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Biomedical subjects

E H Gerlach

Publications and source records attributed to E H Gerlach.

At least 19 recordsLinked to original sources
PubMed1992

Comparison of fixed concentration and fixed ratio options for testing susceptibility of gram-negative bacilli to piperacillin and piperacillin/tazobactam.

Piperacillin combined with tazobactam was tested at both a fixed ratio (8:1) and fixed tazobactam concentration (4 micrograms/ml) against 2,685 consecutively isolated gram-negative bacilli and 56 highly piperacillin-resistant isolates. Tazobactam significantly enhanced the spectrum of piperacillin activity. Overall, at a concentration of 16 micrograms/ml piperacillin alone inhibited 78.8% of the Enterobacteriaceae isolates compared to inhibition of 92.7% and 95.5% by the 8:1 ratio and fixed (4 micrograms/ml) tazobactam combinations, respectively. In MIC tests the two combination options performed comparably against both routine and highly piperacillin-resistant isolates. Synergistic inhibition was observed for comparable numbers of isolates with the two combination options, the most marked effect being seen in the more highly piperacillin-resistant isolates. Both testing options are supported by the available human pharmacokinetic data; however the 8:1 ratio of piperacillin to tazobactam may be preferable given that the clinical formulation contains the two compounds in an 8:1 ratio and this ratio is maintained in vivo.

Drug Synergism↗
PubMed1992

Interpretive criteria and quality control guidelines for lomefloxacin and meropenem in susceptibility tests of Haemophilus influenzae using Haemophilus test medium.

Lomefloxacin and meropenem were tested in a multilaboratory study to establish susceptibility testing interpretive criteria and quality control (QC) guidelines for Haemophilus influenzae using Haemophilus test medium (HTM). Interpretive criteria were established by using triplicate testing of 102 representative H. influenzae strains. Only a susceptible category was proposed for lomefloxacin (greater than or equal to 22 mm and less than or equal to 2 micrograms/ml) and meropenem (greater than or equal to 13 mm and less than or equal to 4 micrograms/ml) due to the lack of resistant isolates. QC range for H. Influenzae ATCC 49247 were established using multiple HTM agar and broth base lots, three disk lots for each drug, and a number of test replicates consistent with the National Committee for Clinical Laboratory Standards M23-T guideline.

Anti-Infective Agents↗
PubMed1992

MIC quality control guidelines for Haemophilus susceptibility tests using cefdinir (FK482), cefepime, cefetamet, cefpirome, ceftibuten, fleroxacin, temafloxacin, clarithromycin, RP59500, and trospectomycin.

A multilaboratory study was performed to establish broth microdilution MIC quality control (QC) guidelines for 10 investigational drugs which previously demonstrated significant activity against Haemophilus influenzae. MIC QC ranges for H. influenzae ATCC 49247 with Haemophilus test medium were determined by using multiple contemporary lots of Haemophilus test medium and the National Committee for Clinical Laboratory Standards' recommended numbers of replicate tests. On the basis of these results, QC ranges (generally modal MIC +/- one log2 dilution) are proposed for cefdinir, cefepime, cefetamet, cefpirome, ceftibuten, fleroxacin, temafloxacin, clarithromycin, RP59500, and trospectomycin. The proposed QC guidelines for clarithromycin and temafloxacin were recently accepted by the National Committee for Clinical Laboratory Standards.

Anti-Bacterial Agents↗
PubMed1992

Disk diffusion quality control guidelines for Haemophilus susceptibility tests using cefdinir, CI-960, fleroxacin, temafloxacin, and trospectomycin.

A multilaboratory study to determine disk diffusion quality control ranges for Haemophilus influenzae ATCC 49247 and five investigational drugs was performed. Multiple lots of Haemophilus Test Medium and antibiotic disks were used for replicate testing in conformance with the recommendations of the National Committee for Clinical Laboratory Standards. Quality control disk zone diameter ranges were proposed for cefdinir, CI-960, fleroxacin, temafloxacin, and trospectomycin.

Anti-Bacterial Agents↗
PubMed1992

MIC and disk diffusion quality control guidelines for Neisseria gonorrhoeae susceptibility tests of cefdinir, cefetamet, CI-960, fleroxacin, lomefloxacin, and temafloxacin.

Cefdinir (FK482), cefetamet (Ro 15-8074), CI-960, fleroxacin, lomefloxacin, and temafloxacin have potent activities against Neisseria gonorrhoeae. They were tested in a multilaboratory study to establish quality control guidelines. Quality control ranges for N. gonorrhoeae ATCC 49226 were determined by using multiple GC agar lots, three disk lots, and a number of test replicates consistent with the M23-T guidelines of the National Committee for Clinical Laboratory Standards. The MIC ranges included 2 to 4 log2 dilution steps. The recommended inhibition zone diameter ranges were generally 7 to 8 mm and included greater than or equal to 91.3% of all recorded study results.

