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 4,089 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This is a report about microbiological investigations with a new Penicillin-derivate. Temocillin is the first beta-lactamase stable Penicillin with an excellent bactericidal effect against almost all clinically important gram-negative aerobic germs. The antibacterial activity of Temocillin was determined against 355 multiresistent Enterobacteriaceae-strains. We ascertained minimal bacteriostatic and the minimal bactericidal concentration with help of macrodilution-test. The ratio of resistant strains amounted to 0.8%. In vitro investigations with the combination Temocillin and Gentamicin (checker-board-technique) showed 91% indifference and 9% addition, respectively, in 35 Enterobacteriaceae-strains, investigated. Resistances against Temocillin and Ampicillin were cultured through subinhibitory concentrations to predict parallel resistances possible.
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PMID:[Studies with temocillin]. 280 Jun 45

Combinations of two beta-lactam antibiotics may be advantageous in certain clinical situations, providing a synergistic activity against specific organisms or a broad spectrum of antibiotic coverage. Depending on the combination and the bacteria, synergism, indifference, or antagonism can be observed. Synergism may occur when two beta-lactam antibiotics, acting on different penicillin-binding proteins, are combined or when a penicillinase-susceptible beta-lactam antibiotic is protected by another beta-lactam antibiotic acting as a beta-lactamase inhibitor in strains producing a penicillinase (chromosomal or plasmidic). With different species, such as Enterobacter, Citrobacter, indole-positive Proteus, Serratia, Aeromonas, and Pseudomonas, which produce an inducible chromosome-encoded cephalosporinase, antagonism will appear if one of the two combined antibiotics causes induction of the beta-lactamase and the other becomes inactivated by the increased amount of the enzyme. Although most combinations of new beta-lactam antibiotics (ureido-penicillins, third-generation cephalosporins, monobactams) appear to be indifferent, antagonism and possible selection of resistant mutants are the drawbacks of such combinations. Nevertheless, highly active compounds, if used at doses above the minimal inhibitory concentrations, especially in the case of potential cephalosporinase-inducers, may be safe in vivo as far as avoiding antagonism is concerned, but not necessarily with respect to the selection of resistant mutants.
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PMID:Synergism and antagonism in double beta-lactam antibiotic combinations. 348 47

The effect of minocycline on beta-lactamase synthesis in Staphylococcus aureus was examined. Some inhibition of synthesis was detectable in organisms exposed to 0.015 mg minocycline/litre (0.15 of the single cell MIC) and complete inhibition was observed at 0.05 mg drug/litre (0.5 MIC). In contrast, total cell protein synthesis was less susceptible to inhibition by minocycline. Although synthesis of beta-lactamase was inhibited by low concentrations of minocycline, benzylpenicillin and minocycline failed to show synergy when tested in a variety of combinations against penicillinase producing staphylococci. In fact, benzyl-penicillin did not influence the minocycline MIC, and in the majority of cases the same pattern was exhibited by minocycline i.e. it did not generally alter the penicillin MIC. This is an example of true indifference whereby each antibiotic behaves as if the other were not present. The results presented here are discussed in relation to the possibility of therapeutic control of beta-lactamase producing organisms by suppressing the level of enzyme produced.
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PMID:Inhibition of beta-lactamase synthesis in Staphylococcus aureus by minocycline. 387 26

The in vitro antibacterial activity of HR-756 compared to cefoxitin and cefuroxime. 122 multiresistant clinical isolates including Enterobacteriaceae (104) and P. aeruginosa (18), which present particular problems in antibiotic chemotherapy, were selected for study. HR-756 inhibited all the stains of S. marcescens, P. mirabilis and indole-positive Proteus spp. at a concentration of 1,3 and 12 micrograms/ml, respectively; beta-lactamase-producing strains were also susceptible. 90% of K. pneumoniae and more than half of the Enterobacter and P. aeruginosa were inhibited from the drug at a concentration 16 microgram/ml. Cefoxitin and cefuroxime were less active than HR-756. Cefoxitin was more effective against S. marcescens and P. mirabilis while the same was the case with cefuroxime against K. pneumoniae strains. The greater efficiency of HR-756 over cefoxitin and cefuroxime against these multiply resistant isolates seems to be due not only to its indifference to the beta-lactamases but also to its easier penetrability into the bacterial cell.
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PMID:Antibacterial activity of HR-756, cefoxitin and cefuroxine against multiply antibiotic-resistant strains of Enterobacteriaceae and Pseudomonas aeruginosa. 624 1

