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1.  Plasmid-coded ampicillin resistance in Haemophilus ducreyi. 
Seven of the 96 ampicillin-resistant isolates of Haemophilus ducreyi reported in the preceding article (Bilgeri et al., Antimicrob. Agents Chemother. 22:686-688, 1982) were investigated and found to harbor plasmids of 3.95, 5.2, 5.8, and 6.4 megadaltons. All except the 5.8-megadalton plasmid have been shown to code for beta-lactamase. The 6.4- and 5.2-megadalton plasmids of three isolates were conjugally transferable to a streptomycin-resistant mutant of H. ducreyi at high frequencies, perhaps due to the presence in these strains of a high-molecular-weight plasmid.
PMCID: PMC183815  PMID: 6983859
2.  Structural and phenotypic varieties of gentamicin resistance plasmids in hospital strains of Staphylococcus aureus and coagulase-negative staphylococci. 
We previously described a neonatal nursery epidemic of infections caused by a single strain of Staphylococcus aureus bearing a gentamicin resistance plasmid (Vogel et al., Antimicrob. Agents Chemother. 13:466-472, 1978). The same plasmid was present in two isolates of Staphylococcus epidermidis from the patients in this nursery and was transferable interspecifically from either S. aureus or S. epidermidis. During the ensuing 3 years, in the absence of further epidemics, we collected 162 gentamicin-resistant strains of S. aureus and coagulase-negative staphylococci from patients distributed throughout our hospital. Gentamicin resistance plasmids obtained from 41 representative S. aureus and coagulase-negative staphylococcal strains differed as determined by phenotypic and molecular analyses from the plasmid in the neonatal nursery epidemic. Nevertheless, these plasmids were structurally related to each other and to the plasmid of the original epidemic. Our results suggest an evolutionary relationship among these plasmids and support the hypothesis of a genetic reservoir of gentamicin resistance in coagulase-negative staphylococci transferable to S. aureus.
PMCID: PMC182010  PMID: 7103456
3.  S-Adenosyl-L-methionine: macrocin O-methyltransferase activities in a series of Streptomyces fradiae mutants that produce different levels of the macrolide antibiotic tylosin. 
A series of mutants of Streptomyces fradiae selected for increased production of the macrolide antibiotic tylosin was analyzed for levels of expression of macrocin O-methyltransferase, the enzyme which catalyzes the final step in the biosynthesis of tylosin. Increased tylosin production was accompanied by increased macrocin O-methyltransferase in some of the mutants. Increased expression of macrocin O-methyltransferase was due to more rapid early biosynthesis of the enzyme, to reduced decay of enzyme specific activity late in the fermentation, or to combinations of both. Mutant strains which showed rapid loss of enzyme specific activity late in the fermentation converted large amounts of tylosin to relomycin. The most productive mutants, which synthesized elevated levels of macrocin O-methyltransferase, also produced large amounts of macrocin, the substrate for the enzyme. Incomplete conversion of macrocin to tylosin by these mutants may be due to substrate and product inhibition (E. T. Seno and R. H. Baltz, Antimicrob. Agents Chemother. 20:370-377, 1981). The results suggest that both the levels of precursors and the levels of expression of tylosin biosynthetic enzymes are important for efficient production of tylosin.
PMCID: PMC182007  PMID: 7103455
4.  Effects of a Vancomycin-Rifampin Combination on Enterococci 
By the time-kill curve method, a vancomycin-rifampin combination showed neither synergism nor antagonism against 43 of 48 strains of enterococci. Antagonism was demonstrated against five strains.
PMCID: PMC185685  PMID: 7181496
5.  In vitro activity of pipecolic acid amide of clindamycin (U-57930E) on anaerobic bacteria compared with those of clindamycin, cefoxitin, and chloramphenicol. 
In vitro activity of pipecolic acid amide of clindamycin (U-57930E) against 265 isolates of anaerobic bacteria, including 66 strains of Bacteroides fragilis, was compared with those of clindamycin, chloramphenicol, and cefoxitin. At therapeutically achievable concentrations, the activities of all four antibiotics against anaerobic bacteria were similar.
