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Query: UNIPROT:Q29983 (MIC)
 21,138 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vitro susceptibility testing of Listeria monocytogenes most often reveals both ampicillin and penicillin as inhibitory as opposed to bactericidal with activity comparable to chloramphenicol and tetracycline. Yet, the former two penicillins are more effective for Listeria meningitis than are the latter agents. Accordingly, we reassessed the bactericidal activity of agents used in listeriosis in order to determine in vitro methodology that would be more predictive of clinical outcome. We found that bactericidal activity for greater than 48 hr by either minimum inhibitory-minimum bactericidal concentration (MIC-MBC) testing or time-kill kinetic studies was the best predictor of clinical efficacy. This correlation may be due to Listeria being a slow-growing microorganism. In addition to ampicillin and penicillin, we found trimethoprim-sulfamethoxazole, vancomycin, and imipenem to exhibit bactericidal activity for 48 hr. For the first two agents, this is in agreement with the results of clinical experience.
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PMID:Susceptibility testing of Listeria monocytogenes. A reassessment of bactericidal activity as a predictor for clinical outcome. 190 14

Dirithromycin is a 9-N-11-O-oxazine derivative which is formed by condensation of 9(S)-erythromycylamine with 2-(2-methoxyethoxy)acetaldehyde. Dirithromycin is hydrolyzed, either under acidic conditions or in vivo, to its major active metabolite, 9(S)-erythromycylamine. The antimicrobial spectrum of dirithromycin is similar to that of erythromycin; both antibiotics are active against gram-positive bacteria, Legionella spp., Helicobacter pylori, and Chlamydia trachomatis. Comparable results were obtained for each antibiotic in MIC and MBC determinations and in the potential development of resistance in vitro. The effects of human serum, bacterial growth media, test methodology, and inoculum size on MICs were similar for each antibiotic. In standard mouse protection studies, dirithromycin was more efficacious than erythromycin against experimental infections after subcutaneous administration of antibiotic. These results were consistent with pharmacokinetic studies in rodents, which showed that dirithromycin gave more persistent concentrations of antibiotic in serum and tissues than were achieved with erythromycin. These studies indicate that dirithromycin possesses antimicrobial activity comparable to that of erythromycin in vitro but is more active than erythromycin in vivo, which may be attributable to the persistence of antimicrobial activity in the tissue(s) of the test animals.
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PMID:Synthesis and antimicrobial evaluation of dirithromycin (AS-E 136; LY237216), a new macrolide antibiotic derived from erythromycin. 192 52

YM133, the 4"-O-(4-methoxyphenyl)acetyltylosin, is a new macrolide. The in vitro activity of YM133 was compared with those of erythromycin, josamycin, and rokitamycin by an agar dilution method. YM133 inhibited 90% of the tested isolates of Streptococcus pneumoniae, Legionella spp., and anaerobic bacteria at less than or equal to 1.56 micrograms/ml. The drug inhibited 90% of erythromycin-resistant staphylococci and Streptococcus pyogenes at less than or equal to 50 micrograms/ml. YM133 showed activity against erythromycin-, josamycin-, and rokitamycin-resistant (MIC greater than or equal to 100 micrograms/ml) strains of staphylococci, streptococci, Bacteroides spp., and Clostridium spp. Enterococci were less susceptible to other YM133-like macrolides. Unlike other macrolides, YM133 showed killing activity, and the MBC/MIC ratios of YM133 for several strains were 1:32, whereas those of erythromycin were 4:1,024. In a time-kill curve study, the reduction of viable cells started within 2 h after the addition of YM133.
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PMID:In vitro activity of YM133, a new semisynthesized macrolide. 192 95

We studied the activity of the combination of sulbactam and ceftriaxone against a Klebsiella pneumoniae strain producing TEM-3, a new extended-broad-spectrum beta-lactamase, in an endocarditis model. In vitro, ceftriaxone was strongly inactivated in the presence of TEM-3 (MBC, 128 micrograms/ml with an inoculum of 5 x 10(5) CFU/ml). A marked inoculum effect was demonstrated with sulbactam: effective concentrations of inhibitor needed to reduce the MIC and MBC of ceftriaxone to similar levels increased from 1 microgram/ml in the presence of an inoculum of 5 x 10(5) CFU/ml to 20 micrograms/ml in the presence of an inoculum of 1 x 10(7) CFU/ml. In vivo, sulbactam given at 200 mg/kg of body weight every 12 h, a dosage higher than that previously reported to be effective against rabbit endocarditis caused by other microorganisms, was not sufficient to restore the complete activity of ceftriaxone given at 30 mg/kg once daily for 4 days. This insufficient activity may be correlated with the presence of a high level of beta-lactamase inside the vegetations, as indicated by a quantitative in vitro assay of beta-lactamase activity in the cardiac vegetation, suggesting an insufficient inactivation of the extended-broad-spectrum beta-lactamase in vivo.
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PMID:Ceftriaxone-sulbactam combination in rabbit endocarditis caused by a strain of Klebsiella pneumoniae producing extended-broad-spectrum TEM-3 beta-lactamase. 207 99