Anti-Infective Agents↗
PubMed1979

Piperacillin susceptibility tests by the single-disk agar diffusion technique.

Piperacillin is a new semisynthetic penicillin with a spectrum of activity broader than that of carbenicillin or ticarcillin. Studies were performed to establish standards for agar diffusion susceptibility tests with piperacillin disks. Tests with 100-, 150-, and 200-micrograms piperacillin disks and with 100-micrograms carbenicillin disks were evaluated. With both penicillins, 100-micrograms disks were satisfactory, in spite of the fact that piperacillin is a larger molecule and diffuses at a slower rate. With both carbenicillin and piperacillin disks, resistant strains of Staphylococcus aureus produced zones less than or equal to 28 mm and susceptible strains gave zones greater than or equal to 29 mm in diameter. When testing other microorganisms, zone standards of less than or equal to 13 mm for resistant (minimal inhibitory concentration, greater than or equal to 256 micrograms/ml) and greater than or equal to 17 mm for susceptible (minimal inhibitory concentration, less than or equal to 64 micrograms/ml) are recommended for tests with 100-micrograms piperacillin disks. Similar zone standards are currently recommended for carbenicillin and ticarcillin disk tests.

Bacteria↗
PubMed1979

Increased production of beta-lactamase under anaerobic conditions in some strains of Escherichia coli.

A simple biological assay to detect beta-lactamase activity exhibited by selected cultures of Escherichia coli was used to test enzyme production in cells incubated aerobically and anerobically. Anaerobic incubation resulted in increased size of zones of drug inactivation by some beta-lactamase-producing strains. The beta-lactamase activity of cell lysates was determined iodometrically for aerobically and anaerobically grown cells. The specific beta-lactamase activity for anaerobically grown cells was three to five times greater than for aerobically grown cells. Beta-lactamase production was determined to be constitutive in all strains and to be plasmid mediated, as demonstrated by transfer to E. coli K-12 by conjugation.

Aerobiosis↗
PubMed1979

Fortimicin A: collaborative in vitro susceptibility. Comparison with amikacin and gentamicin against 11,840 clinical bacterial isolates.

The susceptibility of 11,840 clinical bacterial isolates to fortimicin A was determined by agar dilution or broth microdilution methods and compared with their susceptibility to amikacin and gentamicin. In general, the in vitro activity of fortimicin A was essentially the same as that of amikacin. Significant exceptions were the increased effectiveness of fortimicin A against Serratia marcescens and the greater activity of amikacin against Pseudomonas and other nonfermentative gram-negative bacilli. On a weight-for-weight basis, gentamicin showed greater activity than the other two antimicrobial drugs against most species; S. Marcescens was the major exception. However, at concentrations equivalent to achievable nontoxic serum levels, the proportion of isolates inhibited by the three drugs was quite comparable. There were several strains with unusually high resistance to one or more of the tested antibiotics. These usually occurred in one of the six participating institutions and could be traced to specific enzyme-producing or permeability mutants endemic to that particular institution.

Amikacin↗
PubMed1979

Methods of measuring zones of inhibition with the Bauer-Kirby disk susceptibility test.

Standard Bauer-Kirby disk tests were performed with 85 selected isolates, each tested in triplicate by four different investigators. Each disk test was observed, and zone diameters were measured, under two lighting conditions (transmitted light and reflected light). The two lighting systems produced similar zone measurements (+/-2 mm) with 96% of the tests. When there were greater differences, zones appeared to be larger when observed with reflected light. Interlaboratory reproducibility was much greater when using reflected light rather than transmitted light. We concluded that zone diameters should be measured from the back of the plate while it is resting on, or held 2 to 3 inches [ca. 5.1 to 7.6 cm] above, a black, nonreflecting, flat surface, illuminated by a reflected light source.

Anti-Bacterial Agents↗
PubMed1979

Simple inoculum standardizing system for antimicrobial disk susceptibility tests.

A collaborative study was undertaken to evaluate a simple, convenient device which expedites inoculum standardization for antimicrobial disk susceptibility tests. The Inocupac system (Minnesota Mining & Manufacturing [3M] Co., St. Paul, Minn.) was used to perform disk tests in parallel with the standard Bauer-Kirby method. Five investigators tested 100 selected isolates, each in triplicate. Inter- and intralaboratory precision of both disk procedures was essentially comparable. The Inocupac system failed to consistently provide satisfactory growth with some streptococci, but when testing common gram-negative bacilli, staphylococci, and most enterococci, the Inocupac system gave zones about the same size (+/-2 mm) as the Bauer-Kirby procedure. Interpretive agreement between the two test systems varied from 90 to 99% with different antimicrobial agents, and repeated tests with the Bauer-Kirby method demonstrated the same degree of interpretive agreement. The Inocupac system is a valid alternative method for inoculating disk susceptibility tests.