PMCID: PMC183741  PMID: 6927289
6.  In vitro activity of the two principal oxidative metabolites of metronidazole against Bacteroides fragilis and related species. 
Metronidazole and its two principal oxidative metabolites were tested in vitro against 20 clinical isolates of the Bacteroides fragilis group. Both metabolites were bactericidal, and the exhibited 65 and 5%, respectively, of the inhibitory effect of metronidazole. Additive or weak synergistic effects resulted in combination with the parent compound.
PMCID: PMC183695  PMID: 7125628
7.  Treatment of Infections Caused by Ampicillin-Resistant Pathogens with a Combination of Ampicillin and CP-45,899 
Eleven patients infected with ampicillin-resistant organisms were treated with a combination of CP-45,899, a β-lactamase inhibitor, and ampicillin. All infections were controlled within 7 days without any signs of toxicity.
PMCID: PMC181928  PMID: 6285812
8.  In vitro susceptibilities of Aeromonas hydrophila against new antibiotics. 
The antibiotic susceptibilities of 16 clinical isolates of Aeromonas hydrophila obtained from cancer patients with septicemia were studied. Of the new beta-lactam antibiotics tested, azthreonam and moxalactam were the most active, followed by cefoperazone, cefotaxime, and ceftizoxime. Excellent activity was demonstrated by chloroamphenicol, tetracycline, aminoglycosides, and trimethoprim-sulfamethoxazole. Semisynthetic penicillins had no appreciable activity against this organism.
PMCID: PMC183774  PMID: 7137987
9.  Yersinia enterocolitica: Comparative In Vitro Activities of Seven New β-Lactam Antibiotics 
Minimum inhibitory concentrations of seven new β-lactam derivatives were determined against 35 isolates of Yersinia enterocolitica. Ceftizoxime and ceftriaxone were the most active of the antimicrobial agents tested.
PMCID: PMC183687  PMID: 7125625
10.  Activity of pirlimycin (U57930E) against strains of the Bacteroides fragilis group. 
The activities of pirlimycin (U57930E), lincomycin, clindamycin, erythromycin, josamycin, oleandomycin, and spiramycin were compared against strains of the Bacteroides fragilis group. Pirlimycin was the most active; the 90% minimal inhibitory concentration was 1 microgram/ml, and the activity range was 0.125 to 4 micrograms/ml. This drug was fourfold more active than any of the other drugs, including clindamycin. The minimal bactericidal concentration (range, 0.5 to 16 micrograms/ml) shows that pirlimycin behaves as a bacteriostatic antibiotic.
PMCID: PMC185677  PMID: 7181494
11.  Gentamicin Does Not Chelate Calcium 
The influence of increasing gentamicin concentrations on ionized calcium concentration was determined in pH-controlled, phosphate-buffered saline and normal human serum with an ion-specific calcium electrode. No evidence of calcium chelation was found.
PMCID: PMC181964  PMID: 7081982
12.  High-pressure liquid chromatographic method for determination of Sch 29482 in human serum. 
A high-pressure liquid chromatographic method was developed for quantitative determination in human serum of a new penem antibiotic known as Sch 29482 (5R,6S,8R-2-ethylthio-6(1-hydroxyethyl)penem-3-carboxylic acid). The method involves serum extraction at an acid pH with ether, followed by separation on a reverse-phase column and UV light detection at 254 nm. This technique produced a good linear relationship between the peak height ratio and the Sch 29482 concentration, which ranged from 0.09 to 35.64 micrograms/ml. In addition, this procedure proved to be quite specific for Sch 29482, since all beta-lactam antibiotics tested did not interfere with the assay. For high concentrations (greater than 0.5 micrograms/ml), the mean values obtained from the high-pressure liquid chromatographic method correlated very well (r = 0.997) with those obtained from a microbiological assay. This method is accurate and reproducible, with a sensitivity of about 0.09 micrograms per ml of serum. It is useful for monitoring serum drug levels in animals and humans and can also be used for drug pharmacokinetic studies in humans.