The microbiological activity of cefepime was assessed in vitro against 232 clinical isolates coupled with a pharmacokinetic evaluation at steady state in six patients receiving 1 g every 12 h. MIC90s were less than or equal to 0.25 mg/l for Enterobacteriaceae and streptococci. 1 mg/l for Staphylococcus aureus and 8 mg/l for Pseudomonas aeruginosa. Mean serum concentrations in patients were 62.5 +/- 2.7 mg/l (end infusion) and 1.1 +/- 0.8 mg/l (at 12 h) with an elimination half-life 2.72 +/- 0.59 h. These data together with those published for currently marketed cephalosporins were integrated to generate an Intensity Index incorporating both the magnitude and duration that drug concentrations exceed the MIC during steady-state dosing. Cefepime demonstrated comparable or superior indices to cefazolin against Gram-positive microorganisms and to cefuroxime and ceftazidime against Gram-negatives. Serum bacteriostatic and bactericidal activity from the kinetic samples corresponded with the duration that serum cefepime concentrations exceeded the MIC and MBC, respectively, for selected strains. This pharmacodynamic evaluation suggests that cefepime 1 g every 12 h potentially provides inhibitory serum concentrations for the majority of common Enterobacteriaceae, streptococci and S. aureus over the dosing interval but that higher doses or more frequent administration may be necessary for some pseudomonal infections.
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PMID:Pharmacodynamics of cefepime. 209 15

Ten clinical isolates of Enterococcus faecalis were examined for susceptibility to the bactericidal activity of penicillin. Four of these had MBCs of penicillin equal to 2 to 4 x the MIC, and six exhibited a paradoxical response to penicillin, i.e., the bactericidal activity of the antibiotic had a concentration optimum at 2 to 4 x the MIC and decreased significantly at concentrations above this. We found that the paradoxical response to penicillin was an intrinsic and stable property of a strain, but that its phenotypic expression was not homogeneous; only a fraction of the cell population that died at low concentrations was able to survive at high penicillin concentrations. The size of this fraction increased with increasing antibiotic concentration and reached a maximum in the late-log phase of growth. All 10 strains produced a lytic enzyme that was active on Micrococcus luteus heat-killed cells, whereas only some strains lysed E. faecalis heat-killed cells. Strains producing large amounts of the latter enzyme did not show the paradoxical response to penicillin, whereas mutants of these strains that lacked this enzymatic activity paradoxically responded to the antibiotic activity. In addition, from strains that showed paradoxical response to penicillin and produced only the enzyme that was active on M. luteus, it was possible to isolate mutants that were also capable of lysing E. faecalis cells and that were killed with similar efficiency by all concentrations above the MBC. On the basis of these findings, the paradoxical response to penicillin is explained as a property of certain strains of E. faecalis; this property is genetically characterized by alterations in synthesis or activity of one autolysin but phenotypically expressed only by a few cells that are in a particular physiological condition when exposed to high concentrations of antibiotics.
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PMID:Paradoxical response of Enterococcus faecalis to the bactericidal activity of penicillin is associated with reduced activity of one autolysin. 210 78