Anti-Bacterial Agents↗
PubMed1978

Reassessment of the "class" concept of disk susceptibility testing. Cephalothin disks versus minimal inhibitory concentrations with eleven cephalosporins.

Reassessment of the "class" concept of disk susceptibility testing. Cephalothin disks versus minimal inhibitory concentrations with eleven cephalosporins. Am J Clin Pathol 70: 909--913, 1978. Studies were carried out to determine whether susceptibility or resistance to 11 cephalosporins could be predicted reliably from the results of tests with a single cephalothin disk. The cephalosporins were tested with a microdilution technic and with a standardized disk test. Strains susceptible to a cephalothin disk were predictably susceptible to all other cephalosporins. However, 2--12% of the strains were resistant to cephalothin disks but were susceptible to the more active parenteral drugs cefoxitin, cephamandole, cefuroxime, and BL-S786. Because of differences in antimicrobial activities, the cephalosporins could be divided into three subgroups for purposes of susceptibility testing: one subgroup includes the majority of cephalosporins and may be represented by tests with cephalothin, the second subgroup inclues three active parenteral drugs (cephamandole, cefuroxime, and BL-S786) and may be represented by tests with cefuroxime, and the third subgroup consists of cefoxitin, a cephamycin with a unique broad spectrum of activity. Until the drugs in the second and third subgroups are released for general therapeutic use, the practice of testing only one cephalosporin disk appears to be a reasonably reliable procedure.

Bacteria↗
PubMed1978

Serotyping herpes simplex virus isolated by enzyme-linked immunosorbent assays.

An enzyme-linked immunosorbent assay (ELISA) using a double-antibody sandwich tecnhique has been developed to serotype isolates of herpes simplex virus from clinical sources. The results obtained using this procedure were in agreement with those obtained with a standard neutralization test in typing stock cultures and 32 clinical isolates of herpes simplex virus. Clear differentiation between the two viral serotypes was obtained using rabbit immunoglobulin cross-absorbed with heterologous virus antigen. The ELISA procedure described appears to be a convenient and accurate substitute for the neutralization test in typing herpes simplex viruses. ELISA techniques require relatively small amounts of antigen and antibody and can be performed with very simple equipment.

Enzyme-Linked Immunosorbent Assay↗
PubMed1977

Cefuroxime, a new parenteral cephalosporin: collaborative in vitro susceptibility comparison with cephalothin against 5,887 clinical bacterial isolates.

Cefuroxime, a new parenteral cephalosporin was compared with cephalothin by broth microdilution susceptibility testing against 5,887 routine clinical bacterial isolates in four large clinical laboratories. The minimal inhibitory concentrations (MICs) of cefuroxime against the Enterobacteriaceae were consistently lower than those of cephalothin. This was most striking among the Enterobacter species, which were generally susceptible to cefuroxime (MIC </= 8 mug/ml), but resistant to cephalothin. Similar results occurred with Haemophilus species, Acinetobacter anitratus, meningococci, and Aeromonas hydrophilia, but Pseudomonas species and enterococci were resistant to high concentrations of both drugs. Streptococci showed slightly greater susceptibility to cefuroxime than to cephalothin. By contrast, staphylococci were more susceptible to cephalothin. Bacteroides fragilis was resistant to cefuroxime, but other anaerobes were generally susceptible.

Bacteria↗
PubMed1977

Piperacillin (T-1220), a new semisynthetic penicillin: in vitro antimicrobial activity comparison with carbenicillin, ticarcillin, ampicillin, cephalothin, cefamandole and cefoxitin.

Piperacillin (T-1220) is a new semisynthetic penicillin with an unusually broad spectrum of antimicrobial activity. In vitro comparisons of this drug with 6 other beta-lactam antimicrobics (ticarcillin, carbenicillin, ampicillin, cephalothin, cefamandole and cefoxitin) were conducted. These included minimal inhibitory concentrations (MIC) against 394 bacterial isolates, the minimal lethal concentrations (MLC) against 79 of those, as well as the effect of inoculum size on the MIC and MLC of the drugs. Piperacillin had significantly greater activity than did the other penicillins against Pseudomonas species and Klebsiella pneumoniae. Against P. aeruginosa piperacillin was 8- and 16-fold more active than ticarcillin and carbenicillin, respectively. The MLC of piperacillin rarely differed from the MIC by more than one log2 dilutions except against P. aeruginosa in which the MLC was 4-fold greater or more than the MIC of 45% of isolates tested. Ticarcillin, carbenicillin and cefoxitin showed minimal inoculum size effects. Cefamandole results showed the greatest inoculum size variation with 55% and 37% of isolates showing an 8-fold increase in MIC and MLC respectively by increasing inoculum from 10(5) to 10(7) CFU/ml. Piperacillin was intermediately effected having 25% of strains greater than 8-fold increase in MIC.

Ampicillin↗