PMCID: PMC185671  PMID: 7181491
13.  In vitro activity of new beta-lactam antibiotics and other antimicrobial drugs against anaerobic isolates from obstetric and gynecological infections. 
The in vitro activities of N-formimidoyl thienamycin, clindamycin, chloramphenicol, metronidazole, cefoperazone, cefotaxime, cefoxitin, moxalactam, penicillin G, and piperacillin were determined against 158 anaerobic bacteria isolated from endometrial wash cultures of women with pelvic infections. In general, N-formimidoyl thienamycin was the most active, with all organisms inhibited by less than or equal to 0.5 microgram/ml. Chloramphenicol, clindamycin, and metronidazole inhibited all organisms by less than or equal to 8 microgram/ml. The penicillins and cephalosporins exhibited variable activity of lesser degrees.
PMCID: PMC183823  PMID: 7181484
14.  Comparative Stability of Newly Introduced β-Lactam Antibiotics to Renal Dipeptidase 
Renal dipeptidase purified from swine kidney hydrolyzed N-formimidoyl thienamycin, carpetimycins A and B, and Sch29482, but not azthreonam, penicillin G, or cephaloridine.
PMCID: PMC183816  PMID: 7181478
15.  In vitro comparison of clindamycin and pirlimycin (U-57930E) activity against Staphylococcus aureus. 
The activities of clindamycin and its derivative, pirlimycin (U-57930E), were compared against 100 strains of Staphylococcus aureus, using a microtiter broth dilution technique. Minimal inhibitory concentrations demonstrated that pirlimycin was comparable to clindamycin but offered no increase in activity against either methicillin-susceptible or methicillin-resistant S. aureus.
PMCID: PMC183736  PMID: 6927639
16.  Susceptibility of Nocardia asteroides to various antibiotics, including newer beta-lactams, trimethoprim-sulfamethoxazole, amikacin, and N-formimidoyl thienamycin. 
The susceptibility of 26 isolates of Nocardia asteroides to several antibiotics was determined by the agar dilution technique. Many currently available beta-lactam antibiotics were ineffective. Cefotaxime, cefmenoxime, and N-formimidoyl thienamycin were active against these strains, with 80% minimal inhibitory concentrations of 4, 4, and 2 micrograms/ml, respectively. Amikacin was the most effective agent tested.
PMCID: PMC182064  PMID: 7051971
17.  Failure of Padac Test Strips to Detect Staphylococcal β-Lactamase 
Padac test strips failed to detect the production of β-lactamase by 10 strains of penicillin-resistant staphylococci.
PMCID: PMC182059  PMID: 6981377
18.  Stability of antimicrobial agents in peritoneal dialysate. 
The stability of cephapirin, gentamicin, penicillin G, nafcillin, ticarcillin, and vancomycin was tested in peritoneal dialysate at 25 degrees C for 24 h. All of the antimicrobial agents were stable except penicillin G, which lost 25% of activity over 24 h (P less than 0.01). The once-daily preparation of drug-dialysate solution is feasible for the treatment of peritonitis in patients on continuous ambulatory peritoneal dialysis.
PMCID: PMC181931  PMID: 7103451
19.  Cefamandole treatment of Salmonella bacteremia. 
The efficacy of cefamandole in the treatment of 19 patients with salmonella bacteremia was evaluated. Although all of the salmonella strains isolated were highly susceptible to cefamandole in vitro, a therapeutic failure was observed in 7 (36.8%) of the 19 patients.
PMCID: PMC181882  PMID: 7073269
20.  Pharmacokinetics of Cefadroxil and Cefaclor During an Eight-Day Dosage Period 
The concentrations of cefadroxil and cefaclor in serum were studied in eight healthy volunteers receiving 1,000 mg of both substances three times per day for 8 days. Intraindividual comparisons showed an increase in peak serum levels of cefadroxil from days 1 to 8 in seven of eight volunteers. Cefaclor peak concentrations did not rise during the 8 days.
