin and piperacillin are clearly too big to pass through the channel constriction, dianionic carbenicillin does not find an efficient binding region in the constriction zone. Carbenicillin's favorable interactions are limited to the extracellular vestibule. These observations confirm our earlier suggestion that a set of high-affinity sites at the narrowest part of the OmpF channel improves a drug's ability to cross the membrane via the pore.

Anti-Bacterial Agents↗
PubMed1980

Piperacillin: evaluation against inpatient and gentamicin-resistant bacteria.

When species-matched collections, each consisting of 128 bacterial strains, were compared, inpatient organisms were found to be significantly more resistant to piperacillin than outpatient organisms. A collection of 143 gentamicin-resistant gram-negative bacilli was significantly more resistant to piperacillin than a species-matched collection of gentamicin-sensitive organisms. Piperacillin resistance was transferred by conjugation from isolates of 8 different Enterobacteriaceae species to a recipient Escherichia coli strain. In each of 67 mating experiments in which transfer of carbenicillin resistance by conjugation occurred, resistance to ticarcillin, azlocillin and piperacillin was also transferred. As in previous studies, piperacillin was found to be markedly more active against non-fastidious gram-negative bacilli than carbenicillin, ticarcillin or azlocillin. Nevertheless, piperacillin resistance, apparently plasmid mediated, was detected in multiple species.

Bacteria↗
PubMed1984

Relevance of in vitro antibacterial activities and pharmacokinetic properties of antipseudomonal beta-lactam antibiotics to their therapeutic effects on urinary tract infection caused by Pseudomonas aeruginosa P 9 in mice.

The therapeutic effects of seven antipseudomonal beta-lactam antibiotics on experimental urinary tract infection caused by Pseudomonas aeruginosa P 9 in mice were compared, and the results were analyzed in relation to their in vitro antibacterial activities and pharmacokinetic properties. The CD50 values were (mg/kg): cefsulodin, 6.19; cefoperazone, 162; sulbenicillin, 167; ticarcillin, 184; azlocillin, 121; mezlocillin, 390; and piperacillin, 227. Cefsulodin was more active than the other antibiotics not only in therapeutic effects but also in in vitro antibacterial effects evaluated according to growth inhibitory, bactericidal, and bacteriolytic activities. It also penetrated and persisted well in the kidney of mice. The therapeutic effects of cefoperazone, azlocillin, and piperacillin were much less than expected from their in vitro antibacterial activities; the CD50 values were more than 18-fold as large as that of cefsulodin, whereas the differences of their MIC values were less than four-fold.

Animals↗
PubMed1991

[Resistance of intestinal strains of Bacteroides to antibiotics and chemotherapeutic agents].

Antibacterial therapy of anaerobic infections usually involves chemotherapy. The basis of therapy is assessment of the minimal inhibitory concentration (MIC) of antibiotic or chemotherapeutic agents needed to eliminate the suspected causal agents of infection. The authors assessed MIC of 9 selected antibiotics and chemotherapeutic agents (metronidazole, chloramphenicol, clindamycin, azlocillin, mezlocillin, cephoxitin, oxytetracycline, lincomycin, erythromycin) by the dilution method in blood agar in 157 strains of the most important types of the genus Bacteroides which were isolated in 1985-1989 from different clinical materials in Bratislava and in Halle (GDR). All tested strains were sensitive to metronidazole and chloramphenicol. Resistance to clindamycin was very rare. Strains resistant to azlocillin, mezlocillin and cephotoxin were more frequent. A high resistance to lincomycin, oxytetracycline and erythromycin was found. Difference in sensitivity of strains from the CSSR and GDR were slight. Similarly results of the present work differed little from those of previous work.

Bacteroides↗
PubMed1986

Comprehensive evaluation of ciprofloxacin in combination with beta-lactam antibiotics against Enterobacteriaceae and Pseudomonas aeruginosa.