Infections in the cerebrospinal fluid (CSF) occur in an area of impaired host defenses; therefore, bactericidal antibiotics that reach adequate concentrations in the CSF are necessary for treatment. Measurements of antibiotic penetration into the CSF include CSF inhibitory and bactericidal titers, the absolute antibiotic concentration in the CSF, and the CSF: serum concentration ratio. We present the case of a patient with Listeria monocytogenes meningitis who failed to respond clinically to standard therapy, and whose organism demonstrated tolerance to Ampicillin (MBC: MIC = 258:1) that successfully responded to trimethoprim-sulfamethoxazole (TMP-SMX). The CSF peak bactericidal titer to TMP-SMX was 1:8, corresponding to that reported as necessary for successful outcome in patients with meningitis. The CSF peak: MBC ratios for TMP and SMX were less than 3:1 and equal to 3:1, respectively. These individual ratios are lower than those suggested for successful treatment of meningitis; however, the recommended ratios were established using single agents and did not account for synergistic activity with a drug combination such as TMP-SMX. The failure of standard therapy in this patient underscores the importance of MIC/MBC testing when tolerance is suspected or when CSF penetration of antibiotics is relatively poor. In addition, measurements of CSF inhibitory and bactericidal titers, which incorporate the antibiotic concentration in the CSF, susceptibility of the infecting microorganism, and host defense factors, may be useful in monitoring patients with meningitis.
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PMID:Pharmacodynamics of trimethoprim-sulfamethoxazole in Listeria meningitis: a case report. 211 50

The in vitro activity of tosufloxacin (A-61827; T-3262) against 15 clinical isolates of Chlamydia trachomatis and 31 recent clinical isolates of Neisseria gonorrhoeae, including 15 spectinomycin-resistant N. gonorrhoeae and 16 penicillinase-producing N. gonorrhoeae, was determined. Tosufloxacin was compared with doxycycline, ciprofloxacin, and temafloxacin against C. trachomatis. Susceptibility testing was performed by using McCoy cell monolayers. The in vitro activity of tosufloxacin against N. gonorrhoeae was compared with that of ciprofloxacin, temafloxacin, doxycycline, ceftriaxone, and spectinomycin by using an agar dilution method. Tosufloxacin was as active as temafloxacin against C. trachomatis (MIC for 90% of strains tested [MIC90], 0.25 microgram/ml; MBC for 90% of strains tested [MBC90], 0.25 microgram/ml) and was almost as active as doxycycline (MIC90, 0.06 microgram/ml; MBC90, 0.125 microgram/ml). Ciprofloxacin, temafloxacin, and tosufloxacin were extremely active against N. gonorrhoeae, including spectinomycin-resistant N. gonorrhoeae and penicillinase-producing N. gonorrhoeae, with MIC90s of 0.004, 0.015, and 0.008 microgram/ml, respectively. Ceftriaxone was slightly less active (MIC90, 0.03 microgram/ml), and doxycycline was the least active drug tested (MIC90, 4.0 micrograms/ml). Tosufloxacin and temafloxacin had excellent activity against the C. trachomatis and N. gonorrhoeae strains tested.
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PMID:In vitro activity of tosufloxacin (A-61827; T-3262) against selected genital pathogens. 211 30

The MICs and MBCs of 21 antimicrobial agents were determined for 103 strains of Listeria monocytogenes isolated in the UK and 27 strains of other Listeria species. Ampicillin, penicillin, azlocillin, imipenem, gentamicin, netilmicin, amikacin, erythromycin, rifampicin, trimethoprim, clindamycin and vancomycin had good activity, while cephalothin, chloramphenicol, ciprofloxacin and ofloxacin were less active, and cefuroxime, enoxacin, norfloxacin and fosfomycin were the least active. Tetracycline had good activity against many strains, but the MIC was high for some. Unlike the other Listeria species tested, Listeria ivanovii was susceptible to fosfomycin. Inoculum size and media employed were shown to affect the MBC, tryptose phosphate broth yielding higher MBCs than Mueller-Hinton or Isosensitest broths.
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PMID:In vitro antimicrobial susceptibility of Listeria monocytogenes isolated in the UK and other Listeria species. 212 39

To assess the potential efficacy of trimethoprim-sulfamethoxazole (TMP-SMX) against serious enterococcal infections, we used a rat enterococcal endocarditis model comparing TMP-SMX therapy (500 mg of TMP plus 2,500 mg of SMX per kg of body weight per day given every 8 h by intragastric gavage) with intravenous ampicillin therapy (1,000 mg/kg per day). Despite concentrations of active drug in serum well in excess of the MIC and MBC, the mean residual vegetation bacterial titer in TMP-SMX-treated rats was similar to that in untreated controls (8.4 +/- 1.1 versus 8.6 +/- 1.3 log10 CFU/g) and significantly higher than that in the ampicillin-treated group (3.6 +/- 1.5 log10 CFU/g; P less than or equal to 0.001). This demonstrates discordance between in vitro activity and in vivo efficacy of TMP-SMX in serious enterococcal infection.
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PMID:Failure of trimethoprim-sulfamethoxazole therapy in experimental enterococcal endocarditis. 212 91


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