PMCID: PMC185721  PMID: 7159069
21.  Susceptibility of Haemophilus influenzae type b to cefaclor and influence of inoculum size. 
Cefaclor appeared to be an effective antibiotic against both beta-lactamase-positive and beta-lactamase-negative strains of Haemophilus influenzae type b when tested with 10(5) colony-forming units per ml. With inocula in excess of 10(6) colony-forming units per ml, these organisms were neither inhibited nor killed at concentrations of 400 micrograms/ml. This inoculum effect was also demonstrated in time-kill curve studies.
PMCID: PMC185688  PMID: 6983863
22.  Effect of calcium, magnesium, and zinc on ticarcillin and tobramycin alone and in combination against Pseudomonas aeruginosa. 
Correlation between in vitro and in vivo test results for synergy between carboxypenicillins and aminoglycosides against Pseudomonas aeruginosa is poor. Although the divalent cation content of culture media is known to affect aminoglycoside susceptibility testing for P. aeruginosa, this effect of divalent cations has not been examined for synergy testing of carboxypenicillin-aminoglycoside interaction against P. aeruginosa. The minimal inhibitory concentrations (MICs) of tobramycin and ticarcillin and the interaction of these drugs in combination were studied by a microtitration method for 36 strains of P. aeruginosa in Mueller-Hinton broth with varying supplements of calcium, magnesium, and zinc. The supplementation of Mueller-Hinton broth to 50 or 100 mg of calcium per liter had a significant effect in increasing the tobramycin MIC (P less than 0.01), as well as decreasing the degree of synergy between ticarcillin and tobramycin (P less than 0.01). Supplementation to 20 mg of magnesium per liter, 1.0 mg of zinc per liter, or both did not significantly affect tobramycin MIC or the interaction of tobramycin and ticarcillin. Supplementation to 50 or 100 mg of calcium per liter rendered any additional effect of magnesium and zinc on aminoglycoside MIC and aminoglycoside-carboxypenicillin interaction negligible. If these results for ticarcillin and tobramycin are confirmed for other carboxypenicillins and aminoglycosides, then the Mueller-Hinton broth used for P. aeruginosa aminoglycoside susceptibility and synergy testing may need to be supplemented only with calcium at a concentration of 50 mg/liter.
PMCID: PMC185669  PMID: 6817707
23.  Evaluation of the Cathra inoculating device for susceptibility testing of methicillin-susceptible and methicillin-resistant Staphylococcus aureus strains. 
We compared the antimicrobial susceptibility results obtained with the Cathra replicator and reference methods when Staphylococcus aureus strains were tested by using agar dilution techniques. The Cathra replicator and the 0.001-ml calibrated loop gave results that fell within +/- 1 log2 dilution for greater than or equal to 95% of isolates when methicillin and cefamandole were tested.
PMCID: PMC185680  PMID: 6924824
24.  Concentrations of cefoxitin in gallbladder bile of cholecystectomy patients. 
Cefoxitin was administered in a dose of 2 g intravenously to 17 patients scheduled for cholecystectomy. The concentrations of this agent in serum and gallbladder bile were measured simultaneously upon opening of the abdominal cavity. Concentrations of cefoxitin in excess of 10 microgram/ml were present in the gallbladder bile of 12 of the 13 patients from samples obtained between 35 and 165 min after cefoxitin infusion. Cystic or common duct obstruction did not preclude entry of the drug into gallbladder bile.
PMCID: PMC183822  PMID: 7181483
25.  High-pressure liquid chromatographic assay of ceftizoxime with an anion-exchange extraction technique. 
An anion-exchange extraction method was used in conjunction with high-pressure liquid chromatography for assay of ceftizoxime in 181 serum samples. Comparison of this method with bioassay gave a linear regression line described by Y = 1.11 + 0.98 X, with a correlation coefficient of 0.984. The anion-exchange extraction method is a fast, reliable method of preparing serum samples containing ceftizoxime for assay by liquid chromatography.
PMCID: PMC183737  PMID: 6100429

Results 1-25 (444)