Aztreonam, a synthetic monobactam antimicrobial agent specifically active against aerobic, gram-negative microorganisms, was studied in combination with the extended-spectrum penicillins azlocillin and piperacillin against 46 strains of Pseudomonas aeruginosa. Of these strains, 4.3% were synergistically inhibited, and 19.7% showed evidence for an additive effect of the antibiotics. All other strains showed indifference. The addition of cefoxitin to these combinations increased the MICs of azlocillin and piperacillin by two to three tubes, whereas zero- to one-tube increases were noted for aztreonam MICs. Attempts to block cefoxitin-induced beta-lactamase production by using clindamycin were unsuccessful even at high clindamycin concentrations.
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PMID:Effect of aztreonam in combination with azlocillin or piperacillin on Pseudomonas aeruginosa. 644 Apr 74

The in-vitro activity of cefotetan, a recently developed cephamycin, was investigated under various experimental conditions. The compound showed moderate activity against Staphylococcus aureus and Streptococcus pyogenes, no activity against Pseudomonas aeruginosa and Streptococcus faecalis, but a high activity against Enterobacteriaceae, including beta-lactamase-producing strains. Haemophilus influenzae also was fairly susceptible. The MBC was usually equal to or two- or fourfold higher than MIC. Medium composition, pH and inoculum size had minimal influence on its activity. About 50% of recent clinical isolates of Bacteroides fragilis were susceptible to cefotetan, but some were highly resistant. Killing curves of cefotetan against different bacterial strains indicated that it was rapidly bactericidal at concentrations equal to MIC or two- to fourfold higher. However, some strains showed regrowth after initial inhibition. Combination of cefotetan with aminoglycosides, or with cefazolin, cefotaxime, moxalactam or piperacillin resulted either in synergy, addition or indifference according to the bacterial strain and the nature of the combination. Antagonism was never observed. Human serum protein binding varied from 75 to 86% according to the assay method. Binding with horse serum protein was about 28%.
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PMID:In-vitro antibacterial activity of cefotetan. 657 25

The in vitro antibacterial activity of eight newer beta-lactam antibiotics (mecillinam, piperacillin, mezlocillin, cefoxitin, cefotaxime, moxalactam, ceftriaxone and ceftazidime) was determined against 87 cephalothin-resistant strains of Enterobacteriaceae isolated during 6 months in a general hospital. Ceftriaxone, cefotaxime, moxalactam and ceftazidime proved to be highly active; only a minority of strains required higher concentrations than 0.125 microgram/ml for inhibition of growth. Cefoxitin, mecillinam, mezlocillin and piperacillin were less active. Mecillinam displayed greater efficacy against Escherichia coli, Klebsiella and Enterobacter spp., while the same was the case for piperacillin against Proteus mirabilis and Serratia marcescens, and for cefoxitin against indole-positive Proteus spp. The production of beta-lactamase was correlated with a reduced activity of mecillinam, mezlocillin and piperacillin but not of cefoxitin or the other beta-lactamase-stable cephalosporins. However, some strains, mainly those of Proteus, Enterobacter and Serratia, though resistant to mecillinam, mezlocillin and piperacillin did not produce beta-lactamases. This observation might indicate that ceftriaxone, moxalactam, cefotaxime and ceftazidime, besides their indifference to beta-lactamases, are characterized also by a high degree of intrinsic activity.
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PMID:Comparison of in vitro activities of eight new beta-lactam compounds against cephalothin-resistant Enterobacteriaceae from hospital patients. 661 May 38