1-cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7-piperazine-1-ylquinoline-3-carboxylic acid (ciprofloxacin, Bay o-9867, Bay q-3939) was evaluated by checkerboard assay in combination with ampicillin, ticarcillin, mezlocillin, azlocillin, piperacillin, cefamandole, cefoxitin, cefotaxime, and ceftazidime. A total of 220 clinical isolates of enterobacteriaceae and Pseudomonas aeruginosa (11 species, 20 strains each) were examined. Predominantly additive combination effects were seen with all antibiotic combinations tested. Synergy was obtained with only a few test strains while antagonistic drug interactions were not observed at all. Time-kill experiments which were performed to assess the bactericidal activities, confirmed these findings. The antibiotic combinations were also evaluated in vivo using a model of experimental thigh muscle infection in neutropenic mice. In-difference or additive therapeutic effects resulted when the beta-lactam compounds and ciprofloxacin were given in combination at doses which were also effective alone. Subinhibitory doses of azlocillin and mezlocillin, on the other hand, appeared to increase the efficacy of ciprofloxacin. The influence of various application schedules was examined by time-kill experiments and in mice. Sequential administration of the drugs at intervals of 2 h did not alter the combination effects regardless of the sequence of administration.

Animals↗
PubMedDate not supplied

[Antibiotic resistance of Pseudomonas aeruginosa: a fact and a problem at the University Hospital Center of Cocody (Abidjan)].

The in vitro activity of 4 beta lactam compounds (carbenicillin, ampicillin, cefotaxim, azlocillin), 4 aminoglycosides (gentamicin, dibekacin, netilmicin, amikacin), chloramphénicol and tetracyclin chlorhydrate was studied on 30 strains of Pseudomonas aeruginosa. Amikacin is the most efficient with 97% of sensitive strains, then dibekacin (80%), azlocillin (76%) and carbenicillin (73%). Gentamicin and netilmicin are the less efficient with respectively 43% and 63% resistant strains. Chloramphenicol, ampicillin and cefotaxim have not any activity on these strains. This study reveals that 3% of the strains are polyresistant.

Anti-Bacterial Agents↗
PubMed1987

[Epidemiology of Pseudomonas aeruginosa hospital infection in the Ivory Coast].

210 P. aeruginosa hospital strains isolated at Abidjan from pathological samples or contaminated material were studied by means of serotyping, biotyping, phage-typing and for their resistance to eleven antibiotics. 87% were classified into 14 serogroups: O:1, O:2, O:3, O:4, O:5, O:6, O:8, O:9, O:10, O:11, O:12, O:13, O:15, O:16. No strains were O:7 or O:14. The presence of an ortho-nitrophenyl beta-d-galactopyranoside hydrolase was demonstrated in 42 strains belonging to the serogroup O:11. Sixty-five phage-types were defined but 37% of strains were untypable by phages. The incidence of resistance to each tested antibiotic was as follows: carbenicillin 49%, mezlocillin 44%, ticarcillin 34%, azlocillin 25%, cefamandole 94%, latamoxef 15%, cefotaxime 41%, cefsulodin 32%, tobramycin 35%, amikacin 7%, gentamicin 39%. Thirty-eight strains were multiresistant to carbenicillin, mezlocillin, ticarcillin, azlocillin, and four strains to eleven antibiotics. These results are compared with data of the scientific literature on the epidemiology of hospital Pseudomonas infection.

Bacteriophage Typing↗
PubMed1987

[Sensitivity of Pseudomonas aeruginosa to beta-lactam antibiotics. Apropos of 338 strains isolated at the Regional Hospital Center at Nantes in 1984].

The MIC of 338 Pseudomonas aeruginosa strains isolated in 1984, in a French hospital, was determined by an agar dilution method, using seven beta-lactam antibiotics: ticarcillin, azlocillin, piperacillin, cefoperazone, ceftriaxone, cefsulodin and ceftazidime. The MIC50-MIC90 were respectively: 32-64, 8-32, 8-16, 8-16, 16-64, 4-16, 2-4 mg/l. Ticarcillin was the most frequently effective compound (95% of the strains were susceptible), 90% of the strains were susceptible to ceftazidime or piperacillin, 87% to azlocillin and 84% to cefsulodin. Cefoperazone and ceftriaxone were much less effective (43% and 19% of the strains, respectively). The study of the resistance patterns showed a higher percentage (80%) of strains susceptible to all the penicillins than the percentage of strains susceptible to cephalosporins, most of them however were susceptible to both cefsulodin and ceftazidime. It also showed the relatively low frequency of resistant strains by inducible cephalosporinase or decreased permeability. Serovar 0.12 was characterized by its multi-resistance to beta-lactam antibiotics.

Anti-Bacterial Agents↗