The bactericidal effects of ceftibuten in combination with netilmicin, isepamicin or ciprofloxacin against two strains of Escherichia coli and three of Klebsiella pneumoniae were studied by the killing curve method. Interpretation of the results was made on a statistical basis by comparing the bactericidal effects observed when the antibiotics were tested alone with those when they were tested in combination. The results were also assessed by survival probabilities according to the ratio of the number of viable bacteria at time t(N(t)) to the initial number of viable bacteria (N(0)). The effects of the combinations were defined in terms of antagonism, indifference, single agonism, addition and synergy by taking account of the confidence intervals of the survival probabilities. All of the combinations exhibited bactericidal activities which were time-dependent. Synergy was demonstrated when ceftibuten was combined with the aminoglycosides, except against the two extended-spectrum beta-lactamase-producing strains of K. pneumoniae, but not when ceftibuten and ciprofloxacin were combined. Antagonism was not demonstrated with any of the combinations.
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PMID:A statistical evaluation of the bactericidal effects of ceftibuten in combination with aminoglycosides and ciprofloxacin. 812 33

As a basic study of combination therapy for bacterial meningitis, in vitro combined effect of meropenem (MEPM) and various antimicrobial agents against beta-lactamase-nonproducing ampicillin-resistant Haemophilus influenzae (BLNAR) and penicillin-resistant Streptococcus pneumoniae (PRSP) was investigated. The following findings were obtained. 1. In the checker board assay using 23 clinical isolates of BLNAR, MEPM+cefotaxime (CTX), MEPM+ampicillin (ABPC), and MEPM+rifampicin (RFP) showed synergistic effect (21 strains, 6 strains, 4 strains, respectively) or additive effect (2 strains, 17 strains, 19 strains, respectively). 2. In the checker board assay using 19 clinical isolates of PRSP, MEPM+CTX, MEPM+teicoplanin (TEIC), and MEPM+RFP showed synergistic effect (5 strains, 8 strains, 1 strain, respectively), additive effect (14 strains, 11 strains, 17 strains, respectively) or indifference (0 strain, 0 strain, 1 strain, respectively). 3. The time-kill assay with BLNAR demonstrated synergistic bactericidal effect of MEPM+CTX and MEPM+RFP, but not MEPM+ABPC. 4. The time-kill assay with PRSP demonstrated synergistic or additive bactericidal effect of MEPM+CTX, MEPM+TEIC, and MEPM+RFP. 5. There were no antagonistic effect in any combination tested in this study. These findings suggest that combination therapy with MEPM and various antimicrobial agents tested in this study are useful in treating bacterial meningitis caused by BLNAR and PRSP.
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PMID:[In vitro combined effect of meropenem and various antimicrobial agents against beta-lactamase-nonproducing ampicillin-resistant Haemophilus influenzae and penicillin-resistant Streptococcus pneumoniae]. 1599 57

Coagulase-negative staphylococci (CoNS) are the leading cause of late-onset sepsis (LOS) in neonates. Increasing resistance of CoNS to beta-lactams and aminoglycosides has led to widespread use of vancomycin, which in turn may lead to resistance to vancomycin. Thus, combination therapy of LOS has been advocated. We aimed to determine the interaction of oxacillin and gentamicin against CoNS. In 2005, 34 isolates of oxacillin- and gentamicin-resistant CoNS were obtained from blood samples of neonates with LOS. Combination effect was tested using the checkerboard method, E-test with the other antibiotic incorporated in the medium (E-test-1) and two E-test strips placed in a cross-formation (E-test-2). Of 34 isolates 61.8%, 53% and 73.5% revealed synergy or an additive effect when tested by the checkerboard method, E-test-1 and E-test-2, respectively. Results of all three tests were concordant for six (17.6%) isolates, four showing synergy, and two indifference. Our in vitro results support that combination therapy with penicillinase-resistant penicillin and aminoglycoside can be an alternative to vancomycin.
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PMID:In vitro synergy of oxacillin and gentamicin against coagulase-negative staphylococci from blood cultures of neonates with late-onset sepsis. 2329 72


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